Satellite mega-constellations have overtaken the population of spacecraft since the first Starlink launch in 2019, but the regulation on mega-constellations has lagged. The brightness and quantity of mega-constellation satellites can interfere with astronomical surveys, add naked-eye visible objects to the sky, congest low-Earth orbit, and their launches add pollutants to the atmosphere. Quantitative measurements of the brightness of these mega-constellations are lacking since their high relative motion makes them challenging to track with scientific instruments. We present measurements of AST SpaceMobile’s five Block 1 BlueBird satellites: an average V magnitude of 3.9 ± 1.1, with the brightest observation reaching V magnitude 1.2 ± 0.3 and the faintest V magnitude 6.4 ± 0.3. Our measurements reveal an average brightness seven times brighter than mitigation targets cited in FCC filings and peak values over 200 times brighter than the International Astronomical Union’s recommended threshold (V magnitude 7). Now, AST SpaceMobile is expected to deploy over 200 Block 2 satellites that are each three times larger (199 m2) which would be three times brighter than Block 1 (all else being equal), and regulations have not changed. The brightness of the current mega-constellations highlights the lack of enforceable photometric standards and environmental reporting, marking a critical regulatory gap that impacts both space and ground-based astronomy.
ISSN: 1538-3873
The Publications of the Astronomical Society of the Pacific publishes original research in astronomy and astrophysics; innovations in instrumentation, data analysis, and software; tutorials, dissertation summaries, and conference summaries; and invited reviews on contemporary topics.
- The following article is Open accessAST SpaceMobile Satellite Brightness and the Limits of Orbital Regulation
Owen Miller et al 2026 PASP 138 074508
- The following article is Open accessThe Origin of WHAM Point Source 46
S. R. Kulkarni et al 2026 PASP 138 084301
The Wisconsin Hα Mapper surveyed the entire Galactic sky in Hα (∣vLSR∣ ≲ 100 km s−1) to approximately 0.1 Rayleigh (R), albeit with a 1° beam. Reynolds et al. (2005) reported “point sources” which stood out against the Galactic background in space and velocity. Half of the sources are associated with plausible planetary nebulae and OB stars. Reynolds et al. suggested sub dwarfs for one quarter of the sources. Here, we investigate one such source, WPS 46, for which Reynolds et al. suggested the sub-dwarf PG 0931+691 to provide the source of ionization. With the Keck Cosmic Web Imager we found numerous nebular emission lines within the vicinity of WPS 46, but we failed to find Hα emission in the arc-minute vicinity of PG 0931+691. The line ratios (BPT diagram and [S ii]/Hα) combined with the morphology are more consistent with AGN or LI(N)ER-like ionization than with pure warm ionized medium or H ii region-like photoionization. Separately, we offer compelling reasons to argue that PG 0931+691 cannot be the source of ionizing power for WPS 46. We suggest that WPS 46 is associated with an intermediate velocity complex (IVC) and that Hα and nebula emission may arise as a result of a shock. We conclude by outlining a plan of action of using SDSS’s Local Volume Mapper along with deep narrow band imagery obtained by amateur astronomers to explore and study the ionized sky on sub-degree scales, in general, and specifically studies of IVC and high-velocity complexes.
- The following article is Open accessA Heterogeneous Testbed Architecture for Real-time Adaptive RFI Mitigation in Radio Astronomy Receivers
Yohan A. Aparicio and Manuel Jimenez 2026 PASP 138 075006
View article, A Heterogeneous Testbed Architecture for Real-time Adaptive RFI Mitigation in Radio Astronomy ReceiversPDF, A Heterogeneous Testbed Architecture for Real-time Adaptive RFI Mitigation in Radio Astronomy ReceiversRadio-frequency interference (RFI) increasingly constrains the detection of weak astronomical signals in L- and S-band receivers, motivating real-time mitigation architectures that balance suppression capability, latency, scalability, hardware efficiency, and cost. The growing complexity of dynamic interference environments and the computational demands of adaptive mitigation techniques further motivate the exploration of alternative processing strategies. Accordingly, this work investigates a heterogeneous field-programmable gate array (FPGA) –graphics processing unit (GPU) testbed architecture for real-time adaptive RFI mitigation efficacy in wideband radio astronomy receivers. The proposed digital back-end integrates an AMD Zynq UltraScale+ RFSoC with a GPU-accelerated parallel processing cluster plus a 100 GbE communication infrastructure providing support for serial, parallel, and heterogeneous execution models. System performance was assessed under representative astronomical and interference scenarios using a multidimensional evaluation framework that quantified latency, FPGA resource utilization, and signal quality with metrics that included mean square error, output signal-to-noise ratio, and cancellation depth. Results indicate that performance depends on the interplay between computational complexity, execution strategy, and hardware architecture. Parallel RFSoC execution improved efficiency for moderate-complexity algorithms, whereas heterogeneous FPGA–GPU processing achieved the lowest latency and enabled scalable execution for computationally intensive algorithms while preserving signal quality. Overall, the proposed architecture enables stable low-latency operation, robust signal reconstruction, and scalable processing, providing a reproducible and cost-efficient framework for real-time RFI mitigation in radio astronomy receivers.
- The following article is Open accessThe Expected Yield of Venus Zone Terrestrial Planets from PLATO
Stephen R. Kane et al 2026 PASP 138 074402
View article, The Expected Yield of Venus Zone Terrestrial Planets from PLATOPDF, The Expected Yield of Venus Zone Terrestrial Planets from PLATOThe characterization of terrestrial exoplanets and the conditions that lead to divergent climate outcomes is a primary goal of exoplanetary science. The Venus Zone (VZ) provides a framework for identifying planets that may have experienced runaway greenhouse processes similar to Venus, and the statistical properties of such planets bear directly on models of planetary habitability. Here we present a quantitative estimate of the expected yield of VZ terrestrial planets from ESA’s PLAnetary Transits and Oscillations of stars (PLATO) mission. We combine the predicted PLATO planet yield for Earth-size (0.8–1.25 R⊕) and super-Earth (1.25–2.0 R⊕) planets with empirical occurrence rates for VZ terrestrial planets derived from Kepler data. Under conservative assumptions, we estimate that PLATO will detect ∼170–280 VZ terrestrial planets (0.8–2.0 R⊕), including ∼40–80 Earth-size (0.8–1.25 R⊕) planets, during a nominal 4 yr mission. For the bright P1 sample (V ≤ 11), we estimate ∼50–85 terrestrial and ∼13–22 Earth-size VZ detections, enabling radial velocity mass determination and atmospheric characterization of the most favorable targets with JWST and future facilities. We discuss the implications of this yield for comparative studies of Earth-Venus divergence, synergies with the DAVINCI, VERITAS, and EnVision missions to Venus, and the role of PLATO in advancing our understanding of the runaway greenhouse boundary.
- The following article is Open accessConstraints on the VHE Counterpart of Two Binary Black Hole Mergers Observed by the MAGIC and CTAO LST-1 Telescopes
K. Abe et al 2026 PASP 138 084101
View article, Constraints on the VHE Counterpart of Two Binary Black Hole Mergers Observed by the MAGIC and CTAO LST-1 TelescopesPDF, Constraints on the VHE Counterpart of Two Binary Black Hole Mergers Observed by the MAGIC and CTAO LST-1 TelescopesWe present very-high-energy gamma-ray observations of two binary black hole merger candidates, GW240615_113620 and GW241125_010116, performed with the Major Atmospheric Gamma Imaging Cherenkov (MAGIC) telescopes and the first Large-Sized Telescope of the Cherenkov Telescope Array Observatory’s (CTAO LST-1). GW240615_113620 was the best localized event of the fourth observing run of the LIGO-Virgo-KAGRA gravitational waves interferometers. GW241125_010116 was temporally and spatially coincident with a sub-threshold short-duration burst detected with the Swift-Burst Alert Telescope, the Swift-X-Ray Telescope and the Einstein Probe Follow-up X-ray Telescope. We observed the two events in stereoscopic mode, taking advantage of the improved sensitivity of joint MAGIC+LST-1 observations. No detection was achieved in the GeV–TeV gamma-ray band for any of the two sources. The unfavourable observing conditions of both events posed a challenge for a standard analysis and therefore a non standard analysis was necessary for both objects. Owing to the small localization area and the association with a GRB-like burst respectively, these events represented an unprecedented opportunity to study in details the electromagnetic emission from binary black holes merger events and, in particular, we discussed two theoretical models that predict a detectable gamma-ray emission and the possible future applications.
- The following article is Open accessA Deep Census of Brown Dwarfs in the COSMOS-Web Field
French Tsocheff A. Festin et al 2026 PASP 138 084402
View article, A Deep Census of Brown Dwarfs in the COSMOS-Web FieldPDF, A Deep Census of Brown Dwarfs in the COSMOS-Web Field“Failed Stars,” or Brown Dwarfs are substellar objects that are incapable of sustained hydrogen fusion. They are invaluable for understanding the low-mass end of the substellar initial mass function. Historically, studies relating to brown dwarfs have been limited to our immediate solar neighborhood. In turn, the galaxy-wide distribution of these objects is generally unconstrained until the inception of the James Webb Telescope (JWST). We aimed to construct an expanded, high-reliability catalog of brown dwarf candidates and perform a definitive test of brown dwarf number counts at kiloparsec (kpc) distances by leveraging the complete 0.54 deg2 COSMOS-Web JWST survey. We applied a systematic filtering pipeline to the COSMOS 2025 catalog to isolate the candidates. A mixture of data reduction steps was implemented, such as initial morphological selection, quality flags, S/N & magnitude limits, and a color selection criterion designed to find the characteristic V-shaped spectral energy distribution of brown dwarfs. The physical properties of our final candidates were derived via a dual-model Markov Chain Monte Carlo analysis using the Sonora Bobcat and SAND atmospheric models. Our search managed to find a final promising sample of 76 brown dwarf candidates with effective temperatures from 809–1803 K, log surface gravity (log(g)) from 3.0–5.5, and distances spanning 0.2–3.1 kpc. The sample includes several chemically interesting objects, such as three potentially ancient, metal-poor halo candidates with metallicity [M/H] = −2.4 and an alpha enhancement [α/Fe] > 0.0. The cumulative number counts of our sample show excellent agreement with standard galactic models scaled to the local census, confirming that these models hold at large distances. This work positions itself as covering the widest distance range to date, providing a crucial dataset for constraining the substellar mass function and serving as a foundational resource for future spectroscopic follow-up.
- The following article is Open accessThe Tartu Observatory Fiber-fed Echelle Spectrograph (TOFES) Data Reduction Pipeline
Sandipan P. D. Borthakur et al 2026 PASP 138 084501
View article, The Tartu Observatory Fiber-fed Echelle Spectrograph (TOFES) Data Reduction PipelinePDF, The Tartu Observatory Fiber-fed Echelle Spectrograph (TOFES) Data Reduction PipelineWe introduce the data reduction pipeline for the Tartu Observatory Fiber-fed Echelle Spectrograph (TOFES). TOFES is installed in the Coudé room and will be connected to the 1.5 m Tartu Observatory AZT-12 telescope through a four-channel instrument adapter to be mounted at the Cassegrain focus of the telescope. The spectrograph has an average spectral resolution of ∼30,000 and covers the 390–900 nm wavelength band in a single exposure. The data reduction pipeline, based on the PyReduce package, was tested on spectra of the Sun. We also present the Spectroscopy-Toolbox package, which was developed to provide additional tools for diagnostics and spectral line identification for radial velocity measurements. The spectrograph will address a range of scientific questions, including the stellar characterisation of Herbig Ae/Be stars to measure accretion contamination from their protoplanetary disks, the stellar characterisation of exoplanet host-stars including the Ariel space mission targets, and radial velocity monitoring of large-scale atmospheric variability in massive stars.
- The following article is Open accessStatistical Inference of Fast Radio Burst Environments Using Galaxy Number Density
Vignesh V. V. Rao et al 2026 PASP 138 084103
View article, Statistical Inference of Fast Radio Burst Environments Using Galaxy Number DensityPDF, Statistical Inference of Fast Radio Burst Environments Using Galaxy Number DensityFast radio bursts (FRBs) are bright, millisecond-duration radio transients of unknown origin. They are categorized as repeaters and non-repeaters, possibly indicating distinct progenitor types. However, validating this distinction is difficult because of the limited number of localized FRBs. Large-scale galactic environments can provide insight into the nature of the host galaxies of FRB and their progenitors. High-number-density regions are typically associated with old galaxies, whereas low-number-density regions are linked to young star-forming or less massive quiescent galaxies. In this study, we use galaxy number density to statistically assess the environments of 19 repeaters and 253 non-repeaters from CHIME Catalog 1, using galaxies from the WISE × PS1 catalog. A Kolmogorov–Smirnov (KS) test showed no significant difference between the two populations (pKS = 0.673). This result indicates that the statistical significance of the difference could depend on small-number statistics, highlighting the necessity of future FRB samples. Intriguingly, a comparison of FRBs with random galaxy fields suggests that FRBs may preferentially occur in underdense galactic environments with a median p-value (pKS) = 2.84 × 10−2 compared to random galaxy apertures.
- The following article is Open accessAligned, Multiple-transient Events in the First Palomar Sky Survey
Beatriz Villarroel et al 2025 PASP 137 104504
View article, Aligned, Multiple-transient Events in the First Palomar Sky SurveyPDF, Aligned, Multiple-transient Events in the First Palomar Sky SurveyOld, digitized astronomical images taken before the human spacefaring age offer a rare glimpse of the sky before the era of artificial satellites. In this paper, we present the first optical searches for artificial objects with high specular reflections near the Earth. We follow the method proposed in Villarroel et al. and use a transient sample drawn from Solano et al. We use images from the First Palomar Sky Survey to search for multiple (within a plate exposure) transients that, in addition to being point-like, are aligned along a narrow band. We provide a shortlist of the most promising candidate alignments, including one with ∼3.9σ statistical significance. These aligned transients remain difficult to explain with known phenomena, even if rare optical ghosting producing point-like sources cannot be fully excluded at present. We explore remaining possibilities, including fast reflections from highly reflective objects in geosynchronous orbit, or emissions from artificial sources high above Earth’s atmosphere. We also find a highly significant (∼22σ) deficit of POSS-I transients within Earth's shadow when compared with the theoretical hemispheric shadow coverage at 42,164 km altitude. The deficit is still present though at reduced significance (∼7.6σ) when a more realistic plate-based coverage is considered. This study should be viewed as an initial exploration into the potential of archival photographic surveys to reveal transient phenomena, and we hope it motivates more systematic searches across historical data sets.
- The following article is Open accessCorrigendum: “Chemical Signatures of AGB Mass Transfer in Gaia White Dwarf Companions” (2026, PASP, 138, 024201)
Natsuko Yamaguchi et al 2026 PASP 138 079201
- The following article is Open accessThermally Inflated Accretors in Post-mass Transfer Binaries: A35 and its Class Revisited
Soumyadeep Bhattacharjee et al 2026 PASP 138 084202
View article, Thermally Inflated Accretors in Post-mass Transfer Binaries: A35 and its Class RevisitedPDF, Thermally Inflated Accretors in Post-mass Transfer Binaries: A35 and its Class RevisitedA small but growing class of binaries containing hot (Teff ∼ 105 K) white dwarfs (WDs) and rapidly rotating, apparently subgiant companions—including the prototype, A35—show companions that are too large and luminous to be ordinary main-sequence stars yet too numerous to be explained as finely tuned near-twin binaries. We argue that these stars are instead main-sequence accretors temporarily inflated out of thermal equilibrium by recent mass transfer. For the subgiant of A35, a new Gaia DR3 astrometric orbit (Porb = 790 days) combined with updated photometric and spectroscopic constraints yield Teff ≈ 4925 ± 75 K, R ≈ 3 ± 0.05 R⊙, near-solar metallicity, and rapid rotation aligned with the orbit (vrot ≈ 195 ± 3 km s−1), indicating substantial recent accretion and spin-up. Dynamical mass limits disfavor a coeval twin-binary origin, supporting the inflated-accretor interpretation. We test this scenario using self-consistent Modules for Experiments in Stellar Astrophysics binary evolution calculations with a new accretion prescription in which accreted material retains a fraction of its infall energy, against the default of setting its entropy to that of the accretor’s surface. The accretor expands to giant-like radii when
is high yet remains within its Roche lobe, allowing stable mass transfer even for mass ratios traditionally considered unstable. After mass transfer ceases, the star contracts on Myr timescales through a bloated, rapidly rotating phase whose temperatures, radii, and spins match those observed in A35–type systems. This framework naturally explains the population and unifies A35-type binaries with post-AGB binaries, blue lurkers, and wide WD+main-sequence systems as successive stages of the same post-mass-transfer evolutionary pathway. - The following article is Open accessThe Dynamics of Planetary Ejection
Malena Rice et al 2026 PASP 138 082001
The ubiquity of free-floating planets inferred from microlensing and direct imaging surveys suggests that planetary ejection—a process in which planets initially born encircling a stellar host become gravitationally unbound—is common. Four overarching mechanisms have been proposed to induce planetary ejection: close approaches of neighboring planets, instabilities in binary or multi-star systems, stellar and planetary flybys, and post-main-sequence stellar evolution. Here we review the mechanisms underlying planetary ejection, as well as predictions derived from each. Current and upcoming microlensing surveys offer the potential to test existing models and distinguish between planetary ejection mechanisms, providing further insight into the demographic-level architectures of exoplanets across stellar environments.
- The following article is Open accessFeasibility Study for Novel Application of Southern Sky La Paz Survey Low-dispersion Spectral Plates in Recent Astrophysics
Tauseef Ahmad Zafar et al 2026 PASP 138 084509
View article, Feasibility Study for Novel Application of Southern Sky La Paz Survey Low-dispersion Spectral Plates in Recent AstrophysicsPDF, Feasibility Study for Novel Application of Southern Sky La Paz Survey Low-dispersion Spectral Plates in Recent AstrophysicsWe present a comprehensive characterisation of the La Paz Southern Sky Survey, a collection of 915 photographic plates obtained in La Paz, Bolivia, between 1926 and 1929 by the German Bolivia astronomical expedition under the auspices of the Astrophysical Observatory Potsdam. The survey covers 91 Kapteyn Selected Areas south of declination −24° and records an estimated 50,000–60,000 individual stellar spectra in low-dispersion objective-prism mode, the large majority of which have never been individually examined or classified. We provide a detailed description of the historical and instrumental background of the survey, the characteristics of the three plate series, and the ongoing digitisation programme at Sonneberg Observatory, which to date has produced high-resolution TIFF scans of 168 Series 1 (single-prism) plates. The single-prism plates have a mean spectral dispersion of ∼18 nm mm−1 and record spectra over the wavelength range (∼3400–6900 Å; 340–690 nm) with a mean photographic limiting magnitude of approximately 11.8 mag for spectral classification. Cross-matching of seven survey fields against the Wray emission-line catalogue and the Strasbourg–ESO Catalogue of Galactic Planetary Nebulae identifies 15 known emission-line objects and at least one planetary nebula within SA 156 (Ophiuchus/Scorpius), and 43 known emission-line objects and at least three planetary nebulae within SA 173 (Vela/Carina) fields for which digitised La Paz plates are available at Sonneberg Observatory. These cross-matches establish the presence of independently confirmed emission-line sources on the digitised plates and define the priority targets for forthcoming pipeline validation. As a first identification step, all 19 Wray objects brighter than approximately 12 mag in SA 173 have been individually located on a single digitised Series 1 plate (plate 60066), using the brighter field stars as positional references, and finder charts have been produced for each object. Visual inspection of the spectral crops reveals candidate emission features in four of the identified objects, the emission-line star CD−44 5201 (= Wray 15-338 = Hen 3-252) and the variable stars S Vel, RS Vel, and RW Vel, pending quantitative confirmation from the full-resolution scans. A computational pipeline for automated emission-line detection is under development; spectroscopic recovery of these known targets and full quantitative performance evaluation will be the subject of a forthcoming publication. The La Paz archive represents a unique temporal resource: its ∼1926–1929 observational epoch provides a ∼100 yr baseline relative to contemporary spectroscopy that is inaccessible to any ongoing survey.
- The following article is Open accessFirst Very Long Baseline Interferometry Fringe Detection at 690 GHz
Ming-Tang Chen et al 2026 PASP 138 084104
View article, First Very Long Baseline Interferometry Fringe Detection at 690 GHzPDF, First Very Long Baseline Interferometry Fringe Detection at 690 GHzWe report the first very long baseline interferometry (VLBI) experiment conducted in the 690 GHz atmospheric window. On 2024 November 21, observations with the Atacama Large Millimeter/submillimeter Array, the Atacama Pathfinder EXperiment (APEX), and the James Clerk Maxwell Telescope (JCMT) were carried out using ALMA’s newly developed Band 9 phasing capability. Fringes were detected on the ALMA–APEX baseline during a scan of the quasar J0423–0120, with a signal-to-noise ratio of ∼12 and useful fringe recovery over solution intervals of order tens of seconds, representing the highest-frequency ground-based VLBI fringe detection reported to date. No fringes were found on the ALMA–JCMT baseline, despite excellent weather conditions, consistent with sensitivity predictions and supporting baseline performance models. The ALMA Phasing System maintained stable phasing at Band 9 for ∼1–2 minutes before gradually degrading, indicating limitations under these observing conditions. Our analysis shows that, under excellent weather conditions, 690 GHz VLBI can still support fringe recovery over short solution intervals, despite rapid atmospheric phase fluctuations at these frequencies. This work validated key elements of near-terahertz VLBI operation and establishes a technical foundation for routine observations in the 690 GHz atmospheric window.
- The following article is Open accessA Deep Census of Brown Dwarfs in the COSMOS-Web Field
French Tsocheff A. Festin et al 2026 PASP 138 084402
View article, A Deep Census of Brown Dwarfs in the COSMOS-Web FieldPDF, A Deep Census of Brown Dwarfs in the COSMOS-Web Field“Failed Stars,” or Brown Dwarfs are substellar objects that are incapable of sustained hydrogen fusion. They are invaluable for understanding the low-mass end of the substellar initial mass function. Historically, studies relating to brown dwarfs have been limited to our immediate solar neighborhood. In turn, the galaxy-wide distribution of these objects is generally unconstrained until the inception of the James Webb Telescope (JWST). We aimed to construct an expanded, high-reliability catalog of brown dwarf candidates and perform a definitive test of brown dwarf number counts at kiloparsec (kpc) distances by leveraging the complete 0.54 deg2 COSMOS-Web JWST survey. We applied a systematic filtering pipeline to the COSMOS 2025 catalog to isolate the candidates. A mixture of data reduction steps was implemented, such as initial morphological selection, quality flags, S/N & magnitude limits, and a color selection criterion designed to find the characteristic V-shaped spectral energy distribution of brown dwarfs. The physical properties of our final candidates were derived via a dual-model Markov Chain Monte Carlo analysis using the Sonora Bobcat and SAND atmospheric models. Our search managed to find a final promising sample of 76 brown dwarf candidates with effective temperatures from 809–1803 K, log surface gravity (log(g)) from 3.0–5.5, and distances spanning 0.2–3.1 kpc. The sample includes several chemically interesting objects, such as three potentially ancient, metal-poor halo candidates with metallicity [M/H] = −2.4 and an alpha enhancement [α/Fe] > 0.0. The cumulative number counts of our sample show excellent agreement with standard galactic models scaled to the local census, confirming that these models hold at large distances. This work positions itself as covering the widest distance range to date, providing a crucial dataset for constraining the substellar mass function and serving as a foundational resource for future spectroscopic follow-up.
- The following article is Open accessThe Dynamics of Planetary Ejection
Malena Rice et al 2026 PASP 138 082001
The ubiquity of free-floating planets inferred from microlensing and direct imaging surveys suggests that planetary ejection—a process in which planets initially born encircling a stellar host become gravitationally unbound—is common. Four overarching mechanisms have been proposed to induce planetary ejection: close approaches of neighboring planets, instabilities in binary or multi-star systems, stellar and planetary flybys, and post-main-sequence stellar evolution. Here we review the mechanisms underlying planetary ejection, as well as predictions derived from each. Current and upcoming microlensing surveys offer the potential to test existing models and distinguish between planetary ejection mechanisms, providing further insight into the demographic-level architectures of exoplanets across stellar environments.
- What I Wished I Knew When I Began Building Astronomical Instruments
Daniel Fabricant 2026 PASP 138 073002
View article, What I Wished I Knew When I Began Building Astronomical InstrumentsPDF, What I Wished I Knew When I Began Building Astronomical InstrumentsThis paper describes lessons learned over a long career building astronomical instruments. Although these lessons are based on one person’s experiences, they were learned while working on major and minor instrument projects with many scientific and engineering colleagues. When I interact with colleagues entering the field, I am reminded that the “obvious” approaches were in fact learned over many years by observing others develop instruments, by receiving good advice, and by making mistakes. I hope to help others avoid making all of the same mistakes.
- The following article is Open accessMagnetohydrodynamic Precipitation
G. Mark Voit et al 2026 PASP 138 073001
Circumgalactic gas around massive galaxies and in galaxy-cluster cores generally has a volume-filling component—an atmosphere—with a temperature determined by the potential-well depth of the central galaxy’s halo. If the atmosphere is near hydrostatic equilibrium and is stable to convection, then it can remain nearly homogeneous, as long as it is not too dense. But if its density is great enough, it becomes prone to producing a rain of cold clouds that fall toward the galaxy’s center and accrete onto its central black hole. Here we explain how relatively weak magnetic fields enhance a galactic atmosphere’s tendency to produce cold clouds and how the cold gas becomes organized into vertically elongated, highly magnetized filaments descending at sub-Keplerian speeds. It is intended to complement recent numerical simulations of the process and to serve as a guide to interpreting both simulations and observations of the filamentary gas in hot galactic atmospheres.
- The following article is Open accessA Review of Machine Learning in Astronomical Plate Digitization and Survey Data
Tauseef Ahmad Zafar and René Hudec 2026 PASP 138 061001
View article, A Review of Machine Learning in Astronomical Plate Digitization and Survey DataPDF, A Review of Machine Learning in Astronomical Plate Digitization and Survey DataPhotographic plate archives spanning more than a century of sky coverage constitute an irreplaceable temporal baseline for variable and transient phenomena. Digitization projects—including DASCH (Harvard), APPLAUSE (Germany), NAROO (France) and the Digitized First Byurakan Survey (DFBS)—have rendered more than 500,000 plates machine-readable, but extracting scientific knowledge from these heterogeneous, defect-laden datasets requires purpose-built machine learning (ML) pipelines that differ fundamentally from those developed for modern CCD surveys. Existing reviews treat either plate digitization or general ML in astronomy; none systematically addresses the specific challenges—nonlinear photometric response, artifact morphology, spectrum blending, label scarcity, and distributional mismatch—that arise when modern ML methods are applied to inhomogeneous archival plate data. This review provides: (i) a unified treatment of the calibration prerequisites (Hurter–Driffield linearisation, WCS quality, artifact masking) that must precede any ML application to plate data; (ii) an in-depth methodological analysis of CNN-based spectral classification applied to the DFBS—the most extensive existing ML result on digitized objective-prism plates—including a critical evaluation of accuracy, label bias, and evaluation protocol shortcomings; (iii) a structured comparison of ML performance on photometric and spectroscopic tasks for both modern CCD surveys and digitized plate archives; and (iv) concrete evaluation protocol recommendations (source-held-out splits, macro-averaged metrics, cross-observatory validation) and a benchmark wish-list to enable reproducible, comparable results. CNN classifiers achieve 80%–85% overall accuracy on DFBS spectra, compared to >99% on SDSS/LAMOST spectra at similar S/N—a gap attributable primarily to spectrum blending, label distributional mismatch, and the absence of standardised evaluation protocols. Transfer learning and self-supervised pretraining offer the most promising paths to closing this gap. With standardised calibration products, open benchmarks, and robust domain-adaptation pipelines, century-long plate archives can power discoveries of rare transients, illuminate long-term AGN and stellar variability, and serve as a testbed for domain adaptation across instruments and epochs.
- The following article is Open accessThe Cohesive Object Sequence: The Mass–Density Distribution of Astronomical Objects from Asteroids to Stars
Gabriel M Steward and Matthew Hedman 2026 PASP 138 041001
View article, The Cohesive Object Sequence: The Mass–Density Distribution of Astronomical Objects from Asteroids to StarsPDF, The Cohesive Object Sequence: The Mass–Density Distribution of Astronomical Objects from Asteroids to StarsPlotting the mass–density of a wide range of astronomical objects as a function of their mass reveals that the vast majority of these objects fall along a “cohesive object sequence” that extends all the way from asteroids to the largest stars. Trends and features within this sequence reflect fundamental astronomical processes and phenomena, including the gravitational contraction of progressively higher-mass planets and the onset of nuclear reactions within stars. Meanwhile, compact stellar remnants fall well off this sequence, reflecting their extreme natures. This type of plot is therefore useful both for showcasing the relationships and connections between a wide range of astronomical objects and for clarifying the distinctions used to identify particular types of objects.
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- The following article is Open accessThermally Inflated Accretors in Post-mass Transfer Binaries: A35 and its Class Revisited
Soumyadeep Bhattacharjee et al 2026 PASP 138 084202
View article, Thermally Inflated Accretors in Post-mass Transfer Binaries: A35 and its Class RevisitedPDF, Thermally Inflated Accretors in Post-mass Transfer Binaries: A35 and its Class RevisitedA small but growing class of binaries containing hot (Teff ∼ 105 K) white dwarfs (WDs) and rapidly rotating, apparently subgiant companions—including the prototype, A35—show companions that are too large and luminous to be ordinary main-sequence stars yet too numerous to be explained as finely tuned near-twin binaries. We argue that these stars are instead main-sequence accretors temporarily inflated out of thermal equilibrium by recent mass transfer. For the subgiant of A35, a new Gaia DR3 astrometric orbit (Porb = 790 days) combined with updated photometric and spectroscopic constraints yield Teff ≈ 4925 ± 75 K, R ≈ 3 ± 0.05 R⊙, near-solar metallicity, and rapid rotation aligned with the orbit (vrot ≈ 195 ± 3 km s−1), indicating substantial recent accretion and spin-up. Dynamical mass limits disfavor a coeval twin-binary origin, supporting the inflated-accretor interpretation. We test this scenario using self-consistent Modules for Experiments in Stellar Astrophysics binary evolution calculations with a new accretion prescription in which accreted material retains a fraction of its infall energy, against the default of setting its entropy to that of the accretor’s surface. The accretor expands to giant-like radii when
is high yet remains within its Roche lobe, allowing stable mass transfer even for mass ratios traditionally considered unstable. After mass transfer ceases, the star contracts on Myr timescales through a bloated, rapidly rotating phase whose temperatures, radii, and spins match those observed in A35–type systems. This framework naturally explains the population and unifies A35-type binaries with post-AGB binaries, blue lurkers, and wide WD+main-sequence systems as successive stages of the same post-mass-transfer evolutionary pathway. - The following article is Open accessThe Dynamics of Planetary Ejection
Malena Rice et al 2026 PASP 138 082001
The ubiquity of free-floating planets inferred from microlensing and direct imaging surveys suggests that planetary ejection—a process in which planets initially born encircling a stellar host become gravitationally unbound—is common. Four overarching mechanisms have been proposed to induce planetary ejection: close approaches of neighboring planets, instabilities in binary or multi-star systems, stellar and planetary flybys, and post-main-sequence stellar evolution. Here we review the mechanisms underlying planetary ejection, as well as predictions derived from each. Current and upcoming microlensing surveys offer the potential to test existing models and distinguish between planetary ejection mechanisms, providing further insight into the demographic-level architectures of exoplanets across stellar environments.
- The following article is Open accessFeasibility Study for Novel Application of Southern Sky La Paz Survey Low-dispersion Spectral Plates in Recent Astrophysics
Tauseef Ahmad Zafar et al 2026 PASP 138 084509
View article, Feasibility Study for Novel Application of Southern Sky La Paz Survey Low-dispersion Spectral Plates in Recent AstrophysicsPDF, Feasibility Study for Novel Application of Southern Sky La Paz Survey Low-dispersion Spectral Plates in Recent AstrophysicsWe present a comprehensive characterisation of the La Paz Southern Sky Survey, a collection of 915 photographic plates obtained in La Paz, Bolivia, between 1926 and 1929 by the German Bolivia astronomical expedition under the auspices of the Astrophysical Observatory Potsdam. The survey covers 91 Kapteyn Selected Areas south of declination −24° and records an estimated 50,000–60,000 individual stellar spectra in low-dispersion objective-prism mode, the large majority of which have never been individually examined or classified. We provide a detailed description of the historical and instrumental background of the survey, the characteristics of the three plate series, and the ongoing digitisation programme at Sonneberg Observatory, which to date has produced high-resolution TIFF scans of 168 Series 1 (single-prism) plates. The single-prism plates have a mean spectral dispersion of ∼18 nm mm−1 and record spectra over the wavelength range (∼3400–6900 Å; 340–690 nm) with a mean photographic limiting magnitude of approximately 11.8 mag for spectral classification. Cross-matching of seven survey fields against the Wray emission-line catalogue and the Strasbourg–ESO Catalogue of Galactic Planetary Nebulae identifies 15 known emission-line objects and at least one planetary nebula within SA 156 (Ophiuchus/Scorpius), and 43 known emission-line objects and at least three planetary nebulae within SA 173 (Vela/Carina) fields for which digitised La Paz plates are available at Sonneberg Observatory. These cross-matches establish the presence of independently confirmed emission-line sources on the digitised plates and define the priority targets for forthcoming pipeline validation. As a first identification step, all 19 Wray objects brighter than approximately 12 mag in SA 173 have been individually located on a single digitised Series 1 plate (plate 60066), using the brighter field stars as positional references, and finder charts have been produced for each object. Visual inspection of the spectral crops reveals candidate emission features in four of the identified objects, the emission-line star CD−44 5201 (= Wray 15-338 = Hen 3-252) and the variable stars S Vel, RS Vel, and RW Vel, pending quantitative confirmation from the full-resolution scans. A computational pipeline for automated emission-line detection is under development; spectroscopic recovery of these known targets and full quantitative performance evaluation will be the subject of a forthcoming publication. The La Paz archive represents a unique temporal resource: its ∼1926–1929 observational epoch provides a ∼100 yr baseline relative to contemporary spectroscopy that is inaccessible to any ongoing survey.
- The following article is Open accessFirst Very Long Baseline Interferometry Fringe Detection at 690 GHz
Ming-Tang Chen et al 2026 PASP 138 084104
View article, First Very Long Baseline Interferometry Fringe Detection at 690 GHzPDF, First Very Long Baseline Interferometry Fringe Detection at 690 GHzWe report the first very long baseline interferometry (VLBI) experiment conducted in the 690 GHz atmospheric window. On 2024 November 21, observations with the Atacama Large Millimeter/submillimeter Array, the Atacama Pathfinder EXperiment (APEX), and the James Clerk Maxwell Telescope (JCMT) were carried out using ALMA’s newly developed Band 9 phasing capability. Fringes were detected on the ALMA–APEX baseline during a scan of the quasar J0423–0120, with a signal-to-noise ratio of ∼12 and useful fringe recovery over solution intervals of order tens of seconds, representing the highest-frequency ground-based VLBI fringe detection reported to date. No fringes were found on the ALMA–JCMT baseline, despite excellent weather conditions, consistent with sensitivity predictions and supporting baseline performance models. The ALMA Phasing System maintained stable phasing at Band 9 for ∼1–2 minutes before gradually degrading, indicating limitations under these observing conditions. Our analysis shows that, under excellent weather conditions, 690 GHz VLBI can still support fringe recovery over short solution intervals, despite rapid atmospheric phase fluctuations at these frequencies. This work validated key elements of near-terahertz VLBI operation and establishes a technical foundation for routine observations in the 690 GHz atmospheric window.
- The following article is Open accessA Deep Census of Brown Dwarfs in the COSMOS-Web Field
French Tsocheff A. Festin et al 2026 PASP 138 084402
View article, A Deep Census of Brown Dwarfs in the COSMOS-Web FieldPDF, A Deep Census of Brown Dwarfs in the COSMOS-Web Field“Failed Stars,” or Brown Dwarfs are substellar objects that are incapable of sustained hydrogen fusion. They are invaluable for understanding the low-mass end of the substellar initial mass function. Historically, studies relating to brown dwarfs have been limited to our immediate solar neighborhood. In turn, the galaxy-wide distribution of these objects is generally unconstrained until the inception of the James Webb Telescope (JWST). We aimed to construct an expanded, high-reliability catalog of brown dwarf candidates and perform a definitive test of brown dwarf number counts at kiloparsec (kpc) distances by leveraging the complete 0.54 deg2 COSMOS-Web JWST survey. We applied a systematic filtering pipeline to the COSMOS 2025 catalog to isolate the candidates. A mixture of data reduction steps was implemented, such as initial morphological selection, quality flags, S/N & magnitude limits, and a color selection criterion designed to find the characteristic V-shaped spectral energy distribution of brown dwarfs. The physical properties of our final candidates were derived via a dual-model Markov Chain Monte Carlo analysis using the Sonora Bobcat and SAND atmospheric models. Our search managed to find a final promising sample of 76 brown dwarf candidates with effective temperatures from 809–1803 K, log surface gravity (log(g)) from 3.0–5.5, and distances spanning 0.2–3.1 kpc. The sample includes several chemically interesting objects, such as three potentially ancient, metal-poor halo candidates with metallicity [M/H] = −2.4 and an alpha enhancement [α/Fe] > 0.0. The cumulative number counts of our sample show excellent agreement with standard galactic models scaled to the local census, confirming that these models hold at large distances. This work positions itself as covering the widest distance range to date, providing a crucial dataset for constraining the substellar mass function and serving as a foundational resource for future spectroscopic follow-up.
- The following article is Open accessStatistical Inference of Fast Radio Burst Environments Using Galaxy Number Density
Vignesh V. V. Rao et al 2026 PASP 138 084103
View article, Statistical Inference of Fast Radio Burst Environments Using Galaxy Number DensityPDF, Statistical Inference of Fast Radio Burst Environments Using Galaxy Number DensityFast radio bursts (FRBs) are bright, millisecond-duration radio transients of unknown origin. They are categorized as repeaters and non-repeaters, possibly indicating distinct progenitor types. However, validating this distinction is difficult because of the limited number of localized FRBs. Large-scale galactic environments can provide insight into the nature of the host galaxies of FRB and their progenitors. High-number-density regions are typically associated with old galaxies, whereas low-number-density regions are linked to young star-forming or less massive quiescent galaxies. In this study, we use galaxy number density to statistically assess the environments of 19 repeaters and 253 non-repeaters from CHIME Catalog 1, using galaxies from the WISE × PS1 catalog. A Kolmogorov–Smirnov (KS) test showed no significant difference between the two populations (pKS = 0.673). This result indicates that the statistical significance of the difference could depend on small-number statistics, highlighting the necessity of future FRB samples. Intriguingly, a comparison of FRBs with random galaxy fields suggests that FRBs may preferentially occur in underdense galactic environments with a median p-value (pKS) = 2.84 × 10−2 compared to random galaxy apertures.
- The following article is Open accessInvestigation of Calcium Dust in the Interstellar Medium
Ya-Yu Chu et al 2026 PASP 138 084302
View article, Investigation of Calcium Dust in the Interstellar MediumPDF, Investigation of Calcium Dust in the Interstellar MediumCalcium is a highly depleted element in the interstellar medium (ISM), however its composition in the solid phase remains elusive. The detection of Ca-bearing dust has been limited due to its lack of distinct spectral features in the cold phase of the diffuse ISM. X-rays provide a direct method for exploring the absorption and scattering properties of interstellar dust. In this study, we utilize high-resolution X-ray absorption spectroscopy to characterize Ca-bearing dust analogs at the Ca K-edge using X-ray Absorption Fine Structure. We present new X-ray absorption spectra of seven calcium-bearing interstellar dust analogs measured at the National Synchrotron Radiation Research Center in Taiwan. The extinction cross sections, calculated from the laboratory measurements are incorporated in the dust absorption model AMOL of the X-ray spectral fitting tool SPEX. We select three Low Mass X-ray Binaries (LMXBs) with high column densities, GX 340+00, GX 5–1, and GX 13+1, as background sources to study the intervening ISM along their sightlines. The best-fit models are compared with Chandra archive data using SPEX. Additionally, we employ simulations with the XRISM and NewAthena telescopes to achieve enhanced resolution and more effective coverage at the energy range near the Ca K-edge. These simulations set the boundary conditions for the future X-ray observation of calcium in the interstellar medium.
- The following article is Open accessA Catalog of Homogeneously Derived Stellar Parameters for Spectroscopic Survey Stars
Stefan Y. Stefanov et al 2026 PASP 138 084201
View article, A Catalog of Homogeneously Derived Stellar Parameters for Spectroscopic Survey StarsPDF, A Catalog of Homogeneously Derived Stellar Parameters for Spectroscopic Survey StarsUniformly derived stellar parameters are vital for exoplanet demographic studies because they directly influence the inferred planetary masses, radii, and bulk densities. This study presents a new homogeneous catalog of physical stellar parameters for 5533 single stars observed by the HARPS, HIRES, and CARMENES radial-velocity (RV) surveys. Stellar parameters are determined using a Bayesian framework with two independent sets of stellar evolutionary models: MIST and PARSEC, using published spectroscopic parameter estimates and catalog values as priors. The resulting stellar effective temperatures, masses, radii, and surface gravities are compared and evaluated for consistency with stellar parameters listed in major exoplanet catalogs. While our estimates show consistency with those listed in external catalogs, we identify method-dependent differences in stellar masses for low-mass and pre-main-sequence stars, as well as G and K giants, where isochrone-based solutions may be affected by age–mass degeneracies. For low-mass stars such as M-dwarfs, the catalog provides masses derived from established mass–luminosity empirical relations, which tend to be more reliable. This catalog provides the largest uniformly derived stellar reference sample for Doppler survey targets and also illustrates the applicability and limitations of stellar-parameter homogenisation methods for future RV exoplanet demographics studies.
- The following article is Open accessClassifying Quasar Types Without a Spectrum
Adrien Hélias et al 2026 PASP 138 084507
View article, Classifying Quasar Types Without a SpectrumPDF, Classifying Quasar Types Without a SpectrumDistinguishing between Type 1 and Type 2 quasars is important because it helps us understand accretion regimes, black hole mass scaling, disk instabilities and feedback processes in active galaxies. Although spectroscopy provides robust classification, it does not scale well with the millions of quasars observed in modern surveys, as it requires substantial time and resources to acquire a good spectrum. On the photometry side, quasar light curves are always irregularly sampled and affected by the specifics of photometric surveys, making them difficult to analyze. In this work, we show that we can use irregularly sampled light curves from the Zwicky Transient Facility to classify quasar types without a spectrum, using Slepian Wavelet Variance. This technique allows us to decompose the variance of light curves into multiple timescales. We use agglomerative hierarchical clustering to classify 516 Type 1 and 238 Type 2 quasars from the MILLIQUAS catalogue, solely based on their wavelet variance curves. We obtain a recovery rate of 99% for Type 1 and 87% for Type 2 quasars, and the few misclassified quasars show the opposite variability behaviour to their spectral type. In contrast to structure functions and the Damped Random Walk model, Slepian Wavelet Variance offers a complementary, model-independent view of variability across short and long timescales.
- The following article is Open accessEnhancing Imaging Efficiency in Synthetic Aperture Imaging Instruments with Parallel-spectrum Method-based Imaging Algorithm
Yuanyuan Zhang et al 2026 PASP 138 084504
View article, Enhancing Imaging Efficiency in Synthetic Aperture Imaging Instruments with Parallel-spectrum Method-based Imaging AlgorithmPDF, Enhancing Imaging Efficiency in Synthetic Aperture Imaging Instruments with Parallel-spectrum Method-based Imaging AlgorithmHigh-speed and real-time processing of synthetic aperture imaging systems constitutes a critical foundation for monitoring solar activities and advancing imaging measurement applications. Solar eruptive events evolve rapidly over timescales ranging from milliseconds to seconds. Therefore, accelerating imaging algorithms to realize real-time imaging is critical for tracking and capturing such transient eruptive events. This paper proposes an imaging algorithm based on parallel Two-Dimensional Inverse Fast Fourier Transform (2D-IFFT), called the parallel-spectral method, aimed at improving imaging speed. The parallel-spectrum method innovatively replaces complex deconvolution with highly computationally efficient 2D-IFFT, thus resolving the critical challenge of real-time processing for massive data generated by large-scale antenna arrays. It also introduces the concept of block processing, substituting traditional row-column processing, thereby achieving a breakthrough in synthetic aperture imaging from offline to real-time processing. Specifically, the sampling points distributed arbitrarily on the uv-plane are interpolated onto a regular grid. Then, a block-processed 2D-IFFT is employed to initially reconstruct the visibility data on the standard grid into an image of the observed target, with the imaging algorithm theory mapped onto the hardware circuit. This method can simplify the signal processing chain, enhance the parallelism of algorithms, and facilitate hardware circuit implementation. Compared to traditional imaging algorithms, the proposed algorithm achieves a faster computational rate and superior tracking performance for transient events. Experiments using real observational data obtained from the Nancy heliograph demonstrate that the parallel-spectral algorithm not only accurately reconstructs the original image but also significantly reduces the imaging time from 14 ms to 17 μs. This study achieved a breakthrough in transitioning large-scale antenna array imaging from offline to real-time processing. The parallel-spectrum method is not only well-suited for real-time imaging measurements in instrumentation applications but also establishes a research groundwork for high temporal resolution imaging of the synthetic aperture solar imager slated for development by the research group.
- emcee: The MCMC Hammer
Daniel Foreman-Mackey et al 2013 PASP 125 306
We introduce a stable, well tested Python implementation of the affine-invariant ensemble sampler for Markov chain Monte Carlo (MCMC) proposed by Goodman & Weare (2010). The code is open source and has already been used in several published projects in the astrophysics literature. The algorithm behind emcee has several advantages over traditional MCMC sampling methods and it has excellent performance as measured by the autocorrelation time (or function calls per independent sample). One major advantage of the algorithm is that it requires hand-tuning of only 1 or 2 parameters compared to ∼N2 for a traditional algorithm in an N-dimensional parameter space. In this document, we describe the algorithm and the details of our implementation. Exploiting the parallelism of the ensemble method, emcee permits any user to take advantage of multiple CPU cores without extra effort. The code is available online at http://dan.iel.fm/emcee under the GNU General Public License v2.
- Galactic Stellar and Substellar Initial Mass Function
Gilles Chabrier 2003 PASP 115 763
View article, Galactic Stellar and Substellar Initial Mass FunctionPDF, Galactic Stellar and Substellar Initial Mass FunctionWe review recent determinations of the present‐day mass function (PDMF) and initial mass function (IMF) in various components of the Galaxy—disk, spheroid, young, and globular clusters—and in conditions characteristic of early star formation. As a general feature, the IMF is found to depend weakly on the environment and to be well described by a power‐law form for m≳1 M⊙ and a lognormal form below, except possibly for early star formation conditions. The disk IMF for single objects has a characteristic mass around mc ∼ 0.08 M⊙ and a variance in logarithmic mass σ ∼ 0.7, whereas the IMF for multiple systems has mc ∼ 0.2 M⊙ and σ ∼ 0.6. The extension of the single MF into the brown dwarf regime is in good agreement with present estimates of L‐ and T‐dwarf densities and yields a disk brown dwarf number density comparable to the stellar one, nBD ∼ n* ∼ 0.1 pc−3. The IMF of young clusters is found to be consistent with the disk field IMF, providing the same correction for unresolved binaries, confirming the fact that young star clusters and disk field stars represent the same stellar population. Dynamical effects, yielding depletion of the lowest mass objects, are found to become consequential for ages ≳130 Myr. The spheroid IMF relies on much less robust grounds. The large metallicity spread in the local subdwarf photometric sample, in particular, remains puzzling. Recent observations suggest that there is a continuous kinematic shear between the thick‐disk population, present in local samples, and the genuine spheroid one. This enables us to derive only an upper limit for the spheroid mass density and IMF. Within all the uncertainties, the latter is found to be similar to the one derived for globular clusters and is well represented also by a lognormal form with a characteristic mass slightly larger than for the disk, mc ∼ 0.2–0.3 M⊙, excluding a significant population of brown dwarfs in globular clusters and in the spheroid. The IMF characteristic of early star formation at large redshift remains undetermined, but different observational constraints suggest that it does not extend below ∼1 M⊙. These results suggest a characteristic mass for star formation that decreases with time, from conditions prevailing at large redshift to conditions characteristic of the spheroid (or thick disk) to present‐day conditions. These conclusions, however, remain speculative, given the large uncertainties in the spheroid and early star IMF determinations.
These IMFs allow a reasonably robust determination of the Galactic present‐day and initial stellar and brown dwarf contents. They also have important galactic implications beyond the Milky Way in yielding more accurate mass‐to‐light ratio determinations. The mass‐to‐light ratios obtained with the disk and the spheroid IMF yield values 1.8–1.4 times smaller than for a Salpeter IMF, respectively, in agreement with various recent dynamical determinations. This general IMF determination is examined in the context of star formation theory. None of the theories based on a Jeans‐type mechanism, where fragmentation is due only to gravity, can fulfill all the observational constraints on star formation and predict a large number of substellar objects. On the other hand, recent numerical simulations of compressible turbulence, in particular in super‐Alfvénic conditions, seem to reproduce both qualitatively and quantitatively the stellar and substellar IMF and thus provide an appealing theoretical foundation. In this picture, star formation is induced by the dissipation of large‐scale turbulence to smaller scales through radiative MHD shocks, producing filamentary structures. These shocks produce local nonequilibrium structures with large density contrasts, which collapse eventually in gravitationally bound objects under the combined influence of turbulence and gravity. The concept of a single Jeans mass is replaced by a distribution of local Jeans masses, representative of the lognormal probability density function of the turbulent gas. Objects below the mean thermal Jeans mass still have a possibility to collapse, although with a decreasing probability.
- The following article is Open accessCASA, the Common Astronomy Software Applications for Radio Astronomy
The CASA Team et al 2022 PASP 134 114501
View article, CASA, the Common Astronomy Software Applications for Radio AstronomyPDF, CASA, the Common Astronomy Software Applications for Radio AstronomyCASA, the Common Astronomy Software Applications, is the primary data processing software for the Atacama Large Millimeter/submillimeter Array (ALMA) and the Karl G. Jansky Very Large Array (VLA), and is frequently used also for other radio telescopes. The CASA software can handle data from single-dish, aperture-synthesis, and Very Long Baseline Interferometery (VLBI) telescopes. One of its core functionalities is to support the calibration and imaging pipelines for ALMA, VLA, VLA Sky Survey, and the Nobeyama 45 m telescope. This paper presents a high-level overview of the basic structure of the CASA software, as well as procedures for calibrating and imaging astronomical radio data in CASA. CASA is being developed by an international consortium of scientists and software engineers based at the National Radio Astronomy Observatory (NRAO), the European Southern Observatory, the National Astronomical Observatory of Japan, and the Joint Institute for VLBI European Research Infrastructure Consortium (JIV-ERIC), under the guidance of NRAO.
- The Zwicky Transient Facility: Surveys and Scheduler
Eric C. Bellm et al 2019 PASP 131 068003
View article, The Zwicky Transient Facility: Surveys and SchedulerPDF, The Zwicky Transient Facility: Surveys and SchedulerWe present a novel algorithm for scheduling the observations of time-domain imaging surveys. Our integer linear programming approach optimizes an observing plan for an entire night by assigning targets to temporal blocks, enabling strict control of the number of exposures obtained per field and minimizing filter changes. A subsequent optimization step minimizes slew times between each observation. Our optimization metric self-consistently weights contributions from time-varying airmass, seeing, and sky brightness to maximize the transient discovery rate. We describe the implementation of this algorithm on the surveys of the Zwicky Transient Facility and present its on-sky performance.
- ATLAS: A High-cadence All-sky Survey System
J. L. Tonry et al 2018 PASP 130 064505
View article, ATLAS: A High-cadence All-sky Survey SystemPDF, ATLAS: A High-cadence All-sky Survey SystemTechnology has advanced to the point that it is possible to image the entire sky every night and process the data in real time. The sky is hardly static: many interesting phenomena occur, including variable stationary objects such as stars or QSOs, transient stationary objects such as supernovae or M dwarf flares, and moving objects such as asteroids and the stars themselves. Funded by NASA, we have designed and built a sky survey system for the purpose of finding dangerous near-Earth asteroids (NEAs). This system, the “Asteroid Terrestrial-impact Last Alert System” (ATLAS), has been optimized to produce the best survey capability per unit cost, and therefore is an efficient and competitive system for finding potentially hazardous asteroids (PHAs) but also for tracking variables and finding transients. While carrying out its NASA mission, ATLAS now discovers more bright (m < 19) supernovae candidates than any ground based survey, frequently detecting very young explosions due to its 2 day cadence. ATLAS discovered the afterglow of a gamma-ray burst independent of the high energy trigger and has released a variable star catalog of 5 × 106 sources. This is the first of a series of articles describing ATLAS, devoted to the design and performance of the ATLAS system. Subsequent articles will describe in more detail the software, the survey strategy, ATLAS-derived NEA population statistics, transient detections, and the first data release of variable stars and transient light curves.
- The following article is Open accessThe Zwicky Transient Facility: Data Processing, Products, and Archive
Frank J. Masci et al 2019 PASP 131 018003
View article, The Zwicky Transient Facility: Data Processing, Products, and ArchivePDF, The Zwicky Transient Facility: Data Processing, Products, and ArchiveThe Zwicky Transient Facility (ZTF) is a new robotic time-domain survey currently in progress using the Palomar 48-inch Schmidt Telescope. ZTF uses a 47 square degree field with a 600 megapixel camera to scan the entire northern visible sky at rates of ∼3760 square degrees/hour to median depths of g ∼ 20.8 and r ∼ 20.6 mag (AB, 5σ in 30 sec). We describe the Science Data System that is housed at IPAC, Caltech. This comprises the data-processing pipelines, alert production system, data archive, and user interfaces for accessing and analyzing the products. The real-time pipeline employs a novel image-differencing algorithm, optimized for the detection of point-source transient events. These events are vetted for reliability using a machine-learned classifier and combined with contextual information to generate data-rich alert packets. The packets become available for distribution typically within 13 minutes (95th percentile) of observation. Detected events are also linked to generate candidate moving-object tracks using a novel algorithm. Objects that move fast enough to streak in the individual exposures are also extracted and vetted. We present some preliminary results of the calibration performance delivered by the real-time pipeline. The reconstructed astrometric accuracy per science image with respect to Gaia DR1 is typically 45 to 85 milliarcsec. This is the RMS per-axis on the sky for sources extracted with photometric S/N ≥ 10 and hence corresponds to the typical astrometric uncertainty down to this limit. The derived photometric precision (repeatability) at bright unsaturated fluxes varies between 8 and 25 millimag. The high end of these ranges corresponds to an airmass approaching ∼2—the limit of the public survey. Photometric calibration accuracy with respect to Pan-STARRS1 is generally better than 2%. The products support a broad range of scientific applications: fast and young supernovae; rare flux transients; variable stars; eclipsing binaries; variability from active galactic nuclei; counterparts to gravitational wave sources; a more complete census of Type Ia supernovae; and solar-system objects.
- batman: BAsic Transit Model cAlculatioN in Python
Laura Kreidberg 2015 PASP 127 1161
View article, batman: BAsic Transit Model cAlculatioN in PythonPDF, batman: BAsic Transit Model cAlculatioN in PythonI introduce batman, a Python package for modeling exoplanet transit and eclipse light curves. The batman package supports calculation of light curves for any radially symmetric stellar limb darkening law, using a new integration algorithm for models that cannot be quickly calculated analytically. The code uses C extension modules to speed up model calculation and is parallelized with OpenMP. For a typical light curve with 100 data points in transit, batman can calculate one million quadratic limb-darkened models in 30 s with a single 1.7 GHz Intel Core i5 processor. The same calculation takes seven minutes using the four-parameter nonlinear limb darkening model (computed to 1 ppm accuracy). Maximum truncation error for integrated models is an input parameter that can be set as low as 0.001 ppm, ensuring that the community is prepared for the precise transit light curves we anticipate measuring with upcoming facilities. The batman package is open source and publicly available at https://github.com/lkreidberg/batman.
- The Karl G. Jansky Very Large Array Sky Survey (VLASS). Science Case and Survey Design
M. Lacy et al 2020 PASP 132 035001
View article, The Karl G. Jansky Very Large Array Sky Survey (VLASS). Science Case and Survey DesignPDF, The Karl G. Jansky Very Large Array Sky Survey (VLASS). Science Case and Survey DesignThe Very Large Array Sky Survey (VLASS) is a synoptic, all-sky radio sky survey with a unique combination of high angular resolution (≈2
5), sensitivity (a 1σ goal of 70 μJy/beam in the coadded data), full linear Stokes polarimetry, time domain coverage, and wide bandwidth (2–4 GHz). The first observations began in 2017 September, and observing for the survey will finish in 2024. VLASS will use approximately 5500 hr of time on the Karl G. Jansky Very Large Array (VLA) to cover the whole sky visible to the VLA (decl. > −40°), a total of 33 885 deg. The data will be taken in three epochs to allow the discovery of variable and transient radio sources. The survey is designed to engage radio astronomy experts, multi-wavelength astronomers, and citizen scientists alike. By utilizing an “on the fly” interferometry mode, the observing overheads are much reduced compared to a conventional pointed survey. In this paper, we present the science case and observational strategy for the survey, and also results from early survey observations. - Las Cumbres Observatory Global Telescope Network
T. M. Brown et al 2013 PASP 125 1031
Las Cumbres Observatory Global Telescope (LCOGT) is a young organization dedicated to time-domain observations at optical and (potentially) near-IR wavelengths. To this end, LCOGT is constructing a worldwide network of telescopes, including the two 2 m Faulkes telescopes, as many as 17 × 1 m telescopes, and as many as 23 × 40 cm telescopes. These telescopes initially will be outfitted for imaging and (excepting the 40 cm telescopes) spectroscopy at wavelengths between the atmospheric UV cutoff and the roughly 1-μm limit of silicon detectors. Since the first of LCOGT’s 1 m telescopes are now being deployed, we lay out here LCOGT’s scientific goals and the requirements that these goals place on network architecture and performance, we summarize the network’s present and projected level of development, and we describe our expected schedule for completing it. In the bulk of the paper, we describe in detail the technical approaches that we have adopted to attain desired performance. In particular, we discuss our choices for the number and location of network sites, for the number and sizes of telescopes, for the specifications of the first generation of instruments, for the software that will schedule and control the network’s telescopes and reduce and archive its data, and for the structure of the scientific and educational programs for which the network will provide observations.
- The following article is Open accessThe All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0
C. S. Kochanek et al 2017 PASP 129 104502
View article, The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0PDF, The All-Sky Automated Survey for Supernovae (ASAS-SN) Light Curve Server v1.0The All-Sky Automated Survey for Supernovae (ASAS-SN) is working toward imaging the entire visible sky every night to a depth of
mag. The present data covers the sky and spans ∼2–5 years with ∼100–400 epochs of observation. The data should contain some ∼1 million variable sources, and the ultimate goal is to have a database of these observations publicly accessible. We describe here a first step, a simple but unprecedented web interface https://asas-sn.osu.edu/ that provides an up to date aperture photometry light curve for any user-selected sky coordinate. The V band photometry is obtained using a two-pixel (160) radius aperture and is calibrated against the APASS catalog. Because the light curves are produced in real time, this web tool is relatively slow and can only be used for small samples of objects. However, it also imposes no selection bias on the part of the ASAS-SN team, allowing the user to obtain a light curve for any point on the celestial sphere. We present the tool, describe its capabilities, limitations, and known issues, and provide a few illustrative examples.
Journal resources
Journal information
- 1889-present
Publications of the Astronomical Society of the Pacific
Online ISSN: 1538-3873
Print ISSN: 0004-6280