Ground-based observations around 1.4 mu m are normally limited by strong absorption of telluric water-vapor. However, Dome A, Antarctica has exceptionally dry conditions that offer a unique opportunity for observations in this band. We designed a new filter covering 1.34-1.48 mu m, namely W ' , and installed it on the Antarctic Infrared Binocular Telescope (AIRBT) at Dome A in 2025. AIRBT comprises two identical 15 cm optical tube assemblies and two InGaAs cameras equipped with J and W ' filters, respectively. With this Early Data Release (EDR), we aim to evaluate the performance of the W ' band at Dome A to observe objects with water-vapor features. This EDR covers similar to 20 deg2 in the Galactic plane using similar to 20,000 images in three nights. For 2 s exposures, the 5 sigma limiting magnitude histogram peaks at J similar to 11.5 mag (Vega) and W 'similar to 9.9 mag, respectively. The J-W ' versus J - H color-color diagram distinguishes ultracool candidates with water-vapor-absorption features from reddened early type stars. Furthermore, later-type stars tend to exhibit stronger water-vapor absorption. Some sources show larger Delta W ' than Delta J across the three nights, which we attribute to variations of their water-vapor-absorption depth. We conclude that it will be efficient to search for ultracool stars and estimate their spectral subtypes using W ' band imaging at Dome A, where the atmospheric transmission is high and stable.

We announce a recently detected outburst that is currently only a few months old, and probably of FU Orionis type. The progenitor to the outburst was an emission-line, flat-spectrum spectral energy distribution young stellar object located in the W5 region, though somewhat outside the main star formation action. We present optical, near-infrared, and mid-infrared lightcurves that illustrate the quiescent state of [KAG2008] 13656 and its subsequent Δ r ≈ −4 mag and Δ J ≈ −3 mag outburst over ∼75 days in late-2025. Follow-up optical and near-infrared spectroscopy confirms the expected features from an FU Ori disk and outflow.

We present a near-infrared census of stellar large-amplitude variables (LAVs) observed by the Palomar Gattini-IR (PGIR) surveyor from 2019-2021. Over the three-year time period, PGIR performed a brightness-limited survey of the Northern sky (similar to 18,000 deg(2)) to J-band AB magnitudes similar to 13 within and similar to 15 outside the Galactic plane. From similar to 70 million stars detected in PGIR reference images, we provide a spectral and photometric library of the 128 largest amplitude stellar variables detected to median SNR > 10 for more than 50 epochs with more than 5 high-amplitude detections, peak-to-peak magnitudes >= 2, and von Neumann ratios <= 0.2. We obtained medium-resolution near-infrared spectra with TripleSpec on the 200 inch Hale Telescope at Palomar Observatory and SpeX at NASA's Infrared Telescope Facility. The spectral census consists of 82 evolved and dust-obscured Asymptotic Giant Branch stars, 16 R Coronae Borealis stars, 13 young-stellar or pre-main-sequence objects, 8 symbiotic binaries, 7 erratic carbon- and oxygen-rich giants, and 2 RV Tauri supergiants. The spectral and photometric dataset serves as an atlas of near-infrared LAVs and a repository of evolved stars, eruptive variables, and binary systems for future deeper infrared surveys.

Infrared time-domain surveys remain significantly underdeveloped compared with their optical counterparts. We have developed the Antarctic Infrared Binocular Telescope (AIRBT) to study the dynamic infrared sky at Dome A, Antarctica, taking advantage of the superb infrared observational conditions at this site. AIRBT consists of two identical 15 cm f /3 optical tube assemblies and two cost-effective indium gallium arsenide (InGaAs) cameras equipped with J and H filters, respectively. The cameras have 640 × 512 15 μ m pixels, giving a scale of 6 . ″ 9 pixel −1 and a field of view of 1.22 × 0.97 deg 2 . We characterize the performance of the InGaAs cameras, including bias, readout noise, dark current, nonlinearity, and photon transfer curve (PTC). Our analysis highlights the distinct behaviors of InGaAs cameras compared with charge-coupled devices. The bias and readout noise show temperature dependence. In addition, the noise measured from the PTCs has additional components increasing with exposure time. On-sky tests were conducted in 2022 October including system calibration, limiting depth, and photometric precision. For a single 3 s exposure, we achieved 5 σ limiting magnitudes of 11.2 mag (Vega system) in J band and 9.7 mag in H band. The best photometric precision reached 20 mmag at the bright end, which could be further improved to sub-percent levels through image stacking. AIRBT was installed at Dome A in 2023 January, and scientific observations began as soon as darkness set in.

We present Cryoscope, a new 50 deg 2 field-of-view, 1.2 m aperture, K dark survey telescope to be located at Dome C, Antarctica. Cryoscope has an innovative optical–thermal design wherein the entire telescope is cryogenically cooled. Cryoscope also explores new detector technology to cost-effectively tile the full focal plane. Leveraging the dark Antarctic sky and minimizing telescope thermal emission, Cryoscope achieves unprecedented deep, wide, fast, and red observations, matching and exceeding volumetric survey speeds from the Ultraviolet Explorer, Vera Rubin Observatory, Nancy Grace Roman Space Telescope, SPHEREx, and NEO Surveyor. By providing coverage beyond wavelengths of 2 μ m, we aim to create the most comprehensive dynamic movie of the most obscured reaches of the Universe. Cryoscope will be a dedicated discovery engine for electromagnetic emission from coalescing compact binaries, Earth-like exoplanets orbiting cold stars, and multiple facets of time-domain, stellar, and solar system science. In this paper, we describe the scientific drivers and technical innovations for this new discovery engine operating in the K dark passband, why we choose to deploy it in Antarctica, and the status of a fifth-scale prototype designed as a Pathfinder to retire technological risks prior to full-scale implementation. We plan to deploy the Cryoscope Pathfinder to Dome C in 2026 December and the full-scale telescope by 2030.

Located at the highest point on the Antarctic Plateau’s ice sheet, Dome A is generally believed to be one of the best places on Earth for nighttime astronomy in the optical and near-infrared (NIR) bands. Daytime optical/NIR site characteristics are yet to be quantified, however. Here we report the first daytime observations of bright stars at the J band during the austral summer of 2023/2024. The experiments were conducted using a 150 mm telescope with a field of view of 0 . ° 87 × 0 . ° 69 and a pixel size of 2 . ″ 5. The sky brightness at zenith was measured to be ∼5.2 mag arcsec −2 at noon when the solar elevation was ∼27°, and it slightly darkened to ∼5.8 mag arcsec −2 at midnight with a solar elevation angle of ∼10°. Stars as faint as J = 10.06 mag were significantly detected at 5 σ levels with an effective exposure time of 175 s around midnight. The pathfinding experiments indicate that a sensitivity ∼2 mag deeper can be reached by the planned 1 m class telescopes, taking advantage of the small free atmosphere seeing. Considering the high latitude and the extremely high fraction of clear days at this site, valuable bright transients with J ≲ 12 mag, such as (super)novae in the local universe and space debris at low orbits, within ∼1/4 of the whole sky around the south celestial pole can be timely discovered and continuously monitored throughout the year.

Located at Dome A, the highest point on the Antarctic plateau, China’s Kunlun station is a premier ground-based photometric observatory. Its cold, dry, and stable atmosphere allows continuous observation for over 40 days during polar winter, ideal for detecting short-period transiting exoplanets. Since 2008, the Antarctic Survey Telescopes (AST3) project has pursued the CHESPA program to search for exoplanet candidates. During the austral winters in 2016 and 2017, the AST3-II telescope surveyed fields located in the southern continuous viewing zone of the Transiting Exoplanet Survey Satellite (TESS). This paper presents the second data release from CHESPA, encompassing photometric data for over 85,000 bright ( m _i ≤ 15) stars. The survey achieved a photometric precision of approximately 2 mmag at optimal brightness levels. To illustrate the data quality, we present a catalog of 203 newly identified variable stars showing brightness variations over 5 mmag based on the 2017 observations, as compared to Data Release 1. Among these, 26 are newly recognized periodic variables that are not listed in the AAVSO database ( https://www.aavso.org/ ), and 86 are in the TESS Candidate Target List. These variables required rigorous examination to eliminate false-positive signals in the transiting exoplanets search.

Long Period Variables (LPVs) are stars with periods of several hundred days, representing the late, dust-enshrouded phase of stellar evolution in low to intermediate mass stars. In this paper, we present a catalog of 154,755 LPVs using near-IR lightcurves from the Palomar Gattini-IR (PGIR) survey. PGIR has been surveying the entire accessible northern sky (delta > -28 degrees) in the J-band at a cadence of 2-3 days since 2018 September, and has produced J-band lightcurves for more than 60 million sources. We used a gradient-boosted decision tree classifier trained on a comprehensive feature set extracted from PGIR lightcurves to search for LPVs in this data set. We developed a parallelized and optimized code to extract features at a rate of similar to 0.1 s per lightcurve. Our model can successfully distinguish LPVs from other stars with a true positive rate of 95%. Cross-matching with known LPVs, we find 70,369 (similar to 46%) new LPVs in our catalog.

Dome-C in the Antarctic Plateau is a privileged site for Astronomy, with one of the lowest concentrations of water vapor in the world, providing a pristine atmospheric window for IR observations. Together with the long winter nights, this allows for extended continuous observational campaigns. At the Concordia Station, ASTEP has taken advantage of the weather and long nights to observe long-period transiting exoplanets for over a decade. With the Cryoscope Pathfinder we now plan to take advantage of the dark IR window between 2.35 and 2.55𝜇m. The unique design of Cryoscope Pathfinder is optimized for a very wide field of view and very thermal background. It is a cryogenic 0.26 m telescope designed for observations in K-dark with a field of view of 16 deg^2. This is the first step for a much more ambitious project, the full scale 1-meter class Cryoscope telescope, with a field of view of 50 deg^2. The initial science drivers are the study of exoplanets and of the infrared transient sky, where it will play a major role in the localization of gravitational wave sources. Furthermore, many other science topics will be enabled by Cryoscope and through synergies with other surveys.

The Dynamic REd All-sky Monitoring Survey (DREAMS) is a near-infrared fully automated all-sky survey that will be conducted using a custom built 0.5m telescope that will be located at the Australian National University's Siding Spring Observatory. The telescope feeds 6 individual InGasAs cameras spanning a total field-of-view of 3.8sq.deg using a novel optomechanical design. Here we present the finished details of the telescope construction and its measured performance as well as details of the survey it will perform of the Southern transient sky.

Palomar Gattini-IR (PGIR) is a wide-field, synoptic infrared time domain survey covering approximate to 15,000 sq. deg. of the accessible sky at approximate to 1-3 night cadence to a depth of J approximate to 13.0 and approximate to 14.9 Vega mag in and outside the Galactic plane, respectively. Here, we present the first data release of J-band light curves of Two Micron All Sky Survey (2MASS) sources within the survey footprint covering approximately the first four years of operations. We describe the construction of the source catalog based on 2MASS point sources, followed by exposure filtering criteria and forced PSF photometry. The catalog contains light curves of approximate to 286 million unique sources with 2MASS magnitudes of J < 15.5 mag, with a total of approximate to 50 billion photometric measurements and approximate to 20 billion individual source detections at signal-to-noise-ratio > 3. We demonstrate the photometric fidelity of the catalog by (i) quantifying the magnitude-dependent accuracy and uncertainty of the photometry with respect to 2MASS and (ii) comparing against forced PGIR aperture photometry for known variable sources. We present simple filtering criteria for selecting reliable photometric measurements as well as example Python notebooks for users. This catalog is one of the largest compilation of nightly cadence, synoptic infrared light curves to date, comparable to those in the largest optical surveys, providing a stepping stone to upcoming infrared surveys in the coming decade.

The mechanism of X-ray outbursts in Be X-ray binaries remains a mystery, and understanding their circumstellar discs is crucial for a solution of the mass-transfer problem. In particular, it is important to identify the Be star activities (e.g. pulsations) that cause mass ejection and, hence, disc formation. Therefore, we investigated the relationship between optical flux oscillations and the infrared (IR) excess in a sample of five Be X-ray binaries. Applying the Lomb-Scargle technique to high-cadence optical light curves from the Transiting Exoplanet Survey Satellite (TESS), we detected several significant oscillation modes in the 3-24 h period range for each source. We also measured the IR excess (a proxy for disc growth) of those five sources, using J-band light curves from Palomar Gattini-IR. In four of the five sources, we found anticorrelations between the IR excess and the amplitude of the main flux oscillation modes. This result is inconsistent with the conventional idea that non-radial pulsations drive mass ejections. We propose an alternative scenario where internal temperature variations in the Be star cause transitions between pulsation-active and mass-ejection-active states.

Dome A in Antarctica likely has the best observing conditions on the Earth's surface in the near-infrared owing to its sky-light background and superior seeing conditions. This work introduces the system design and on-sky performance of the first wide field-of-view near-infrared telescope at Dome A. We present the lens design, tolerance analysis and stray light analysis of the optical system. We then evaluate a preliminary alignment method suitable for daytime use based on visual inspection. Finally, we describe a direct drive motor with maze structures, and an optical system with thermal compensation that is specially designed for the extreme environment in Antarctica. The on-sky performances demonstrate that this pilot near-infrared telescope not only successfully explores new technologies for extreme environments, but also presents an opportunity for 2670 hr of uninterrupted synergistic observation with the 0.5 m AST3-2 telescope at Dome A. The distinctive attributes of our design render it invaluable in many astronomical fields and holds significant promise for the monitoring of space debris and near-earth asteroids.

We study the evolution of the FU Ori object V960 Mon since its outburst, using available multi-wavelength photometric time series over 8 years, complemented by several epochs of moderate-dispersion spectrophotometry. We find that the source fading can be well-described by a decrease in the temperature of the inner disk, which results from a combination of decreasing accretion rate and increasing inner disk radius. We model the system with a disk atmosphere model that produces the observed variations in multi-band photometry (this paper) and high resolution spectral lines (a companion paper).

ABSTRACT AST3-2 is the second of the three Antarctic Survey Telescopes, aimed at wide-field time-domain optical astronomy. It is located at Dome A, Antarctica, which is by many measures the best optical astronomy site on the Earth’s surface. Here we present the data from the AST3-2 automatic survey in 2016 and the photometry results. The median 5σ limiting magnitude in i-band is 17.8 mag and the light-curve precision is 4 mmag for bright stars. The data release includes photometry for over 7 million stars, from which over 3500 variable stars were detected, with 70 of them newly discovered. We classify these new variables into different types by combining their light-curve features with stellar properties from surveys such as StarHorse.

Atmospheric seeing is one of the most important parameters for evaluating and monitoring an astronomical site. Moreover, being able to predict the seeing in advance can guide observing decisions and significantly improve the efficiency of telescopes. However, it is not always easy to obtain long-term and continuous seeing measurements from a standard instrument such as differential image motion monitor (DIMM), especially for those unattended observatories with challenging environments such as Dome A, Antarctica. In this paper, we present a novel machine learning-based framework for estimating and predicting seeing at a height of 8 m at Dome A, Antarctica, using only the data from a multi-layer automated weather station (AWS). In comparison with DIMM data, our estimate has a root mean square error (RMSE) of 0.18 arcsec, and the RMSE of predictions 20 minutes in the future is 0.12 arcsec for the seeing range from 0 to 2.2 arcsec. Compared with the persistence, where the forecast is the same as the last data point, our framework reduces the RMSE by 37 percent. Our method predicts the seeing within a second of computing time, making it suitable for real-time telescope scheduling.

ABSTRACTThe radiance of sky brightness differs principally with wavelength passband. Atmospheric scattering of sunlight causes the radiation in the near-infrared band. The Antarctic is a singular area of the planet, marked by an unparalleled climate and geographical conditions, including the coldest temperatures and driest climate on Earth, which leads it to be the best candidate site for observing in infrared bands. At present, there are still no measurements of night-sky brightness at DOME A. We have developed the Near-Infrared Sky Brightness Monitor (NISBM) in the J, H, and Ks bands for measurements at DOME A. The instruments were installed at DOME A in 2019 and early results of NIR sky brightness from 2019 January–April have been obtained. The variation of sky background brightness with solar elevation and scanning angle is analysed. The zenith sky flux intensity for the early night at DOME A in the J band is in the 600–1100 μJy arcsec−2 range, that in the H band is between 1100 and 2600 μJy arcsec−2, and that in the Ks band is in the range ∼200–900 μJy arcsec−2. This result shows that the sky brightness in J and H bands is close to that of Ali in China and Mauna Kea in the USA. The sky brightness in the Ks band is much better than that in Ali, China and Mauna Kea, USA. This shows that, from our early results, DOME A is a good site for astronomical observation in the Ks band.

We present the discovery and multiwavelength characterization of SRGA J181414.6-225604, a Galactic hard X-ray transient discovered during the ongoing SRG/ART-XC sky survey. Using data from the Palomar Gattini-IR survey, we identify a spatially and temporally coincident variable infrared (IR) source, IRAS 18111-2257, and classify it as a very-late-type (M7–M8), long-period (1502 ± 24 days), and luminous (M K ≈ −9.9 ± 0.2) O-rich Mira donor star located at a distance of ≈14.6+2.9 −2.3 kpc. Combining multicolor photometric data over the last ≈25 yr, we show that the IR counterpart underwent a recent (starting ≈800 days before the X-ray flare) enhanced mass-loss (reaching ≈2.1 × 10−5 M ⊙ yr−1) episode, resulting in an expanding dust shell obscuring the underlying star. Multi-epoch follow-up observations from Swift, NICER, and NuSTAR reveal a ≈200 day long X-ray outburst reaching a peak luminosity of L X ≈ 2.5 × 1036 erg s−1, characterized by a heavily absorbed (N H ≈ 6 × 1022 cm−2) X-ray spectrum consistent with an optically thick Comptonized plasma. The X-ray spectral and timing behavior suggest the presence of clumpy wind accretion, together with a dense ionized nebula overabundant in silicate material surrounding the compact object. Together, we show that SRGA J181414.6-225604 is a new symbiotic X-ray binary in outburst, triggered by an intense dust-formation episode of a highly evolved donor. Our results offer the first direct confirmation for the speculated connection between enhanced late-stage donor mass loss and the active lifetimes of symbiotic X-ray binaries.

We present a detailed analysis of SN 2020qmp, a nearby type IIP core-collapse supernova (CCSN), discovered by the Palomar Gattini-IR (PGIR) survey in the galaxy UGC07125. We illustrate how the multiwavelength study of this event helps our general understanding of stellar progenitors and circumstellar medium (CSM) interactions in CCSNe. We also highlight the importance of near-infrared (NIR) surveys for early detections of SNe in dusty environments. SN 2020qmp displays characteristic hydrogen lines in its optical spectra, as well as a plateau in its optical LC, hallmarks of a type IIP SN. We do not detect linear polarization during the plateau phase, with a 3 sigma upper limit of 0.78 Through hydrodynamical LC modeling and an analysis of its nebular spectra, we estimate a progenitor mass of around 11 solar masses, and an explosion energy of around 0.8e51 erg. We find that the spectral energy distribution cannot be explained by a simple CSM interaction model, assuming a constant shock velocity and steady mass-loss rate, and the excess X-ray luminosity compared with the synchrotron radio luminosity suggests deviations from equipartition. Finally, we demonstrate the advantages of NIR surveys over optical surveys for the detection of dust-obscured CCSNe in the local universe. Specifically, our simulations show that the Wide-Field Infrared Transient Explorer will detect about 14 more CCSNe out of 75 expected in its footprint within 40 Mpc, over five years than an optical survey equivalent to the Zwicky Transient Facility would detect. We have determined or constrained the main properties of SN 2020qmp and of its progenitor, highlighting the value of multiwavelength follow-up observations of nearby CCSNe. We have also shown that forthcoming NIR surveys will finally enable us to do a nearly complete census of CCSNe in the local universe.