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The 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.

 

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.

 

We present optical and infrared (IR) light curves of the enshrouded massive binary NaSt1 (WR 122) with observations from Palomar Gattini-IR (PGIR), the Zwicky Transient Facility (ZTF), the Katzman Automatic Imaging Telescope (KAIT), and the All-Sky Automated Survey for Supernovae (ASAS-SN). The optical and IR light curves span between 2014 July and 2020 Oct., revealing periodic, sinusoidal variability from NaSt1 with a P=305.2±1.0 d period. We also present historical IR light curves taken between 1983 July and 1989 May that also indicate NaSt1 exhibits long-term IR variability on timescales of ∼decades. Fixed-period sinusoidal fits to the recent optical and IR light curves show that amplitude of NaSt1's variability is different at different wavelengths and also reveal significant phase offsets of ∼18 d between the ZTF r and PGIR J light curves.We interpret the ∼300 d period of the observed variability as the orbital period of a binary system in NaSt1. Assuming a circular orbit and adopting a range of combined stellar mass values in the range 20-100 M⊙ in NaSt1, we estimate orbital separations of ∼2-4 au. We suggest that the sinusoidal photometric variability of NaSt1 may arise from variations in the line-of-sight optical depth toward circumstellar optical/IR emitting regions throughout its orbit due to colliding-wind dust formation. We provide an interpretation on the nature of NaSt1 and speculate that the mass-transfer process may have been triggered by Roche-lobe overflow (RLOF) during an eruptive phase of a Ofpe/WN9 star. Lastly, we claim that NaSt1 ceased RLOF mass transfer ≲3400 yr ago. 

Abstract The nova rate in the Milky Way remains largely uncertain, despite its vital importance in constraining models of Galactic chemical evolution as well as understanding progenitor channels for Type Ia supernovae. The rate has been previously estimated to be in the range of ≈10–300 yr −1 , either based on extrapolations from a handful of very bright optical novae or the nova rates in nearby galaxies; both methods are subject to debatable assumptions. The total discovery rate of optical novae remains much smaller (≈5–10 yr −1 ) than these estimates, even with the advent of all-sky optical time-domain surveys. Here, we present a systematic sample of 12 spectroscopically confirmed Galactic novae detected in the first 17 months of Palomar Gattini-IR (PGIR), a wide-field near-infrared time-domain survey. Operating in the J band (≈1.2 μ m), which is significantly less affected by dust extinction compared to optical bands, the extinction distribution of the PGIR sample is highly skewed to a large extinction values (>50% of events obscured by A V ≳ 5 mag). Using recent estimates for the distribution of Galactic mass and dust, we show that the extinction distribution of the PGIR sample is commensurate with dust models. The PGIR extinction distribution is inconsistent with that reported in previous optical searches (null-hypothesis probability <0.01%), suggesting that a large population of highly obscured novae have been systematically missed in previous optical searches. We perform the first quantitative simulation of a 3 π time-domain survey to estimate the Galactic nova rate using PGIR, and derive a rate of ≈ 43.7 − 8.7 + 19.5 yr −1 . Our results suggest that all-sky near-infrared time-domain surveys are well poised to uncover the Galactic nova population.