Palomar Gattini-IR is a new wide-field, near-infrared (NIR) robotic time domain survey operating at Palomar Observatory. Using a 30 cm telescope mounted with a H2RG detector, Gattini-IR achieves a ...field of view (FOV) of 25 sq. deg. with a pixel scale of 8 7 in J-band. Here, we describe the system design, survey operations, data processing system and on-sky performance of Palomar Gattini-IR. As a part of the nominal survey, Gattini-IR scans 7500 square degrees of the sky every night to a median 5 depth of 15.7 AB mag outside the Galactic plane. The survey covers 15,000 square degrees of the sky visible from Palomar with a median cadence of 2 days. A real-time data processing system produces stacked science images from dithered raw images taken on sky, together with point-spread function (PSF)-fit source catalogs and transient candidates identified from subtractions within a median delay of 4 hr from the time of observation. The calibrated data products achieve an astrometric accuracy (rms) of 0 7 with respect to Gaia DR2 for sources with signal-to-noise ratio > 10, and better than 0 35 for sources brighter than 12 Vega mag. The photometric accuracy (rms) achieved in the PSF-fit source catalogs is better than 3% for sources brighter than 12 Vega mag and fainter than the saturation magnitude of 8.5 Vega mag, as calibrated against the Two Micron All Sky Survey catalog. The detection efficiency of transient candidates injected into the images is better than 90% for sources brighter than the 5 limiting magnitude. The photometric recovery precision of injected sources is 3% for sources brighter than 13 mag, and the astrometric recovery rms is 0 9. Reference images generated by stacking several field visits achieve depths of 16.5 AB mag over 60% of the sky, while it is limited by confusion in the Galactic plane. With a FOV 40× larger than any other existing NIR imaging instrument, Gattini-IR is probing the reddest and dustiest transients in the local universe such as dust obscured supernovae in nearby galaxies, novae behind large columns of extinction within the galaxy, reddened microlensing events in the Galactic plane and variability from cool and dust obscured stars. We present results from transients and variables identified since the start of the commissioning period.
Abstract
We report the discovery of a likely outbursting Class I young stellar object, associated with the star-forming region NGC 281-W (distance ∼2.8 kpc). The source is currently seen only at ...infrared wavelengths, appearing in both the Palomar Gattini InfraRed (1.2
μ
m) and the Near-Earth Object Wide-field Infrared Survey Explorer (3.4 and 4.6
μ
m) photometric time-domain surveys. Recent near-infrared imaging reveals a new, extended scattered light nebula. Recent near-infrared spectroscopy confirms the similarity of PGIR 20dci to FU Ori–type sources, based on strong molecular absorption in CO, H
2
O, and OH; weak absorption in several atomic lines; and a warm wind/outflow as indicated by a P Cygni profile in the He
i
λ
10830 line. This is a rare case of an FU Ori star with a well-measured long-term photometric rise before a sharper outburst, and the second instance of an FU Ori star with a documented two-step brightening in the mid-infrared.
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.
The Mars rover Opportunity has explored Victoria crater, a approximately 750-meter eroded impact crater formed in sulfate-rich sedimentary rocks. Impact-related stratigraphy is preserved in the ...crater walls, and meteoritic debris is present near the crater rim. The size of hematite-rich concretions decreases up-section, documenting variation in the intensity of groundwater processes. Layering in the crater walls preserves evidence of ancient wind-blown dunes. Compositional variations with depth mimic those approximately 6 kilometers to the north and demonstrate that water-induced alteration at Meridiani Planum was regional in scope.
Developmental and epileptic encephalopathies (DEEs) are severe neurodevelopmental disorders often beginning in infancy or early childhood that are characterized by intractable seizures, abundant ...epileptiform activity on EEG, and developmental impairment or regression. CACNA1E is highly expressed in the central nervous system and encodes the α1-subunit of the voltage-gated CaV2.3 channel, which conducts high voltage-activated R-type calcium currents that initiate synaptic transmission. Using next-generation sequencing techniques, we identified de novo CACNA1E variants in 30 individuals with DEE, characterized by refractory infantile-onset seizures, severe hypotonia, and profound developmental impairment, often with congenital contractures, macrocephaly, hyperkinetic movement disorders, and early death. Most of the 14, partially recurring, variants cluster within the cytoplasmic ends of all four S6 segments, which form the presumed CaV2.3 channel activation gate. Functional analysis of several S6 variants revealed consistent gain-of-function effects comprising facilitated voltage-dependent activation and slowed inactivation. Another variant located in the domain II S4-S5 linker results in facilitated activation and increased current density. Five participants achieved seizure freedom on the anti-epileptic drug topiramate, which blocks R-type calcium channels. We establish pathogenic variants in CACNA1E as a cause of DEEs and suggest facilitated R-type calcium currents as a disease mechanism for human epilepsy and developmental disorders.
We report on a complete set of early optical afterglows of gamma-ray bursts (GRBs) obtained with the Robotic Optical Transient Search Experiment (ROTSE-III) telescope network from 2005 March through ...2007 June. This set is comprised of 12 afterglows with early optical and Swift/X-Ray Telescope observations, with a median ROTSE-III response time of 45 s after the start of Delta *g-ray emission (8 s after the GCN notice time). These afterglows span 4 orders of magnitude in optical luminosity, and the contemporaneous X-ray detections allow multi-wavelength spectral analysis. Excluding X-ray flares, the broadband synchrotron spectra show that the optical and X-ray emission originate in a common region, consistent with predictions of the external forward shock in the fireball model. However, the fireball model is inadequate to predict the temporal decay indices of the early afterglows, even after accounting for possible long-duration continuous energy injection. We find that the optical afterglow is a clean tracer of the forward shock, and we use the peak time of the forward shock to estimate the initial bulk Lorentz factor of the GRB outflow, and find 100 Delta *G0 1000, consistent with expectations.
The domes, or local elevation maxima, on the Antarctic plateau provide a unique opportunity for ground-based astronomy in that the turbulent boundary layer is so thin that a telescope on a small ...tower can be in the free atmosphere, i.e., the portion of the atmosphere in which the turbulence is decoupled from the effect of the Earth’s surface. There, it can enjoy a free atmosphere which itself appears to offer superior conditions to that of temperate sites. This breaks the problem of characterizing the turbulence at Antarctic plateau sites into two separate tasks: determining the variability, distribution and thickness of the boundary layer, and characterizing the free atmosphere. In this article we tackle the first of these tasks using a high-resolution, low minimum sample height sonic radar (SODAR) called Snodar that has been specifically designed to characterize the Antarctic boundary thickness and structure. Snodar delivers a vertical resolution of 0.9 m, with a minimum sampling height of 8 m. Snodar sampled the first 180 m of the atmosphere with 0.9 m resolution every 10 s at Dome A, Antarctica between 2009 February 4 and 2009 August 18. The median thickness of the boundary layer over this period was 13.9 m, with the 25th and 75th percentiles at 9.7 m and 19.7 m, respectively. The data collected from Dome A also show that, while the boundary layer can be stable for several hundred hours at a time, it can also be highly variable and must be sampled on the time scale of minutes to properly characterize its thickness.
We present the first direct measurements of the terahertz atmospheric transmission above Dome A, the highest point on the Antarctic plateau at an elevation of 4.1 km. The best-quartile atmospheric ...transmission during the Austral winter is 80% at a frequency of 661 GHz (453 μm), corresponding to a precipitable water vapor column of 0.1 mm. Daily averages as low as 0.025 mm were observed. The Antarctic atmosphere is very stable, and excellent observing conditions generally persist for many days at a time. The exceptional conditions over the high Antarctic plateau open new far-infrared spectral windows to ground-based observation. These windows contain important spectral-line diagnostics of star formation and the interstellar medium which would otherwise only be accessible to airborne or space telescopes.
Abstract
We are undertaking the first systematic infrared (IR) census of R Coronae Borealis (RCB) stars in the Milky Way, beginning with IR light curves from the Palomar Gattini IR (PGIR) survey. The ...PGIR is a 30 cm
J
-band telescope with a 25 deg
2
camera that is surveying 18,000 deg
2
of the northern sky (
δ
> −28°) at a cadence of 2 days. We present PGIR light curves for 922 RCB candidates selected from a mid-IR color-based catalog. Of these 922, 149 are promising RCB candidates, as they show pulsations or declines similar to RCB stars. The majority of the candidates that are not RCB stars are either long-period variables (LPVs) or RV Tauri stars. We identify IR color-based criteria to better distinguish between RCB stars and LPVs. As part of a pilot spectroscopic run, we obtain NIR spectra for 26 of the 149 promising candidates and spectroscopically confirm 11 new RCB stars. We detect strong He
i
λ
10830 features in the spectra of all RCB stars, likely originating within high-velocity (200–400 km s
−1
) winds in their atmospheres. Nine of these RCB stars show
12
C
16
O and
12
C
18
O molecular absorption features, suggesting that they are formed through a white dwarf merger. We detect quasiperiodic pulsations in the light curves of five RCB stars. The periods range between 30 and 125 days and likely originate from the strange-mode instability in these stars. Our pilot run results motivate a dedicated IR spectroscopic campaign to classify all RCB candidates.
Abstract
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 × 10
36
erg s
−1
, characterized by a heavily absorbed (
N
H
≈ 6 × 10
22
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.
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