HD 53143 is a mature Sun-like star and host to a broad disk of dusty debris, including a cold outer ring of planetesimals near 90 AU. Unlike most other inclined debris disks imaged at visible ...wavelengths, the cold disk around HD 53143 appears as disconnected "arcs" of material, with no forward scattering side detected to date. We present new, deeper Hubble Space Telescope (HST) Space Telescope Imaging Spectrograph (STIS) coronagraphic observations of the HD 53143 debris disk and show that the forward scattering side of the disk remains undetected. By fitting our KLIP-reduced observations via forward modeling with an optically thin disk model, we show that fitting the visible wavelength images with an azimuthally symmetric disk with unconstrained orientation results in an unphysical edge-on orientation that is at odds with recent ALMA observations, while constraining the orientation to that observed by ALMA results in nearly isotropically scattering dust. We show that the HD53143 host star exhibits significant stellar variations due to spot rotation and revisit age estimates for this system.
We present ALMA 1.3 mm observations of the HD~53143 debris disk - the first infrared or millimeter image produced of this ~1 Gyr-old solar-analogue. Previous HST STIS coronagraphic imaging did not ...detect flux along the minor axis of the disk which could suggest a face-on geometry with two 'clumps' of dust. These ALMA observations reveal a disk with a strikingly different structure. In order to fit models to the millimeter visibilities and constrain the uncertainties on the disk parameters, we adopt an MCMC approach. This is the most eccentric debris disk observed to date with a forced eccentricity of \(0.21\pm0.02\), nearly twice that of the Fomalhaut debris disk, and also displays apocenter glow. Although this eccentric model fits the outer debris disk well, there are significant interior residuals remaining that may suggest a possible edge-on inner disk, which remains unresolved in these observations. Combined with the observed structure difference between HST and ALMA, these results suggest a potential previous scattering event or dynamical instability in this system. We also note that the stellar flux changes considerably over the course of our observations, suggesting flaring at millimeter wavelengths. Using simultaneous TESS observations, we determine the stellar rotation period to be \(9.6\pm0.1\) days.
This study evaluated different perspectives on the relationship of trait anxiety to symptom report. Baseline trait anxiety was related to (a) initial symptoms reported 2 days after beginning ...chemotherapy, (b) posttreatment symptoms reported 2 days after cessation of medication, and (c) retrospective reports of initial symptoms (made concurrently with posttreatment reports). Associations were significant for vague psychophysiological symptoms but not for concrete visible symptoms. Path models indicated that the relationship of anxiety to retrospective report of vague symptoms was due to both enhanced encoding and facilitated recall of symptoms. Further analyses revealed, however, that this relationship reflects symptoms stability rather than anxiety-related differences in attention. Anxious and nonanxious patients appear to be equally accurate in their retrospective report of symptoms.
Astrophysical transients with rapid development on sub-hour timescales are intrinsically rare. Due to their short durations, events like stellar superflares, optical flashes from gamma-ray bursts, ...and shock breakouts from young supernovae are difficult to identify on timescales that enable spectroscopic followup. This paper presents the Evryscope Fast Transient Engine (EFTE), a new data reduction pipeline designed to provide low-latency transient alerts from the Evryscopes, a North-South pair of ultra-wide-field telescopes with an instantaneous footprint covering 38% of the entire sky, and tools for building long-term light curves from Evryscope data. EFTE leverages the optical stability of the Evryscopes by using a simple direct image subtraction routine suited to continuously monitoring the transient sky at minute cadence. Candidates are produced within the base Evryscope two-minute cadence for 98.5% of images, and internally filtered using VetNet, a convolutional neural network real-bogus classifier. EFTE provides an extensible, robust architecture for transient surveys probing similar timescales, and serves as the software testbed for the real-time analysis pipelines and public data distribution systems for the Argus Array, a next generation all-sky observatory with a data rate 62x higher than Evryscope.
We fabricate metal/a-Si/metal thin film switches which incorporate hot-wire chemical vapor deposition (HWCVD) Si layers. A H-diluted gas mixture is used to grow the B-doped, 1000 Å hydrogenated ...amorphous silicon (a-Si:H) layers at approximately 10 Å/s. We compare switching behavior in Cr/a-Si:H(p)/Ag and c-Si(p)/a-Si:H(p)/Ag structures containing p-type hydrogenated amorphous silicon. We observed that the switching is polarity-dependent only in the sample on c-Si(p). Switching to a low-resistance state occurs at 0.4 mA/cm
2 when any of the metal contacts are biased positive. When the c-Si(p) is biased positive holes are injected and no switching occurs even up to 4 A/cm
2. We suggest that the switching requires a blocking metal/a-Si(p) contact, possibly because local electrical breakdown initiates metal filament formation.
We present the first analysis of JWST near-infrared spectroscopy of stellar
flares from TRAPPIST-1 during transits of rocky exoplanets. Four flares were
observed from 0.6--2.8 $\mu$m with NIRISS and ...0.6--3.5 $\mu$m with NIRSpec
during transits of TRAPPIST-1b, f, and g. We discover P$\alpha$ and Br$\beta$
line emission and characterize flare continuum at wavelengths from 1--3.5
$\mu$m for the first time. Observed lines include H$\alpha$,
P$\alpha$-P$\epsilon$, Br$\beta$, He I $\lambda$0.7062$\mu$m, two Ca II
infrared triplet (IRT) lines, and the He I IRT. We observe a reversed Paschen
decrement from P$\alpha$-P$\gamma$ alongside changes in the light curve shapes
of these lines. The continuum of all four flares is well-described by blackbody
emission with an effective temperature below 5300 K, lower than temperatures
typically observed at optical wavelengths. The 0.6--1 $\mu$m spectra were
convolved with the TESS response, enabling us to measure the flare rate of
TRAPPIST-1 in the TESS bandpass. We find flares of 10$^{30}$ erg large enough
to impact transit spectra occur at a rate of 3.6$\substack{+2.1 \\ -1.3}$ flare
d$^{-1}$, $\sim$10$\times$ higher than previous predictions from K2. We measure
the amount of flare contamination at 2 $\mu$m for the TRAPPIST-1b and f
transits to be 500$\pm$450 and 2100$\pm$400 ppm, respectively. We find up to
80% of flare contamination can be removed, with mitigation most effective from
1.0--2.4 $\mu$m. These results suggest transits affected by flares may still be
useful for atmospheric characterization efforts.
We present millimeter, optical, and soft X-ray observations of a stellar flare with an energy squarely in the regime of typical X1 solar flares. The flare was observed from Proxima Cen on 2019 May 6 ...as part of a larger multi-wavelength flare monitoring campaign and was captured by Chandra, LCOGT, du Pont, and ALMA. Millimeter emission appears to be a common occurrence in small stellar flares that had gone undetected until recently, making it difficult to interpret these events within the current multi-wavelength picture of the flaring process. The May 6 event is the smallest stellar millimeter flare detected to date. We compare the relationship between the soft X-ray and millimeter emission to that observed in solar flares. The X-ray and optical flare energies of 10\(^{30.3\pm0.2}\) and 10\(^{28.9\pm0.1}\) erg, respectively, the coronal temperature of T=11.0\(\pm\)2.1 MK, and the emission measure of 9.5\(\pm\)2.2 X 10\(^{49}\) cm\(^{-3}\) are consistent with M-X class solar flares. We find the soft X-ray and millimeter emission during quiescence are consistent with the Gudel-Benz Relation, but not during the flare. The millimeter luminosity is >100X higher than that of an equivalent X1 solar flare and lasts only seconds instead of minutes as seen for solar flares.
Using photometric data collected by Evryscope-South, we search for nearby young variable systems on the upper-main sequence (UMS) and pre-main sequence (PMS). The Evryscopes are all-sky high-cadence ...telescope arrays operating in the Northern and Southern hemispheres. We base our search on a Gaia-selected catalog of young neighborhood upper- and pre-main sequence stars which were chosen through both astrometric and photometric criteria. We analyze 44,971 Evryscope-South light curves in search of variability. We recover 615 variables, with 378 previously known, and 237 new discoveries including 84 young eclipsing binary (EB) candidates. We discover a new highly eccentric binary system and recover a further four previously known systems, with periods ranging from 299 to 674 hr. We find 158 long-period (>50 hr) candidate EB systems, 9 from the PMS and 149 from the UMS, which will allow constraints on the mass-radius-age relation. These long-period EBs include a 179.3 hr PMS system and a 867.8 hr system from the UMS. For PMS variable candidates we estimate system ages, which range from 1 to 23 Myr for non-EBs and from 2 to 17 Myr for EBs. Other non-EB discoveries that show intrinsic variability will allow relationships between stellar rotation rates, ages, activity, and mass to be characterized.
The nearby ultracool dwarf TRAPPIST-1 possesses several Earth-sized terrestrial planets, three of which have equilibrium temperatures that may support liquid surface water, making it a compelling ...target for exoplanet characterization. TRAPPIST-1 is an active star with frequent flaring, with implications for the habitability of its planets. Superflares (stellar flares whose energy exceeds 10^33 erg) can completely destroy the atmospheres of a cool star's planets, allowing ultraviolet radiation and high-energy particles to bombard their surfaces. However, ultracool dwarfs emit little ultraviolet flux when quiescent, raising the possibility of frequent flares being necessary for prebiotic chemistry that requires ultraviolet light. We combine Evryscope and Kepler observations to characterize the high-energy flare rate of TRAPPIST-1. The Evryscope is an array of 22 small telescopes imaging the entire Southern sky in g' every two minutes. Evryscope observations, spanning 170 nights over 2 years, complement the 80-day continuous short-cadence K2 observations by sampling TRAPPIST-1's long-term flare activity. We update TRAPPIST-1's superflare rate, finding a cumulative rate of 4.2 (+1.9 -0.2) superflares per year. We calculate the flare rate necessary to deplete ozone in the habitable-zone planets' atmospheres, and find that TRAPPIST-1's flare rate is insufficient to deplete ozone if present on its planets. In addition, we calculate the flare rate needed to provide enough ultraviolet flux to power prebiotic chemistry. We find TRAPPIST-1's flare rate is likely insufficient to catalyze some of the Earthlike chemical pathways thought to lead to RNA synthesis, and flux due to flares in the biologically relevant UV-B band is orders of magnitude less for any TRAPPIST-1 planet than has been experienced by Earth at any time in its history.
Stellar RV jitter due to surface activity may bias the RV semi-amplitude and mass of rocky planets. The amplitude of the jitter may be estimated from the uncertainty in the rotation period, allowing ...the mass to be more accurately obtained. We find candidate rotation periods for 17 out of 35 TESS Objects of Interest (TOI) hosting <3 R_Earth planets as part of the Magellan-TESS Survey, which is the first-ever statistically robust study of exoplanet masses and radii across the photo-evaporation gap. Seven periods are 3+ sigma detections, two are 1.5+ sigma, and 8 show plausible variability but the periods remain unconfirmed. The other 18 TOIs are non-detections. Candidate rotators include the host stars of the confirmed planets L 168-9 b, the HD 21749 system, LTT 1445 A b, TOI 1062 b, and the L 98-59 system. 13 candidates have no counterpart in the 1000 TOI rotation catalog of Canto Martins et al. (2020). We find periods for G3-M3 dwarfs using combined light curves from TESS and the Evryscope all-sky array of small telescopes, sometimes with longer periods than would be possible with TESS alone. Secure periods range from 1.4 to 26 d with Evryscope-measured photometric amplitudes as small as 2.1 mmag in g'. We also apply Monte Carlo sampling and a Gaussian Process stellar activity model from the code exoplanet to the TESS light curves of 6 TOIs to confirm the Evryscope periods.
