Search Publications
Toward the ICRF3: Astrometric Comparison of the USNO 2016A VLBI Solution with ICRF2 and Gaia DR1
Dorland, Bryan N.; Makarov, Valeri V.; Johnson, Megan C. +2 more
The VLBI USNO 2016A (U16A) solution is part of a work-in-progress effort by USNO toward the preparation of the ICRF3. Most of the astrometric improvement with respect to the ICRF2 is due to the re-observation of the VCS sources. Our objective in this paper is to assess U16A’s astrometry. A comparison with ICRF2 shows statistically significant offs…
Is the Young Star RZ Piscium Consuming Its Own (Planetary) Offspring?
Kastner, J. H.; Punzi, K. M.; Melis, C. +4 more
The erratically variable star RZ Piscium (RZ Psc) displays extreme optical dropout events and strikingly large excess infrared emission. To ascertain the evolutionary status of this intriguing star, we obtained observations of RZ Psc with the European Space Agency’s X-ray Multi-Mirror Mission (XMM-Newton), as well as high-resolution optical spectr…
Accurate Ground-based Near-Earth-Asteroid Astrometry Using Synthetic Tracking
Preston, Robert A.; Lazio, Joseph; Zhai, Chengxing +13 more
Accurate astrometry is crucial for determining orbits of near-Earth-asteroids (NEAs) and therefore better tracking them. This paper reports on a demonstration of 10 mas level astrometric precision on a dozen NEAs using the Pomona College 40 inch telescope, at the JPL’s Table Mountain Facility. We used the technique of synthetic tracking (ST), in w…
The Star-grazing Bodies in the HD 172555 System
Roberge, Aki; Brown, Alexander; Grady, C. A. +3 more
Kiefer et al. reported the detection of infalling Ca II absorption in HD 172555, a member of the β Pictoris Moving Group (βPMG). We obtained HST Space Telescope Imaging Spectrograph and Cosmic Origins Spectrograph spectroscopy of this star at 2 epochs separated by a week, and we report the discovery of infalling gas in resonant transitions of Si I…
Stellar Variability at the Main-sequence Turnoff of the Intermediate-age LMC Cluster NGC 1846
Contreras Ramos, R.; Vivas, A. K.; Strader, J. +2 more
Intermediate-age (IA) star clusters in the Large Magellanic Cloud (LMC) present extended main-sequence turn-offs (MSTO) that have been attributed to either multiple stellar populations or an effect of stellar rotation. Recently it has been proposed that these extended main sequences can also be produced by ill-characterized stellar variability. He…
Far-ultraviolet Spectroscopy of Recent Comets with the Cosmic Origins Spectrograph on the Hubble Space Telescope
Weaver, Harold A.; Feldman, Paul D.; A'Hearn, Michael F. +2 more
Since its launch in 1990, the Hubble Space Telescope (HST) has served as a platform with unique capabilities for remote observations of comets in the far-ultraviolet region of the spectrum. Successive generations of imagers and spectrographs have seen large advances in sensitivity and spectral resolution enabling observations of the diverse proper…
Light Element Abundances and Multiple Populations in M10
Vesperini, Enrico; Gerber, Jeffrey M.; Friel, Eileen D.
We present CN and CH band measurements for 137 red giant branch (RGB) and asymptotic giant branch (AGB) stars in the Galactic globular cluster M10. Our measurements come from low-resolution spectroscopy taken with the Hydra spectrograph on the WIYN-3.5 m telescope. We use these measurements to identify two populations of stars within the cluster, …
EPIC 246851721 b: A Tropical Jupiter Transiting a Rapidly Rotating Star in a Well-aligned Orbit
Vanderburg, Andrew; Bieryla, Allyson; Latham, David W. +15 more
We report the discovery of EPIC 246851721 b, a “tropical” Jupiter in a 6.18-day orbit around the bright (V = 11.439) star EPIC 246851721 (TYC 1283-739-1). We present a detailed analysis of the system using K2 and ground-based photometry, radial velocities, Doppler tomography, and adaptive optics imaging. From our global models, we infer that the h…
Yes, Multi-periodic Dwarfs in Upper Scorpius Are Binaries
Tokovinin, Andrei; Briceño, Cesar
We found that multi-periodic low-mass stars discovered by Kepler K2 in the Upper Scorpius association are close binaries with typical separations of the order of 10 au and large mass ratios. These stars were surveyed by speckle interferometry at the SOAR telescope with spatial resolution of 0.″04. Out of 129 observed targets, we resolved 70 pairs …
Optical Coronagraphic Spectroscopy of AU Mic: Evidence of Time Variable Colors?
Weinberger, Alycia J.; Debes, John H.; Donaldson, Jessica K. +4 more
We present coronagraphic long slit spectra of AU Mic’s debris disk taken with the STIS instrument aboard the Hubble Space Telescope. Our spectra are the first spatially-resolved, scattered light spectra of the system’s disk, which we detect at projected distances between approximately 10 and 45 au. Our spectra cover a wavelength range between 5200…