Search Publications
The Swan: Data-driven Inference of Stellar Surface Gravities for Cool Stars from Photometric Light Curves
Huber, Daniel; Ness, Melissa K.; Wheeler, Adam +1 more
Stellar light curves are well known to encode physical stellar properties. Precise, automated, and computationally inexpensive methods to derive physical parameters from light curves are needed to cope with the large influx of these data from space-based missions such as Kepler and TESS. Here we present a new methodology that we call "The Swan," a…
Direct Imaging of Exoplanets beyond the Radial Velocity Limit: Application to the HD 134987 System
Gonzalez-Quiles, Junellie; Kane, Stephen R.; Girard, Julien H. +4 more
Future direct imaging missions will primarily observe planets that have been previously detected, mostly via the radial velocity (RV) technique, to characterize planetary atmospheres. In the meantime, direct imaging may discover new planets within existing planetary systems that have bright enough reflected flux but insufficient signals for other …
Concordance: In-flight Calibration of X-Ray Telescopes without Absolute References
Drake, Jeremy J.; Guainazzi, Matteo; van Dyk, David A. +7 more
We describe a process for cross-calibrating the effective areas of X-ray telescopes that observe common targets. The targets are not assumed to be "standard candles" in the classic sense, in that we assume that the source fluxes have well-defined, but a priori unknown values. Using a technique developed by Chen et al. that involves a statistical m…
Asteroseismology of iota Draconis and Discovery of an Additional Long-period Companion
Chaplin, William J.; Kane, Stephen R.; Stassun, Keivan G. +25 more
Giant stars as known exoplanet hosts are relatively rare due to the potential challenges in acquiring precision radial velocities and the small predicted transit depths. However, these giant host stars are also some of the brightest in the sky and so enable high signal-to-noise ratio follow-up measurements. Here, we report on new observations of t…
Rotation Periods of TESS Objects of Interest from the Magellan-TESS Survey with Multiband Photometry from Evryscope and TESS
Law, Nicholas M.; Teske, Johanna; Wang, Sharon Xuesong +8 more
Stellar radial-velocity (RV) jitter due to surface activity may bias the RV semiamplitude 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 &…
Disintegration of Long-period Comet C/2019 Y4 (ATLAS). I. Hubble Space Telescope Observations
Mutchler, Max; Weaver, Harold A.; Jewitt, David +8 more
The near-Sun comet C/2019 Y4 (ATLAS) is the first member of a long-period comet group observed to disintegrate well before perihelion. Here we present our investigation into this disintegration event using images obtained in a three-day Hubble Space Telescope campaign. We identify two fragment clusters produced by the initial disintegration event,…
Speckle Imaging Characterization of Radial Velocity Exoplanet Systems
Henry, Gregory W.; Kane, Stephen R.; Howell, Steve B. +10 more
We conducted speckle imaging observations of 53 stellar systems that were members of long-term radial velocity (RV) monitoring campaigns and exhibited substantial accelerations indicative of planetary or stellar companions in wide orbits. Our observations were made with blue and red filters using the Differential Speckle Survey Instrument at Gemin…
New Infrared Spectral Indices of Luminous Cold Stars: From Early K to M Types
Menten, Karl M.; Zhu, Qingfeng; Kudritzki, Rolf-Peter +4 more
We present infrared spectral indices (1.0-2.3 µm) of Galactic late-type giants and red supergiants (RSGs). We used existing and new spectra obtained at resolution power R = 2000 with SpeX on the IRTF telescope. While a large CO equivalent width (EW), at 2.29 µm ([CO, 2.29] ≳ 45 Å) is a typical signature of RSGs later than spectral type…
Spatially Resolving the Star Formation Histories of Three Nearby Nuclear Star Clusters
Neumayer, Nadine; Kacharov, Nikolay; Seth, Anil C. +4 more
The formation of nuclear star clusters (NSCs) remains an open question. In this work, we use spatially-resolved HST/STIS spectroscopic observations of three nearby NSCs (hosted by NGC 5102, NGC 5206, and NGC 205) to constrain their formation histories by exploring radial variations of the stellar populations within each cluster. Utilizing full-spe…
Unlocking the Origins of Ultracool Dwarf Radio Emission
Hughes, A. G.; White, J. A.; Boley, A. C. +2 more
Empirical trends in stellar X-ray and radio luminosities suggest that low-mass ultracool dwarfs (UCDs) should not produce significant radio emission. Defying these expectations, strong nonthermal emission has been observed in a few UCDs in the 1-10 GHz range, with a variable component often attributed to global aurorae and a steady component attri…