Search Publications
Perfecting Our Set of Spectrophotometric Standard DA White Dwarfs
Rest, Armin; Matheson, Thomas; Raddi, Roberto +17 more
We verified for photometric stability a set of DA white dwarfs with Hubble Space Telescope magnitudes from the near-ultraviolet to the near-infrared and ground-based spectroscopy by using time-spaced observations from the Las Cumbres Observatory network of telescopes. The initial list of 38 stars was whittled to 32 final ones, which comprise a hig…
X-Ray and Radio Observations of Central Black Holes in Nearby Low-mass Early-type Galaxies: Preliminary Evidence for Low Eddington Fractions
Neumayer, Nadine; Strader, Jay; Seth, Anil C. +5 more
We present new radio and X-ray observations of two nearby (<4 Mpc) low-mass early-type galaxies with dynamically confirmed central black holes: NGC 5102 and NGC 205. NGC 5102 shows a weak nuclear X-ray source and has no core radio emission. However, for the first time we demonstrate that it shows luminous extended radio continuum emission in lo…
Discovery of a Filamentary Synchrotron Structure Connected to the Coherent Magnetic Field in the Outer Galaxy
Ricci, R.; Safi-Harb, S.; Kothes, R. +9 more
Using data from the Galactic Arecibo L-band Feed Array Continuum Transit Survey, we report the discovery of two previously unidentified, very compressed, thin, and straight polarized filaments approximately centered at Galactic coordinates, (l, b) = (182.°5, - 4.°0), which we call G182.5-4.0. Using data from the Isaac Newton Telescope Galactic Pla…
Detection of Stellar-like Abundance Anomalies in the Slow Solar Wind
Warren, Harry P.; Brooks, David H.; Baker, Deborah +2 more
The elemental composition of the Sun's hot atmosphere, the corona, shows a distinctive pattern that is different from the underlying surface or photosphere. Elements that are easy to ionize in the chromosphere are enhanced in abundance in the corona compared to their photospheric values. A similar pattern of behavior is often observed in the slow-…
Calibrating the Cepheid Period-Wesenheit Relation in the Gaia Bands Using Galactic Open-cluster Cepheids
Xu, Ye; Liu, Dejian; Hao, Chaojie +3 more
Establishing the period-Wesenheit relation requires independent and accurate distance measurements of classical Cepheids (DCEPs). The precise distances provided by associated open clusters independently calibrate the period-Wesenheit relations of DCEPs. 51 DCEPs associated with open clusters are compiled using the constraints of five-dimensional a…
A Hydro-based MCMC Analysis of SNR 0509-67.5: Revealing the Explosion Properties from Fluid Discontinuities Alone
Hughes, John P.; Arunachalam, Prasiddha; Hovey, Luke +1 more
Using Hubble Space Telescope/ACS Hα images of SNR 0509-67.5 taken ~10 yr apart, we measure the forward shock (FS) proper motions (PMs) at 231 rim locations. The average shock radius and velocity are 3.66 ± 0.036 pc and 6315 ± 310 km s-1. Hydrodynamic simulations, recast as similarity solutions, provide models for the supernova remnant's…
The Dynamic Coupling of Streamers and Pseudostreamers to the Heliosphere
Antiochos, S. K.; Higginson, A. K.; Wyper, P. F. +3 more
The slow solar wind is generally believed to result from the interaction of open and closed coronal magnetic flux at streamers and pseudostreamers. We use three-dimensional magnetohydrodynamic simulations to determine the detailed structure and dynamics of open-closed interactions that are driven by photospheric convective flows. The photospheric …
Observed Rate Variations in Superflaring G-type Stars
Yang, Kai; Crowley, James; Wheatland, Michael S.
Flare occurrence on the Sun is highly variable, exhibiting both short-term variation due to the emergence and evolution of active regions, and long-term variation from the solar cycle. On solar-like stars, more energetic stellar flares (superflares) have been observed, and it is of interest to determine whether the observed rates of superflare occ…
A Ghost in Boötes: The Least-Luminous Disrupted Dwarf Galaxy
Conroy, Charlie; Ting, Yuan-Sen; Cargile, Phillip A. +9 more
We report the discovery of Specter, a disrupted ultrafaint dwarf galaxy revealed by the H3 Spectroscopic Survey. We detected this structure via a pair of comoving metal-poor stars at a distance of 12.5 kpc, and further characterized it with Gaia astrometry and follow-up spectroscopy. Specter is a 25° × 1° stream of stars that is entirely invisible…
He II Lyα Transmission Spikes and Absorption Troughs in Eight High-resolution Spectra Probing the End of He II Reionization
Richter, Philipp; Hennawi, Joseph F.; Worseck, Gábor +3 more
We present statistics of He II Lyα transmission spikes and large-scale absorption troughs using archival high-resolution (R = λ/Δλ ≃ 12,500-18,000) far-UV spectra of eight He II-transparent quasars obtained with the Cosmic Origins Spectrograph on the Hubble Space Telescope. The sample covers the redshift range 2.5 ≲ z ≲ 3.8, thereby probing the ra…