Search Publications
The First Dynamical Mass Determination of a Nitrogen-rich Wolf-Rayet Star Using a Combined Visual and Spectroscopic Orbit
Monnier, John D.; Lanthermann, Cyprien; Anugu, Narsireddy +11 more
We present the first visual orbit for the nitrogen-rich Wolf-Rayet binary, WR 133 (WN5o + O9I), based on observations made with the CHARA Array and the MIRC-X combiner. This orbit represents the first visual orbit for a WN star and only the third Wolf-Rayet star with a visual orbit. The orbit has a period of 112.8 days, a moderate eccentricity of …
Sympathetic Filament Eruptions within a Fan-spine Magnetic System
Shen, Yuandeng; Zhou, Chengrui; Zhou, Xinping +3 more
It is unclear whether successive filament eruptions at different sites within a short time interval are physically connected or not. Here, we present the observations of successive eruptions of a small and a large filament in a tripolar magnetic field region whose coronal magnetic field showed as a fan-spine magnetic system. By analyzing the multi…
Far-Infrared Line Diagnostics: Improving N/O Abundance Estimates for Dusty Galaxies
Lamarche, C.; Stacey, G. J.; Higdon, J. +8 more
The nitrogen-to-oxygen (N/O) abundance ratio is an important diagnostic of galaxy evolution because the ratio is closely tied to the growth of metallicity and the star formation history in galaxies. Estimates for the N/O are traditionally made with optical lines that could suffer from extinction and excitation effects, so the N/O is arguably measu…
EPIC 228782059: Asteroseismology of What Could Be the Coolest Pulsating Helium-atmosphere White Dwarf (DBV) Known
Hermes, J. J.; Fu, J. -N.; Vanderbosch, Zachary P. +5 more
We present analysis of a new pulsating helium-atmosphere (DB) white dwarf, EPIC 228782059, discovered from 55.1 days of K2 photometry. The long-duration, high-quality light curves reveal 11 independent dipole and quadruple modes, from which we derive a rotational period of 34.1 ± 0.4 hr for the star. An optimal model is obtained from a series of g…
Discovery of a Candidate Hypervelocity Star Originating from the Sagittarius Dwarf Spheroidal Galaxy
Huang, Yang; Chang, Jiang; Zhang, Huawei +5 more
In this Letter, we report the discovery of an intriguing hypervelocity star (HVS; J1443+1453) candidate that is probably from the Sagittarius Dwarf Spheroidal galaxy (Sgr dSph). The star is an old and very metal-poor low-mass main-sequence turn-off star (age ∼14.0 Gyr and [Fe/H] = -2.23 dex) and has a total velocity of ${559.01}_{-87.40}^{+135.07}…
High-frequency Wave Power Observed in the Solar Chromosphere with IBIS and ALMA
Kowalski, Adam F.; Cranmer, Steven R.; Reardon, Kevin P. +3 more
We present observational constraints on the chromospheric heating contribution from acoustic waves with frequencies between 5 and 50 mHz. We use observations from the Dunn Solar Telescope in New Mexico, complemented with observations from the Atacama Large Millimeter Array collected on 2017 April 23. The properties of the power spectra of the vari…
Discovery of 40.5 ks Hard X-Ray Pulse-phase Modulations from SGR 1900+14
Suzuki, H.; Enoto, T.; Makishima, K. +4 more
X-ray timing properties of the magnetar SGR 1900+14 were studied, using the data taken with Suzaku in 2009 and NuSTAR in 2016, for a time lapse of 114 and 242 ks, respectively. On both occasions, the object exhibited the characteristic two-component spectrum. The soft component, dominant in energies below ~5 keV, showed a regular pulsation, with a…
The Pulsating White Dwarf G117-B15A: Still the Most Stable Optical Clock Known
Kepler, S. O.; Hermes, J. J.; Bell, Keaton J. +14 more
The pulsating hydrogen atmosphere white dwarf star G 117-B15A has been observed since 1974. Its main pulsation period at 215.19738823(63) s, observed in optical light curves, varies by only (5.12 ± 0.82) × 10-15 s s-1 and shows no glitches, as pulsars do. The observed rate of period change corresponds to a change of the pulsa…
The Black Hole Mass of NGC 4151 from Stellar Dynamical Modeling
Vasiliev, Eugene; Onken, Christopher A.; Bentz, Misty C. +2 more
The mass of a supermassive black hole (MBH) is a fundamental property that can be obtained through observational methods. Constraining MBH through multiple methods for an individual galaxy is important for verifying the accuracy of different techniques and for investigating the assumptions inherent in each method. However, th…
Correlated X-Ray and Optical Variability in the O-type Supergiant ζ Puppis
Moffat, Anthony F. J.; Richardson, Noel D.; Nichols, Joy S. +11 more
Analysis of the recent long exposure Chandra X-ray observation of the early-type O star ζ Pup shows clear variability with a period previously reported in optical photometric studies. These 813 ks of HETGS observations taken over a roughly one-year time span have two signals of periodic variability: (1) a high-significance period of 1.7820 ± 0.000…