Search Publications
The Overlooked Role of Stellar Variability in the Extended Main Sequence of LMC Intermediate-age Clusters
Contreras Ramos, R.; Vivas, A. K.; Strader, J. +2 more
Intermediate-age star clusters in the Large Magellanic Cloud show extended main sequence turnoffs (MSTOs) that are not consistent with a canonical single stellar population. These broad turnoffs have been interpreted as evidence for extended star formation and/or stellar rotation. Since most of these studies use single frames per filter to do the …
A Comprehensive Archival Chandra Search for X-Ray Emission from Ultracompact Dwarf Galaxies
Greene, Jenny E.; Mulchaey, John; Pandya, Viraj
We present the first comprehensive archival study of the X-ray properties of ultracompact dwarf (UCD) galaxies, with the goal of identifying weakly accreting central black holes in UCDs. Our study spans 578 UCDs distributed across 13 different host systems, including clusters, groups, fossil groups, and isolated galaxies. Of the 336 spectroscopica…
Hubble Space Telescope Constraints on the Winds and Astrospheres of Red Giant Stars
Harper, Graham M.; Wood, Brian E.; Müller, Hans-Reinhard
We report on an ultraviolet spectroscopic survey of red giants observed by the Hubble Space Telescope, focusing on spectra of the Mg II h and k lines near 2800 Å in order to study stellar chromospheric emission, winds, and astrospheric absorption. We focus on spectral types between K2 III and M5 III, a spectral type range with stars that are nonco…
A Candidate Planetary-mass Object with a Photoevaporating Disk in Orion
Fang, Min; Pascucci, Ilaria; Apai, Dániel +2 more
In this work, we report the discovery of a candidate planetary-mass object with a photoevaporating protoplanetary disk, Proplyd 133-353, which is near the massive star θ 1 Ori C at the center of the Orion Nebula Cluster (ONC). The object was known to have extended emission pointing away from θ 1 Ori C, indicating ongoing exte…
Evidence from SOFIA Imaging of Polycyclic Aromatic Hydrocarbon Formation along a Recent Outflow in NGC 7027
Sahai, R.; Ressler, M. E.; Lau, R. M. +1 more
We report spatially resolved (FWHM ∼ 3.″8-4.″6) mid-IR imaging observations of the planetary nebula (PN) NGC 7027 taken with the 2.5 m telescope on board the Stratospheric Observatory for Infrared Astronomy (SOFIA). Images of NGC 7027 were acquired at 6.3, 6.6, 11.1, 19.7, 24.2, 33.6, and 37.1 µ {{m}} using the Faint Object Infrared Camera f…
Compact E+A Galaxies as a Progenitor of Massive Compact Quiescent Galaxies at 0.2 < z < 0.8
Hwang, Ho Seong; Geller, Margaret J.; Damjanov, Ivana +5 more
We search the Sloan Digital Sky Survey and the Baryon Oscillation Sky Survey to identify ∼5500 massive compact quiescent galaxy candidates at 0.2 < z < 0.8. We robustly classify a subsample of 438 E+A galaxies based on their spectral properties and make this catalog publicly available. We examine sizes, stellar population ages, and kinematic…
Symbiotic Stars in X-Rays. III. Suzaku Observations
Nuñez, N. E.; Nelson, T.; Mukai, K. +2 more
We describe the X-ray emission as observed by Suzaku from five symbiotic stars that we selected for deep Suzaku observations after their initial detection with ROSAT, ASCA, and Swift. We find that the X-ray spectra of all five sources can be adequately fit with absorbed optically thin thermal plasma models, with either single- or multi-temperature…
UV Spectroscopy of Star-grazing Comets Within the 49 Ceti Debris Disk
Roberge, Aki; Miles, Brittany E.; Welsh, Barry
We present the analysis of time-variable Doppler-shifted absorption features in far-UV spectra of the unusual 49 Ceti debris disk. This nearly edge-on disk is one of the brightest known and is one of the very few containing detectable amounts of circumstellar (CS) gas as well as dust. In our two visits of Hubble Space Telescope STIS spectra, varia…
The Prevalence and Impact of Wolf-Rayet Stars in Emerging Massive Star Clusters
Massey, Philip; Johnson, Kelsey E.; Indebetouw, Rémy +1 more
We investigate Wolf-Rayet (WR) stars as a source of feedback contributing to the removal of natal material in the early evolution of massive star clusters. Despite previous work suggesting that massive star clusters clear out their natal material before the massive stars evolve into the WR phase, WR stars have been detected in several emerging mas…
Soft X-Ray Excess from Shocked Accreting Plasma in Active Galactic Nuclei
Tombesi, Francesco; Takahashi, Masaaki; Clark, Peter +2 more
We propose a novel theoretical model to describe the physical identity of the soft X-ray excess that is ubiquitously detected in many Seyfert galaxies, by considering a steady-state, axisymmetric plasma accretion within the innermost stable circular orbit around a black hole (BH) accretion disk. We extend our earlier theoretical investigations on …