Search Publications
General Physical Properties of Gamma-Ray-emitting Narrow-line Seyfert 1 Galaxies
Ajello, M.; Fabian, A. C.; Brenneman, L. +4 more
We present the results of a detailed multiwavelength study of a sample of 16 narrow-line Seyfert 1 (NLSy1) galaxies known in γ-rays so far. This includes a focused X-ray spectral analysis, to compare them with a more general NLSy1 population, and a broadband spectral energy distribution (SED) modeling considering the leptonic radiative processes t…
A Photometric and Spectroscopic Investigation of the DB White Dwarf Population Using SDSS and Gaia Data
Genest-Beaulieu, C.; Bergeron, P.
We present a comprehensive analysis of DB white dwarfs drawn from the Sloan Digital Sky Survey, based on model fits to ugriz photometry and medium-resolution spectroscopy from the Sloan Digital Sky Survey. We also take advantage of the exquisite trigonometric parallax measurements recently obtained by the Gaia mission. Using the so-called photomet…
A Radio Source Coincident with the Superluminous Supernova PTF10hgi: Evidence for a Central Engine and an Analog of the Repeating FRB 121102?
Berger, E.; Chatterjee, S.; Cordes, J. M. +9 more
We present the detection of an unresolved radio source coincident with the position of the Type I superluminous supernova (SLSN) PTF10hgi (z = 0.098) about 7.5 yr post-explosion, with a flux density of F ν (6 GHz) ≈ 47.3 µJy and a luminosity of L ν (6 GHz) ≈ 1.1 × 1028 erg s-1 Hz-1. Th…
Aggregate Hazes in Exoplanet Atmospheres
de Pater, Imke; Morley, Caroline V.; Gao, Peter +1 more
Photochemical hazes have frequently been used to interpret exoplanet transmission spectra that show an upward slope toward shorter wavelengths and weak molecular features. While previous studies have only considered spherical haze particles, photochemical hazes composed of hydrocarbon aggregate particles are common throughout the solar system. We …
The COS CGM Compendium. III. Metallicity and Physical Properties of the Cool Circumgalactic Medium at z ≲ 1
Lehner, Nicolas; Howk, J. Christopher; O'Meara, John M. +3 more
We characterize the metallicities and physical properties of cool, photoionized gas in a sample of 152 z ≲ 1 strong Lyα forest systems (SLFSs, absorbers with 15 < log N H I < 16.2). The sample is drawn from our Cosmic Origins Spectrograph (COS) circumgalactic medium compendium (CCC), an ultraviolet survey of H I-selected circumga…
Varstrometry for Off-nucleus and Dual Sub-Kpc AGN (VODKA): How Well Centered Are Low-z AGN?
Shen, Yue; Hwang, Hsiang-Chih; Liu, Xin +1 more
Off-nucleus active galactic nuclei (AGN) can be signposts of inspiraling supermassive black holes (SMBHs) on galactic scales, or accreting SMBHs recoiling after the coalescence of an SMBH binary or slingshot from three-body interactions. Because of the stochastic variability of AGN, the measured photocenter of an unresolved AGN-host system will di…
An Initial Overview of the Extent and Structure of Recent Star Formation within the Serpens Molecular Cloud Using Gaia Data Release 2
Herczeg, Gregory J.; Jose, Jessy; Johnstone, Doug +7 more
The dense clusters within the Serpens Molecular Cloud are among the most active regions of nearby star formation. In this paper, we use Gaia DR2 parallaxes and proper motions to statistically measure ∼1167 kinematic members of Serpens, few of which have been previously identified, to evaluate the star formation history of the complex. The optical …
A Gaia-Enceladus Analog in the EAGLE Simulation: Insights into the Early Evolution of the Milky Way
Helmi, Amina; Tissera, Patricia B.; Bignone, Lucas A.
We identify a simulated Milky Way analog in the EAGLE suite of cosmological hydrodynamical simulations. This galaxy not only shares similar global properties as the Milky Way, but was specifically selected because its merger history resembles that currently known for the Milky Way. In particular we find that this Milky Way analog has experienced i…
Evidence for the Third Stellar Population in the Milky Way’s Disk
Beers, Timothy C.; Lee, Young Sun; Carollo, Daniela +6 more
The Milky Way is a unique laboratory in which stellar properties can be measured and analyzed in detail. In particular, stars in the older populations encode information on the mechanisms that led to the formation of our Galaxy. In this article, we analyze the kinematics, spatial distribution, and chemistry of a large number of stars in the solar …
The Near-ultraviolet Continuum Radiation in the Impulsive Phase of HF/GF-type dMe Flares. I. Data
Kowalski, Adam F.; Hawley, Suzanne L.; Valenti, Jeff A. +8 more
We present near-UV (NUV) flare spectra from the Hubble Space Telescope (HST)/Cosmic Origins Spectrograph during two moderate-amplitude U-band flares on the dM4e star GJ 1243. These spectra are some of the first accurately flux-calibrated, NUV flare spectra obtained over the impulsive phase in M dwarf flares. We observed these flares with a fleet o…