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Short versus Long and Collapsars versus Non-collapsars: A Quantitative Classification of Gamma-Ray Bursts
Piran, Tsvi; Bromberg, Omer; Nakar, Ehud +1 more
Gamma-ray bursts (GRBs) are traditionally divided into long and short according to their durations (lg2 s). It was generally believed that this reflects a different physical origin: collapsars (long) and non-collapsars (short). We have recently shown that the duration distribution of collapsars is flat, namely, independent of the duration, at shor…
Accretion Rates for T Tauri Stars Using Nearly Simultaneous Ultraviolet and Optical Spectra
Edwards, Suzan; Brown, Alexander; Calvet, Nuria +9 more
We analyze the accretion properties of 21 low-mass T Tauri stars using a data set of contemporaneous near-UV (NUV) through optical observations obtained with the Hubble Space Telescope Imaging Spectrograph and the ground-based Small and Medium Aperture Research Telescope System, a unique data set because of the nearly simultaneous broad wavelength…
Dust in the Polar Region as a Major Contributor to the Infrared Emission of Active Galactic Nuclei
Hönig, S. F.; Kishimoto, M.; Tristram, K. R. W. +7 more
Dust around active galactic nuclei (AGNs) is distributed over a wide range of spatial scales and can be observed in the infrared (IR). It is generally assumed that the distribution on parsec scales forms a geometrically and optically thick entity in the equatorial plane around the accretion disk and broad-line region—dubbed "dust torus"—that emits…
The Bimodal Metallicity Distribution of the Cool Circumgalactic Medium at z <~ 1
Lehner, N.; Prochaska, J. X.; Fox, A. J. +7 more
We assess the metal content of the cool (~104 K) circumgalactic medium (CGM) about galaxies at z <~ 1 using an H I-selected sample of 28 Lyman limit systems (LLS; defined here as absorbers with 16.2 <~ log N H I <~ 18.5) observed in absorption against background QSOs by the Cosmic Origins Spectrograph on board the H…
Stellar Kinematics of z ~ 2 Galaxies and the Inside-out Growth of Quiescent Galaxies
van Dokkum, Pieter G.; Franx, Marijn; Bezanson, Rachel +6 more
Using stellar kinematics measurements, we investigate the growth of massive, quiescent galaxies from z ~ 2 to today. We present X-Shooter spectra from the UV to NIR and dynamical mass measurements of five quiescent massive (>1011 M ⊙) galaxies at z ~ 2. This triples the sample of z > 1.5 galaxies with well-constrained (…
The SL2S Galaxy-scale Lens Sample. IV. The Dependence of the Total Mass Density Profile of Early-type Galaxies on Redshift, Stellar Mass, and Size
Treu, Tommaso; Gavazzi, Raphaël; Marshall, Philip J. +4 more
We present optical and near-infrared spectroscopy obtained at Keck, Very Large Telescope, and Gemini for a sample of 36 secure strong gravitational lens systems and 17 candidates identified as part of the Strong Lensing Legacy Survey. The deflectors are massive early-type galaxies in the redshift range zd = 0.2-0.8, while the lensed sou…
Stellar Diameters and Temperatures. III. Main-sequence A, F, G, and K Stars: Additional High-precision Measurements and Empirical Relations
von Braun, Kaspar; White, Russel; Goldfinger, P. J. +13 more
Based on CHARA Array measurements, we present the angular diameters of 23 nearby, main-sequence stars, ranging from spectral types A7 to K0, 5 of which are exoplanet host stars. We derive linear radii, effective temperatures, and absolute luminosities of the stars using Hipparcos parallaxes and measured bolometric fluxes. The new data are combined…
Discovery, Progenitor and Early Evolution of a Stripped Envelope Supernova iPTF13bvn
Kulkarni, S. R.; Cenko, S. Bradley; Wheeler, J. Craig +26 more
The intermediate Palomar Transient Factory reports our discovery of a young supernova, iPTF13bvn, in the nearby galaxy, NGC 5806 (22.5 Mpc). Our spectral sequence in the optical and infrared suggests a Type Ib classification. We identify a blue progenitor candidate in deep pre-explosion imaging within a 2σ error circle of 80 mas (8.7 pc). The cand…
The Structure of the Milky Way's Hot Gas Halo
Bregman, Joel N.; Miller, Matthew J.
The Milky Way's million degree gaseous halo contains a considerable amount of mass that, depending on its structural properties, can be a significant mass component. In order to analyze the structure of the Galactic halo, we use XMM-Newton Reflection Grating Spectrometer archival data and measure O VII Kα absorption-line strengths toward 26 active…
HST Spectral Mapping of L/T Transition Brown Dwarfs Reveals Cloud Thickness Variations
Burrows, Adam; Apai, Dániel; Radigan, Jacqueline +3 more
Most directly imaged giant exoplanets are fainter than brown dwarfs with similar spectra. To explain their relative underluminosity, unusually cloudy atmospheres have been proposed. However, with multiple parameters varying between any two objects, it remained difficult to observationally test this idea. We present a new method, sensitive time-res…