Search Publications
Caltech-NRAO Stripe 82 Survey (CNSS). V. AGNs That Transitioned to Radio-loud State
Gromadzki, Mariusz; Hallinan, Gregg; Ishwara-Chandra, C. H. +6 more
A recent multiyear Caltech-NRAO Stripe 82 Survey revealed a group of objects that appeared as new radio sources after >5-20 yr of absence. They are transient phenomena with respect to the Faint Images of the Radio Sky at Twenty Centimeters survey and constitute the first unbiased sample of renewed radio activity. Here we present a follow-up, ra…
Hybrid Comptonization and Electron-Positron Pair Production in the Black-hole X-Ray Binary MAXI J1820+070
Poutanen, Juri; Zdziarski, Andrzej A.; Szanecki, Michał +6 more
We study X-ray and soft gamma-ray spectra from the hard state of the accreting black-hole binary MAXI J1820+070. We perform an analysis of two joint spectra from NuSTAR and INTEGRAL, covering the range of 3-650 keV, and of an average joint spectrum over the rise of the hard state, covering the 3-2200 keV range. The spectra are well modeled by Comp…
Dynamical Analysis of the Dark Matter and Central Black Hole Mass in the Dwarf Spheroidal Leo I
Gebhardt, Karl; Zeimann, Greg; Thomas, Jens +4 more
We measure the central kinematics for the dwarf spheroidal galaxy Leo I using integrated-light measurements and previously published data. We find a steady rise in the velocity dispersion from 300″ into the center. The integrated-light kinematics provide a velocity dispersion of 11.76 ± 0.66 km s-1 inside 75″. After applying appropriate…
A Blueprint for the Milky Way's Stellar Populations. III. Spatial Distributions and Population Fractions of Local Halo Stars
Beers, Timothy C.; An, Deokkeun
We analyze the observed spatial, chemical and dynamical distributions of local metal-poor stars, based on photometrically derived metallicity and distance estimates along with proper motions from the Gaia mission. Along the Galactic prime meridian, we identify stellar populations with distinct properties in the metallicity versus rotational veloci…
Robotic Reverberation Mapping of the Southern Seyfert NGC 3783
Onken, Christopher A.; Bentz, Misty C.; Valluri, Monica +1 more
We present spectroscopic and photometric monitoring of NGC 3783 conducted throughout the first half of 2020. Time delays between the continuum variations and the response of the broad optical emission lines were clearly detected, and we report reverberation measurements for Hβ, He II λ4686, Hγ, and Hδ. From the time delay in the broad Hβ emission …
Thermal Emission and Radioactive Lines, but No Pulsar, in the Broadband X-Ray Spectrum of Supernova 1987A
Fransson, Claes; Alp, Dennis; Larsson, Josefin
Supernova 1987A offers a unique opportunity to study an evolving supernova in unprecedented detail over several decades. The X-ray emission is dominated by interactions between the ejecta and the circumstellar medium, primarily the equatorial ring (ER). We analyze 3.3 Ms of NuSTAR data obtained between 2012 and 2020, and two decades of XMM-Newton …
Compact Starburst Galaxies with Fast Outflows: Central Escape Velocities and Stellar Mass Surface Densities from Multiband Hubble Space Telescope Imaging
Moustakas, John; Coil, Alison L.; Rudnick, Gregory H. +21 more
We present multiband Hubble Space Telescope imaging that spans rest-frame near-ultraviolet through near-infrared wavelengths ( ${\lambda }_{\mathrm{rest}}=0.3$ -1.1 µm) for 12 compact starburst galaxies at z = 0.4-0.8. These massive galaxies ( ${{ \mathcal M }}_{* }\sim {10}^{11}\,{{ \mathcal M }}_{\odot }$ ) are driving very fast outflows (…
Pursuing the Origin of the Gamma Rays in RX J1713.7-3946 Quantifying the Hadronic and Leptonic Components
Inoue, Tsuyoshi; Tachihara, Kengo; Fukui, Yasuo +5 more
We analyzed the TeV gamma-ray image of a supernova remnant RX J1713.7-3946 (RX J1713) through a comparison with the interstellar medium (ISM) and nonthermal X-rays. The gamma-ray data sets at two energy bands of >2 TeV and >250-300 GeV were obtained with H.E.S.S. and utilized in the analysis. We employed a new methodology, which assumes that…
Deciphering the Kinematic Structure of the Small Magellanic Cloud through Its Red Giant Population
van der Marel, Roeland P.; Kallivayalil, Nitya; Zivick, Paul
We present a new kinematic model for the Small Magellanic Cloud (SMC), using data from the Gaia Data Release 2 catalog. We identify a sample of astrometrically well-behaved red giant (RG) stars belonging to the SMC and cross-match with publicly available radial velocity (RV) catalogs. We create a 3D spatial model for the RGs, using RR Lyrae for di…
An Exquisitely Deep View of Quenching Galaxies through the Gravitational Lens: Stellar Population, Morphology, and Ionized Gas
Richard, Johan; Zibetti, Stefano; Brammer, Gabriel B. +6 more
This work presents an in-depth analysis of four gravitationally lensed red galaxies at z = 1.6-3.2. The sources are magnified by factors of 2.7-30 by foreground clusters, enabling spectral and morphological measurements that are otherwise challenging. Our sample extends below the characteristic mass of the stellar mass function and is thus more re…