Search Publications
Analysis of Low Excitation HDO Transitions toward the High-mass Star-forming Regions G34.26+0.15, W51e1/e2, and W49N
Kulczak-Jastrzębska, Magda
We present observations of the ground state 10,1-00,0 rotational transition of HDO at 464.925 GHz and the 11,0-10,1 transition at 509.292 GHz, toward three high-mass star-forming regions: G34.26+0.15, W49N, and W51e1/e2, carried out with the Caltech Submillimeter Observatory. For th…
A Universal Transition in Atmospheric Diffusion for Hot Subdwarfs Near 18,000 K
Dalessandro, E.; Salaris, M.; Bedin, L. R. +6 more
In the color-magnitude diagrams of globular clusters, when the locus of stars on the horizontal branch extends to hot temperatures, discontinuities are observed at colors corresponding to ∼12,000 and ∼18,000 K. The former is the “Grundahl jump” that is associated with the onset of radiative levitation in the atmospheres of hot subdwarfs. The latte…
The Radial Distribution of Mono-metallicity Populations in the Galactic Disk as Evidence for Two-phase Disk Formation
Domínguez-Tenreiro, R.; Obreja, A.; Brook, C. B. +2 more
Recent determinations of the radial distributions of mono-metallicity populations (MMPs, I.e., stars in narrow bins in [Fe/H] within wider [α/Fe] ranges) by the SDSS-III/APOGEE DR12 survey cast doubts on the classical thin- and thick-disk dichotomy. The analysis of these observations led to the non-[α /Fe] enhanced populations splitting into MMPs …
Constraining the Dust Opacity Law in Three Small and Isolated Molecular Clouds
Di Francesco, J.; Sadavoy, S.; Kainulainen, J. +6 more
Density profiles of isolated cores derived from thermal dust continuum emission rely on models of dust properties, such as mass opacity, that are poorly constrained. With complementary measures from near-infrared extinction maps, we can assess the reliability of commonly used dust models. In this work, we compare Herschel-derived maps of the optic…
Time Evolution of Elemental Ratios in Solar Energetic Particle Events
Dalla, S.; Cohen, C. M. S.; Mewaldt, R. A. +1 more
Heavy ion ratio abundances in solar energetic particle (SEP) events, e.g., Fe/O, often exhibit decreases over time. Using particle instruments on the Advanced Composition Explorer, Solar and Heliospheric Observatory and Solar Terrestrial Relations Observatory spacecraft, we analyzed heavy ion data from 4 SEP events taking place between 2006 Decemb…
MAXI J1957+032: An Accreting Neutron Star Possibly in a Triple System
Ravi, V.
I present an optical characterization of the Galactic X-ray transient source MAXI J1957+032. This system flares by a factor of ≳104 every few hundred days, with each flare lasting ∼5 days. I identify its quiescent counterpart to be a late-K/early-M dwarf star at a distance of 5 ± 2 kpc. This implies that the peak 0.5{--}10 {keV} luminos…
CO-DARK Star Formation and Black Hole Activity in 3C 368 at Z = 1.131: Coeval Growth of Stellar and Supermassive Black Hole Masses
Riechers, D.; Stacey, G.; Lamarche, C. +7 more
We present the detection of four far-infrared fine-structure oxygen lines, as well as strong upper limits for the CO(2-1) and [N II] 205 µm lines, in 3C 368, a well-studied radio-loud galaxy at z = 1.131. These new oxygen lines, taken in conjunction with previously observed neon and carbon fine-structure lines, suggest a powerful active gala…
An Incipient Debris Disk in the Chamaeleon I Cloud
Hernández, J.; Ribas, Á.; McClure, M. K. +5 more
The point at which a protoplanetary disk becomes a debris disk is difficult to identify. To better understand this, here we study the ∼40 au separation binary T 54 in the Chamaeleon I cloud. We derive a K5 spectral type for T 54 A (which dominates the emission of the system) and an age of ∼2 Myr. However, the dust disk properties of T 54 are consi…
High-resolution X-Ray Spectroscopy of the Seyfert 1 Galaxy Mrk 1040. Revealing the Failed Nuclear Wind with Chandra
Behar, E.; Turner, T. J.; Kraemer, S. B. +6 more
High-resolution X-ray spectroscopy of the warm absorber in the nearby X-ray bright Seyfert 1 galaxy Mrk 1040 is presented. The observations were carried out in the 2013-2014 timeframe using the Chandra High Energy Transmission Grating with a total exposure of 200 ks. A multitude of absorption lines from Ne, Mg, and Si are detected from a wide vari…
JVLA Observations of IC 342: Probing Star Formation in the Nucleus
Goss, W. M.; Johnson, K. E.; Kepley, Amanda A. +2 more
IC 342 is a nearby, late-type spiral galaxy with a young nuclear star cluster surrounded by several giant molecular clouds. The IC 342 nuclear region is similar to the Milky Way and therefore provides an interesting comparison. We explore star formation in the nucleus using radio recombination line (RRL) and continuum emission at 5, 6.7, 33, and 3…