Search Publications
A Dust-scattering Halo of 4U 1630-47 Observed with Chandra and Swift: New Constraints on the Source Distance
Maccarone, T. J.; Tomsick, J. A.; Kalemci, E.
We have observed the Galactic black hole transient 4U 1630-47 during the decay of its 2016 outburst with Chandra and Swift to investigate the properties of the dust-scattering halo created by the source. The scattering halo shows a structure that includes a bright ring between 80″ and 240″ surrounding the source, and a continuous distribution beyo…
Gravitationally Unstable Condensations Revealed by ALMA in the TUKH122 Prestellar Core in the Orion A Cloud
Sanhueza, Patricio; Choi, Minho; Tatematsu, Ken'ichi +5 more
We have investigated the TUKH122 prestellar core in the Orion A cloud using ALMA 3 mm dust continuum, N2H+ (J = 1-0), and CH3OH ({J}K={2}K-{1}K) molecular-line observations. Previous studies showed that TUKH122 is likely on the verge of star formation because the turbulence is almos…
CO in Protostars (COPS): Herschel-SPIRE Spectroscopy of Embedded Protostars
Larson, Rebecca L.; Lee, Jeong-Eun; Bouwman, Jeroen +13 more
We present full spectral scans from 200 to 670 µm of 26 Class 0+I protostellar sources obtained with Herschel-SPIRE as part of the “COPS-SPIRE” Open Time program, complementary to the DIGIT and WISH Key Programs. Based on our nearly continuous, line-free spectra from 200 to 670 µm, the calculated bolometric luminosities (L bol
A Stealth CME Bracketed between Slow and Fast Wind Producing Unexpected Geoeffectiveness
Wang, Rui; Liu, Ying D.; Hu, Huidong +2 more
We investigate how a weak coronal mass ejection (CME) launched on 2016 October 8 without obvious signatures in the low corona produced a relatively intense geomagnetic storm. Remote sensing observations from SDO, STEREO, and SOHO and in situ measurements from Wind are employed to track the CME from the Sun to the Earth. Using a graduated cylindric…
Variable Nature of Magnetically Driven Ultra-fast Outflows
Behar, Ehud; Tombesi, Francesco; Shrader, Chris +3 more
Among a number of active galactic nuclei that drive ionized outflows in X-rays, a low-redshift (z = 0.184) quasar, PDS 456, is long known to exhibit one of the exemplary ultra-fast outflows (UFOs). However, the physical process of acceleration mechanisms is yet to be definitively constrained. In this work, we model the variations of the Fe K UFO p…
Probing the Inner Disk Emission of the Herbig Ae Stars HD 163296 and HD 190073
Monnier, John D.; Kraus, Stefan; Le Bouquin, Jean-Baptiste +16 more
The physical processes occurring within the inner few astronomical units of protoplanetary disks surrounding Herbig Ae stars are crucial to setting the environment in which the outer planet-forming disk evolves and put critical constraints on the processes of accretion and planet migration. We present the most complete published sample of high ang…
Seasonal Evolution of Titan's Stratosphere Near the Poles
Flasar, F. M.; Lavvas, P.; Coustenis, A. +5 more
In this Letter, we report the monitoring of seasonal evolution near Titan’s poles. We find Titan’s south pole to exhibit since 2010 a strong temperature decrease and a dramatic enhancement of several trace species such as complex hydrocarbons and nitriles (HC3N and C6H6 in particular) previously only observed at hi…
A Model Connecting Galaxy Masses, Star Formation Rates, and Dust Temperatures across Cosmic Time
Conroy, Charlie; Johnson, Benjamin D.; Loeb, Abraham +2 more
We investigate the evolution of dust content in galaxies from redshifts z = 0 to z = 9.5. Using empirically motivated prescriptions, we model galactic-scale properties—including halo mass, stellar mass, star formation rate, gas mass, and metallicity—to make predictions for the galactic evolution of dust mass and dust temperature in main-sequence g…
The Age of the Old Metal-poor Globular Cluster NGC 6397 Using WFC3/IR Photometry
Brown, Thomas M.; Gennaro, Mario; Cohen, Roger E. +2 more
Globular clusters (GCs) in the Milky Way represent the ideal laboratory to establish the age of the oldest stellar populations and to measure the color-magnitude relation of stars. Infrared (IR) photometry of these objects provides a new opportunity to accomplish this task. In particular, at low stellar masses, the stellar main sequence (MS) in an…
A High-precision Trigonometric Parallax to an Ancient Metal-poor Globular Cluster
Riess, A.; Brown, T. M.; Casertano, S. +5 more
Using the Wide Field Camera 3 (WFC3) on the Hubble Space Telescope (HST), we have obtained a direct trigonometric parallax for the nearest metal-poor globular cluster, NGC 6397. Although trigonometric parallaxes have been previously measured for many nearby open clusters, this is the first parallax for an ancient metal-poor population—one that is …