Search Publications
Illuminating the Darkest Gamma-Ray Bursts with Radio Observations
Menten, K. M.; Greiner, J.; Berger, E. +21 more
We present X-ray, optical, near-infrared (IR), and radio observations of gamma-ray bursts (GRBs) 110709B and 111215A, as well as optical and near-IR observations of their host galaxies. The combination of X-ray detections and deep optical/near-IR limits establish both bursts as "dark." Sub-arcsecond positions enabled by radio detections lead to ro…
On the Redshift of the Very High Energy Blazar 3C 66A
Furniss, A.; Williams, D. A.; Prochaska, J. X. +2 more
As a bright gamma-ray source, 3C 66A is of great interest to the high-energy astrophysics community, having a potential for placing cosmological constraints on models for the extragalactic background light (EBL) and the processes which contribute to this photon field. No firm spectroscopic redshift measurement has been possible for this blazar due…
Deep Multi-telescope Photometry of NGC 5466. I. Blue Stragglers and Binary Systems
Dalessandro, E.; Bellazzini, M.; Beccari, G. +4 more
We present a detailed investigation of the radial distribution of blue straggler star (BSS) and binary populations in the Galactic globular cluster NGC 5466, over the entire extension of the system. We used a combination of data acquired with the Advanced Camera for Survey on board the Hubble Space Telescope, the LBC-blue mounted on the Large Bino…
A Double-peaked Outburst of A 0535+26 Observed with INTEGRAL, RXTE, and Suzaku
Klochkov, D.; Santangelo, A.; Wilms, J. +18 more
The Be/X-ray binary A 0535+26 showed a normal (type I) outburst in 2009 August. It is the fourth in a series of normal outbursts associated with the periastron, but is unusual because it presented a double-peaked light curve. The two peaks reached a flux of ~450 mCrab in the 15-50 keV range. We present results of the timing and spectral analysis o…
Direct Determination of the HF/H2 Abundance Ratio in Interstellar Gas
Neufeld, D. A.; Richter, M. J.; Indriolo, Nick +1 more
We report the first detection of the v = 1-0, R(0) ro-vibrational transition of HF at 2.499385 µm arising from interstellar gas. The line is seen in absorption toward three background sources—HD 154368, Elias 29, and AFGL 2136 IRS 1—all of which have reported H2 column densities determined from observations of H2. This …
Using Megamaser Disks to Probe Black Hole Accretion
Greene, Jenny E.; den Brok, Mark; Peng, Chien Y. +7 more
We examine the alignment between H2O megamaser disks on subparsec scales with circumnuclear disks and bars on <500 pc scales observed with the Hubble Space Telescope (HST)/WFC3. The HST imaging reveals young stars, indicating the presence of gas. The megamaser disks are not well aligned with the circumnuclear bars or disks as traced …
The He II Post-reionization Epoch: HST/COS Observations of the Quasar HS1700+6416
Shull, J. Michael; Syphers, David
The reionization epoch of singly ionized helium (He II) is believed to start at redshifts z ~ 3.5-4 and be nearly complete by z ~= 2.7. We explore the post-reionization epoch with far-ultraviolet spectra of the bright, high-redshift quasar HS1700+6416 taken by the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope, which show strong H…
The Molecular Gas Density in Galaxy Centers and how it Connects to Bulges
Drory, Niv; Fisher, David B.; Bolatto, Alberto +3 more
In this paper we present gas density, star formation rate (SFR), stellar masses, and bulge-disk decompositions for a sample of 60 galaxies. Our sample is the combined sample of the BIMA SONG, CARMA STING, and PdBI NUGA surveys. We study the effect of using CO-to-H2 conversion factors that depend on the CO surface brightness, and also th…
Recurrent Two-sided Loop-type Jets due to a Bipole Emerging below Transequatorial Loops
Yang, Bo; Yang, Jiayan; Bi, Yi +3 more
We report four successive two-sided loop-type jets centered around a small bipole emerging below transequatorial interconnecting loops (TILs). They occurred at the very first emerging stage of the bipole in a short recurrent period of only 12 minutes. During this term, the emerging flux consisted of a main bipole, but showed a mixed-polarity field…
The Star Cluster System in the Nearby Starburst Galaxy M82
Hwang, Narae; Lee, Myung Gyoon; Lim, Sungsoon
We present a photometric study of star clusters in the nearby starburst galaxy M82 based on the UBVI-, YJ- and H-band Hubble Space Telescope images. We find 1105 star clusters with V < 23 mag. Of those, 1070 are located in the disk region, while 35 star clusters are in the halo region. The star clusters in the disk are composed of a dominant bl…