Search Publications
Determination of the Mass of IGR J17091-3624 from "Spectro-temporal" Variations during the Onset Phase of the 2011 Outburst
Nandi, A.; Mandal, S.; Iyer, N.
The 2011 outburst of the black hole candidate IGR J17091-3624 followed the canonical track of state transitions along with the evolution of quasi-periodic oscillation (QPO) frequencies before it began exhibiting various variability classes similar to GRS 1915+105. We use this canonical evolution of spectral and temporal properties to determine the…
Herschel-ATLAS: the connection between star formation and AGN activity in radio-loud and radio-quiet active galaxies
Ivison, R. J.; Fritz, J.; Hardcastle, M. J. +6 more
We examine the relationship between star formation and active galactic nuclei (AGN) activity by constructing matched samples of local (0 < z < 0.6) radio-loud and radio-quiet AGN in the Herschel-Astrophysical Terahertz Large Area Survey fields. Radio-loud AGN are classified as high-excitation and low-excitation radio galaxies using their emi…
Signals of a light dark force in the galactic center
Weiner, Neal; Liu, Jia; Xue, Wei
Recent evidence for an excess of gamma rays in the GeV energy range about the Galactic Center have refocused attention on models of dark matter in the low mass regime ( m χ ≲ m Z /2). Because this is an experimentally well-trod energy range, it can be a challenge to develop simple models that explain this excess, consistent…
Helium and multiple populations in the massive globular cluster NGC 6266 (M 62)
Milone, A. P.
Recent studies suggest that the helium content of multiple stellar populations in globular clusters (GCs) is not uniform. The range of helium varies from cluster to cluster with more massive GCs having, preferentially, large helium spread. GCs with large helium variations also show extended-blue horizontal branch (HB). I exploit Hubble Space Teles…
The Spatial Distribution of the Young Stellar Clusters in the Star-forming Galaxy NGC 628
Cignoni, M.; Dale, D. A.; Calzetti, D. +21 more
We present a study of the spatial distribution of the stellar cluster populations in the star-forming galaxy NGC 628. Using Hubble Space Telescope broadband WFC3/UVIS UV and optical images from the Treasury Program LEGUS (Legacy ExtraGalactic UV Survey), we have identified 1392 potential young (≲ 100 Myr) stellar clusters within the galaxy using a…
Multiwavelength Observations of a Partially Eruptive Filament on 2011 September 8
Feng, L.; Cheng, X.; Guo, Y. +5 more
In this paper, we report our multiwavelength observations of a partial filament eruption event in NOAA active region (AR) 11283 on 8 September 2011. A magnetic null point and the corresponding spine and separatrix surface are found in the AR. Beneath the null point, a sheared arcade supports the filament along the highly complex and fragmented pol…
The High-mass Stellar Initial Mass Function in M31 Clusters
Bell, Eric F.; Dolphin, Andrew E.; Skillman, Evan D. +16 more
We have undertaken the largest systematic study of the high-mass stellar initial mass function (IMF) to date using the optical color-magnitude diagrams (CMDs) of 85 resolved, young (4 {Myr}\lt t\lt 25 {Myr}), intermediate mass star clusters (103-104 M⊙), observed as part of the Panchromatic Hubble Andromeda Treasur…
SN2014J gamma rays from the 56Ni decay chain
Wang, Wei; Diehl, Roland; Greiner, Jochen +7 more
Context. The detection and measurement of gamma-ray lines from the decay chain of 56Ni provides unique information about the explosion in supernovae. SN2014J at 3.3 Mpc is a sufficiently-nearby supernova of type Ia so that such measurements have been feasible with the gamma-ray spectrometer SPI on ESA's INTEGRAL gamma-ray observatory. <…
Broadband Observations of the Compton-thick Nucleus of NGC 3393
Harrison, F. A.; Stern, D.; Treister, E. +16 more
We present new Nuclear Spectroscopic Telescope Array (NuSTAR ) and Chandra observations of NGC 3393, a galaxy reported to host the smallest separation dual active galactic nuclei (AGN) resolved in the X-rays. While past results suggested a 150 pc separation dual AGN, three times deeper Chandra imaging, combined with adaptive optics and radio imagi…
The systematic search for z ≳ 5 active galactic nuclei in the Chandra Deep Field South
Schawinski, Kevin; Koss, Michael; Weigel, Anna K. +3 more
We investigate early black hole (BH) growth through the methodical search for z ≳ 5 active galactic nuclei (AGN) in the Chandra Deep Field South. We base our search on the Chandra 4-Ms data with flux limits of 9.1 × 10-18 (soft, 0.5-2 keV) and 5.5 × 10-17 erg s-1 cm-2 (hard, 2-8 keV). At z ∼ 5, this corr…