Search Publications
Differences in the AGN Populations of Groups and Clusters: Clues to AGN Evolution
Shen, Yue; Raychaudhury, Somak; Mulchaey, John S. +2 more
We combine optical and X-ray data for eight low-redshift (z~0.06) poor groups of galaxies from the XI (XMM-IMACS) Groups Project to study the AGN population in the group environment. Among ~140 group members, we identify five AGNs based on their optical emission lines. None of these optically selected AGNs are detected by XMM-Newton. One additiona…
A Spitzer IRAC Census of the Asymptotic Giant Branch Populations in Local Group Dwarfs. I. WLM
Skillman, Evan D.; Gehrz, Robert D.; Woodward, Charles E. +2 more
We present Spitzer IRAC observations at 3.6 and 4.5 µm along with optical data from the Local Group Galaxies Survey to investigate the evolved stellar population of the Local Group dwarf irregular galaxy WLM. These observations provide a nearly complete census of the AGB stars. We find that 39% of the infrared-detected AGB stars are not dete…
Dressing a Naked Quasar: Star Formation and Active Galactic Nucleus Feedback in HE 0450-2958
Feain, Ilana J.; Ekers, Ronald D.; Papadopoulos, Padelis P. +1 more
We present Australia Telescope Compact Array radio continuum observations of the quasar/galaxy system HE 0450-2958. An asymmetric triple linear morphology is observed, with the central radio component coincident with the quasar core and a second radio component associated with a companion galaxy at a projected distance of 7 kpc from the quasar. Th…
X-Ray-Emitting Ejecta of Supernova Remnant N132D
Reynolds, Stephen P.; Borkowski, Kazimierz J.; Hendrick, Sean P.
The brightest supernova remnant in the Magellanic Clouds, N132D, belongs to the rare class of oxygen-rich remnants, about a dozen objects that show optical emission from pure heavy-element ejecta. They originate in explosions of massive stars that produce large amounts of O, although only a tiny fraction of that O is found to emit at optical wavel…
Joint Hα and X-Ray Observations of Massive X-Ray Binaries. III. The Be X-Ray Binaries HDE 245770 = A0535+26 and X Persei
Gies, D. R.; Grundstrom, E. D.; Boyajian, T. S. +9 more
We present results from an Hα monitoring campaign of the Be X-ray binary systems HDE 245770 = A0535+26 and X Per. We use the Hα equivalent widths together with adopted values of the Be star effective temperature, disk inclination, and disk outer boundary to determine the half-maximum emission radius of the disk as a function of time. The observati…
High-Resolution X-Ray Spectroscopy of the Ultracompact LMXB Pulsar 4U 1626-67
Chakrabarty, Deepto; Schulz, Norbert S.; Cottam, Jean +2 more
We report results from four recent observations of the ultracompact LMXB pulsar 4U 1626-67. These observations obtained high-resolution X-ray spectra with Chandra HETGS and XMM RGS, allowing us to study in detail the prominent Ne and O emission-line complexes. The observations were spaced over a period of 3 yr, enabling us to monitor the line regi…
The Energy-dependent X-Ray Timing Characteristics of the Narrow-Line Seyfert 1 Mrk 766
Turner, T. J.; Papadakis, I.; Reeves, J. N. +3 more
We present the energy-dependent power spectral density (PSD) and cross spectral properties of Mrk 766, obtained from combining data obtained during an XMM-Newton observation spanning six revolutions in 2005 with data obtained from an XMM-Newton long look in 2001. The PSD shapes and rms-flux relations are found to be consistent between the 2001 and…
Localized Enhancements of Fe+10 Density in the Corona as Observed in Fe XI 789.2 nm during the 2006 March 29 Total Solar Eclipse
Morgan, Huw; Habbal, Shadia Rifai; Jaeggli, Sarah +5 more
The first ever image of the full solar corona in the Fe XI 789.2 nm spectral line was acquired during the total solar eclipse of 2006 March 29. Several striking features stand out in the processed image: (1) The emission extended out to at least 3 Rsolar in streamers. (2) A bubble-like structure, occupying a cone of about 45° and reachi…
The Case for Optically Thick High-Velocity Broad-Line Region Gas in Active Galactic Nuclei
Gaskell, C. Martin; Snedden, Stephanie A.
A combined analysis of the profiles of the main broad quasar emission lines in both Hubble Space Telescope and optical spectra shows that while the profiles of the strong UV lines are quite similar, there is frequently a strong increase in the Lyα/Hα ratio in the high-velocity gas. We show that the suggestion that the high-velocity gas is opticall…
Global Coronal Mass Ejections
Zhukov, Andrei N.; Veselovsky, Igor S.
Observations of the low solar corona in the extreme ultraviolet and in soft X-rays evidence a close relationship of coronal dimmings and coronal mass ejections (CMEs). Dimmings are usually interpreted as places of plasma evacuation during a CME. We characterize a CME by the apparent angular extent of associated dimmings above the solar limb and de…