Search Publications
Observation of Solar Wind Charge Exchange Emission from Exospheric Material in and Outside Earth's Magnetosheath 2008 September 25
Lepri, S. T.; Kuntz, K. D.; Snowden, S. L. +4 more
A long XMM-Newton exposure is used to observe solar wind charge exchange (SWCX) emission from exospheric material in and outside Earth's magnetosheath. The light curve of the O VII (0.5-0.62 keV) band is compared with a model for the expected emission, and while the emission is faint and the light curve has considerable scatter, the correlation is…
Probing The Origins of the C IV and Fe Kα Baldwin Effects
Brandt, W. N.; Wu, Jian; Schneider, Donald P. +3 more
We use UV/optical and X-ray observations of 272 radio-quiet Type 1 active galactic nuclei and quasars to investigate the C IV Baldwin Effect (BEff). The UV/optical spectra are drawn from the Hubble Space Telescope, International Ultraviolet Explorer and Sloan Digital Sky Survey archives. The X-ray spectra are from the Chandra and XMM-Newton archiv…
A High Yield of New Sightlines for the Study of Intergalactic Helium: Far-UV-Bright Quasars from the SDSS, GALEX, AND HST
Anderson, Scott F.; Schneider, Donald P.; York, Donald G. +6 more
Investigations of He II Lyα (304 Å rest-frame) absorption toward a half-dozen quasars at z ~ 3-4 have demonstrated the great potential of helium studies of the intergalactic medium, but the current critically small sample size of clean sightlines for the He II Gunn-Peterson test limits confidence in cosmological inferences, and a larger sample is …
The Correlation Between X-ray and UV Properties of BAL QSOs
Zhang, Kai; Wang, Tinggui; Wang, Junxian +4 more
We compile a large sample of broad absorption line (BAL) quasars with X-ray observations from the XMM-Newton archive data and Sloan Digital Sky Survey Data Release 5. The sample consists of 41 BAL QSOs. Among 26 BAL quasars detected in X-ray, spectral analysis is possible for 12 objects. X-ray absorption is detected in all of them. Complementary t…
Non-LTE Modeling of the Near-Ultraviolet Band of Late-Type Stars
Hauschildt, P. H.; Short, C. Ian
We investigate the ability of both LTE and non-LTE (NLTE) models to fit the near-UV band absolute flux distribution, f λ(λ), and individual spectral line profiles of three standard stars for which high-quality spectrophotometry and high-resolution spectroscopy are available: The Sun (G2 V), Arcturus (K2 III), and Procyon (F5 IV-V). We i…
Xmm-Newton Discovery of 2.6 s Pulsations in the Soft Gamma-Ray Repeater SGR 1627-41
Tiengo, A.; Götz, D.; Mereghetti, S. +6 more
After nearly a decade of quiescence, the soft gamma-ray repeater SGR 1627-41 reactivated on 2008 May 28 with a bursting episode followed by a slowly decaying enhancement of its persistent emission. To search for the still unknown spin period of this SGR taking advantage of its high flux state, we performed on 2008 September 27-28 a 120 ks long X-r…
Hubble Space Telescope Images and KPNO Spectroscopy of the Binary Black Hole Candidate SDSS J153636.22+044127.0
Lauer, Tod R.; Boroson, Todd A.
We present Hubble Space Telescope WFPC2/PC images and KPNO 4 m long-slit spectroscopy of the QSO SDSS J153636.22+044127.0, which we advanced as a candidate binary supermassive black hole. The images reveal a close companion coincident with the radio source identified by Wrobel & Laor. It appears to be consistent with a Mg ~ -21.4 el…
Effect of Polarimetric Noise on the Estimation of Twist and Magnetic Energy of Force-Free Fields
Gosain, Sanjay; Joshi, Jayant; Tiwari, Sanjiv Kumar +1 more
The force-free parameter α, also known as helicity parameter or twist parameter, bears the same sign as the magnetic helicity under some restrictive conditions. The single global value of α for a whole active region gives the degree of twist per unit axial length. We investigate the effect of polarimetric noise on the calculation of global α value…
A New Sample of Buried Active Galactic Nuclei Selected from the Second XMM-Newton Serendipitous Source Catalogue
Awaki, Hisamitsu; Terashima, Yuichi; Noguchi, Kazuhisa
We present the results of X-ray spectral analysis of 22 active galactic nuclei (AGNs) with a small scattering fraction selected from the Second XMM-Newton Serendipitous Source Catalogue using hardness ratios. They are candidates of buried AGNs, since a scattering fraction, which is a fraction of scattered emission by the circumnuclear photoionized…
A Strong Excess in the 20-100 keV Emission of NGC 1365
Maiolino, R.; Bianchi, S.; Elvis, M. +8 more
We present a new Suzaku observation of the obscured active galactic nucleus in NGC 1365, revealing an unexpected excess of X-rays above 20 keV of at least a factor ~2 with respect to the extrapolation of the best-fitting 3-10 keV model. Additional Swift-BAT and Integral-IBIS observations show that the 20-100 keV is concentrated within ~1.5 arcmin …