Related papers: The Evolving XUV Absorber in NGC3516
It is thought that ultraluminous X-ray sources (ULXs) are mainly powered by super-Eddington accreting neutron stars or black holes as shown by recent discovery of X-ray pulsations and relativistic winds. This work presents a follow up study…
We report the detection of an absorbed central X-ray source and its strong, rapid variability in NGC4395, the least luminous Seyfert nucleus known. The X-ray source exhibits a number of flares with factors of 3-4 flux changes during a half…
Recent intensive monitoring campaigns of active galactic nuclei (AGN) have provided simultaneous X-ray, UV, and optical data of unprecedented quality. The observations reveal a strong correlation between the UV and optical variability, but…
In order to investigate the connection between the X-ray, UV and optical spectral line regions, we selected a sample of AGN which have the strong Fe K-alpha line and analyze the UV and optical spectral lines. Here we present an example of…
We observed Circinus X-1 twice during a newly reached low-flux phase near zero orbital phase using the High-Energy Transmission Grating Spectrometer (HETGS) onboard Chandra. In both observations the source did not show the P Cygni lines we…
Recent {\it ASCA} observations confirm the presence of X-ray absorption due to partially ionized gas in many Seyfert 1 galaxies; the so-called warm absorber. Constraints on the location of the warm material are presented with the conclusion…
Stellar soft X-ray ([1, 100] Angstrom) and Extreme Ultraviolet (also EUV, [100, 920] Angstrom; jointly, XUV) radiation affects the evolution and chemistry of exoplanet atmospheres. It is however uncertain to what extent the radiation's…
An overview of the results of observations for the transient X-ray pulsar 4U 0115+63, a member of a binary system with a Be star, since its discovery to the present day (~40 years) based on data from more than dozen observatories and…
We report the discovery of narrow X-ray absorption features from the dipping low-mass X-ray binary X 1624-490 during an XMM-Newton observation in 2001 February. The features are identified with the K alpha absorption lines of Fe xxv and Fe…
We present the first analysis of the X-ray warm absorber and nuclear obscuration in the Seyfert 1.8 galaxy ESO 113-G010. We used archival data from a 100 ks XMM-Newton observation made in 2005. From high resolution spectroscopy analysis of…
We present 0.5-8.0 keV Chandra observations of six bright quasars that represent extrema in quasar emission-line properties -- three quasars each with small and large blueshifts of the CIV emission line with respect to the systemic redshift…
We have observed the soft X-ray transient XTE J0421+56 in quiescence with XMM-Newton. The observed spectrum is highly unusual being dominated by a broad feature at 6.5 keV and can be modeled by a strongly absorbed continuum. The spectra of…
After 3 years of quiescence, the globular cluster NGC 6440 exhibited a bright transient X-ray source turning on in August 2001, as noted with the RXTE All-Sky Monitor. We carried out a short target of opportunity observation with the…
We present results of the Suzaku observation of the dipping, periodically bursting low mass X-ray binary XB 1323-619 in which we concentrate of the spectral evolution in dipping in the energy range 0.8 - 70 keV. It is shown that spectral…
We present a study of the variations in the absorbing column density of 25 X-ray defined Seyfert 2 galaxies, as inferred from hard X-ray observations, on timescales from months to several years. We show that a significant variation of N$_H$…
We present results from a coordinated FUSE, HST/STIS and Chandra campaign to study intrinsic UV and X-ray absorption in the outflow of the Seyfert 1 galaxy NGC 7469. Previous non-simultaneous observations of this outflow found two distinct…
We present the first X-ray detection of resonant absorption from warm/hot local gas either in our Galaxy, or in the Intergalactic space surrounding our Galaxy, along the line of sight toward the blazar PKS 2155-304. The Chandra HRCS-LETG…
Mrk 590 is a Changing Look AGN currently in an unusual repeat X-ray and UV flaring state. Here, we report on deep X-ray observations with XMM-Newton, NuSTAR, and NICER, obtained at a range of X-ray flux levels. We detect a prominent soft…
In recent years it has become clear that understanding the absorption present in AGN is essential given its bearing on unification models. We present the most recent XMM-Newton observation of Mrk 6, with the goal of understanding the nature…
In a continuing survey of active galactic nuclei observed by the Far Ultraviolet Spectroscopic Explorer, we provide a deeper analysis of intrinsic absorption features found in 35 objects. Our survey is for low-redshift and…