Related papers: Analysis of a State Changing Supersoft X-ray Sourc…

We present a 100 yr optical lightcurve of the recently discovered supersoft X-ray source RX~J0019.8+2156 as deduced from photographic plates of Harvard and Sonneberg Observatory. Apart from the periodic orbital variations two different…

Resonant soft X-ray scattering (RSXS) is a powerful technique for probing both spatial and electronic structures within solid-state systems. We present a newly developed RSXS capability at beamline 13-3 of the Stanford Synchrotron Radiation…

In this paper we present a temporal and spectral analysis of X-ray data from the XMM and Chandra observations of the ultrasoft and variable Seyfert galaxy RX J1301.9+2747. In both observations the source clearly displays two distinct states…

We presented the results of an analysis of four XMM-Newton observations of the starburst galaxy IC342 taken over a four-year span from 2001 to 2005, with an emphasis on investigating the long-term flux and spectral variability of the X-ray…

We report the results of XMM-Newton and BeppoSAX observations of the radio and X-ray emitting star LS I +61 303, likely associated with the gamma-ray source 2CG 135+01 and recently detected also at TeV energies. The data include a long…

We present spectroscopy and photometry of the LMC supersoft binary system RX~J0513.9-6951. We derive a refined spectroscopic period of P$=0.761\pm0.004$~d, which is consistent with the value obtained from long term photometric monitoring…

Tidal disruption events (TDEs) are usually discovered at X-ray or optical wavelengths through their transient nature. A characteristic spectral feature of X-ray detected TDEs is a "supersoft" X-ray emission, not observed in any other…

The nearby galaxy NGC 300 is hosting two luminous transient supersoft X-ray sources with bolometric luminosities above 3x10^38 erg/s, assuming simple black-body spectra with temperatures around 60-70 eV. For one of these, SSS1, a periodic…

Soft Ultra-Luminous X-ray (ULXs) sources are a subclass of the ULXs that can switch from a supersoft spectral state, where most of the luminosity is emitted below 1 keV, to a soft spectral state with significant emission above 1 keV. In a…

We show that the model proposed by Esin, McClintock & Narayan (1997) for the low state, intermediate state and high state of the black hole soft X-ray transient, Nova Muscae 1991, is consistent with the spectral evolution of the black hole…

Cygnus X-3 is an enigmatic X-ray binary, that is both an exceptional accreting system and a cornerstone for the population synthesis studies. Prominent X-ray and radio properties follow a well-defined pattern, yet the physical reasons for…

We report on the spectral evolution of a new X-ray transient, MAXI J0556-332, observed by MAXI, Swift, and RXTE. The source was discovered on 2011 January 11 (MJD=55572) by MAXI Gas Slit Camera all-sky survey at (l,b)=(238.9deg, -25.2deg),…

We present Swift observations of the black hole X-ray transient, GRO J1655-40, during the recent outburst. With its multiwavelength capabilities and flexible scheduling, Swift is extremely well-suited for monitoring the spectral evolution…

We present results of a search for supernova remnants (SNRs) in archival Chandra images of M33. We have identified X-ray SNRs by comparing the list of Chandra, X-ray sources in M33 with tabulations of SNR candidates identified from (1)…

In the study of black-hole transients, an important problem that still needs to be answered is how the high-energy part of the spectrum evolves from the low-hard to the high-soft state, given that they have very different properties. Recent…

We investigate the spectral and temporal properties of ultra-luminous X-ray source (ULX) NGC~55~ULX1 using {\it Swift}, {\it XMM-Newton} and {\it NuSTAR} observations conducted during 2013--2021. In these observations, the source flux…

The luminosity range at and just below the 10^39 erg/s cut-off for defining ultraluminous X-ray sources (ULXs) is a little-explored regime. It none-the-less hosts a large number of X-ray sources, and has great potential for improving our…

We study three transient X-ray sources, that were bright in the central region of M31 galaxy in the year 2000. Observations with Chandra and XMM-Newton allowed us for the first time in the history of X-ray astronomy, to build light curves…

We present evidence for the presence of a weak compact jet during a soft X-ray state of Cygnus X-1. Very-high-resolution radio observations were taken with the VLBA, EVN and MERLIN during a hard-to-soft spectral state change, showing the…

The deep homogeneous survey of the large Local-Group spiral galaxy M 31 is a milestone project for X-ray astronomy, as it allows a detailed X-ray inventory of an archetypal low-star-formation-rate galaxy like our own. We present first…