Related papers: X-Ray Off States and Optical Variability in CAL 83

We have studied the very long-term temporal properties of the optical emission from Be X-ray binaries (BeX) in the Small Magellanic Cloud over a ~ 16 yr baseline, using light curves from the MACHO and OGLE databases. All the BeX in our…

We have conducted a 3-month program of simultaneous optical, soft and hard X-ray monitoring of the LMXB 4U1636-536/V801 Ara using the SMARTS 1.3m telescope and archival RXTE/ASM and Swift/XRT data. 4U1636-536 has been exhibiting a large…

Using the 9 years of continuous data now available from the Burst And Transient Source Experiment (BATSE) aboard CGRO, we have measured orbital periods and produced folded lightcurves for 8 High Mass X-ray Binaries (HMXB). Given the length…

In this study we revisit public data on the supersoft X-ray source CAL 83 in the Large Magellanic Cloud. A significant part of our analysis is focused on XMM-Newton X-ray observations, in which updated data reduction procedures and quality…

Long-term variations are well-known in Be X-ray binaries, and are attributed to non-orbital changes in the structure of the Be circumstellar (equatorial) disc. However, the timescales involved are so long (tens of days, to years) that…

XSS J12270-4859 (henceforth J12270) is the first low-mass X-ray binary to exhibit a transition, taking place at the end of 2012, from an X-ray active state to a radio pulsar state. The X-ray emission based on archival XMM-Newton…

The variable source OGLE-UCXB-01 is the first OGLE-discovered ultracompact X-ray binary (UCXB). The 12-year long-term OGLE optical photometry of this source shows a period of P= 12.8 min and a fast period decreasing rate Pdot= -9.2E-11 s…

Long-term X-ray modulations on timescales from tens to hundreds of days have been widely studied for X-ray binaries located in the Milky Way and the Magellanic Clouds. For other nearby galaxies, only the most luminous X-ray sources can be…

SAX J2103.5+4545 is the Be/X-ray binary with the shortest orbital period. It shows extended bright and faint X-ray states that last for a few hundred days. The main objective of this work is to investigate the relationship between the X-ray…

We present the results of a 17 ks Chandra ACIS-S observation of the nearby dwarf spiral galaxy NGC 4395. Chandra affords the first high-quality, broadband X-ray detection of the active nucleus of this object that is uncontaminated by nearby…

We present results on parallaxes, magnitudes and proper motions for 17 optically identified massive X-ray binaries (MXRB) which were observed during the Hipparcos astrometry mission. This sample includes the sources detected in the…

We have detected a transient X-ray source in the M31 bulge through a continuing monitoring campaign with the Chandra ACIS-I camera. The source was detected at R.A.=00:42:33.428 +/- 0.11'', Dec.=+41:17:03.37 +/- 0.11'' in only a single…

This paper reports X-ray spectral observations of a relatively nearby z = 0.048 BL Lacertae (BL Lac) object 1ES1959+650, which is a potential TeV emitter. The observations include 31 short pointings made by the Unconventional Stellar Aspect…

We present a 50 ks Chandra ACIS-I X-ray observation of the Bower et al. VLA archival field. The observations reach a limiting sensitivity of ~1E-4 counts/s, corresponding to a flux of a few times 1E-15 erg/s/cm^2 for the models we explore.…

Four VY Scl-type nova-like systems were observed in X-rays both during the low and the high optical states. They are BZ Cam, MV Lyr, TT Ari, and V794 Aql. Using archival ROSAT, Swift and SUZAKU observations we found that the X-ray flux for…

Northern auroral regions of Earth were imaged with energetic photons in the 0.1-10 keV range using the High-Resolution Camera (HRC-I) aboard the Chandra X-ray Observatory at 10 epochs (each ~20 min duration) between mid-December 2003 and…

ROTSE IIId (The Robotic Optical Transient Experiment) observations of X-ray binary system 4U 0115+634/V635 Cas obtained during 2004 June and 2005 January make possible, for the first time, to study the correlation between optical and type…

While narrow absorption lines (NALs) are relatively stable, broad absorption lines (BALs) and mini-BAL systems usually show violent time variability within a few years via a mechanism that is not yet understood. In this study, we examine…

We report long-term simultaneous optical and (RXTE) X-ray observations of the soft X-ray transient and low mass X-ray binary X1608-52 spanning from 1999 to 2001. In addition to the usual X-ray outburst and quiescent states, X1608-52 also…

The recurrent nova IM Nor was observed twice in X-rays with Chandra ACIS-S, 1 and 6 months after the optical outburst. It was not detected in the first observation, with an upper limit on the X-ray luminosity in the 0.2-10 keV range L(x) <…