Related papers: Optical Spectroscopic Observations of Cyg X-1=HDE …
Using XMM data, we study for the first time the X-ray emission of HM1 and IC2944/2948. Low-mass, pre-main-sequence objects with an age of a few Myr are detected, as well as a few background or foreground objects. Most massive stars in both…
The Of?p star CPD -28 2561 was monitored at high energies with XMM-Newton and HST. In X-rays, this magnetic oblique rotator displays bright and hard emission that varies by ~55% with rotational phase. These changes occur in phase with…
We observed the Galactic black hole Cygnus X-1 with the Chandra High Energy Transmission Grating Spectrometer for 30 kiloseconds on 4 January, 2001. The source was in an intermediate state, with a flux that was approximately twice that…
Recent observations of the high-mass X-ray binary Cygnus X-1 have shown that both the companion star (41 solar masses) and the black hole (21 solar masses) are more massive than previously estimated. Furthermore, the black hole appears to…
An extended XMM-Newton observation of the luminous narrow line Seyfert galaxy PG 1211+143 in 2014 has revealed a more complex high velocity wind, with components distinguished in velocity, ionization level, and column density. Here we…
Aims: The VY Scl system (anti-dwarf nova) V751 Cyg is examined following a claim of a super-soft spectrum in the optical low state. Methods: A serendipitous XMM-Newton X-ray observation and, 21 months later, Swift X-ray and UV observations,…
CH Cygni is a symbiotic star consisting of an M giant and an accreting white dwarf, which is known to be a highly variable X-ray source with a complex, two-component, spectra. Here we report on two Suzaku observations of CH Cyg, taken in…
Vela X-1 is the archetype of high-mass X-ray binaries, composed of a neutron star and a massive B supergiant. The supergiant is a source of a strong radiatively-driven stellar wind. The neutron star sweeps up this wind, and creates a huge…
Two different models have been put forward to explain the origin of the X-ray emission of the unusual X-ray source 1E 1024.0-5732/Wack 2134: a high-mass X-ray binary system (HMXB) and a colliding wind binary (CWB). We present new optical…
We present a detailed study of the high mass X-ray binary Vela X-1, using observations performed by Insight-HXMT in 2019 and 2020, concentrating on timing analysis and spectral studies including pulse phase-resolved spectroscopy. The…
We present near-infrared polarimetric observations of the black hole X-ray binaries Swift J1357.2-0933 and A0620-00. In both sources, recent studies have demonstrated the presence of variable infrared synchrotron emission in quiescence,…
We present the results of new X-ray observations of XMMU 122939.7+075333, the black hole (BH) in the globular cluster RZ 2109 in the Virgo Cluster galaxy NGC 4472. A combination of non-detections and marginal detections in several recent…
We studied the optical counterpart of the intermediate-mass black hole candidate HLX-1 in ESO 243-49. We used a set of Very Large Telescope imaging observations from 2010 November, integrated by Swift X-ray data from the same epoch. We…
Some recent observational results impose significant constraints on all the models that have been proposed to explain the Galactic black-hole X-ray sources in the hard state. In particular, it has been found that during the hard state of…
Recently, the accretion geometry of the black-hole X-ray binary Cyg X-1 was probed with the X-ray polarization. The position angle of the X-ray emitting flow was found to be aligned with the position angle of the radio jet in the plane of…
A decade ago the archetypal Seyfert-1 galaxy NGC 5548 was discovered to have undergone major spectral changes. The soft X-ray flux had dropped by a factor of 30 while new broad and blueshifted UV absorption lines appeared. This was…
The properties of the interacting, eccentric orbit binary V1507 Cyg (HD187399) are examined with spectra that cover wavelengths from 0.63 to 0.68um. The spectrum of the brightest star is very similar to that of the B8 I star Beta Ori,…
We report on a detailed optical spectroscopic follow-up of the black hole transient MAXI J1820+070 (ASASSN-18ey). The observations cover the main part of the X-ray binary outburst, when the source alternated between hard and soft states…
The hard X-rays in Cyg X-1 and similar black hole sources are possibly produced in an active corona atop an accretion disk. We suggest that the observed weakness of X-ray reflection from the disk is due to bulk motion of the emitting hot…
We present optical ESO time-series and UV archival (FUSE, HST, IUE) spectroscopy of the H-rich central star of He 2-138. Our study targets the central star wind in a very young planetary nebula, and explores physical conditions that may…