Related papers: Decoding the X-ray flare from MAXI J0709-159 using…
We revisit various sets of published results from X-ray and optical studies of the Galactic black hole (BH) candidate MAXI J0637-430, which went into outburst in 2019. Combining the previously reported values of peak outburst luminosity,…
A high-resolution spectrum of the helium-rich `hot subdwarf' GALEX J184559.8-413827 (J1845-4138) obtained with SALT HRS demonstrates it to be the first extreme helium (EHe) star to be discovered in nearly 40 years. A quantitative analysis…
IGR J17511-3057 is a low mass X-ray binary hosting a neutron star and is one of the few accreting millisecond X-ray pulsars with X-ray bursts. We report on a 20ksec Chandra grating observation of IGR J17511-3057, performed on 2009 September…
We report on a giant stellar flare from the RS CVn-type binary UX Arietis, detected with the Monitor of All-sky X-ray Image (MAXI) and followed by a 12-day optical spectroscopic campaign using the 3.8~m Seimei Telescope. The flare released…
We present time-resolved spectroscopy of the soft X-ray transient XTE J2123-058 in outburst. A useful spectral coverage of 3700-6700A was achieved spanning two orbits of the binary, with single epoch coverage extending to \~9000A. The…
Aims: We conducted the first X-ray observations of the newly erupting FU Ori-type outburst in HBC 722 (V2493 Cyg) with the aim to characterize its X-ray behavior and near-stellar environment during early outburst. Methods: We used data from…
A rare group of high mass X-ray binaries (HMXBs) are known that also exhibit MeV, GeV, and/or TeV emission ("gamma-ray binaries"). Expanding the sample of gamma-ray binaries and identifying unknown Fermi sources are currently of great…
We present spectral and timing analysis of NuSTAR observations of RX J0520.5$-$6932 in the 3-79 keV band collected during its outburst in January 2014. The target was observed on two epochs and we report the detection of a cyclotron…
HD 49798 is a hot subdwarf of O spectral type in a 1.55 day orbit with the X-ray source RX J0648.0-4418, a compact object with spin period of 13.2 s. We use recent data from the NICER instrument, joined with archival data from XMM-Newton…
We observed RX J0520.5-6932 in the X-rays and studied the optical light curve of its counterpart to verify it as a Be/X-ray binary. We performed an XMM-Newton anticipated target of opportunity observation in January 2013 during an X-ray…
We report the discovery of an eclipsing polar, 2XMMi J225036.9+573154, using XMM-Newton. It was discovered by searching the light curves in the 2XMMi catalogue for objects showing X-ray variability. Its X-ray light curve shows a total…
The Neutron Star Interior Composition Explorer (NICER) has extensively monitored the August 2019 outburst of the 401 Hz millisecond X-ray pulsar SAX J1808.4-3658. In this Letter, we report on the detection of a bright helium-fueled Type I…
New high variability extragalactic sources may be identified by comparing the flux of sources seen in the XMM-Newton Slew Survey with detections and upper limits from the ROSAT All Sky Survey. In November 2012, X-ray emission was detected…
We report a serendipitous detection of an intense X-ray flare from the Tycho reference source HD 161084 during a Suzaku observation of the Galactic Center region for 20 ks. The X-ray Imaging Spectrometer (XIS) recorded a flare from this…
We present new Chandra X-ray observations of the transient black hole X-ray binary MAXI J1659-152 in quiescence. These observations were made more than one year after the end of the source's 2010-2011 outburst. We detect the source at a…
Swift J1357.2$-$0933 is a black-hole candidate X-ray transient, which underwent its third outburst in 2019, during which several multi-wavelength observations were carried out.~Here, we report results from the \emph{Neil Gehrels Swift} and…
Accurate photometric CoRoT space observations of a secondary seismological target, HD 174884, led to the discovery that this star is an astrophysically important double-lined eclipsing spectroscopic binary in an eccentric orbit (e of about…
We present medium-resolution optical spectroscopy with the SOAR telescope of the O star secondary of the high-mass gamma-ray binary 1FGL J1018.6-5856 to help determine whether the primary is a neutron star or black hole. We find that the…
We present results obtained from near-infrared JHK spectroscopic observations of novae V2491 Cyg and V597 Pup in the early declining phases of their 2007 and 2008 outbursts respectively. In both objects, the spectra displayed emission lines…
Optical spectra were obtained of the optical counterpart of the high latitude soft X-ray transient XTE J1118+480 near its quiescent state with the new 6.5 m MMT and the 4.2 m WHT. The spectrum exhibits broad, double-peaked, emission lines…