Related papers: Disk reflection and a possible disk wind during a …
Accretion disk winds are revealed in Chandra gratings spectra of black holes. The winds are hot and highly ionized (typically composed of He-like and H-like charge states), and show modest blue-shifts. Similar line spectra are sometimes…
We report on the nearly simultaneous \nicer{} and \nustar{} observations of the known X-ray transient XTE~J1739-285. These observations provide the first sensitive hard X-ray spectrum of this neutron star X-ray transient. The source was…
We report on an observation of the neutron star low-mass X-ray binary Serpens X-1, made with NuSTAR. The extraordinary sensitivity afforded by NuSTAR facilitated the detection of a clear, robust, relativistic Fe K emission line from the…
We analyzed simultaneous archival XMM-Newton and RXTE observations of the X-ray binary and black hole candidate Swift J1753.5-0127. In a previous analysis of the same data a soft thermal component was found in the X-ray spectrum, and the…
We present results for the first observed outburst from the transient X-ray binary source MAXI J0637-430. This study is based on eight observations from the Nuclear Spectroscopic Telescope Array (NuSTAR) and six observations from the Neil…
We present \nustar{} observation of the atoll type neutron star (NS) low-mass X-ray binary (LMXB) Serpens~X-1 (Ser~X-1) performed on 17 February 2018. We observed Ser~X-1 in a soft X-ray spectral state with 3-79 keV luminosity of…
Recurring outbursts associated with matter flowing onto compact stellar remnants (black-holes, neutron stars, white dwarfs) in close binary systems, provide strong test beds for constraining the poorly understood accretion process. The…
We report the spectral analysis of accretion powered millisecond X-ray pulsar SAX J1748.9-2021 from the NuSTAR observation made during its 2015 outburst. The spectra displayed a broad emission line at $\sim 6.5$ keV with line width of $\sim…
We present a broadband spectral analysis of the atoll source 4U~1636-536 observed for $\sim92$ ks with \nustar{}. The source was found to be in a low-luminosity state during this observation with $3-79 \kev{}$ X-ray luminosity of $L_{3-79…
We present the results of an analysis of data from XMM-Newton and CHANDRA observations of the high luminosity narrow-line quasar PG 1404+226. We confirm a strong soft X-ray excess in the X-ray spectrum and we find rapid variability (a…
We report on XMM-Newton observations of the galactic supersoft X-ray source RX J0925.7-4758. The RGS spectrum exhibits a wealth of spectral features from iron and oxygen. XMM-Newton data confirm the finding of previous Chandra HETGS/MEG…
We report on the first simultaneous $NICER$ and $NuSTAR$ observations of the neutron star (NS) low-mass X-ray binary 4U 1735$-$44, obtained in 2018 August. The source was at a luminosity of $\sim1.8~(D/5.6\ \mathrm{kpc})^{2}\times10^{37}$…
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…
An X-ray monitoring campaign with Chandra and Swift confirms that 1RXS J171824.2-402934 is accreting at the lowest rate among the known persistently accreting low-mass X-ray binaries. A thermonuclear X-ray burst was detected with the…
The first discovered accreting millisecond pulsar, SAX J1808.4-3658, went into X-ray outburst in April 2015. We triggered a 100 ks XMM-Newton ToO, taken at the peak of the outburst, and a 55 ks NuSTAR ToO, performed four days apart. We…
The accreting millisecond X-ray pulsar SAX J1808.4--3658 shows peculiar low luminosity states known as "reflares" after the end of the main outburst. During this phase the X-ray luminosity of the source varies by up to three orders of…
We present the results from the spectral and timing analysis of the accreting neutron star 1A~1744-361 from the \nustar{} observation performed in its 2022 outbursts. The unabsorbed bolometric X-ray luminosity during this observation in the…
We present a spectral analysis of NuSTAR and NICER observations of the luminous, persistently accreting neutron star (NS) low-mass X-ray binary Cygnus X-2. The data were divided into different branches that the source traces out on the…
We report the presence of a highly ionized absorber in the transient, eclipsing low-mass X-ray binary AX J1745.6-2901, observed from Feb. 26 to 29, 2024 with XRISM's Resolve and Xtend instruments. During a soft/high state without dips,…
An outburst of the accreting X-ray millisecond pulsar SAX J1808.4-3658 in October-November 2002 was followed by the Rossi X-ray Timing Explorer for more than a month. We demonstrate how the area covered by the hotspot at the neutron star…