Related papers: Variable Thermal Emission from Aql X-1 in Quiescen…
We present the results of continued monitoring of the quiescent neutron star low-mass X-ray binary XTE J1701-462 with Chandra and Swift. A new Chandra observation from 2010 October extends our tracking of the neutron star surface…
We have monitored the transient neutron star low-mass X-ray binary 1RXS J180408.9-342058 in quiescence after its ~4.5 month outburst in 2015. The source has been observed using Swift and XMM-Newton. Its X-ray spectra were dominated by a…
(Abridge) We observed the accreting millisecond X-ray pulsars XTE J0929-314 and XTE J1751-305 in their quiescent states using Chandra. From XTE J0929-314 we detected 22 photons (0.3-8 keV) in 24.4 ksec, resulting in a count rate of 9 x…
The structure and composition of the crust of neutron stars plays an important role in their thermal and magnetic evolution, hence in setting their observational properties. One way to study the crust properties is to measure how it cools…
Aql X-1 was observed in a Low Intensity State (LIS), a state that is usually characterized by high optical but low X-ray flux. Our daily monitoring of the source using the 1.3m telescope in Cerro Tololo Inter-America Observatory operated by…
Aql X-1 is the prototypical low mass X-ray binary transient. The Rossi X-ray Timing Explorer All Sky Monitor provided a ~16 yr coverage revealing 20 outbursts. This is by far the most extensive legacy of outbursts from the same source. We…
The measurement of neutron star mass and radius is one of the most direct way to distinguish between various dense matter equations of state. The mass and radius of accreting neutron stars hosted in low mass X-ray binaries can be…
We analyse new optical spectroscopic, direct-image and X-ray observations of the recently discovered a high proper motion cataclysmic variable V1838 Aql. The data were obtained during its 2013 superoutburst and its subsequent quiescent…
We report on a series of Swift/XRT observations, performed between February and 22 March 2012, during the quiescent state of the neutron-star X-ray binary SAX J1750.8-2900. In these observations, the source was either just detected or…
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…
We report results from a 30 ks observation of Cygnus X-1 with the High Energy Transmission Grating Spectrometer (HETGS) on board the {\em Chandra X-ray Observatory}. Numerous absorption lines were detected in the HETGS spectrum. The lines…
We analyzed optical/X-ray quasi-simultaneous light curves of Aql X-1, obtained by MAXI (Monitor of All-sky X-ray Image), ZTF (Zwicky Transient Facility) and LCO (Las Cumbres Observatory) in about 3.6 years from 2016, for understanding…
The thermal evolution of young neutron stars (NSs) reflects the neutrino emission properties of their cores. Heinke et al. (2010) measured a 3.6+/-0.6% decay in the surface temperature of the Cassiopeia A (Cas A) NS between 2000 and 2009,…
Using PCA data from the Rossi X-Ray Timing Explorer (RXTE), we track the spectral states of the neutron star transient system Aql X-1 through a complete outburst cycle. We find a hard-to-soft state transition during the very early, rising…
We report on quasi-simultaneous observations from radio to X-ray frequencies of the neutron star X-ray binary Aql X-1 over accretion state transitions during its 2016 outburst. All the observations show radio to millimetre spectra…
We report the results of two Chandra ACIS-S observations from February and August 2003 of the highly X-ray variable Narrow-Line Seyfert 1 galaxy RX J2217.9--5941. Observations spanning the time from the ROSAT All Sky Survey (RASS) through…
We present an analysis of multi-timescale variability in line-of-sight X-ray absorbing gas as a function of optical classification in a large sample of Seyfert AGN to derive the first X-ray statistical constraints for clumpy-torus models.…
We present deeper Chandra observations for weak-line quasars (WLQs) in a representative sample that previously had limited X-ray constraints, and perform X-ray photometric analyses to reveal the full range of X-ray properties of WLQs. Only…
The recurrent nova T Pyx was observed with the X-ray gratings of Chandra and XMM-Newton, 210 and 235 days, respectively, after the discovery of the 2011 April 14 outburst. The X-ray spectra show prominent emission lines of C, N, and O, with…
We present an analysis of several high-resolution Chandra grating observations of the X-ray binary pulsar Her X-1. With a total exposure of 170 ks, the observations are separated by years and cover three combinations of orbital and…