Search results for " X-Rays: General"
showing 10 items of 22 documents
AE Aurigae: First detection of non-thermal X-ray emission from a bow shock produced by a runaway star
2012
Runaway stars produce shocks when passing through interstellar medium at supersonic velocities. Bow shocks have been detected in the mid-infrared for several high-mass runaway stars and in radio waves for one star. Theoretical models predict the production of high-energy photons by non-thermal radiative processes in a number sufficiently large to be detected in X-rays. To date, no stellar bow shock has been detected at such energies. We present the first detection of X-ray emission from a bow shock produced by a runaway star. The star is AE Aur, which was likely expelled from its birthplace due to the encounter of two massive binary systems and now is passing through the dense nebula IC 405…
A relativistically smeared spectrum in the neutron star X-ray binary 4U 1705−44: looking at the inner accretion disc with X-ray spectroscopy
2009
Iron emission lines at 6.4-6.97 keV, identified with fluorescent Kalpha transitions, are among the strongest discrete features in the X-ray band. These are therefore one of the most powerful probes to infer the properties of the plasma in the innermost part of the accretion disc around a compact object. In this paper we present a recent XMM observation of the X-ray burster 4U 1705-44, where we clearly detect a relativistically smeared iron line at about 6.7 keV, testifying with high statistical significance that the line profile is distorted by high velocity motion in the accretion disc. As expected from disc reflection models, we also find a significant absorption edge at about 8.3 keV; th…
On the Spectral Evolution of Cygnus X-2 along its Color-Color Diagram
2002
We report on the results of a broad band (0.1-200 keV) spectral study of Cyg X-2 using two BeppoSAX observations taken in 1996 and 1997, respectively, for a total effective on-source time of ~100 ks. The color-color (CD) and hardness-intensity (HID) diagrams show that the source was in the horizontal branch (HB) and normal branch (NB) during the 1996 and 1997 observation, respectively. Five spectra were selected around different positions of the source in the CD/HID, two in the HB and three in the NB. These spectra are fit to a model consisting of a disk blackbody, a Comptonization component, and two Gaussian emission lines at ~1 keV and ~6.6 keV, respectively. The addition of a hard power-…
NuSTARandXMM–Newtonbroad-band spectrum of SAX J1808.4–3658 during its latest outburst in 2015
2018
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 report here the results of a detailed spectral analysis of both the XMM-Newton and NuSTAR spectra. While the XMM-Newton spectrum appears much softer than in previous observations, the NuSTAR spectrum confirms the results obtained with XMM-Newton during the 2008 outburst. We find clear evidence of a broad iron line that we interpret as produced by reflection from the inner accretion disk. For the first time, we use a self-consistent reflection model to fit the…
Testing reflection features in 4U 1705-44 with XMM-Newton, BeppoSAX, and RXTE in the hard and soft states
2012
We use data of the bright atoll source 4U 1705-44 taken with XMM-Newton, BeppoSAX and RXTE both in the hard and in the soft state to perform a self-consistent study of the reflection component in this source. Although the data from these X-ray observatories are not simultaneous, the spectral decomposition is shown to be consistent among the different observations, when the source flux is similar. We therefore select observations performed at similar flux levels in the hard and soft state in order to study the spectral shape in these two states in a broad band (0.1-200 keV) energy range, with good energy resolution, and using self-consistent reflection models. These reflection models provide…
Spectral analysis of the dipping LMXB system XB 1916-053
2019
Context: XB 1916-053 is a low mass X-ray binary system (LMXB) hosting a neutron star (NS) and showing periodic dips. The spectrum of the persistent emission was modeled with a blackbody component having a temperature between 1.31 and 1.67 keV and with a Comptonization component with an electron temperature of 9.4 keV and a photon index $\Gamma$ between 2.5 and 2.9. The presence of absorption features associated with highly ionized elements suggested the presence of partially ionized plasma in the system. Aims: In this work we performed a study of the spectrum of XB 1916-053, which aims to shed light on the nature of the seed photons that contribute to the Comptonization component. Methods: …
ChandraObservation of Cir X‐1 near the Periastron Passage: Evidence for an X‐Ray Jet?
2008
We present the results of a 25 ks long Chandra observation of the peculiar source Cir X-1 near the periastron passage. We report precise X-ray coordinates of the source, which were compatible with the optical and radio counterpart coordinates. We focus on the study of the detected emission features using the High Energy Transmission Grating Spectrometer on board the Chandra satellite. We detect emission lines associated with Mg XII, Si XIII, Si XIV, S XV, S XVI, Ar XVII, Ar XVIII, Ca XIX, Ca XX, Fe XXV, and Fe XXVI, showing an average redshift of 470 km s-1. The most intense emission features can be fitted with two lines; this is more evident for the 6.6 keV emission feature, which shows a …
JEM–X: The X-ray monitor aboard INTEGRAL
2003
The JEM-X monitor provides X-ray spectra and imaging with arcminute angular resolution in the 3 to 35 keV band. The good angular resolution and the low energy response of JEM-X plays an important role in the identification of gamma ray sources and in the analysis and scientific interpretation of the combined X-ray and gamma ray data. JEM-X is a coded aperture instrument consisting of two identical, coaligned telescopes. Each of the detectors has a sensitive area of 500 cm 2 , and views the sky through its own coded aperture mask. The two coded masks are inverted with respect to each other and provides an angular resolution of 3 0 across an eective field of view of about 10 diameter.
The Chandra COSMOS Survey, I: Overview and Point Source Catalog
2009
The Chandra COSMOS Survey (C-COSMOS) is a large, 1.8 Ms, Chandra} program that has imaged the central 0.5 sq.deg of the COSMOS field (centered at 10h, +02deg) with an effective exposure of ~160ksec, and an outer 0.4sq.deg. area with an effective exposure of ~80ksec. The limiting source detection depths are 1.9e-16 erg cm(-2) s(-1) in the Soft (0.5-2 keV) band, 7.3e(-16) erg cm^-2 s^-1 in the Hard (2-10 keV) band, and 5.7e(-16) erg cm(-2) s(-1) in the Full (0.5-10 keV) band. Here we describe the strategy, design and execution of the C-COSMOS survey, and present the catalog of 1761 point sources detected at a probability of being spurious of <2e(-5) (1655 in the Full, 1340 in the Soft, and…
JEM–X inflight performance
2003
We summarize the inflight performance of JEM-X, the X-ray monitor on the INTEGRAL mission during the initial ten months of operations. The JEM-X instruments have now been tuned to stable operational conditions. The performance is found to be close to the pre-launch expectations. The ground calibrations and the inflight calibration data permit to determine the instruments characteristics to fully support the scientific data analysis. Reglero Velasco, Victor, Victor.Reglero@uv.es ; Martinez Nuñez, Silvia, Silvia.Martinez@uv.es