Search results for " X-ray: stars"
showing 5 items of 5 documents
Spectral Evolution of Scorpio X‐1 along its Color‐Color Diagram
2007
We analyze a large collection of RXTE archive data of the bright X‐ray source Scorpius X‐1 in order to study the broadband spectral evolution of the source for different values of the inferred mass accretion rate by selecting energy spectra from its Color‐Color Diagram. We model the spectra with the combination of two absorbed components: a soft thermal component, which can be interpreted as thermal emission from an accretion disk, and a hybrid Comptonization component, which self‐consistently includes the Fe Kα fluorescence line and the Compton reflected continuum. The presence of hard emission in Scorpius X‐1 has been previously reported, however, without a clear relation with the accreti…
Relativistically Smeared Iron Lines in the Spectra of Bright NS LMXB
2009
We present preliminary results of a study on three bright accreting low-mass X-ray binaries hosting a neutron star, based on XMM-Newton observations. These sources (GX 340+0, GX 349+2 and SAX J1808.4-3658) show a broad Fe K alpha iron line in their spectra. This feature can be well described by relativistic line profile in each case; the good spectral resolution of the EPIC/PN and the high statistics spectra allow to put very good constraints on the disk geometry and ionization stage of the reflecting matter.
A self-consistent approach to the reflection component in 4U 1705-44
2010
High-resolution spectroscopy has recently revealed in many neutron-star Low-Mass X-ray binaries that the shape of the broad iron line observed in the 6.4-6.97 keV range is consistently well fitted by a relativistically smeared line profile. We show here spectral fitting results using a newly developed self-consistent reflection model on XMM-Newton data of the LMXB 4U 1705-44 during a period when the source was in a bright soft state. This reflection model adopts a blackbody prescription for the shape of the impinging radiation field, that we physically associate with the boundary layer emission. © 2010 American Institute of Physics.
X-ray Flares in Orion Low Mass Stars
2007
Context. X-ray flares are common phenomena in pre-main sequence stars. Their analysis gives insights into the physics at work in young stellar coronae. The Orion Nebula Cluster offers a unique opportunity to study large samples of young low mass stars. This work is part of the Chandra Orion Ultradeep project (COUP), an ~10 day long X-ray observation of the Orion Nebula Cluster (ONC). Aims. Our main goal is to statistically characterize the flare-like variability of 165 low mass (0.1-0.3 M_sun) ONC members in order to test and constrain the physical scenario in which flares explain all the observed emission. Methods. We adopt a maximum likelihood piece-wise representation of the observed X-r…
A method to constrain the neutron star magnetic field in Low Mass X-ray Binaries
2005
We describe here a method to put an upper limit to the strength of the magnetic field of neutron stars in low mass X‐ray binaries for which the spin period and the X‐ray luminosity during X‐ray quiescent periods are known. This is obtained using simple considerations about the position of the magnetospheric radius during quiescent periods. We applied this method to the accreting millisecond pulsar SAX J1808.4‐3658, which shows coherent X‐ray pulsations at a frequency of ∼ 400 Hz and a quiescent X‐ray luminosity of ∼ 5 × 1031 ergs/s, and found that B ⩽ 5 × 108 Gauss in this source. Combined with the lower limit inferred from the presence of X‐ray pulsations, this constrains the SAX J1808.4‐3…