0000000001156199
AUTHOR
A. D'ai
showing 11 related works from this author
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…
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 …
X-ray spectroscopic study of the ADC source X1822-371
2011
We analyse two Chandra HETGS (High Energy Transmission Grating Spectrometer) observations and one XMM-Newton observation. The HETGS and XMM/Epic-pn observed X 1822-371 for 140 and 50 ks, respectively. We extracted an averaged spectrum and five spectra from five selected orbital-phase intervals that are 0.04-0.25, 0.25-0.50, 0.50-0.75, 0.95-1.04; the orbital phase zero corresponds to the eclipse time. The spectra cover the energy band between 0.4 and 12 keV. We confirm the presence of local neutral matter that partially covers the X-ray emitting region; the equivalent hydrogen column is 3.5 × 1022 cm-2 and the covered fraction is around 60 %. We detected and identified several emission lines…
A newly discovered accreting pulsar in Terzan 5
2011
The 11 Hz accreting pulsar, IGR J17480-2446, was recently discovered in the globular cluster Terzan 5. The analisys of the Doppler shifts induced by the orbital motion reveals how the neutron star belongs to a ∼ 21.3 hr binary system with a companion star of 0.4-1.5 M. The X-ray pulsar spins up while accreting at an average rate of 1.48(2)×10−12 Hz s−1, in agreement with the accretion of disc matter angular momentum given the observed luminosity. From the presence of pulsations at different accretion rates we constrain the magnetic field to lie within ∼2×108 and ∼2×1010 G. From this estimate, the value of the spin period and of the observed spin-up rate, we associate this source with the st…
Testing Rate Dependent corrections on timing mode EPIC-pn spectra of the accreting Neutron Star GX 13+1
2014
When the EPIC-pn instrument on board XMM-Newton is operated in Timing mode, high count rates (>100 cts/s) of bright sources may affect the calibration of the energy scale, resulting in a modification of the real spectral shape. The corrections related to this effect are then strongly important in the study of the spectral properties. Tests of these calibrations are more suitable in sources which spectra are characterised by a large number of discrete features. Therefore, in this work, we carried out a spectral analysis of the accreting Neutron Star GX 13+1, which is a dipping source with several narrow absorption lines and a broad emission line in its spectrum. We tested two different co…
Finding a 61.0-day orbital period for the HMXB 4U 1036-56 with the Swift-BAT monitoring
2013
Since November 2004, the Burst Alert Telescope on board Swift is producing a monitoring of the entire sky in the 15-150 keV band, recording the timing and spectral behavior of the detected sources. Here we study the properties of the HMXB 4U 1036-56 using both the BAT survey data and those from a Swift-XRT observation. A folding analysis performed on the BAT light curve of the first 100 months of survey unveils a periodic modulation with a period of 61.0 days, tied to the presence in the BAT light curve of several intensity enhancements lasting ~1/4 of P_0. We explain this modulation as the orbital period of the binary system. The position of 4U 1036-56 on the Corbet diagram, the derived se…
Swiftdiscovery of the orbital period of the high mass X-ray binary IGR J015712−7259 in the Small Magellanic Cloud
2013
In the last years the hard X-ray astronomy has made a significant step forward, thanks to the monitoring of the IBIS/ISGRI telescope on board the INTEGRAL satellite and of the Burst Alert Telescope (BAT) on board of the Swift observatory. This has provided a huge amount of novel information on many classes of sources. We have been exploiting the BAT survey data to study the variability and the spectral properties of the new high mass X-ray binary sources detected by INTEGRAL. In this letter we investigate the properties of IGR J015712-7259. We perform timing analysis on the 88-month BAT survey data and on the XRT pointed observations of this source. We also report on the broad-band 0.2-150 …
Study of the reflection spectrum of the accreting neutron star GX 3+1 using XMM-Newton and INTEGRAL
2015
Broad emission features of abundant chemical elements, such as Iron, are commonly seen in the X-ray spectra of accreting compact objects and their studies can provide useful information about the geometry of the accretion processes. In this work, we focus our attention on GX 3+1, a bright, persistent accreting low mass X-ray binary, classified as an atoll source. Its spectrum is well described by an accretion disc plus a stable comptonizing, optically thick corona which dominates the X-ray emission in the 0.3-20 keV energy band. In addition, four broad emission lines are found and we associate them with reflection of hard photons from the inner regions of the accretion disc where doppler an…
Broad-band Spectral Evolution of Scorpius X-1 along its Color-Color Diagram
2007
We analyze a large collection of RXTE archive data from April 1997 to August 2003 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 studying energy spectra from selected regions in the Z-track of its Color-Color Diagram. A two-component model, consisting of a soft thermal component interpreted as thermal emission from an accretion disk and a thermal Comptonization component, is unable to fit the whole 3--200 keV energy spectrum at low accretion rates. Strong residuals in the highest energy band of the spectrum require the addition of a third component that can be fitted with a …
XIPE: the x-ray imaging polarimetry explorer
2016
XIPE, the X-ray Imaging Polarimetry Explorer, is a mission dedicated to X-ray Astronomy. At the time of writing XIPE is in a competitive phase A as fourth medium size mission of ESA (M4). It promises to reopen the polarimetry window in high energy Astrophysics after more than 4 decades thanks to a detector that efficiently exploits the photoelectric effect and to X-ray optics with large effective area. XIPE uniqueness is time-spectrally-spatially- resolved X-ray polarimetry as a breakthrough in high energy astrophysics and fundamental physics. Indeed the payload consists of three Gas Pixel Detectors at the focus of three X-ray optics with a total effective area larger than one XMM mirror bu…
X-ray bursts and burst oscillations from the slowly spinning X-ray pulsar IGR J17480-2446 (Terzan 5)
2011
The newly discovered 11-Hz accreting pulsar, IGR J17480-2446, located in the globular cluster Terzan 5, has shown several bursts with a recurrence time as short as a few minutes. The source shows the shortest recurrence time ever observed from a neutron star. Here we present a study of the morphological, spectral and temporal properties of 107 bursts observed by the Rossi X-ray Timing Explorer. The recurrence time and the fluence of the bursts clearly anticorrelate with the increase in the persistent X-ray flux. The ratio between the energy generated by the accretion of mass and that liberated during bursts indicates that helium is ignited in a hydrogen-rich layer. Therefore, we conclude th…