Search results for " Individual"
showing 10 items of 565 documents
The BeppoSAX 0.1 - 18 keV Spectrum of the Bright Atoll Source GX 9+1: an Indication of the Source Distance
2005
We report the results of a long, 350 ks, BeppoSAX observation of the bright atoll source GX 9+1 in the 0.12 - 18 keV energy range. During this observation GX 9+1 showed a large count rate variability in its lightcurve. From its color - color diagram we selected six zones and extracted the source energy spectrum from each zone. We find that the model, composed of a blackbody plus a Comptonized component absorbed by an equivalent hydrogen column of similar to 1.4 x 10(22) cm(-2), fits the spectra in the energy range 1 - 18 keV well; however, below 1 keV a soft excess is present. We find that the spectrum of GX 9+1, in the 0.12 - 18 keV energy range, is well fitted by the model above, if we us…
Broadband observations of the X-ray burster 4U1705-44 with Beppo SAX
2016
4U 1705-44 is one of the most-studied type I X-ray burster and Atoll sources. This source represents a perfect candidate to test different models proposed to self-consistently track the physical changes occurring between different spectral states because it shows clear spectral state transitions. The broadband coverage, the sensitivity and energy resolution of the BeppoSAX satellite offers the opportunity to disentangle the components that form the total X-ray spectrum and to study their changes according to the spectral state. Using two BeppoSAX observations carried out in August and October 2000, respectively, for a total effective exposure time of about 100 ks, we study the spectral evol…
First observations of the X-ray transient EXO 2030+375 with IBIS/ISGRI
2003
We present a first INTEGRAL observation of the 42s transient X-ray pulsar EXO 2030+375 with IBIS/ISGRI. The source was detected during Cyg X-1 observations in December 2002. We analyzed observations during the outburst period from 9 to 21 December 2002 with a total exposure time of ~770 kiloseconds. EXO 2030+375 was almost always detected during single ~30 minute exposures in the 18-45 energy bands. The source light curve shows the characteristic outburst shape observed in this source.
Tracking the evolution of the accretion flow in MAXI J1820+070 during its hard state with the JED-SAD model
2021
X-ray binaries in outburst typically show two canonical X-ray spectral states, i.e. hard and soft states, in which the physical properties of the accretion flow and of the jet are known to change. Recently, the JED-SAD paradigm has been proposed for black hole X-ray binaries, aimed to address the accretion-ejection interplay in these systems. According to this model, the accretion flow is composed by an outer standard Shakura-Sunyaev disk (SAD) and an inner hot Jet Emitting Disk (JED). The JED produces both the hard X-ray emission, effectively playing the role of the hot corona, and the radio jets. In this paper, we use the JED-SAD model to describe the evolution of the accretion flow in th…
A detailed study of the rise phase of a long duration X-ray flare in the young star TWA 11B
2010
We analyzed a long duration flare observed in a serendipitous XMM-Newton detection of the M star CD-39 7717B (TWA 11B), member of the young stellar association TW Hya (~ 8 Myr). Only the rise phase (with a duration of ~ 35 ks) and possibly the flare peak were observed. We took advantage of the high count-rate of the X-ray source to carry out a detailed analysis of its spectrum during the whole exposure. After a careful analysis, we interpreted the rise phase as resulting from the ignition of a first group of loops (event A) which triggered a subsequent two-ribbon flare (event B). Event A was analyzed using a single-loop model, while a two-ribbon model was applied for event B. Loop semi-leng…
The 30 Year Search for the Compact Object in SN 1987A
2018
Despite more than 30 years of searches, the compact object in Supernova (SN) 1987A has not yet been detected. We present new limits on the compact object in SN 1987A using millimeter, near-infrared, optical, ultraviolet, and X-ray observations from ALMA, VLT, HST, and Chandra. The limits are approximately 0.1 mJy ($0.1\times 10^{-26}$ erg s$^{-1}$ cm$^{-2}$ Hz$^{-1}$) at 213 GHz, 1 Lsun ($6\times 10^{-29}$ erg s$^{-1}$ cm$^{-2}$ Hz$^{-1}$) in optical if our line-of-sight is free of ejecta dust, and $10^{36}$ erg s$^{-1}$ ($2\times 10^{-30}$ erg s$^{-1}$ cm$^{-2}$ Hz$^{-1}$) in 2-10 keV X-rays. Our X-ray limits are an order of magnitude less constraining than previous limits because we use a…
A Hard Look at the Neutron Stars and Accretion Disks in 4U 1636-53, GX 17+2, and 4U 1705-44 with NuStar
2017
We present $\emph{NuSTAR}$ observations of neutron star (NS) low-mass X-ray binaries: 4U 1636-53, GX 17+2, and 4U 1705-44. We observed 4U 1636-53 in the hard state, with an Eddington fraction, $F_{\mathrm{Edd}}$, of 0.01; GX 17+2 and 4U 1705-44 were in the soft state with fractions of 0.57 and 0.10, respectively. Each spectrum shows evidence for a relativistically broadened Fe K$_{\alpha}$ line. Through accretion disk reflection modeling, we constrain the radius of the inner disk in 4U 1636-53 to be $R_{in}=1.03\pm0.03$ ISCO (innermost stable circular orbit) assuming a dimensionless spin parameter $a_{*}=cJ/GM^{2}=0.0$, and $R_{in}=1.08\pm0.06$ ISCO for $a_{*}=0.3$ (errors quoted at 1 $\sig…
The Deep Rho Ophiuchi XMM-Newton Observation (DROXO)
2005
International audience; We present the X-ray data and the analysis status of the DROXO (Deep Rho Oph XMM-Newton Observation) project, aimed to mainly characterize the spectro-variability properties of YSOs in the nearby and very young ρ Oph star forming region. We focus on a few selected initial scientific results for few interesting YSOs, such as Elias 29 and YLW16A. In Elias 29 we see the 6.4 keV fluorescent Fe line as already reported in literature, whereas in YLW16A we do not detect the fluorescent line at odd with previous findings. Hence we conclude that the line intensity does change with time (and/or physical conditions).
To Be Continued: The Genidentity of Physical and Biological Processes
2016
The concept of genidentity has been proposed as a way to better understand identity through time, especially in physics and biology. The genidentity view is utterly anti-substantialist in so far as it suggests that the identity of X through time does not presuppose whatsoever the existence of a permanent “core” or “substrate” of X. Yet applications of this concept to real science have been scarce and unsatisfying. In this paper, our aim is to show that a well-defined concept of functional genidentity can be crucial to shed light on identity through time in classical physics and especially in biology. Finally, we show that understanding identity on the basis of continuity suggests a move tow…
Le collégien en difficulté : un constat local et des propositions d'aide individualisée
2003
For some years now, the management of pupil diversity has been the subject of considerable debate, both at the level of the education system and within separate establishments. The principal questions concern the actions to be implemented to allow all pupils to acquire a common base of knowledge and skills during the four years of lower secondary education. Numerous systems have been developed in recent years: remedial teaching, differentiated pedagogy, individual support, reorganisation of timetables, the grouping of pupils, diversified careers, etc., but tangible results have not always been observed. A worrying percentage of pupils still enter lower secondary education with serious learn…