ترغب بنشر مسار تعليمي؟ اضغط هنا

AD Leonis: Flares observed by XMM-Newton and Chandra

434   0   0.0 ( 0 )
 نشر من قبل E. J. M. van den Besselaar
 تاريخ النشر 2003
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

The M-dwarf AD Leonis has been observed with the Reflection Grating Spectrometers and the European Photon Imaging Camera aboard XMM-Newton and also with the Low Energy Transmission Grating Spectrometer aboard the Chandra X-ray Observatory. In the observation taken with XMM-Newton five large flares produced by AD Leo were identified and only one in the observation taken with Chandra. A quiescent level to the lightcurves is difficult to define, since several smaller flares mutually overlap each other. However, we defined a quasi-steady state outside of obvious flares or flare decays. The spectra from the flare state and the quasi-steady state are analysed separately. From these spectra the temperature structure was derived with a multi-temperature model and with a differential emission measure model. The multi-temperature model was also used to determine the relative abundances of C, N, O, Ne, Mg, Si, S, and Fe. He-like ions, such as O VII and Ne IX, produce line triplets which are used to determine or constrain the electron temperature and electron density of the corresponding ion. During the flare state a higher emission measure at the hottest temperature is found for both XMM-Newton and Chandra observations. The derived abundances suggest the presence of an inverse First Ionization Potential effect in the corona of AD Leo.



قيم البحث

اقرأ أيضاً

429 - B. Gendre 2005
We present a catalog of XMM-Newton and Chandra observations of gamma-ray burst (GRB) afterglows, reduced in a common way using the most up-to-date calibration files and software. We focus on the continuum properties of the afterglows. We derive the s pectral and temporal decay indices for 16 bursts. We place constraints on the burst environment and geometry. A comparison of the fast XMM-Newton follow-up and the late Chandra observations shows a significant difference in those parameters, likely produced by a transition from jet expansion taking place between two and ten days after the burst. We do not observe a significant shrinking of the luminosity distribution when we correct for beaming; more burst observations are needed to confirm this result. We also compare our results with those obtained by BeppoSAX and SWIFT; there is no strong discrepancy between the afterglow fluxes observed with these satellites when we carefully take into account the different median observation time of each observatory.
118 - A. Hands , R. Warwick , M. Watson 2002
In A0-1 we proposed an ambitious long-term survey of selected regions of our Galaxy (the XGPS survey) using the EPIC CCD cameras on XMM-Newton. The first phase of the programme, which aims to survey a strip of the Galactic Plane in the Scutum region, is currently underway. Here we report on the preliminary results from the first 15 survey pointings. We show that the XGPS survey strategy of fairly shallow (5-10 ks) exposures but wide-angle coverage is well tuned to the goal of providing a large catalogue of predominantly Galactic sources at relatively faint X-ray fluxes in the hard 2-6 keV band.
74 - P.T. OBrien 2003
Analysis of observations with XMM-Newton have made a significant contribution to the study of Gamma-ray Burst (GRB) X-ray afterglows. The effective area, bandpass and resolution of the EPIC instrument permit the study of a wide variety of spectral fe atures. In particular, strong, time-dependent, soft X-ray emission lines have been discovered in some bursts. The emission mechanism and energy source for these lines pose major problems for the current generation of GRB models. Other GRBs have intrinsic absorption, possibly related to the environment around the progenitor, or possible iron emission lines similar to those seen in GRBs observed with BeppoSAX. Further XMM-Newton observations of GRBs discovered by the Swift satellite should help unlock the origin of the GRB phenomenon over the next few years.
105 - L. C. Gallo 2003
We present a 20 ks XMM-Newton observation of the prototypical Narrow-Line Seyfert 1 galaxy IZw1. The best-fit model to the data is a double blackbody plus a dominant power-law, on which complex soft absorption (possibly a blended edge or absorption l ines) and/or OVII emission are superimposed, as well as strong Fe Kalpha emission. The iron feature in the high-energy spectra appears broad; however, on close examination of the EPIC pn data, there exists the possibility that the broad emission feature can be attributed to a neutral Fe Kalpha line in addition to a blend of He- and H-like Fe Kalpha lines. The light curve shows a strong, hard X-ray flare concentrated in the 3-12 keV band. The flare appears to induce spectral variability, showing spectral hardening to be occuring as the flare intensifies. A detailed examination suggests that the spectral variability is most likely due to an increase in the 3-12 keV flux relative to the soft flux during the flare. A difference spectrum and complete modelling of the flare and non-flare spectra show intrinsic changes only in the normalisation of the continuum components and not in their shape parameters. The timing results are consistent with the flare originating in the accretion disc corona. The iron emission line(s) do not appear to respond to changes in the continuum flux during the flare; the iron lines are stronger in equivalent width during the low-flux (non-flare) states, and weaker during the flare.
The discovery of the X-ray source IGR J17252-3616 by INTEGRAL was reported on 9 February 2004. Regular monitoring by INTEGRAL shows that IGR J17252-3616 is a persistent hard X-ray source with an average count rate of 0.96 counts/s (~6.4 mCrab) in the 20-60 keV energy band. A follow-up observation with XMM-Newton, which was performed on 21 March 21 2004, showed that the source is located at R.A.(2000.0)=17h25m11.4 and Dec.=-36degr1658.6 with an uncertainty of 4. The only infra-red counterpart to be found within the XMM-Newton error circle was 2MASS J17251139-3616575, which has a Ks-band magnitude of 10.7 and is located 1 away from the XMM-Newton position. The analysis of the combined INTEGRAL and XMM-Newton observations shows that the source is a binary X-ray pulsar with a spin period of 413.7 s and an orbital period of 9.72 days. The spectrum can be fitted with a flat power law plus an energy cut off (Gamma~0.02,Ecut~8.2 keV) or a Comptonized model (kTe~5.5 keV, tau~7.8). The spectrum also indicates a large hydrogen column density of Nh~15x1e22 atoms/cm-2 suggesting an intrinsic absorption. The Fe Kalpha line at 6.4 keV is clearly detected. Phase-resolved spectroscopy does not show any variation in the continuum except the total emitted flux. The absorption is constant along the pulse phase. This source can be associated with EXO 1722-363 as both systems show common timing and spectral features. The observations suggest that the source is a wind-fed accreting pulsar accompanied by a supergiant star.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا