اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThe orbital period of the dipping, bursting, globular cluster X-ray source XB 1746-371 from Rossi X-ray Timing Explorer observations
57
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We present results from two long observations of XB 1746-371 by the Rossi X-ray Timing Explorer (RXTE) in 2002 January and May, lasting 4 and 5 days respectively. Dips are observed in the X-ray light curves with a depth of 25 per cent, largely independent of energy within the usable band of the PCA instrument of 2.1 - 16.0 keV. X-ray bursting and flaring activity are also evident. The dips define the orbital period of the system, and using a power spectral analysis and a cycle counting technique we derive an accurate period of P_orb = 5.16 +/- 0.01 hr. The previously-reported candidate period of 5.73$pm$0.15 hr, obtained using Ginga data, is inconsistent with our determination, perhaps due to the weakness of the dipping and the variability of the source during that observation. The dips in the RXTE observations presented here do not align with the Ginga period, however our improved period is consistent with a wide range of archival data.
قيم البحث
اقرأ أيضاً
We present the results of hard-X-ray observations of four broad-line radio galaxies (BLRGs) with the Rossi X-Ray Timing Explorer (RXTE). The original motivation behind the observations was to search for systematic differences between the BLRGs and th
eir radio-quiet counterparts, the Seyfert galaxies. We do, indeed, find that the Fe K-alpha lines and Compton reflection components, which are hallmarks of the X-ray spectra of Seyferts galaxies, are weaker in BLRGs by about a factor of 2. This observational result is in agreement with the conclusions of other recent studies of these objects. We examine several possible explanations for this systematic difference, including beaming of the primary X-rays away from the accretion disk, a low iron abundance, a small solid angle subtended by the disk to the primary X-ray source, and dilution of the observed spectrum by beamed X-rays from the jet. We find that a small solid angle subtended by the disk to the primary X-ray source is a viable and appealing explanation, while all others suffer from drawbacks. We interpret this as an indication of a difference in the inner accretion disk structure between Seyfert galaxies and BLRGs, namely that the inner accretion disks of BLRGs have the form of an ion-supported torus or an advection-dominated accretion flow, which irradiates the geometrically thin outer disk.
In X-ray binaries, rapid variability in X-ray flux of greater than an order of magnitude on time-scales of a day or less appears to be a signature of wind accretion from a supergiant companion. When the variability takes the form of rare, brief, brig
ht outbursts with only faint emission between them, the systems are called Supergiant Fast X-ray Transients (SFXTs). We present data from twice-weekly scans of the Galactic bulge by the Rossi X-ray Timing Explorer (RXTE) that allow us to compare the behaviour of known SFXTs and possible SFXT candidates with the persistently bright supergiant X-ray binary 4U 1700-377. We independently confirm the orbital periods reported by other groups for SFXTs SAX J1818.6-1703 and IGR J17544-2619. The new data do not independently reproduce the orbital period reported for XTE J1739-302, but slightly improve the significance of the original result when the data are combined. The bulge source XTE J1743-363 shows a combination of fast variability and a long-term decline in activity, the latter behaviour not being characteristic of supergiant X-ray binaries. A far-red spectrum of the companion suggests that it is a symbiotic neutron star binary rather than a high-mass binary, and the reddest known of this class: the spectral type is approximately M8 III.
The Rossi X-ray Timing Explorer made a short (10 ks) observation of the radio galaxy Centaurus A on 14 August 1996. Analysis of the combined 2.5-240 keV spectrum has revealed a heavily absorbed(NH=9.42+/-0.24 e22 cm-2) primary power law (index=1.86+/
-0.015) and an iron line due to fluorescence of cold matter (EW=162+/-25 eV). Flux from either a jet, primary flux scattered into the line of sight, or primary flux seen through a partial absorber was not required. The iron line width is unresolved at the 95% confidence level (sigma < 0.54 keV). No significant variability in the iron line flux is seen from measurements over the last two decades, while the overall continuum flux varied by more than a factor of four, which implies that the line emission region is distant from that of the primary emission. While radio-quiet Seyfert galaxies exhibit spectral components attributable to Compton reflection from cold matter, Cen A reveals no such component (exposed solid angle ratio < 0.09). This supports unified models of active galaxies that have little difference between Seyfert 2 and low luminosity radio galaxies
In 1996 during Rossi X-ray Timing Explorer (RXTE) observations of SGR 1900+14, the 89-s X-ray pulsar XTE J1906+09 was discovered. As a result of monitoring campaigns of SGR 1900+14, XTE J1906+09 was also monitored regularly in 1996 September, 1998 Ma
y-June, 1998 August-1999 July, and 2000 March-2001 January. A search for pulsations in these observations resulted in detections of only the two previously reported outbursts in 1996 September and 1998 August- September. Pulsed flux upper limits for the remaining observations indicate that XTE J1906+09 is a transient X-ray pulsar and therefore likely has a Be star companion. XTE J1906+09 was not detected with the RXTE All Sky Monitor. Pulse timing analysis of the second outburst revealed a sinusoidal signature in the pulse frequencies that is likely produced by periastron passage in an orbit. Fits to pulse phases using an orbital model and quadratic phase model have chi^2 minima at orbital periods of 26-30 days for fixed mass functions of 5, 10, 15, and 20 M_sun. The pulse shape showed intensity and energy dependent variations. Pulse phase spectroscopy was used to quantify the energy dependent variations. The phase averaged spectrum, using the pulse minimum spectrum as the background spectrum to eliminate effects from SGR 1900+14 and the galactic ridge, was well fitted by an absorbed power law with a high energy cutoff. Estimated 2-10 keV peak fluxes, corrected for contributions from the galactic ridge and SGR 1900+14, are 6E-12 ergs/cm^2/s and 1.1E-10 ergs/cm^2/s for the 1996 and 1998 outbursts, respectively. XTE J1906+09 may be a member of an unusual class of Be/X-ray binaries that do not lie on the general spin period versus orbital period correlation with the majority of Be/X-ray binaries.
During a BeppoSAX observation of the low-mass X-ray binary dip source XB 1323-619 a total of 10 type I X-ray bursts and parts of 12 intensity dips were observed. During non-bursting, non-dipping intervals, the 1-150 keV BeppoSAX spectrum can be model
led by a cutoff power-law with a photon index of 1.48 +/- 0.01, a cutoff energy of 44.1 +5.1/-4.4 keV together with a blackbody with kT of 1.77 +/- 0.25 keV contributing ~15% of the 2-10 keV flux. Absorption equivalent to 3.88 +/- 0.16x10^22 H atom cm^(-2) is required. The dips repeat with a period of 2.938 +/- 0.020 hr and span 40% of the orbital cycle. During dips the maximum reduction in 2-10 keV intensity is ~65%. The spectral changes during dips are complex and cannot be modelled by a simple absorber because of the clear presence of part of the non-dip spectrum which is not absorbed. Spectral evolution in dipping can be well modelled by progressive covering of the cutoff power-law component which must be extended, plus rapid absorption of the point-source blackbody. One of the bursts is double and 4 of the bursts occurred during dipping intervals. These bursts have 2-10 keV peak count rates reduced by only 22% on average from those occurring outside the dips, and are not heavily absorbed. One explanation for this lack of absorption is that the bursts temporarily ionize the absorbing material responsible for the dips.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
