ترغب بنشر مسار تعليمي؟ اضغط هنا

A Further Study of the Luminosity-Dependent Cyclotron Resonance Energies of the Binary X-ray Pulsar 4U0115+63 with RXTE

115   0   0.0 ( 0 )
 نشر من قبل Motoki Nakajima
 تاريخ النشر 2006
  مجال البحث فيزياء
والبحث باللغة English
 تأليف Motoki Nakajima




اسأل ChatGPT حول البحث

The present paper reports on the RXTE observations of the binary X-ray pulsar 4U0115+63, covering an outburst in 1999 March-April with 44 pointings. The 3-30 keV PCA spectra and the 15-50 keV HEXTE spectra were analyzed jointly for the cyclotron resonance features. When the 3-50 keV luminosity at an assumed distance of 7 kpc was in the range (5-13)x10^{37} erg s^{-1}, harmonic double cyclotron features were observed in absorption at ~11 and ~22 keV, as was measured previously during typical outbursts. As the luminosity decreased below ~5x10^{37} erg s^{-1}, the second resonance disappeared, and the fundamental resonance energy gradually increased, up to $sim$16 keV at 0.16x10^{37} erg s^{-1}. These results reconfirm the report by Mihara et al. (2004) using Ginga, who observed a single absorption at ~16 keV in a minor (~10^{37} erg s^{-1}) outburst of this object. The luminosity-dependent cyclotron resonance energy may be understood as a result of a decrease in the accretion column height, in response to a decrease in the mass accretion rate.



قيم البحث

اقرأ أيضاً

273 - Y. Terada 2006
The binary X-ray pulsar A0535+262 was observed with the Suzaku X-ray observatory, on 2005 September 14 for a net exposure of 22 ksec. The source was in a declining phase of a minor outburst, exhibiting 3--50 keV luminosity of about $3.7 times 10^{35} $ ergs s$^{-1}$ at an assumed distance of 2 kpc. In spite of the very low source intensity (about 30 mCrab at 20 keV), its electron cyclotron resonance was detected clearly with the Suzaku Hard X-ray Detector, in absorption at about 45 keV. The resonance energy is found to be essentially the same as those measured when the source is almost two orders of magnitude more luminous. These results are compared with the luminosity-dependent changes in the cyclotron resonance energy, observed from 4U 0115+63 and X 0331+53.
172 - S. Sahiner METU 2011
We analyse emph{INTEGRAL} (between 2005 October and 2007 November) and emph{RXTE} (between 2007 June and 2011 March) observations of the accretion powered pulsar 4U 1907+09. From emph{INTEGRAL} IBIS-ISGRI and emph{RXTE}-PCA observations, we update pu lse period history of the source. We construct power spectrum density of pulse frequencies and find that fluctuations in the pulse frequency derivatives are consistent with the random walk model with a noise strength of $1.27times10^{-21}$ Hz s$^{-2}$. From the X-ray spectral analysis of emph{RXTE}-PCA observations, we find that Hydrogen column density is variable over the binary orbit, tending to increase just after the periastron passage. We also show that the X-ray spectrum gets hardened with decreasing X-ray flux. We discuss pulse-to-pulse variability of the source near dipping ingress and egress. We find that the source more likely undergoes in dipping states after apastron until periastron when the accretion from clumpy wind might dominate so that occasional transitions to temporary propeller state might occur.
We present timing and broad-band spectral studies of the high mass X-ray binary pulsar 4U 1909+07 using data from Suzaku observation during 2010 November 2-3. The pulse period of the pulsar is estimated to be 604.11+/-0.14 s. Pulsations are seen in t he X-ray light curve up to ~70 keV. The pulse profile is found to be strongly energy-dependent: a complex, multi-peaked structure at low energy that becomes a simple single peak at higher energy. We found that the 1-70 keV pulse averaged continuum can be fitted by the sum of a black body and a partial covering Negative and Positive power-law with EXponential cutoff (NPEX) model. A weak iron fluorescence emission line at 6.4 keV was detected in the spectrum. An absorption like feature at ~44 keV was clearly seen in the residue of the spectral fitting, independent of the continuum model adopted. To check the possible presence of a CRSF in the spectrum, we normalized the pulsar spectrum with the spectrum of the Crab Nebula. The resulting Crab ratio also showed a clear dip centered at ~44 keV. We performed statistical tests on the residue of the spectral fitting and also on the Crab spectral ratio to determine the significance of the absorption like feature and identified it as a CRSF of the pulsar. We estimated the corresponding surface magnetic field of the pulsar to be 3.8 x 10^12 Gauss.
We studied the radio spectrum of PSR B1259-63 in an unique binary with Be star LS 2883 and showed that the shape of the spectrum depends on the orbital phase. We proposed a qualitative model which explains this evolution. We considered two mechanisms that might influence the observed radio emission: free-free absorption and cyclotron resonance. Recently published results have revealed a new aspect in pulsar radio spectra. There were found objects with turnover at high frequencies in spectra, called gigahertz-peaked spectra (GPS) pulsars. Most of them adjoin such interesting environments as HII regions or compact pulsar wind nebulae (PWN). Thus, it is suggested that the turnover phenomenon is associated with the environment than being related intrinsically to the radio emission mechanism. Having noticed the apparent resemblance between the B1259-63 spectrum and the GPS, we suggest that the same mechanisms should be responsible for both cases. Therefore, the case of B1259-63 can be treated as a key factor to explain the GPS phenomenon observed for the solitary pulsars with interesting environments and also another types of spectra (e.g. with break).
We present a comprehensive timing and spectral studies of Be/X-ray binary pulsar EXO 2030+375 using extensive Rossi X-ray Timing Explorer observations from 1995 till 2011, covering numerous Type I and 2006 Type II outbursts. Pulse profiles of the pul sar were found to be strongly luminosity dependent. At low luminosity, the pulse profile consisted of a main peak and a minor peak that evolved into a broad structure at high luminosity with a significant phase shift. A narrow and sharp absorption dip, also dependent on energy and luminosity, was detected in the pulse profile. Comparison of pulse profiles showed that the features at a particular luminosity are independent of type of X-ray outbursts. This indicates that the emission geometry is solely a function of mass accretion rate. The broadband energy spectrum was described with a partial covering high energy cutoff model as well as a physical model based on thermal and bulk Comptonization in accretion column. We did not find any signature of cyclotron resonance scattering feature in the spectra obtained from all the observations. A detailed analysis of spectral parameters showed that, depending on source luminosity, the power-law photon index was distributed in three distinct regions. It suggests the phases of spectral transition from sub-critical to super-critical regimes in the pulsar as proposed theoretically. A region with constant photon index was also observed in ~(2-4) x 10^37 erg/s range, indicating critical luminosity regime in EXO 2030+375.
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