اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThe nature of the 4th track in GX 5-1: discovery of Fe XXVI RRC in massive flares
37
0
0.0
(
0
)
تأليف
M. J. Church
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We present an explanation of the 4th branch of the Z-track based on analysis of high-quality RXTE data on the source GX 5-1. Spectral analysis shows that the physical evolution on the 4th track is a continuation of the flaring branch which we previously proposed consists of unstable nuclear burning of the accretion flow on the neutron star. In flaring there is a huge increase of the neutron star emission from a volume that increases to a radius of 21 km. The 4th branch is shown to consist of flaring under conditions that the mass accretion rate and thus the total source luminosity is falling. We detect strong emission on the flaring and 4th branches at energies between 7.8 - 9.4 keV inconsistent with origin as Fe K emission, which we suggest is the radiative recombination continua (RRC) of iron Fe XXVI at 9.28 keV and of lower states. Evolution of the emission takes place, the energy falling but the flux increasing strongly, consistent with production in the large volume of unstable nuclear burning around the neutron star which eventually cools.
قيم البحث
اقرأ أيضاً
We report on the detection of a pulsating Fe Ka line in the High Mass X-ray Binary (HMXB) GX 301-2, from a 40-ks Chandra observation near periastron. The pulsations in the Fe Ka emission appeared only in the first 7 ks of the observation, with a peri
od and phase profile similar to those of the continuum. The presence of pulsed fluorescent lines is an unusual property in HMXBs. After 7 ks, the continuum flux increased by a factor of three, the Fe Ka flux increased only by about 10%, and the pulsating signal in the line disappeared. Finally, in the second half of the observation, both the continuum and the line flux dropped by a similar factor of 2. We suggest that the pulsating component of the Fe Ka line is coming from a transient non-isotropic distribution of dense gas around the neutron star, for example an accretion stream induced by periastron passage, or from the illuminated surface of the donor star.
We present NuSTAR observations of the luminous neutron star low-mass X-ray binary (NS LMXB) and Z source GX 5-1. During our three observations made with separations of roughly two days, the source traced out an almost complete Z track. We extract spe
ctra from the various branches and fit them with a continuum model that has been successfully applied to other Z sources. Surprisingly, and unlike most of the (luminous) NS-LMXBs observed with NuSTAR, we do not find evidence for reflection features in any of the spectra of GX 5-1. We discuss several possible explanations for the absence of reflection features. Based on a comparison with other accreting neutron star systems and given the high luminosity of GX 5-1 (~1.6-2.3 times the Eddington luminosity, for a distance of 9 kpc), we consider a highly ionized disk the most likely explanation for the absence of reflection features in GX 5-1.
We report the discovery of radio emission from the accreting X-ray pulsar and symbiotic X-ray binary GX 1+4 with the Karl G. Jansky Very Large Array. This is the first radio detection of such a system, wherein a strongly magnetized neutron star accre
tes from the stellar wind of an M-type giant companion. We measure a $9$ GHz radio flux density of $105.3 pm 7.3$ $mu$Jy, but cannot place meaningful constraints on the spectral index due to a limited frequency range. We consider several emission mechanisms that could be responsible for the observed radio source. We conclude that the observed properties are consistent with shocks in the interaction of the accretion flow with the magnetosphere, a synchrotron-emitting jet, or a propeller-driven outflow. The stellar wind from the companion is unlikely to be the origin of the radio emission. If the detected radio emission originates from a jet, it would show that that strong magnetic fields ($geq 10^{12}$ G) do not necessarily suppress jet formation.
The simultaneous and coupled evolution of horizontal branch oscillation (HBO) and normal branch oscillation (NBO) in Z-type sources suggests that the production of HBO is connected to NBO and is caused by changes in the physical/radiative properties
of the inner accretion disk, although there is a lack of substantial spectral evidence to support this. In this {it Letter}, we present the results of an analysis of a RXTE observation of a Z source GX~5-1, where the 6 Hz NBO is simultaneously detected along with a HBO at 51 Hz. The variations in the intensity and the associated power density spectrum indicate that the HBO and NBO are strongly coupled, originating from the same location in the inner accretion disk. The absence of HBO and NBO in the lower energy bands, an increase in the rms amplitude with energy and a smooth transition among them suggest that they are produced in the hot inner regions of the accretion disk. Based on a spectral analysis, we found a signature of changing or physically modified inner disk front during the coupled HBO and NBO evolution. We explore the various models to explain the observed phenomenon and propose that the NBO is affiliated to the oscillations in the thick/puffed-up inner region of the accretion disk.
We present our Swift monitoring campaign of the slowly rotating neutron star Be/X-ray transient GX 304-1 (spin period of ~275 s) when the source was not in outburst. We found that between its type-I outbursts the source recurrently exhibits a slowly
decaying low-luminosity state (with luminosities of 10^(34-35) erg/s). This behaviour is very similar to what has been observed for another slowly rotating system, GRO J1008-57. For that source, this low-luminosity state has been explained in terms of accretion from a non-ionised (cold) accretion disk. Due to the many similarities between both systems, we suggest that GX 304-1 enters a similar accretion regime between its outbursts. The outburst activity of GX 304-1 ceased in 2016. Our continued monitoring campaign shows that the source is in a quasi-stable low-luminosity state (with luminosities a few factors lower than previously seen) for at least one year now. Using our NuSTAR observation in this state, we found pulsations at the spin period, demonstrating that the X-ray emission is due to accretion of matter onto the neutron star surface. If the accretion geometry during this quasi-stable state is the same as during the cold-disk state, then matter indeed reaches the surface (as predicted) during this latter state. We discuss our results in the context of the cold-disk accretion model.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
