اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThe Nature of Unresolved Soft X-ray Emission from the Galactic Disk
57
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
Although about 40% of the soft X-ray background emission in 0.4 to 1 keV range has extragalactic origins and thus is totally blocked by the Galactic absorption in midplane directions, it decreases at most by about 20 % in midplane. Suzaku observation of the direction, (l, b) = (235, 0), showed an OVII Kalpha emission intensity comparable with that of the MBM-12 on cloud Suzaku observation, but revealed a narrow bump peaked at ~ 0.9 keV. The latter component is partly filling the decrease of the extragalactic component in midplane. The feature can be well represented by a thin thermal emission with a temperature of about 0.8 keV. Because of the high pressure implied for spatially extended hot gas, the emission is likely a sum of unresolved faint sources. We consider a large fraction of the emission originates from faint dM stars. We constructed a model spectrum for spatially unresolved dM stars that consistently explains the observed spectrum and the surface brightness. The model also suggests that the emission from dM stars decreases very rapidly with increasing b, and thus that it cannot compensate entirely the decrease of the extragalactic component at b ~ 2 - 10 deg.
قيم البحث
اقرأ أيضاً
We present measurements of the Galactic halos X-ray emission for 110 XMM-Newton sight lines, selected to minimize contamination from solar wind charge exchange emission. We detect emission from few million degree gas on ~4/5 of our sight lines. The t
emperature is fairly uniform (median = 2.22e6 K, interquartile range = 0.63e6 K), while the emission measure and intrinsic 0.5--2.0 keV surface brightness vary by over an order of magnitude (~(0.4-7)e-3 cm^-6 pc and ~(0.5-7)e-12 erg cm^-2 s^-1 deg^-2, respectively, with median detections of 1.9e-3 cm^-6 pc and 1.5e-12 erg cm^-2 s^-1 deg^-2, respectively). The high-latitude sky contains a patchy distribution of few million degree gas. This gas exhibits a general increase in emission measure toward the inner Galaxy in the southern Galactic hemisphere. However, there is no tendency for our observed emission measures to decrease with increasing Galactic latitude, contrary to what is expected for a disk-like halo morphology. The measured temperatures, brightnesses, and spatial distributions of the gas can be used to place constraints on models for the dominant heating sources of the halo. We provide some discussion of such heating sources, but defer comparisons between the observations and detailed models to a later paper.
Collecting experimental insight into the relativistic particle populations and emission mechanisms at work within TeV-emitting blazar jets, which are spatially unresolvable in most bands and have strong beaming factors, is a daunting task. New observ
ational information has the potential to lead to major strides in understanding the acceleration site parameters. Detection of molecular carbon monoxide (CO) in TeV emitting blazars, however, implies the existence of intrinsic gas, a connection often found in photo-dissociated region models and numerical simulations. The existence of intrinsic gas within a blazar could provide a target photon field for Compton up-scattering of photons to TeV energies by relativistic particles. We investigate the possible existence of intrinsic gas within the three TeV emitting blazars RGB J0710+591, W Comae and 1ES 1959+650 which have measurements or upper limits on molecular CO line luminosity using an independent technique which is based on the spectral analysis of soft X-rays. Evidence for X-ray absorption by additional gas beyond that measured within the Milky Way is searched for in Swift X-ray Telescope (XRT) data between 0.3 and 10 keV. Without complementary information from another measurement, additional absorption could be misinterpreted as an intrinsically curved X-ray spectrum since both models can frequently fit the soft X-ray data. After breaking this degeneracy, we do not find evidence for intrinsically curved spectra for any of the three blazars. Moreover, no evidence for intrinsic gas is evident for RGB J0710+591 and W Comae, while the 1ES 1959+650 XRT data support the existence of intrinsic gas with a column density of $sim1times10^{21}$cm$^{-2}$.
We use the observed unresolved cosmic X-ray background (CXRB) in the 0.5-2 keV band and existing upper limits on the 21-cm power spectrum to constrain the high-redshift population of X-ray sources, focusing on their effect on the thermal history of t
he Universe and the cosmic 21-cm signal. Because the properties of these sources are poorly constrained, we consider hot gas, X-ray binaries and mini-quasars (i.e., sources with soft or hard X-ray spectra) as possible candidates. We find that (1) the soft-band CXRB sets an upper limit on the X-ray efficiency of sources that existed before the end of reionization, which is one-to-two orders of magnitude higher than typically assumed efficiencies, (2) hard sources are more effective in generating the CXRB than the soft ones, (3) the commonly-assumed limit of saturated heating is not valid during the first half of reionization in the case of hard sources, with any allowed value of X-ray efficiency, (4) the maximal allowed X-ray efficiency sets a lower limit on the depth of the absorption trough in the global 21-cm signal and an upper limit on the height of the emission peak, while in the 21-cm power spectrum it sets a minimum amplitude and frequency for the high-redshift peaks, and (5) the existing upper limit on the 21-cm power spectrum sets a lower limit on the X-ray efficiency for each model. When combined with the 21-cm global signal, the CXRB will be useful for breaking degeneracies and helping constrain the nature of high-redshift heating sources.
In this paper the current status of high-energy research on the hard X-ray characteristics of the persistent emission from magnetars is reviewed. Focus is put on recent intriguing results for 1RXS J1708-40, from phase resolved spectral analysis over
a 2 decades wide energy band (~3-300 keV) combining contemporaneous RXTE, XMM and INTEGRAL data. For 1E 1841-045 and SGR 1806-10 we also present updated results. The perspective for future MAXI observations for this source class is also addressed.
We have detected transient X-ray activity from the X-ray burster 4U~0614+091 simultaneously with BATSE/CGRO (20-100 keV) and ASM/RXTE (1-12 keV). The peak fluxes reach approximately 40 mCrab in both instruments over a period of about 20 days. The var
iable emission shows a clear anticorrelation of the hard X-ray flux with the soft X-ray count rate. The observed anticorrelation is another clear counterexample to the notion that only black hole binaries exhibit such correlations. The individual spectra during this period can be fit by power laws with photon indices 2.2+-0.3 (ASM) and 2.7+-0.4 (BATSE), while the combined spectra can be described by a single power law with index 2.09+-0.08. BATSE and the ASM/RXTE are a good combination for monitoring X-ray sources over a wide energy band.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
