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Register a new userSuzaku Discovery of Fe K-Shell Line from the O-Rich SNR G292.0+1.8
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Added by
Fumiyoshi Kamitsukasa
Publication date
2014
fields
Physics
and research's language is
English
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We report the Suzaku/XIS results of the Galactic oxygen-rich supernova remnant (SNR), G292.0+1.8, a remnant of a core-collapse supernova. The X-ray spectrum of G292.0+1.8 consists of two type plasmas, one is in collisional ionization equilibrium (CIE) and the other is in non-equilibrium ionization (NEI). The CIE plasma has nearly solar abundances, and hence would be originated from the circumstellar and interstellar mediums. The NEI plasma has super-solar abundances, and the abundance pattern indicates that the plasma originates from the supernova ejecta with a main sequence of 30-35 Msolar. Iron K-shell line at energy of 6.6 keV is detected for the first time in the NEI plasma.
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We report the global distribution of the intensities of the K-shell lines from the He-like and H-like ions of S, Ar, Ca and Fe along the Galactic plane. From the profiles, we clearly separate the Galactic center X-ray emission (GCXE) and the Galactic ridge X-ray emission (GRXE). The intensity profiles of the He-like K$alpha$ lines of S, Ar, Ca and Fe along the Galactic plane are approximately similar with each other, while not for the H-like Ly$alpha$ lines. In particular, the profiles of H-like Ly$alpha$ of S and Fe show remarkable contrast; a large excess of Fe and almost no excess of S lines in the GCXE compared to the GRXE. Although the prominent K-shell lines are represented by $sim$1 keV and $sim$7 keV temperature plasmas, these two temperatures are not equal between the GCXE and GRXE. In fact, the spectral analysis of the GCXE and GRXE revealed that the $sim$1 keV plasma in the GCXE has lower temperature than that in the GRXE, and vice versa for the $sim$7 keV plasma.
We present high spatial resolution X-ray spectroscopy of supernova remnant G292.0+1.8 with the {sl Chandra} observations. The X-ray emitting region of this remnant was divided into 25 $times$ 25 pixels with a scale of 20$arcsec$ $times$ 20$arcsec$ each. Spectra of 324 pixels were created and fitted with an absorbed one component non-equilibrium ionization model. With the spectral analysis results we obtained maps of absorbing column density, temperature, ionization age, and the abundances for O, Ne, Mg, Si, S, and Fe. The abundances of O, Ne and Mg show tight correlations between each other in the range of about two orders of magnitude, suggesting them all from explosive C/Ne burning. Meanwhile, the abundances of Si and S are also well correlated, indicating them to be the ashes of explosive explosive O-burning or incomplete Si-burbing. The Fe emission lines are not prominent among the whole remnant, and its abundance are significantly deduced, indicating that the reverse shock may have not propagated to the Fe-rich ejecta. Based on relative abundances of O, Ne, Mg, Si and Fe to Si, we suggest a progenitor mass of $25-30 M_{odot}$ for this remnant.
We present observations of a transient He-like Fe K alpha absorption line in Suzaku observations of the black hole binary Cygnus X-1 on 2011 October 5 near superior conjunction during the high/soft state, which enable us to map the full evolution from the start and the end of the episodic accretion phenomena or dips for the first time. We model the X-ray spectra during the event and trace their evolution. The absorption line is rather weak in the first half of the observation, but instantly deepens for ~10 ks, and weakens thereafter. The overall change in equivalent width is a factor of ~3, peaking at an orbital phase of ~0.08. This is evidence that the companion stellar wind feeding the black hole is clumpy. By analyzing the line with a Voigt profile, it is found to be consistent with a slightly redshifted Fe XXV transition, or possibly a mixture of several species less ionized than Fe XXV. The data may be explained by a clump located at a distance of ~10^(10-12) cm with a density of ~10^((-13)-(-11)) g cm^-3, which accretes onto and/or transits the line-of-sight to the black hole, causing an instant decrease in the observed degree of the ionization and/or an increase in density of the accreting matter. Continued monitoring for individual events with future X-ray calorimeter missions such as ASTRO-H and AXSIO will allow us to map out the accretion environment in detail and how it changes between the various accretion states.
We report the discovery of pulsed X-ray emission from the compact object CXOU J112439.1-591620 within the supernova remnant (SNR) G292.0+1.8 using the High Resolution Camera on the Chandra X-ray Observatory. The X-ray period (P=0.13530915 s) is consistent with extrapolation of the radio pulse period of PSR J1124-5916 for a spindown rate of dP/dt=7.6E-13 s/s. The X-ray pulse is single peaked and broad with a FWHM width of 0.23P (83 degrees). The pulse-averaged X-ray spectral properties of the pulsar are well described by a featureless power law model with an absorbing column density, N_H= 3.1E21 atoms/cm^2; photon index, gamma = 1.6; and unabsorbed 0.3-10 keV band luminosity, L_X = 7.2E32 erg/s. We plausibly identify the location of the pulsars termination shock. Pressure balance between the pulsar wind and the larger synchrotron nebula, as well as lifetime issues for the X-ray-emitting electrons, argues for a particle- dominated PWN that is far from the minimum energy condition. Upper limits on the surface temperature of the neutron star are at, or slightly below, values expected from ``standard cooling curves. There is no optical counterpart to the new pulsar; its optical luminosity is at least a factor of 5 below that of the Crab pulsar.
G326.3$-$1.8 (also known as MSH 15$-$56) has been detected in radio as a middle-aged composite supernova remnant (SNR) consisting of an SNR shell and a pulsar wind nebula (PWN), which has been crushed by the SNRs reverse shock. Previous $gamma$-ray studies of SNR G326.3$-$1.8 revealed bright and extended emission with uncertain origin. Understanding the nature of the $gamma$-ray emission allows probing the population of high-energy particles (leptons or hadrons) but can be challenging for sources of small angular extent. With the recent $textit{Fermi}$ Large Area Telescope data release Pass 8, we investigate the morphology of this SNR to disentangle the PWN from the SNR contribution. We perform a morphological and spectral analysis from 300 MeV to 300 GeV. We use the reconstructed events with the best angular resolution to separately investigate the PWN and the SNR emissions, which is crucial to accurately determine the spectral properties of G326.3$-$1.8 and understand its nature. The centroid of the $gamma$-ray emission evolves with energy and is spatially coincident with the radio PWN at high energies (E $>$ 3 GeV). The morphological analysis reveals that a model considering two contributions from the SNR and the PWN reproduces the $gamma$-ray data better than a single-component model. The associated spectral analysis using power laws shows two distinct spectral features, a softer spectrum for the remnant ($Gamma$ = 2.17 $pm$ 0.06) and a harder spectrum for the PWN ($Gamma$ = 1.79 $pm$ 0.12), consistent with hadronic and leptonic origin for the SNR and the PWN respectively. Focusing on the SNR spectrum, we use one-zone models to derive some physical properties and, in particular, we find that the emission is best explained with a hadronic scenario in which the large target density is provided by radiative shocks in HI clouds struck by the SNR.
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