اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدA Cr-K emission line survey in young supernova remnants with Chandra
53
0
0.0
(
0
)
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We performed a Cr-K emission line survey in young supernova remnants (SNRs) with the Chandra archival data. Our sample includes W49B, Cas A, Tycho and Kepler. We confirmed the existence of the Cr line in W49B and discovered this emission line in the other three SNRs. The line center energies, equivalent widths (EWs) and fluxes of the Cr lines are given. The Cr in Cas A is in a high ionization state while that in Tycho and Kepler is in a much lower one. We find a good positive correlation between Cr and Fe line center energies, suggesting a common origin of Cr and Fe in the nucleosynthesis, which is consistent with the theoretical predictions. We propose that the EW ratio between Cr and Fe can be used as a supplementary constraint on the progenitors properties and the explosion mechanism.
قيم البحث
اقرأ أيضاً
Supernova remnants (SNRs) have long been hypothesized as the main source of Galactic Cosmic Rays up to PeV energies. Some of them have indeed been shown to accelerate protons to TeV energies and above. But which of them are indeed efficient accelerat
ors of protons and nuclei? And up to which energies can they accelerate these particles? Measurements of non-thermal emission, especially in the X-ray and gamma-ray regimes, are essential to answer these questions. The High-Altitude Water Cherenkov (HAWC) observatory, surveying the northern TeV gamma-ray sky, is currently the most sensitive wide field-of-view survey instrument in the VHE (very-high-energy, $>$100 GeV) range. With more than three years of data recorded, HAWC is ideally suited for an unbiased survey of gamma-ray emission from galactic SNRs, particularly at TeV energies and above. In this proceeding, I will give an overview of recent measurements of VHE gamma-ray emission from SNRs with the HAWC Observatory. Combined with data from other wavelengths, these measurements are used to derive information about the underlying particle populations such as the maximum acceleration energy and whether leptonic or hadronic processes are responsible for the emission.
Supernova remnants are known to accelerate cosmic rays (CRs) on account of their non-thermal emission of radio waves, X-rays, and gamma rays. However, the ability to accelerate CRs up to PeV-energies has yet to be demonstrated. The presence of cut-of
fs in the gamma-ray spectra of several young SNRs led to the idea that PeV energies might only be achieved during the very initial stages of a remnants evolution. We use the time-dependent acceleration code RATPaC to study the acceleration of cosmic rays in supernovae expanding into dense environments around massive stars, where the plentiful target material might offer a path to the detection of gamma-rays by current and future experiments. We performed spherically symmetric 1-D simulations in which we simultaneously solve the transport equations for cosmic rays, magnetic turbulence, and the hydrodynamical flow of the thermal plasma in the test-particle limit. We investigated typical parameters of the circumstellar medium (CSM) in the freely expanding winds around red supergiant (RSG) and luminous blue variable (LBV) stars. The maximum achievable energy might be limited to sub-PeV energies despite strong magnetic fields close to the progenitor star that enhance turbulence-damping by cascading: we find a maximum CR energy of 100-200 TeV, reached within one month after explosion. The peak luminosity for a LBV progenitor is 1e43 erg/s (1e42 erg/s) at GeV (TeV) energies and, for a RSG progenitor, 1e41 erg/s (1e40 erg/s). All calculated SNe reach their peak gamma-ray luminosity after <~1 month and then fade at a rate ~1/t as long as the SN shock remains in the freely expanding wind of the progenitor. Potentially detectable gamma-ray signals can be expected in the Fermi-LAT waveband weeks to months after an explosion into a freely expanding wind.
Supernova remnants (SNRs) retain crucial information about both their parent explosion and circumstellar material left behind by their progenitor. However, the complexity of the interaction between supernova ejecta and ambient medium often blurs this
information, and it is not uncommon for the basic progenitor type (Ia or core-collapse) of well-studied remnants to remain uncertain. Here we present a powerful new observational diagnostic to discriminate between progenitor types and constrain the ambient medium density of SNRs solely using Fe K-shell X-ray emission. We analyze all extant Suzaku observations of SNRs and detect Fe K alpha emission from 23 young or middle-aged remnants, including five first detections (IC 443, G292.0+1.8, G337.2-0.7, N49, and N63A). The Fe K alpha centroids clearly separate progenitor types, with the Fe-rich ejecta in Type Ia remnants being significantly less ionized than in core-collapse SNRs. Within each progenitor group, the Fe K alpha luminosity and centroid are well correlated, with more luminous objects having more highly ionized Fe. Our results indicate that there is a strong connection between explosion type and ambient medium density, and suggest that Type Ia supernova progenitors do not substantially modify their surroundings at radii of up to several parsecs. We also detect a K-shell radiative recombination continuum of Fe in W49B and IC 443, implying a strong circumstellar interaction in the early evolutionary phases of these core-collapse remnants.
We present dust features and masses observed in young supernova remnants (SNRs) with Spitzer IRS mapping and staring observations of four youngest supernova remnants: SNR 1E102.2-7219 (E0102) in the SMC, Cas A and G11.2-0.3 in our Galaxy, and N132D i
n the LMC. The spectral mapping data revealed a number of dust features which include 21 micron-peak dust and featureless dust in Cas A and 18-micron peak dust in E0102 and N132D. The 18 micron-peak feature is fitted by a mix of MgSiO$_3$ and solid Si dust grains, while the 21-micron peak dust is by a mix of silicates and FeO; we also explore dust fitting using Continuous Distribution of Ellipsoid grain models. We report detection of CO fundamental band from Cas A in near-infrared. We review dust features observed and identified in other SNRs. The dust emission is spatially correlated with the ejecta emission, showing dust is formed in SN ejecta. The spectra of E0102 show rich gas lines from ejecta including strong ejecta lines of Ne and O, including two [Ne III] lines and two [Ne V] lines which allow us to diagnostic density and temperature of the ejecta and measure the ejecta masses. E0102 and N132D show weak or lacking Ar, Si, and Fe ejecta, whereas the young Galactic SNR Cas A show strong Ar, Si, and S and weak Fe. We discuss compositions and masses of dust and association with those of ejecta and finally, dust contribution from SNe to early Universe.
We report on a 95 GHz ($8_0-7_1$ A$^{+}$) methanol (CH$_3$OH) emission survey with the Purple Mountain Observatory Delingha 13.7 m telescope. Eight supernova remnants (SNRs) with angular size $lesssim$ 10 were observed, but emission was only detected
in three SNRs near the Galactic center (Sgr A East, G 0.1-0.1, and G 359.92-0.09). CH$_3$OH emission mainly surrounds the SNRs and can be decomposed into nine spatial peaks with velocity range of eight peaks being (-30, 70) km s$^{-1}$, and the other (70, 120) km s$^{-1}$. They are probably excited by interaction with these SNRs and adjacent molecular gas in the central molecular zone (CMZ), although star formation may play an important role in exciting CH$_3$OH emission in some regions of CMZ. We infer that tidal action is unlikely to be an excitation source for CH$_3$OH emission.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
