* Astronomy

Members Login
Username 
 
Password 
    Remember Me  
Home -> Astronomy News -> Stars/galaxy News -> HESS J1731-347
Post Info TOPIC: HESS J1731-347
Blobrana


L

Posts: 131433
Date:
RE: HESS J1731-347
Permalink  
 

Title: The neutron star in HESS J1731-347: CCOs as laboratories to study the equation of state of superdense matter
Author: D. Klochkov, V. Suleimanov, G. Pühlhofer, D. G. Yakovlev, A. Santangelo, K. Werner

Context: Central Compact Objects (CCOs) in supernova remnants are isolated thermally emitting neutron stars (NSs). They are most probably characterized by a magnetic field strength that is roughly two orders of magnitude lower than that of most of the radio and accreting pulsars. The thermal emission of CCOs can be modelled to obtain constraints on the physical parameters of the star such as its mass, radius, effective temperature, and chemical composition.
Aims: The CCO in HESS, J1731-347 is one of the brightest objects of this class. We present our analysis of two new XMM-Newton observations of the source which increase the total exposure time of the by a factor of five compared to the analyses presented before.
Methods: We use our numerical spectral models for carbon and hydrogen atmospheres to fit the spectrum of the CCO. From our fits, we derive constraints on the physical parameters of the emitting star. We also use the new data to derive new upper limits on pulsations and to confirm the absence of a long-term variability.
Results: The analysis shows that atmosphere spectral models are clearly preferred by the fit over the blackbody function. Under the assumption that the X-ray emission is uniformly produced by the entire star surface, hydrogen atmosphere models lead to uncomfortably large distances of the CCO, above 7-8 kpc. On the other hand, the carbon atmosphere model formally excludes distances above 5-6 kpc and is compatible with the source located in the Scutum-Crux (3 kpc) or Norma-Cygnus (4.5 kpc) Galactic spiral arm. We provide and discuss the corresponding confidence contours in the NS mass-radius plane. The measured effective temperature indicates that the NS is exceptionally hot for the estimated age of 30 kyr. We discuss possible cooling scenarios to explain this property, as well as possible additional constraints on the star mass and radius from cooling theory.

Read more (1322kb, PDF)



__________________
Blobrana


L

Posts: 131433
Date:
Permalink  
 

Title: Suzaku Observations of the Non-thermal Supernova Remnant HESS J1731-347
Authors: Aya Bamba (1), Gerd Puehlhofer (2), Fabio Acero (3), Dmitry Klochkov (2), Wenwu Tian (4,5), Ryo Yamazaki (1), Zhiyuan Li (6), Dieter Horns (7), Karl Kosack (8), Nukri Komin (9) ((1) Aoyama Gakuin U., (2) U. Tuebingen, (3) U. Montpellier, (4) National Astronomical Observatories, (5) U. Calgary, (6) Harvard-Smithsonian Center for Astrophysics, (7) U. Hamburg, (8) CEA Saclay, (9) U. Savoie)

A detailed analysis of the nonthermal X-ray emission from the North-Western and Southern parts of the supernova remnant (SNR) HESS J1731 - 347 with Suzaku is presented. The shell portions covered by the observations emit hard and line-less X-rays. The spectrum can be reproduced by a simple absorbed power-law model with a photon index \Gamma of 1.8-2.7 and an absorption column density N_{H} of (1.0-2.1) x 10^{22} cm^{-2}. These quantities change significantly from region to region; the North-Western part of the SNR has the hardest and most absorbed spectrum. The Western part of the X-ray shell has a smaller curvature than North-Western and Southern shell segments. A comparison of the X-ray morphology to the Very High Energy (VHE) gamma-ray and radio images was performed. The efficiency of electron acceleration and emission mechanism in each portion of the shell are discussed. Thermal X-ray emission from the SNR was searched for but could not be detected at a significant level.

Read more (1651kb, PDF)

 

X-Ray Emission from HESS J1731-347/SNR G353.6-0.7 and central compact source XMMS J173203-344518

Read more  



__________________
Page 1 of 1  sorted by
 
Quick Reply

Please log in to post quick replies.
Home -> Astronomy News -> Stars/galaxy News -> HESS J1731-347


Create your own FREE Forum
Report Abuse 		Powered by ActiveBoard