1997/12/01 by E. A. Magnier, F. A. Primini, S. Prins +2 · 1 citation
Physics and Astronomy · #Gamma-ray bursts and supernovae #Astrophysics and Cosmic Phenomena #Astronomy and Astrophysical Research #Physics #ROSAT #Supernova #Astronomy #Astrophysics #Galaxy
paper · pdf · doi:10.1086/304917
openalex publication_date 1997/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/07/31
We have observed M31 using the ROSAT HRI. We have searched for X-ray emission from supernova remnants (SNRs) previously identified from surveys using narrowband optical observations. We find that a surprisingly small number of the identified SNRs are detected in X-rays at a threshold of ≈ 10 35 ergs s -1 . The absence of detected X-ray flux from many of the optically identified SNRs suggests that the local ISM density in the vicinity of these SNRs is typically quite low, less than 0.1 cm -3 . The few that have been detected likely represent the upper end of the density distribution, having implied ambient densities in the range 0.1 to >10 cm -3 . Since H I observations show that all SNRs are in regions with large column densities, which implies densities of 1-10 cm -3 , a multicomponent ISM must be invoked. Our measured densities are upper limits for the dominant low-density component of the ISM.