G32.1-0.9: a new Galactic supernova remnant?
Abstract
A low surface brightness X-ray source detected serendipitously in ROSAT observations of the Galactic plane near l~32 deg is probably a previously unknown Galactic supernova remnant (SNR). The source, designated G32.1-0.9, has an approximate angular size of 30x30 arcmin^2 and an irregular X-ray morphology with brightening towards the centre. The X-ray spectrum measured by both ROSAT and ASCA is well characterized by a thermal model with a temperature ~0.8 keV and a subsolar metallicity (~0.2). The measured soft X-ray absorption is equivalent to a column density N_H~2.3x10^21 cm^-2, which is about one-quarter of the full Galactic N_H in this direction, thus implying a Galactic origin for the source. The enhanced radio emission in the region of G32.1-0.9 is plausibly interpreted as a low surface brightness partial radio shell. On the basis of the X-ray morphology and X-ray spectrum, coupled with the (albeit less secure) radio evidence, we conclude that G32.1-0.9 is probably a new composite-type Galactic SNR. There are three bright X-ray hotspots, one in each of the north-eastern, south-eastern and south-western quadrants of the source. The first (referred to as hotspot A) has a considerably harder spectrum than the rest of the object and could be an embedded source within the putative SNR or a more distant interloper in chance positional coincidence with G32.1-0.9. All three hotspots could represent regions where the supernova blast-wave has encountered regions of enhanced density within the local ISM. A Sedov analysis gives the distance of G32.1-0.9 to be ~4.6 kpc. The age of the remnant is then ~12000 yr, and the derived luminosity is L_X~8x10^34 erg s^-1.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- December 1997
- DOI:
- 10.1093/mnras/292.2.365
- Bibcode:
- 1997MNRAS.292..365F
- Keywords:
-
- Supernova Remnants;
- X Ray Sources;
- Rosat Mission;
- Milky Way Galaxy;
- Metallicity;
- Signal To Noise Ratios;
- X Ray Spectra;
- Astronomical Models;
- X Ray Absorption;
- Radio Emission;
- Astrophysics;
- ISM: INDIVIDUAL: G32.1-0.9;
- SUPERNOVA REMNANTS;
- X-RAYS: ISM