The optical counterpart to the luminous X-ray supernova remnant in NGC 6946

Abstract

view Abstract Citations (33) References (31) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS The Optical Counterpart to the Luminous X-Ray Supernova Remnant in NGC 6946 Blair, William P. ; Fesen, Robert A. Abstract We identify a high surface brightness optical supernova remnant (SNR) in NGC 6946 that is coincident with a bright soft X-ray point source detected in a ROSAT PSPC image of this galaxy (Schlegel 1994). Optical CCD/interference filter images and spectra show the object to have an observed Hα flux of 1.9 x 10^-14^ ergs cm^-2^ s^-1^, corresponding to an intrinsic Hα luminosity of 2 x 10^38^ (d/5.1 Mpc)^2^ ergs s^- 1^. A moderate-resolution optical spectrum shows normal SNR line emissions, with no high velocities (V <400 km s^-1^) or relative line strengths indicative of enriched heavy element abundances. This suggests a relatively old SNR, a conclusion supported by the presence of an emission nebula at its position on photographic plates dating back to at least 1921. With both an optical line flux and soft X-ray flux exceeding those of other luminous extragalactic SNRs, this object may have an optical luminosity near the maximum limit for SNRs. Assuming current flux levels, we estimate the SNR's age to be <= 3500 yr and suggest its unusual luminosity is due to both its expansion into dense surroundings and a relatively low column density along our line of sight. Publication: The Astrophysical Journal Pub Date: April 1994 DOI: 10.1086/187285 Bibcode: 1994ApJ...424L.103B Keywords: Balmer Series; Data Reduction; H Alpha Line; Light (Visible Radiation); Optical Emission Spectroscopy; Supernova Remnants; X Ray Sources; Charge Coupled Devices; Line Of Sight; Luminosity; Photographic Plates; Rosat Mission; Astrophysics; GALAXIES: INDIVIDUAL NGC NUMBER: NGC 6946; ISM: SUPERNOVA REMNANTS full text sources ADS | data products SIMBAD (6) NED (1) HEASARC (1)