Psn J23160979-4234575 in NGC 7552
Abstract
G. Bock, Runaway Bay, Gold Coast, Queensland, Australia, reports the discovery by P. Marples (Loganholme, Queensland) of a possible supernova (red mag 17.3) on a 30-s unfiltered CCD image (limiting mag 17.5) taken by Marples on Sept. 24.46 UT with a 30-cm Meade LX200R reflector (+ SXV-H9 Starlight Xpress camera) in the course of the Backyard Observatory Supernova Search. The new object is located at R.A. = 23h16m09s.79, Decl. = -42d34'57".5 (equinox 2000.0; reference stars from UCAC4 catalogue), which is 10".9 west and 7".6 north of the nucleus of the galaxy NGC 7552. Nothing is visible at this position on Digitized Sky Survey red and infrared images (limiting red magnitude > 19). An image of the variable is viewable at website URL http://tinyurl.com/ltqr3b5. Bock confirmed the variable at red mag about 17.3 on several 30-s images (limiting mag about 18.0) taken at his Runaway Bay Observatory with a 0.35-m reflector on Sept. 24.5. S. Parker, Canterbury, New Zealand, reports that nothing is visible at this position to a limiting magnitude of about 18.5 on his images from Sept. 2.456, 10.449, and 23.662. The variable was designated PSN J23160979-4234575 when it was posted at the Central Bureau's TOCP webpage. N. Morrell, C. Contreras, C. Gonzalez, and M. M. Phillips, Las Campanas Observatory; M. Stritzinger, E. Y. Hsiao, C. Gall, and S. Holmbo, Aarhus University; F. Taddia, Stockholm University; and P. Sanchez and P. Lira, Universidad de Chile -- on behalf of the Carnegie Supernova Project -- report that an optical spectrogram (range 360-920 nm) of PSN J23160979-4234575, obtained with the Las Campanas du Pont telescope (+ WFCCD) on Sept. 27.2 UT, indicates that it is a "supernova imposter". The visual-wavelength spectrum is dominated by narrow (FWHM about 800 km/s) Balmer emission lines of H-alpha and H-beta. Given the lack of discernible [Ca II] at 729.1 and 732.4 nm, Ca II near-infrared triplet features, and the presence of Na I at 589.3 nm, the variable is found to resemble the early spectrum of the supernova imposter that was designated SN 2002bu (IAUC 7863; Smith et al. 2011, MNRAS 415, 773). Consecutive broad-band optical observations with the Swope telescope spanning Sept. 25-29 UT indicate an approximately constant absolute B-band magnitude of -13.8. The faint intrinsic luminosity, the nature of the visual-wavelength spectrum, and the probable recent non-detection altogether suggests that PSN J23160979-4234575 is a young 2008S-like supernova imposter.
- Publication:
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Central Bureau Electronic Telegrams
- Pub Date:
- October 2014
- Bibcode:
- 2014CBET.3998....1B