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PNV J01335347+3045132 is a Likely Red LPV in M33

ATel #6716; K. Hornoch (Astronomical Institute, Ondrejov, Czech Republic)
on 18 Nov 2014; 22:33 UT
Credential Certification: Allen W. Shafter (aws@nova.sdsu.edu)

Subjects: Optical, Nova, Transient, Variables

Information about a discovery of another possible nova in M33 by the Lick Observatory Supernova Search (LOSS) was recently posted here.

A search for known variable sources close to the position of the PNV J01335347+3045132 reveals a variable object (having amplitude of the brightness changes > 3 mag in Sloan i'-band and color index (g'-i') ~ 3.5 mag around its maximum light) designated No. 143030 in the Deep Canada-France-Hawaii Telescope photometric survey of the entire M33 galaxy - I. Catalogue of 36000 variable point sources, Hartman et al. (2006, MNRAS, 371, 1405). The variable object is located at R.A. = 1h33m53s.53, Decl. = +30o45'13".1 which is 0.78" from the position of the PNV J01335347+3045132. A light curve of the variable taken from Hartman et al. is available through the link below.

A search in the Survey of Local Group Galaxies Currently Forming Stars: I. UBVRI Photometry of Stars in M31 and M33 by Massey et al. (2006, AJ, 131, 2478) reveals no counterpart of the object in the catalog, although the object is visible on a few Massey's I-band images as a faint source. Presence of the object on a few images only (apparently caught well below its maximum light by the Survey) is the reason why it is not in the catalog.

The existing counterpart showing large amplitude brightness changes and a red color is consistent with classification of the PNV J01335347+3045132 as a red LPV in M33, not a nova. This object appears to be yet another case of the "discovery" of a known variable object around its maximum brightness masquerading as a possible M33 nova, e.g., see ATel #4314, #4315, #4341, #6388, #6697, and #6703. M33 is especially rich in red LPV stars that are bright enough around maximum light to be detected by surveys using small telescopes. Such objects can significantly bias the sample of M33 nova candidates unless they are first screened to remove cataloged variable objects, or are spectroscopically classified.

Light curve