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UV/Optical discovery of a Possible Nova in M31

ATel #10098; K. Hornoch (Astronomical Institute, Ondrejov, Czech Republic), M. Henze (CSIC-IEEC), S. C. Williams (Lancaster), H. Kucakova (Astronomical Institute, Charles U., Prague, Czech Republic), M. J. Middleton (Cambridge)
on 19 Feb 2017; 18:13 UT
Credential Certification: Martin Henze (henze@ice.cat)

Subjects: Optical, Ultra-Violet, Nova, Transient

We report the discovery of a possible nova in M31 on a co-added 1080-s R-band CCD frame taken on 2017 Feb. 15.725 UT with the 0.65-m telescope at Ondrejov. The new object is visible also on a few prediscovery frames taken with the same instrumentation. The object designated PNV J00425145+4118352 is located at R.A. = 0h42m51s.45, Decl. = +41o18'35".2 (equinox 2000.0), which is 80.3" east and 146.7" north of the center of M31 (see link to discovery image below).

The object was independently discovered in a routine monitoring observation of the M31 central field with the ultra-violet/optical telescope (UVOT) aboard the Swift satellite. It is clearly detected in a 2.3-ks UVOT observation starting on 2017-02-05.00 UT (MJD 57789.00) with a uvw1 filter (central wavelength 260 nm) magnitude of 18.4 ± 0.2 mag. Nothing was detected at this position in a 1.9-ks observation on 2017-01-22.72 UT (MJD 57775.72) with a 3σ upper limit of 19.5 mag in the same filter.

The position of the object is only 0.5 arcsec away from a know type-II cepheid in the catalogue of Fliri et al. (2006). Comparing our detection images with archival data from the LGGS survey (Massey et al. 2006) we cannot rule out that the two sources might be identical.

Below we list the R-band magnitudes obtained using the 0.65-m telescope at Ondrejov (OND) together with the Sloan r' magnitudes provided by the 2-m Liverpool Telescope at La Palma (LT; Steele et al. 2004):

2017 Jan. 29.732, [19.9 (OND); Feb. 3.804, 19.4 ± 0.3 (OND); 5.709, 19.5 ± 0.4 (OND); 7.825, 19.1 ± 0.1 (LT); 13.828, 18.9 ± 0.3 (OND); 15.725, 19.1 ± 0.25 (OND); 16.768, 18.7 ± 0.15 (OND); 17.831, 18.7 ± 0.1 (LT).

Discovery image

The UV magnitudes are in the UVOT photometric (Vega) system (Poole et al. 2008, Breeveld et al. 2011) and have not been corrected for extinction. We wish to thank the Swift Team for making these observations possible, in particular the duty scientists and the science planners.