Saturday, October 31, 2020

Discovery of a Nova in M31 - M31N 2008-12a

Just few days after the discovery of the nova in M31 designated as AT2020xyv, we report our discovery of another possible nova in M31 on a 240-s R-band CCD frame taken on 2020 Oct. 30.91 UT with the 0.5 m f/8 Ritchey Chretien + CCD FLI PL4240 at MPC Code L07 (Osservatorio Salvatore di Giacomo, Agerola, ITALY), with magnitude R = 18.48 +- 0.10 at coordinates: 

R.A. = 00 45 28.80, Decl.= +41 54 10.0 (equinox 2000.0; Gaia DR2). 

This transient PNV J00452880+4154100 has been independently discovered by Darnley et al. as reported on ATel #14130 of 31 Oct 2020; 07:32 UT and identified by them as the eruption of recurrent Nova M31N 2008-12a.

Our discovery image of this transient (click on it for a bigger version):


M31N 2008-12a is a remarkable recurrent Nova in the Andromeda Galaxy with the "shortest interoutburst time of any known recurrent nova. Since its discovery in December 2008 by two Japanese amateur astronomers, Koichi Nishiyama and Fujio Kabashima, a total of 13 subsequent outbursts have been observed. The mean time between observed eruptions (all observed between late August and December) is 364+/-52 days". 

by Antonio Catapano, Ernesto Guido, Luca Izzo

Tuesday, October 27, 2020

Discovery of a Nova in M31 - AT2020xyv

A new M31 nova candidate was independently discovered on 2020 Oct. 21.741 (by K. Hornoch and H. Kucakova), on 2020 Oct. 21.92 UT (by A. Catapano, L. Izzo, E. Guido, A. Noschese, F. Coccia, L. D'Avino) and 2020 Oct. 22.550 UT (by M. Zhang and X. Gao) and designated as PNV J00423733+4120519 = AT2020xyv = M31N 2020-10e (ATel #14114). This possible nova was first reported on 2020 Oct. 22.56 by Zhang and Gao as a new source of G ~ 16.9 mag on CBAT "Transient Object Followup Reports" (TOCP PNV J00423733+4120519).

Spectroscopic observations of AT2020xyv (PNVJ00423733+4120519) were obtained with the 3.58m TNG telescope equipped with LRS at Observatorio del Roque de los Muchachos in La Palma (Spain) by L. Izzo et al. (ATel #14116). Observations started on October 24 at 01:12:54 UT and they consisted of three exposures of 600s each: "The combined spectrum (covering the range 3,500-8,000 AA, resolving power R = 585) shows bright emission lines of H-alpha and H-beta, the presence of O I 7773 and Fe II lines (multiplet 42 and blended multiplets 37 and 38). From the H-alpha profile, we measure an FWHM of ~4,000 km/s. H-alpha and H-beta lines show P-Cygni profiles (although not prominent) with a minimum at ~ -2,800 km/s. The spectrum is then consistent with a broad-line Fe IIb Classical Nova in M31".

On 2020 Oct. 22.6, we reported on the TOCP our independent discovery of this nova in M31 on a 180-s R-band CCD frame taken on 2020 Oct. 21.92 UT with the 0.5 m f/8 Ritchey Chretien + CCD FLI PL4240 at MPC Code L07 (Osservatorio Salvatore di Giacomo, Agerola, ITALY) at the following coordinates:

R.A. = 00 42 37.33, Decl.= +41 20 52.1 (equinox 2000.0; Gaia DR2).

Our discovery image (click on it for a bigger version):

We have obtained daily BVR photometric observations of this nova with the 0.5m telescope at the Osservatorio Salvatore di Giacomo, Agerola (Italy). We have first detected the nova in BVR images obtained on October 21.92 as a new object in M31 with a magnitude V = 17.70 +- 0.05 mag. The most recent observations of this nova were obtained by us on October 23.85, and we report the following magnitudes: B = 19.39 +- 0.32 mag, V = 18.11 +- 0.12 mag, R = 19.06 +- 0.15 mag.  

AT2020xyv Spectrum - Credit: L.Izzo et al. 

Nothing is visible at this position on our archival images taken on 2020, October 20.83 (limiting B-mag 21). Zhang and Gao reported an upper limits (G > 20.5 mag) in images obtained on October 21.55. Kucacova et al. reported in ATel #14114 the first detection of this nova in images obtained on October 21.74 as an object with R = 18.1 +- 0.2. 

On ATel #14117, Hornoch et al. reported the identification of AT2020xyv as a likely recurrence of M31N 1998-10b, and thus a recurrent nova in M31. Using the updated online catalogue of all historical optical novae and nova candidates in M31 (Pietsch et al. 2007), they found that the measured position of nova AT2020xyv = PNV J00423733+4120519 = M31N 2020-10e "is very close (1.2") to that reported for a nova, M31N 1998-10b, previously discovered as part of the Research-Based Science Education (RBSE) project (Rector et al. 1999). Based on the position of the nova, which is located at an isophotal radius of 8.2' from the center of M31, we compute the probability of a chance positional coincidence between these two novae to be less than 0.01%"

by A. Catapano, L. Izzo, E. Guido, A. Noschese, F. Coccia, L. D'Avino (OASDG; AstroCampania)