On the Probable Progenitor of PNV J05145365-7009486
ATel #13289; Peter Pessev (GRANTECAN, IAC, ULL)
on 13 Nov 2019; 20:39 UT
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Subjects: Infra-Red, Optical, Request for Observations, Nova, Transient
PNV J05145365-7009486 was discovered by the Brazilian Transient Search (BraTS) team on 2019 November 11.2263 UT at 12.0 mag (CCD, unfiltered). It was classified as a He-N Nova in the LMC by Fred Walter (see ATel#13287), based on a spectrum obtained with the Chiron high resolution spectrograph on the SMARTS/CTIO 1.5m telescope at UT 2019 Nov. 12.27. Subsequent report (ATel#13288), based on a deeper exposure acquired earlier on 2019-11-11.91 UT using the High Resolution Spectrograph (HRS) of the 11m Southern African Large Telescope (SALT) confirms the identification of the transient as a He-N LMC nova in the post-maximum stage. Hence, when first detected PNV J05145365-7009486 was already on decline.
A catalog search in a radius of 1 arc second around the transient position was carried out in order to identify possible progenitor. The results included the following cross-identifications:
DENIS J051453.4-700948 at a distance d ~ 0.94 arc seconds and with Gunn-I band magnitude 17.27+/-0.12; MCPS source at d ~ 0.4 arc sec. and magnitudes B=19.79 +/-0.17 V=19.12 +/-0.10 I=18.27 +/-0.14; USNO-A2.0 0150-02788842 at d ~ 0.4 arc seconds and magnitudes Bmag=19.1 and Rmag=17.4; SAGE LMC survey source with ID STISAGEMA J051453.61-700949.0 at d ~ 0.5 arc sec. with [3.6]mag=16.80+/-0.08 and [4.5]mag=16.54+/-0.06. GAIA DR2 returns two sources with IDs 4652135578058116480 and 4652135578095561728, located at distances 0.65 and 0.1 arc seconds respectively. These will be designated as source 1 and 2.
Source 1 has a measured parallax of 0.1102+/-0.538 mas that corresponds to a distance between 1030 and 2536 pc with a best estimate of 1598.6 pc according to Bailer-Jones et al. 2018. It also has a significant proper motion in RA 3.379+/-0.716 mas/yr (in Dec 0.673+/-0.796 mas/yr). This actually places the source in the LMC foreground. The magnitude of source 1 is G=19.441+/-0.006, no color information available. The corresponding absolute G band magnitude, taking into account the Schlafly & Finkbeiner 2011 reddening information coupled with Casagrande & Van den Berg 2018 reddening coefficients is 7.51+0.79-1.16, putting the source in the K3V-M0V spectral class range (Pecaut & Mamajek 2013). If the MCPS color information is taken into account (since source 1 seems consistently detected in the different surveys), then (B-V)_0=1.0+/-0.2 and the corresponding spectral class range is K0V-K5.5V. It is very unlikely that this is the progenitor system in the light of the radial velocity information recovered from the spectra and reported in (ATel#13287 and ATel#13288). Another interesting detail is that source 1 may be variable on its own account. There is 1.00+/-0.18 magnitude difference between the Gunn-I band magnitudes reported in MCPS and DENIS. This is significantly larger than the mean photometric difference between the two surveys, while the distance between the source positions is within the observed distribution as presented by Zaritsky et al. 2004.
Source 2 has G=20.167+/-0.016, no color, parallax, proper motion or distance information. At the mean LMC distance reported by Alves 2003 (m-M)=18.50+/-0.02 and accounting for the extinction as mentioned above, this corresponds to M_G=0.76+/-0.07. Hence, with a large degree of certainty this could be the donor star of the nova system. In this case accounting that both GAIA and BraTS perform unfiltered observations, a rough estimate of eight magnitudes can be done for the amplitude of the event.
Additional data is needed to better constrain the properties of the progenitor system. Further observations of both GAIA DR2 sources are strongly encouraged.