Physical Characteristics of the Progenitor of Nova V6585 Sgr
ATel #14655; B. McCollum (American Univ.), S. Laine (Caltech/IPAC)
on 22 May 2021; 20:08 UT
Credential Certification: Bruce McCollum (mccollub@cua.edu)
Referred to by ATel #: 14671
We performed SED fitting of the progenitor object (Ferreira et al., ATel #14625) of V6585 Sgr (PNV J17581670-2914490; Pearce 2021, CBAT #4952; Taguchi et al., ATel #14513, #14514) using twelve catalog data points from bandpasses g, V, r, i, I, z, Z, Y, J, H, and Ks. The fitting was performed against the BT-Settl set of model atmospheres (Allard et al. 2012, RSPTA, 370, 2765A). The value of Av was varied as a free parameter with possible values from 0.01 up to 5 in order to allow for possible circumstellar extinction. Spitzer IRAC photometry from the GLIMPSE catalog (Benjamin et al. 2003, PASP, 115, 953) is available for this object from the channels at 3.6, 4.5, and 8 um, but not 5.8 um. However, when the IRAC photometry is included, those data points appear as a significant excess relative to the model fit, with the excess increasing at longer wavelengths. We did not include the IRAC photometry in the final fit because inspection of the IRAC images suggests that there is some contamination of the IRAC photometry from unrelated background sources which may create a spurious excess.
The best fit is for Teff = 3750 +/- 150 K, and log g = 3.5 +/- 0.3. The value of Av in the best fit is 1.26 +/- 0.22, assuming the standard Galactic extinction law Rv = 3.1.
We note that this object was observed in the I-band by the OGLE-II survey (Udalski et al. 2000, Acta Astron., 50, 1) at several hundred epochs from 1997 to 2000. The OGLE-II table of photometry shows that almost all measurements of good data quality fall within a range of 0.1 magnitude, revealing no large long-term variations over the period of observations. The formal I-band uncertainty given in the OGLE-II database of the mean magnitude of this object is 0.030 magnitude.
A plot of the model fit and data is available at
http://web.ipac.caltech.edu/staff/seppo/plots/V6585-bestfit.jpg
This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France. This publication makes use of VOSA, developed under the Spanish Virtual Observatory project supported from the Spanish MINECO through grant AyA2017-84089. This work is based in part on archival data obtained with the Spitzer Space Telescope, which was operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by an award issued by JPL/Caltech. This research has made use of the NASA/IPAC Infrared Science Archive, which is funded by the National Aeronautics and Space Administration and operated by the California Institute of Technology.
