Spectral Type of the Cataclysmic Variable ASASSN-20jo

ATel #13943; B. McCollum (American Univ.), S. Laina (Caltech/IPAC)
on 14 Aug 2020; 04:07 UT
Credential Certification: Bruce McCollum (mccollub@cua.edu)

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We performed SED fitting of the unusual cataclysmic variable ASASSN-20jo (ATel # 13942) to the BT-Settle-CIFIST set of model atmospheres (Baraffe et al. 2015, A&A 577A, 42B) using archival photometry in the bandpasses V, r, i, z, y, J, H, Ks, and WISE W1, W2, and W3, along with an upper limit in the WISE W4 band. Because this is a candidate CV, we excluded measurements in bandpasses shorter than V in order to avoid possible contamination from disk emission.

The best fit Teff = 6800 +/- 156 K, corresponding to a spectral type of F1 to F4. The Av was allowed to vary along with the Teff as a free parameter from 0 to 4 to allow for possible strong circumstellar extinction. The best fit value of Av = 0.81 +/- 0.16. This suggests the possibility of significant circumstellar extinction, because as noted by Way et al. (ATel # 13942) the expected Av in this direction is ~0.64. However, the fitting finds no IR excess. The WISE W3 bandpass covers from approximately 8 um to 17 um, which places an upper limit on any thermal emission from material warmer than a few hundred K.

The emission in the shortest-wavelength bandpasses is consistent with a hotter component, because including the g magnitude in the fitting produces a best fit which is a few hundred degrees hotter but of a significantly lower quality as measured by the chi-square value. Including B and GALEX FUV and NUV magnitudes produces a fit which is hotter and lower quality than when g is included. However, including or excluding the V magnitude does not affect the fitting outcome.

A plot of the best model fit and data is available at

http://web.ipac.caltech.edu/staff/seppo/plots/ASASSN-20jo-fit.png

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 publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This publication makes use of data products from the Wide-field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. The Guide Star Catalog-I was produced at the Space Telescope Science Institute under U.S. Government grant. These data are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The Pan-STARRS1 Surveys (PS1) and the PS1 public science archive have been made possible through contributions by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, the Queen's University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation Grant No. AST-1238877, the University of Maryland, Eotvos Lorand University (ELTE), the Los Alamos National Laboratory, and the Gordon and Betty Moore Foundation.