No Infrared Excess in ASASSN-V J060000.76-310027.83

ATel #13361; B. McCollum (American Univ.), S. Laine (Caltech/IPAC)
on 20 Dec 2019; 00:38 UT
Credential Certification: Bruce McCollum (mccollub@cua.edu)

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We performed SED fitting of the unusual fading transient ASASSN-V J060000.76-310027.83 (ATel # 13346, 13349, 13357) to the BT-Settl-CIFIST set of model atmospheres (Baraffe et al. 2015, A&A 577A, 42B) using archival photometry in the bandpasses u, B, g', V, r', i', I, J, H, Ks, W1, W2, and W3, along with loose upper limits from the GALEX FUV and WISE W4 bands.

The object is well fitted by a K dwarf star, consistent with the spectroscopy reported by Buckley & Gromadzki (Atel #13349). The best fit is Teff = 4500 +/- 100 K where the uncertainty represents a two-sigma value. The Av was allowed to vary as a free parameter from 0 to 1 to allow for possible strong circumstellar extinction. The best fit value of Av = 0.06, with a two-sigma uncertainty extending up to Av = 0.36.

According to the Bayestar19 3-D extinction map (Green et al. 2019, arXiv:1905.02734v1), using a distance of 155 pc from Gaia (Bailer-Jones et al. 2018, AJ, 156, 58B), virtually no extinction is expected, which is consistent with our best fit.

The WISE W3 bandpass covers from approximately 8 um to 17 um, so the absence of a significant excess at those wavelengths implies that any substantial amount of circumstellar material would be colder than a few hundred K.

The fact that a precise fit with no outliers is obtained using data points obtained at widely different epochs, i.e. the late 1990's, 2010, and approximately 2016, places some constraint on the variability. Also, there is no significant difference between the J and Ks magnitudes observed by 2MASS on 8 February 1999 and those observed by DENIS at an unspecified epoch from 1996 to September 2001.

A plot of the model fit and data is available at

http://web.ipac.caltech.edu/staff/seppo/plots/ASASSN-V-J060000.76-310027.83.jpg

This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France. This research has made use of data from the AAVSO Photometric All sly Survey (APASS) DR9. This publication makes use of VOSA, developed under the Spanish Virtual Observatory project supported from the Spanish MINECO through grant AyA2017-84089. DENIS is the result of a joint effort involving human and financial contributions of several Institutes mostly located in Europe. It has been supported financially mainly by the French Institut National des Sciences de l'Univers, CNRS, and French Education Ministry, the European Southern Observatory, the State of Baden-Wuerttemberg, and the European Commission under networks of the SCIENCE and Human Capital and Mobility programs, the Landessternwarte, Heidelberg and Institut d'Astrophysique de Paris. 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. This work presents results from the European Space Agency (ESA) space mission Gaia. Gaia data are being processed by the Gaia Data Processing and Analysis Consortium (DPAC). Funding for the DPAC is provided by national institutions, in particular the institutions participating in the Gaia MultiLateral Agreement (MLA).