Infrared Spectroscopy of the Eruptive Variable ASASSN-15qi

ATel #8333; M. S. Connelley, Bo Reipurth (IfA, Univ. Hawaii), Lynne A. Hillenbrand (Caltech)
on 24 Nov 2015; 20:12 UT
Credential Certification: Bo Reipurth (reipurth@ifa.hawaii.edu)

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We report infrared medium-resolution spectroscopy and near-infrared photometry of the eruptive variable ASASSN-15qi = 2MASS J22560882+5831040.

Recently the ASAS-SN transients survey reported that 2MASS J22560882+5831040 between Oct 2 and Oct3, 2015 brightened from V>17.0 to V=13.6, fading slightly to V=13.9 the following night (http://www.astronomy.ohio-state.edu/~assassin/transients.html, Shappee et al. 2014, ApJ, 788:A48).

A low-resolution optical spectrum obtained by Maehara, Ayani, Itoh, Takata & Kawabata (ATel #8147) revealed the Halpha line in emission with a P-Cyg profile, whose absorption component reaches to about -500 km/s. Due to its proximity to an HII region it was classified as a young stellar object, and the authors suggested it might be a FUor or EXor-like object.

Subsequently Stecklum, Eisloffel & Scholz (ATel #8210) reported BVRI photometry of ASASSN-15qi obtained Oct 11, 2015, and found that at V=15.17 the object had further faded relative to the discovery photometry from Oct 3.

We have obtained a cross-dispersed near-infrared spectrum of ASASSN-15qi with SpeX on the NASA Infrared Telescope Facility on Mauna Kea on 2015 October 15.44 UT in photometric conditions. The total on-source integration time was 1440 sec and the spectral range was from 0.7 to 2.5 micron. The resolving power R is around 1300, and the signal-to-noise of the data ranges from around 50 at short wavelengths to around 200 at long wavelengths.

The spectrum shows a smooth continuum with almost no absorption lines, suggesting heavy veiling. The continuum peaks around 1.0 microns, with a nearly linear decline longwards to 2.5 microns. A number of emission lines appear prominently in the spectrum. The Ca II IR triplet lines around 0.86 microns show P Cygni profiles with blue shifted absorption that extends to 700 km/s from the peak of the emission lines. The He I line at 1.083 microns shows a P Cygni profile with a red emission wing possibly extending to over 1000 km/s and a blue shifted absorption trough extending to 1000 km/s from the peak of the emission line. The neighboring Paschen-beta line has a P Cygni profile with an absorption trough 700 km/sec wide. Among other lines, it is notable that the CO bandheads are in emission. The Br-gamma line is in emission showing a symmetrical profile with FWHM=360 km/s and no absorption.

On the night of the observation, the near-IR magnitudes were J=12.15, H=11.62, and K=11.29. For comparison, its 2MASS magnitudes are J=13.70, H=12.92, and K=12.65.

In the IRTF J-band image very faint nebulosity is present, but it is not seen in the K-band image, suggesting that it most likely is a reflection nebula. A faint star is seen 3 arcsec to the NE. It is unclear whether it is a bound companion, since there are quite a few stars in the general field.

All 2MASS sources within a radius of 2 arcmin of the erupting variable have been plotted in a color-color diagram in a search for infrared excess stars that could signify a surrounding population of young stars. Only one star (2000: 22 56 16.346 +58 30 38.20) was found to have an excess, suggesting that the eruptive variable is not part of a rich group of young stars.

ASASSN-15qi appears to show historical signs of variability, as evidenced by the discrepancies among the optical magnitudes reported from various plate catalogs, and in the infrared by the mis-match between 2MASS JHK data and WISE W1,W2 data.

The infrared spectra discussed above can be seen at the URL http://www.astro.caltech.edu/~lah/asassn15qi/

Spectroscopy