Mid-IR Photometry and Near-IR Spectroscopy of the FU Ori Protostar V2775 Ori (HOPS 223)
ATel #8692; William J. Fischer (NASA/GSFC), Emily J. Safron (Lorain County Community College), S. Thomas Megeath (Univ. of Toledo), Susan Terebey (Cal State LA), Edith Soto (Cal State LA), Thomas L. Wilson (NSF), Joseph D. Adams (USRA)
on 14 Feb 2016; 16:40 UT
Credential Certification: William Fischer (wjfischer@gmail.com)
Subjects: Infra-Red, Star, Variables, Young Stellar Object, Pre-Main-Sequence Star
On 2015 November 20.39, we obtained mid-IR photometry of V2775 Ori (HOPS 223) with the FORCAST instrument aboard SOFIA. This is a low-mass embedded young stellar object that was reported to have undergone a luminosity outburst by Caratti o Garatti et al. (2011, A&A, 526, L1). Fischer et al. (2012, ApJ, 756, 99) dated the beginning of the outburst to between 2005 April and 2007 March and discussed the similarity of its near-IR spectrum to that of FU Orionis. Beginning with the 1983 IRAS observations, no previous outburst activity had been detected in this source.
The FORCAST flux densities were 1.32 Jy at 11.1 microns, 2.91 Jy at 19.7 microns, 3.94 Jy at 25.3 microns, 5.82 Jy at 31.5 microns, and 6.36 Jy at 37.1 microns. Uncertainties are approximately 10%.
Fischer et al. (2012) tabulated mid-IR photometry of the source before and after the onset of its outburst. Before the outburst, on 2005 April 2, a flux density of 0.685 Jy at 24 microns was measured with MIPS aboard Spitzer. After the outburst, on 2007 March 12, a flux density of 9.33 Jy at 24 microns was measured with IRS aboard Spitzer. Later, on 2008 November 27, a flux density of 5.01 Jy at 24 microns was measured with MIPS aboard Spitzer. On 2010 March 10-11, flux densities of 1.78 Jy at 12 microns and 4.17 Jy at 22 microns were measured with WISE.
Interpolating linearly in F_nu space between the SOFIA 19.7 and 25.3 micron data, we estimate flux densities of 3.33 Jy at 22 microns and 3.70 Jy at 24 microns at the SOFIA epoch. These are, respectively, 20% and 26% lower than the latest WISE and Spitzer/MIPS measurements but still 5.4 times greater than the pre-outburst 24 micron flux density. Further monitoring is needed to determine whether this is a temporary dip or the beginning of a decline to the source's pre-outburst state.
On 2016 January 18.17, we obtained a K-band spectrum of the source with Triplespec at Palomar. As in previous spectra obtained between 2011 January 27 and 2011 February 1 (Fischer et al. 2012), this spectrum lacks Brackett gamma emission and contains CO bandhead absorption. The equivalent width of the CO 2-0 absorption at 2.29 microns is 10.0 A, the same as in the 2011 spectra.
