New SPIRITS discoveries of Infrared Transients and Variables

ATel #10903; J. E. Jencson, M. M. Kasliwal, S. Adams, D. Cook, S. Tinyanont, S. Kwan, T. Prince (Caltech), R. M. Lau (Caltech/JPL), D. Perley (LJMU), F. Masci, G. Helou, L. Armus, J. Surace, S. D. Van Dyk (Caltech/IPAC), A. Cody (NASA Ames), M. L. Boyer (NASA Goddard), H. E. Bond, A. Monson (PSU), J. Bally (UC Boulder), R. Khan, E. Levesque (U. Washington), O. Fox, R. Williams (STSCI), P. A. Whitelock (SAAO, UCT), S. Mohamed (SAAO), R. D. Gehrz, S. Amodeo, D. Shenoy, R. Carlon, A. Cass, D. Corgan, D. Dykhoff, J. Faella, T. Gburek (U. Minnesota), N. Smith (U. Arizona), M. Cantiello (UCSB), N. Langer (U. Bonn), E. Ofek (WIS), J. Johansson (OKC/WIS), M. Parthasarathy (IIA), E. Hsiao (FSU), M. Phillips, N. Morrell, C. Gonzalez, C. Contreras (LCO), on behalf of the SPIRITS collaboration
on 28 Oct 2017; 05:11 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Jacob Jencson (jj@astro.caltech.edu)

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We report the discoveries of mid-infrared transients/strong variables found in the course of the Spitzer InfraRed Intensive Transients Survey (SPIRITS) using Spitzer Early Release Data (ATel #6644, #7929, #8688, #8940, #9434, #10171, #10172, #10488). Some of these events may belong to an emerging class of infrared (IR) transients known as eSPecially Red Intermediate Luminosity Transient Events (SPRITEs; Kasliwal et al. 2017, ApJ, 839, 88) defined by peak luminosities between those of novae and supernovae in the range -11 > [4.5] > -14 or 6.3 < log(L/Lsun) < 7.5, [3.6]-[4.5] colors between 0.3 and 1.6 mag, and no detected counterpart at optical wavelengths. In the table below, we list peak observed magnitudes at [3.6] and [4.5], and maximum observed [3.6]-[4.5] colors.

 
Name         | RA (J2000)  | Dec (J2000) | Host Galaxy (DM; Ref.) | UT-discovery | Peak [3.6] (abs)  | Peak [4.5] (abs) | Max. [3.6]-[4.5] | Notes 
SPIRITS 17pe | 12:56:47.90 | +21:41:13.4 | M64 (28.7; d)          | 2017-10-13   | 17.3 (-11.4)      | 16.2 (-12.5)     | >1.2             | b,c 
SPIRITS 17nx | 13:18:51.52 | -21:01:35.1 | NGC 5068 (28.7; e)     | 2017-10-12   | 17.1 (-11.6)      | 16.7 (-12.0)     | 0.4              | a,c 
SPIRITS 17mj | 09:55:36.20 | +69:06:21.0 | M81 (27.8; f)          | 2017-06-23   | 16.7 (-11.1)      | 15.9 (-11.9)     | 0.8              | b  
SPIRITS 17mi | 07:36:35.94 | +65:37:26.5 | NGC 2403 (27.5; f)     | 2017-06-25   | ...               | 16.7 (-10.8)     | >1.7             | a 
SPIRITS 17mb | 13:05:11.16 | -49:30:19.0 | NGC 4945 (27.8; g)     | 2017-06-08   | ...               | 15.7 (-12.1)     | >1.2             | b,c 

a) Fainter counterpart in reference (2004-2008).

b) No counterpart in reference (2003-2008).

c) Previous history of variability.

d) Sorce et al. 2014, MNRAS, 444, 527

e) Herrmann et al. 2008, ApJ, 683, 630

f) Tully et al. 2013, ApJ, 146, 86

g) Monachesi et al. 2016, MNRAS, 457, 1419

We encourage continued follow-up to discern the nature of these events. Please contact us if additional information (such as finding charts) is needed. We caution that in most cases we do not have spectroscopic confirmation that these transients belong to the reported host galaxies, and there is some chance that they may be unrelated foreground or background events.