Recent SPIRITS discoveries of Infrared Transients and Variables with Spitzer/IRAC

ATel #11575; 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 26 Apr 2018; 16:26 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, #10903). 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. The more luminous events are candidate obscured supernovae. 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 18x  | 12:41:43.39 |  32:31:49.7 | NGC 4631 (29.4, d)     | 2018-04-10   | 17.3 (-12.1)      | 17.5 (-11.9)     |  0.4             | a 
SPIRITS 18v  | 23:57:54.78 | -32:34:57.1 | NGC 7793 (27.8, e)     | 2018-02-23   | 17.2 (-10.6)      | 16.6 (-11.2)     |  0.7             | a,c 
SPIRITS 18q  | 10:03:12.67 |  68:43:31.2 | NGC 3077 (27.9, e)     | 2018-02-10   | 16.7 (-11.2)      | 15.9 (-12.0)     |  0.8             | a 
SPIRITS 18c  | 03:45:51.92 |  68:07:11.9 | IC 342 (27.6, e)       | 2018-01-01   | 16.2 (-11.4)      | 16.9 (-10.7)     |  ...             | a,c 
SPIRITS 18b  | 03:46:29.85 |  68:00:20.0 | IC 342 (27.6, e)       | 2018-01-01   |  ...              | 15.9 (-11.7)     |  ...             | b 
SPIRITS 17qm | 03:33:38.85 | -36:08:09.4 | NGC 1365 (31.3, f)     | 2017-11-05   | 15.6 (-15.7)      | 15.4 (-15.9)     |  0.6             | a,c 
SPIRITS 17po | 13:37:01.81 | -29:50:26.3 | M83 (28.3, e)          | 2017-10-25   | 17.9 (-10.4)      | 16.8 (-11.5)     | >1.3             | a,c 
SPIRITS 17pc | 12:25:44.43 |  12:39:44.5 | NGC 4388 (31.3, g)     | 2017-10-12   | 15.5 (-15.8)      | 15.0 (-16.3)     |  0.5             | b,c 

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

b) No counterpart in reference (2004 - 2008).

c) Previous history of variability.

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

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

e) Reiss et al. 2016, ApJ, 826, 56

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

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.