TITLE: GCN CIRCULAR NUMBER: 21982 SUBJECT: LIGO/Virgo G298048: Mid-Infrared Spitzer/IRAC Observations at 3.6 and 4.5 microns DATE: 17/10/10 13:57:54 GMT FROM: Mansi M. Kasliwal at Caltech R. M. Lau (Caltech), E. O. Ofek (Weizmann) and M. M. Kasliwal (Caltech) report on behalf of the Global Relay of Observatories Watching Transients Happen (GROWTH) collaboration: On 2017 Sept 29.86 UT, the Spitzer space telescope took deep mid-infrared observations at the position of SSS17a (Coulter et al. LVC GCN 21529) with Channel 1 (3.6 microns) and Channel 2 (4.5 microns) of the Infrared Array Camera (IRAC). We conducted a preliminary analysis of the IRAC Basic Calibrated Data (BCD), including both a median filter subtraction and ZOGY image subtraction to remove the extended emission from the host galaxy NGC 4993. We find possible, marginal evidence for excess emission at the position of SSS17a at 4.5um. We are continuing monitoring with Spitzer/IRAC. We thank the Spitzer Space Telescope team, in particular, Tom Soifer and Nancy Silbermann, for the rapid review and scheduling of these DDT observations (PI Kasliwal). The Spitzer Space Telescope is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.