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Hubble Space Telescope discovery of a multiply imaged, gravitationally lensed supernova

ATel #6729; P. L. Kelly (UC Berkeley), S. A. Rodney (JHU), T. Treu (UCLA), R. J. Foley (Illinois), G. Brammer (STScI), K. B. Schmidt (UC Santa Barbara), A. Zitrin (Caltech), A. Sonnenfeld (UCLA), L.-G. Strolger (STScI), O. Graur (NYU/AMNH), A. V. Filippenko (UC Berkeley), S. W. Jha (Rutgers), A. G. Riess (JHU/STScI), M. Bradac (UC Davis), B. J. Weiner (Arizona), D. Scolnic (Chicago), M. A. Malkan (UCLA), A. von der Linden (DARK), M. Trenti (Melbourne), J. Hjorth (DARK), R. Gavazzi (IAP), A. Fontana (INAF-OAR), J. Merten (Caltech), C. McCully (LCOGT/UC Santa Barbara), T. Jones (W. Kentucky), M. Postman (STScI), A. Dressler (Carnegie Obs.), B. Patel (Rutgers), S. B. Cenko (NASA GSFC), M. L. Graham (UC Berkeley), B. E. Tucker (UC Berkeley), the GLASS and FrontierSN teams
on 21 Nov 2014; 21:17 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Patrick Kelly (pkelly@astro.berkeley.edu)

Subjects: Infra-Red, Optical, Supernovae

We report the discovery of a multiply imaged, gravitationally lensed supernova, forming an Einstein cross around a z=0.544 early-type galaxy in the galaxy cluster MACS J1149.6+2223. The redshift of the supernova host galaxy is 1.491.

The SN (dubbed "SN Refsdal") was discovered in Hubble Space Telescope (HST) observations using the Wide Field Camera 3 Infrared camera (WFC3/IR) taken between 03 November 2014 and 10 November 2014 (UT dates are used throughout) as part of the Grism Lens Amplified Survey from Space (PID: 13459, PI: Treu). Confirmation imaging was provided by the Hubble Frontier Fields (HFF) program (PID: 13504, PI: Lotz) and a new HST director's discretionary program (PID: 14041, PI: Kelly).

SN Refsdal is clearly detected in F140W at four locations, which we call S1, S2, S3, and S4. Three of the SN images (S1, S2, and S3) are also clearly detected in F125W and F105W, with only a marginal detection of S4 in these bands. The J2000 positions are as follows:

ID RA DEC RA_dd DEC_dd
S1 11:49:35.575 +22:23:44.27 177.398229 22.395631
S2 11:49:35.452 +22:23:44.83 177.397717 22.395786
S3 11:49:35.370 +22:23:43.93 177.397375 22.395536
S4 11:49:35.474 +22:23:42.63 177.397808 22.395175

We performed difference-imaging photometry of SN Refsdal, using templates constructed from archival HST data from the CLASH program (PID: 12068, PI: Postman) and early HFF observations. The discovery photometry (from 2014 November 11) yields the following F140W AB magnitudes and uncertainties:

S1: 25.4 +- 0.2 mag
S2: 25.5 +- 0.2 mag
S3: 25.7 +- 0.2 mag
S4: 27.3 +- 0.7 mag

Preliminary analysis of the confirmation imaging taken on 2014 November 20/21 indicates that image S3 is rising, whereas the other images have remained at approximately their discovery brightness.

Supplementary observations are strongly encouraged, though ground-based observations will be challenging. Finder charts are available at
http://archive.stsci.edu/pub/ffsn/macs1149/finder_lens_MACS1149.png
and
http://archive.stsci.edu/pub/ffsn/macs1149/sdss_larger_scale_finder_S1.pdf