Discovery of a Type Ia SN in MACSJ1423

ATel #4778; S. A. Rodney (JHU), T. Holoien (Rutgers University), D. O. Jones (JHU), Or Graur (Tel Aviv University and American Museum of Natural History) and T. Frederiksen (Dark Cosmology Centre) on behalf of the CANDELS+CLASH SN Team
on 2 Feb 2013; 04:03 UT
Distributed as an Instant Email Notice Supernovae
Credential Certification: Steven A. Rodney (rodney@jhu.edu)

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We report the discovery of a Type Ia Supernova (SN) in Hubble Space Telescope (HST) imaging of the galaxy cluster MACSJ1423.8+2404. The SN can not be unambiguously associated with any host galaxy.

The SN was found in subtraction images generated from observations taken on 2013 Jan 19.4. It was not detected in the template epoch observations, taken on 2012 Dec 31.7. The observations were taken with the Hubble Space Telescope ACS-WFC and WFC3-IR as part of CLASH: the Cluster Lensing and Supernova Survey with Hubble (HST program 12065 , PI M. Postman). The position of the supernova is RA = 14:23:47.618, DEC = +24:04:33.32 (J2000.0). The SN is very close on the sky to the core of the MACSJ1423 cluster (9.5 arcsec from the center of the brightest cluster galaxy).

A spectrum of the SN was taken on 2013 Jan 28.9 using the HST ACS G800L grism, as part of the CANDELS+CLASH SN follow-up program (HST Program 13063, PI A. Riess). Using SNID (Blondin and Tonry 2007, Ap.J. 666, 1024), we find that the observed spectral absorption features are consistent with a normal Type Ia SN at the cluster redshift, z=0.545.

The following (Vega) magnitudes are reported:

 
UT_date       MJD    Filter   Mag    Err  Diff? 
2013.01.13  56305.0  F775W   23.71  0.13   no   
2013.01.13  56305.0  F606W   24.22  0.12   no   
2013.01.19  56311.4  F850LP  22.90  0.04   yes  
2013.01.19  56311.4  F775W   23.07  0.12   no   
2013.01.19  56311.4  F110W   23.08  0.12   no   
2013.01.19  56311.4  F160W   22.87  0.04   yes  
2013.01.22  56314.9  F105W   23.08  0.12   no   
2013.01.22  56314.9  F140W   22.83  0.13   no   

The final column indicates whether the aperture photometry was measured on a difference image with no SN light in the template epoch. Due to the apparent lack of a host galaxy, we are able to report magnitudes from search images that lack a template, although the uncertainties are larger due to contamination by intracluster light. These magnitudes and colors are consistent with a Type Ia SN at the cluster redshift, z=0.545.

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