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Extremely Late-Time Photometric Observations of SN 2011fe

ATel #7392; B. J. Shappee (Hubble, Carnegie-Princeton Fellow), K. Z. Stanek, C. S. Kochanek, J. R. Gerke (Ohio State), P. Garnavich (Notre Dame)
on 14 Apr 2015; 16:48 UT
Credential Certification: Benjamin Shappee (shappee@astronomy.ohio-state.edu)

Subjects: Infra-Red, Optical, Supernovae, Transient

We have obtained 2 epochs of extremely late-time optical and infrared (IR) photometric observations of the nearby (6.4 Mpc; Shappee & Stanek 2011) Type Ia Supernova SN2011fe (Nugent et al., ATEL #3581) with WFC3 onboard HST under the Cycle 22 program GO-13737 (PI Shappee). These are the latest photometric observations of any SNe Ia to date and track SN2011fe down to less than a millionth of its maximum brightness.

In the optical, we have obtained images using the WFC3 UVIS channel with the F438W, F555W, and F600LP filters. For each of the UVIS images we first correct CTE at the pixel level using WFC3/UVIS CTE (http://www.stsci.edu/hst/wfc3/tools/cte_tools). We then measure the instrumental Vega Magnitudes using the WFC3 module of the DOLPHOT stellar photometry package (http://americano.dolphinsim.com/dolphot/). The UT dates, epoch relative to B-band maximum light (JD = 2455816.0; Richmond & Smith 2012), and measured optical magnitudes are:

 
UT Date         tBmax (days)       F438W          F555W          F600LP   
Oct 09, 2014    1124               24.956(0.038)  24.485(0.021)  24.841(0.021) 
Apr 06, 2015    1303               25.456(0.043)  25.462(0.026)  25.545(0.030) 

In the IR, we have obtained images using the WFC3 IR channel with the F110W and F160W filters. Emission at the position of the supernova is detected in the IR bands, but the high density of sources and large pixel scale means the image is confusion limited. Further IR imaging is needed to determine the contribution from SN2011fe.

Further observations in Cycle 22 are scheduled for July 2015.

We thank the entire HST team for scheduling and obtaining these observations.