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Constraints on the gamma-ray emission of SN 2011fe after the maximum of light as obtained by INTEGRAL/SPI

ATel #3822; J. Isern (ICE-CSIC/IEEC}, P. Jean (IRAP), E. Bravo (DFEN-UPC), J. Knodlseder (IRAP), R. Diehl (MPE), A. Domingo (CAB-CSIC/INTA), A. Hirschmann (ICE-CSIC/IEEC), P- Hoeflich (Florida Syate Univ.), N. Elias-Rosa (ICE-CSIC/IEEC), M. Hernanz (ICE-CSIC/IEEC), X. Zhang (MPE), C. Badenes (U. Pittsburgh), I. Dominguez (DFMC-UGR), B. Kulebi (ICE-CSIC/IEEC), D. Garcia (DFEN-UPC), C. Jordi (ICC-UB/IEEC), G. Lichti (MPE), G. Vedrenne (CESR, UPS-CNRS), P. Von Ballmoos (IRAP)
on 23 Dec 2011; 12:07 UT
Credential Certification: Eduardo Bravo (eduardo.bravo@upc.edu)

Subjects: Gamma Ray, Supernovae

SN2011fe (RA = 14:03:05.81, Dec = +54:16:25.4; J2000) is a Type Ia supernovae that was discovered in M101 on August 24th 2011, by the Palomar Transient Factory (Nugent et al, ATEL #3581) and probably exploded on August 23 (16:29) 2011 (Nugent et al 20119. The maximum of the blue-band light curve was reached on JD 2455815.3 or IJD 4270.8, about 18 days after the explosion (Tammann and Reindl 2011).

The source was observed with all the instruments on board of INTEGRAL (SPI, IBIS/ISGRI,JEM-X and OMC) at days 6-20 (see Atel #3683) and at days 45-88. Here we report the analysis of the SPI/INTEGRAL observations during the period 45-88 days after the explosion i.e. the public and private (PI J. Isern) observations obtained with SPI from 4297.76 IJD (October 7th 18:10) to 4341.64 IJD (November 20th 15:17). The total observation time was 2950 ks distributed in 890 individual pointings dithering around the SN direction.

The OMC has provided a precise light curve in the visible band. This light curve is well fitted by a one--dimensional delayed detonation model that produces about 0.5 solar masses of 56Ni (model DDTe). The predicted decline rate of this model in the blue band is Delta m15 = 1.2 +- 0.2, in agreement with the values found by Tammann and Riendl (2011).

At this epoch, the expected behavior of the spectrum (see the models of Gomez-Gomar, Isern, Jean 1998, and Milne et al 2004) is dominated by the 847 and 1238 keV lines emitted during the radioactive decay of 56Co and a feature extending from 200 to 511 keV due to the annihilation of the positrons also emitted in these decays. In all cases the lines are kinematically broadened to a width of 20-40 keV, well beyond the SPI spectral resolution, ~ 3 keV. If the lines were narrow, SPI would have been able to detect them with an exposure of ~ 1Ms near the maximum expected to occur between 70 to 100 days after the explosion. Our analysis has not found any one of these lines and this can be attributed to the broadening effect (Gomez-Gomar et al 1998).

The preliminary 95% confidence upper limits (2 sigma) obtained with SPI are:

Energy band (keV)       Flux (ph/s/cm2)
505-525               < 1.05e-4
830-875               < 1.39e-4
835-870               < 1.20e-4
1215-1275           < 1.21e-4
1220-1270           < 1.09e-4
1225-1265           < 0.97e-4

The bounds obtained with the other instruments and the constraints on models will be published elsewhere.

We acknowledge the INTEGRAL Project Scientist Chris Winkler (ESA, ESTEC) and the INTEGRAL personnel for their support to these observations.

Gomez-Gomar, Isern, Jean, MNRAS 295, 1 (1998)
Milne et al, ApJ 613, 1101 (2004)
Nugent et al., Nature 480, 344 (2011)
Tammann and Reindl, arxive 1112.0439 (2011)