- High-resolution observations of SN 2001gd in NGC 5033,
M. A. Pérez-Torres, A. Alberdi, J. M. Marcaide, M. A. Guerrero,
P. Lundqvist, I. I. Shapiro, E. Ros, L. Lara, J. C. Guirado, K. W. Weiler,
& C. J. Stockdale
Monthly Notices of the Royal Astronomical Society, 360:1055-1062
[ PDF |
PostScript ]
- Abstract
We report on 8.4-GHz very-long-baseline interferometry (VLBI)
observations of SN 2001gd in the spiral galaxy NGC 5033 made on 2002
June 26 (2002.48) and 2003 April 8 (2003.27). We used the
interferometric visibility data to estimate angular diameter sizes for
the supernova by model fitting. Our data nominally suggest a relatively
strong deceleration for the expansion of SN 2001gd, but we cannot
dismiss the possibility of a free supernova expansion. From our VLBI
observations on 2003 April 8, we inferred a minimum total energy in
relativistic particles and magnetic fields in the supernova shell of
Emin= (0.3-14) × 1047 erg, and a
corresponding equipartition average magnetic field of Bmin=
50-350 mG. We also present multiwavelength Very Large Array (VLA)
measurements of SN 2001gd made at our second VLBI epoch at frequencies
of 1.4, 4.9, 8.4, 15.0, 22.5 and 43.3 GHz. The VLA data are well fitted
by an optically thin, synchrotron spectrum (?=-1.0 +/- 0.1;
S?~??), partially absorbed by thermal
plasma. We obtain a supernova flux density of 1.02 +/- 0.05 mJy at the
observing frequency of 8.4 GHz for the second epoch, which results in an
isotropic radio luminosity of (6.0 +/- 0.3) × 1036 erg
s-1 between 1.4 and 43.3 GHz, at an adopted distance of 13.1
Mpc. Finally, we report on an XMM-Newton X-ray detection of SN 2001gd on
2002 December 18. The supernova X-ray spectrum is consistent with
optically thin emission from a soft component (associated with emission
from the reverse shock) at a temperature of around 1 keV. The observed
flux corresponds to an isotropic X-ray luminosity of LX= (1.4
+/- 0.4) × 1039 erg s-1 in the 0.3-5 keV
band. We suggest that both radio and X-ray observations of SN 2001gd
indicate that a circumstellar interaction similar to that displayed by
SN 1993J in M 81 is taking place.
Eduardo Ros
ros@mpifr-bonn.mpg.de