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Re: More on M74 supernova

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  • Brian Skiff
    ... Ambiguous wording on my part doesn t help. After I sent the note, the Caltech group who did the VLA observation helpfully sent a follow-up note to their
    Message 1 of 3 , Jan 31, 2002
      >> confusion is one of my strong suits.

      Ambiguous wording on my part doesn't help. After I sent the note,
      the Caltech group who did the VLA observation helpfully sent a follow-up
      note to their original detection report. I've copied this below. The
      VLA detection was of the supernova itself at radio wavelengths, not the very
      short gamma-ray wavelengths. Kulkarni et al nevertheless recommend looking
      for gamma rays (as noted below), since there's doubtless some diffusion even
      from a collimated beam.
      Don't ask me about the other serious astrophysics described in the note
      below---that's stuff I know nothing about, though a gas heated up to 30
      _billion_ degrees sounds extraordinary no matter what. It is clear this is
      not an ordinary nearby supernova like the ones in M81, M51, or the LMC.
      One point worth making, however, is that if you have CCD image of the
      galaxy taken in the last ten days or two weeks, then it may be valuable in
      helping establish the time of the onset of the outburst. The amateur image
      of the M96 supernova taken a week or more before its discovery a few years ago
      was found proved very valuable in constraining models of supernovae eruptions.
      The Moon of course was passing by M74 in the last two weeks, so useful images
      are unlikely to have been taken (or kept).



      The following is a GCN Circular circulated via the AAVSO network.
      For an archive and more information on circulars visit:

      NUMBER: 1238
      SUBJECT: Type Ib/c SN2002ap (SN/GRB?)
      DATE: 02/02/01 04:55:22 GMT
      FROM: Edo Berger at Caltech <ejb@...>

      S. R. Kulkarni and E. Berger report on behalf of the Caltech-NRAO-CARA GRB

      "The early detection of radio emission from SN 2002ap (GCN 1237) has a
      number of interesting ramifications. Given the distance modulus of M74 of
      29.3, the absolute magnitude of the SN is -15.6, and given that the
      optical emission is still rising (IAUC 7810) it is safe to assume that we
      are seeing the SN before maximum. The optical spectroscopy suggests an age
      of 7 days based on analogy with SN 1998bw (IAUC 7811). Adopting this age
      and a typical expansion speed of 30,000 km/s, the inferred brightness
      temperature in the 8.5 GHz band is 3x10^10 K using the 0.4 mJy detection
      of Berger, Kulkarni and Frail (GCN 1237). As in the case of SN 1998bw,
      such a high brightness temperature argues for mildly relativistic
      expansion (see Kulkarni et al. 1998, Nature, 395, 663). If so, we should
      expect strong X-ray emission from inverse Compton scattering of the
      optical SN photons as well as measurable angular diameter of 0.2
      milliarcsecond, both of which are verifiable with Chandra and VLBA
      observations. In addition to these observations, high frequency (sub-mm
      and mm) observations are also required to find the synchrotron self-
      absorption frequency, which is essential for calculating the energy in the
      relativistic blastwave (see Kulkarni et al. 1998, Nature, 395, 663).
      Finally, it would be worthwhile inspecting archival data from gamma-ray
      burst monitors from the past two weeks to search for a faint GRB in the
      same position."

      This message may be cited.

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