Central Bureau for Astronomical Telegrams
IAUC 8024: 2002hh
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Circular No. 8024
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 2002hh IN NGC 6946
P. Meikle, Imperial College, London; S. Mattila, Stockholm
Observatory; and S. Smartt, Institute of Astronomy, Cambridge,
report that infrared observations of the type-II supernova 2002hh
obtained by E. MacDonald, L. Clewley, and G. Dalton at the William
Herschel Telescope (+ infrared camera INGRID) on Nov. 18.86 UT
yield J = 12.30 +/- 0.03, K_s = 11.07 +/- 0.02. Adopting a phase
of 21 +/- 2 days post-explosion, comparison of the J-K_s color with
the infrared-template light curves of Mattila and Meikle (2001,
MNRAS 324, 325) indicates that the supernova is highly reddened,
with E(J-K_s) = 1.0, confirming the result of Filippenko et al.
(IAUC 8007). Using the reddening law of Cardelli et al. (1989,
Ap.J. 345, 245), this yields A(V) about 6.1. Subtracting the
Galactic extinction (Schlegel et al. 1998, Ap.J. 500, 525) yields a
host-galaxy extinction A(V) about 5.0. Adopting a distance of 5.9
Mpc (H_0 = 70; Tully 1988, Nearby Galaxies Catalog) yields de-
reddened absolute magnitudes of M(J) = -18.3 and M(K_s) = -18.5,
which are close to the values given by the templates of Mattila and
Meikle (2001).
D. Pooley and W. H. G. Lewin, Massachusetts Institute of
Technology, on behalf of a larger collaboration, report the
detection of x-ray emission from SN 2002hh with the Chandra x-ray
observatory: "A 30000-s ACIS-S3 observation on Nov. 25.36 UT
revealed a source at R.A. = 20h34m44s.24, Decl. = +60o07'19".3
(equinox 2000.0; +/- 0".5 in each coordinate), in close agreement
with the reported optical and radio positions. A previous Chandra
observation of NGC 6946 on 2001 Sept. 7 (60000 s with ACIS-S3)
shows that no x-ray source was present at this location to a 3-
sigma limiting flux of roughly 7 x 10**-16 erg s**-1 cm**-2 in the
band 0.4-8 keV, corresponding to a limiting luminosity of 3 x
10**36 erg/s for a distance of 6.3 Mpc (Tully 1988, Nearby Galaxies
Catalog, using H_0 = 65 km/s/Mpc). Preliminary spectral fits to
the recent Chandra data (with both MEKAL and power-law models)
indicate a rather hard, highly absorbed spectrum (as expected from
the high reddening reported on IAUC 8007), with a fitted column
density of N_H = 10**22 cm**-2 (compared to N_H = 2-3 x 10**21
cm**-2 reported for just NGC 6946 by Burstein and Heiles 1984,
Ap.J. Suppl. 54, 33). The power-law photon index is found to be
0.6, but the MEKAL temperature could not be accurately measured
because the data prefer a value of kT above 80 keV, which is the
model limit. The unabsorbed 0.4-8-keV luminosity calculated from
both models agrees well and is 5 x 10**38 erg/s. This low x-ray
luminosity supports the indication on IAUC 8018 that there is
little circumstellar interaction taking place."
(C) Copyright 2002 CBAT
2002 November 30 (8024) Daniel W. E. Green
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