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IAUC 7912: 2002dd; GX 339-4

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                                                  Circular No. 7912
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
URL http://cfa-www.harvard.edu/iau/cbat.html  ISSN 0081-0304
Phone 617-495-7440/7244/7444 (for emergency use only)

     Z. Tsvetanov, J. Blakeslee, and H. Ford, Johns Hopkins
University; D. Magee and G. Illingworth, University of California,
Santa Cruz; A. Riess, Space Telescope Science Institute; and the
ACS Science Team report the discovery of a second apparent
supernova (cf. SN 2002dc, IAUC 7908) in observations of the Hubble
Deep Field North taken with the Advanced Camera for Surveys on the
Hubble Space Telescope.  SN 2002dd is located at R.A. =
12h36m55s.35, Decl. = +62o12'46".1 (equinox 2000.0).  The new
object was detected in exposures taken with the F775W filter (at
m_AB = 24.00 +/- 0.12) on May 11.39 UT, with the G800L grism on May
11.52, and with the F850LP filter (at m_AB = 24.15 +/- 0.12) on May
21.17; the on-orbit photometric calibration of the ACS in these
bandpasses has not yet been completed, and the quoted errors are
dominated by the zero-point uncertainty, estimated at 0.1 mag.  The
object was not present in WFPC2 F814W images of the HDFN taken with
the HST in Dec. 1995.  The spectrum extracted from the ACS G800L
grism exposure appears to be that of a type-Ia supernova at a
redshift z = 1.06 observed near maximum.  The spectrum shows
pronounced absorption features due to Ca II H and K and the
iron-peak elements (Fe, Co).  SN 2002dd is located 1".6 east and
0".6 north of the nearest bright reference galaxy (listed as object
3-486.0 in Williams et al. 1996, A.J. 112, 1335); however, this
galaxy cannot be the host, as it has a measured redshift of z =
0.79 (Cohen et al. 1996, Ap.J. 471, L5).  No clear host galaxy can
be identified at present.

GX 339-4
     D. M. Smith, University of California, Berkeley, on behalf of
a collaboration (including T. Belloni, W. A. Heindl, E. Kalemci, R.
Remillard, M. Nowak, J. H. Swank, and S. Corbel), reports that the
blackhole candidate GX 339-4, in outburst since Mar. 26, entered
the rare Very High State (VHS) of x-ray emission around May 6.  The
energy spectrum is dominated by a disk blackbody but has a strong
power-law tail.  The power spectrum of the fast variability
switches among at least three states:  band-limited noise with a
broad quasiperiodic oscillation (QPO) near 9 Hz, red noise with a
narrower QPO near 6 Hz, and a quiet state with almost no
variability.  RXTE/PCA observations are taking place at least twice
weekly.  The RXTE ASM shows that the count rate has started to
decline from its peak.  Monitoring in all other wavebands is
strongly encouraged; the VHS was last observed in 1988 (Miyamoto et
al. 1991, Ap.J. 383, 784).

                      (C) Copyright 2002 CBAT
2002 May 29                    (7912)            Daniel W. E. Green

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