Central Bureau for Astronomical Telegrams
IAUC 8275: RADIO TRANSIENT IN Sco; 2004I
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Circular No. 8275
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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CBAT@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/iau/cbat.html ISSN 0081-0304
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RADIO TRANSIENT IN SCORPIUS
M. P. Rupen, A. J. Mioduszewski, and V. Dhawan, National Radio
Astronomy Observatory, report strong, on-going radio flares from
the microquasar candidate associated with GSC 7861.1088 = 1RXS
J162848.1-415241 (cf. IAUC 7968). Observations with the Very Large
Array (VLA) on Jan. 6, 11, and 22 UT gave flux densities at 8.46
GHz of 0.35 +/- 0.08, 13.8 +/- 0.8, and 6.6 +/- 0.4 mJy,
respectively. Quasi-simultaneous observations at 4.86 GHz on the
last day gave a flux density of 4.9 +/- 0.3 mJy, implying that the
flux density goes as frequency to the power 0.54 +/- 0.16. Such an
inverted radio spectrum is almost invariably associated with the
early, optically thick stage of a strong radio outburst, and this
-- together with the changing radio flux density -- suggests that
the source is currently undergoing a series of radio flares. The
most reliable radio position is that from the Jan. 22 observations
at 4.86 GHz: R.A. = 16h28m47s.283 +/- 0s.003, Decl. =
-41o52'39".05 +/- 0".05 (equinox 2000.0), where the error bars are
statistical, based on a fit using a point source plus a planar
background. This is in excellent agreement with the UCAC2 optical
position (Zacharias et al. 2003, from the Vizier On-line Data
Catalog), which gives position end figures 47s.286, 39".01 (quoted
accuracy 0".01). The VLA data show no obvious signs of extension,
with the best limits coming from the Jan. 11 observations, which
had a beam size of 3".5 x 0".6, with the long axis oriented toward
p.a. 14 deg. A Gaussian fit to those data gave a nominal upper
limit to the extent of 0".3 (full-width at half-maximum). Further
VLA observations are planned, and observations at other wavelengths
(particularly radio, x-ray, and optical) are urgently requested.
SUPERNOVA 2004I IN NGC 1072
C. L. Gerardy, and G. H. Marion, University of Texas at
Austin, report that a low-resolution optical spectrogram
(resolution 600; range 430-700 nm) of SN 2004I (cf. IAUC 8272),
obtained on Jan. 22.13 UT with the 2.7-m Harlan J. Smith Telescope
(+ LCS spectrograph) at McDonald Observatory, shows it to be a
type-II supernova. The spectrum resembles that of SN 1992H, 20
days after explosion (Filippenko 1997, ARAA 35, 309), with weak
H_beta and He I 587.6-nm absorption features superimposed on a blue
continuum, and a strong, broad H_alpha emission feature with little
or no blue-shifted absorption component. Adopting the 8018 km/s
redshift of NGC 1072 (from the NED), the expansion velocity of the
blue edge of the H_alpha feature is about 8600 km/s.
(C) Copyright 2004 CBAT
2004 January 24 (8275) Daniel W. E. Green
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