Central Bureau for Astronomical Telegrams
IAUC 6858: 1998ab; AX J0051-722
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Circular No. 6858
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 1998ab IN NGC 4704
J.-y. Wei, on behalf of the Beijing Astronomical Observatory
supernova survey (via W.-d. Li, Berkeley), reports the discovery of
an apparent supernova (mag 16.1) on Apr. 1.67 UT. SN 1998ab
is located at R.A. = 12h48m47s.24, Decl. = +41o55'28".3 (equinox
2000.0), which is 2" east and 12" north of the center of NGC 4704.
SN 1998ab is not visible on a CCD image taken on Mar. 14.
P. Garnavich, S. Jha, and R. Kirshner, Harvard-Smithsonian
Center for Astrophysics, write: "A spectrum was taken of SN 1998ab
by P. Berlind and M. Calkins with the 1.5-m Tillinghast telescope
on Apr. 4.4 UT. The spectrum shows it to be an unusual type-Ia
supernova, similar to SN 1991T before maximum. Deep absorption
features observed at 437 and 507 nm are the strongest features on a
blue continuum and correspond to Fe III. No Si II is clearly
visible. A broad absorption feature at 381 nm is likely to be Ca
II. Narrow emission lines from the host galaxy give a redshift of
8250 km/s. Concurrent images taken by E. Barton with the Whipple
Observatory's 1.2-m telescope yield estimated magnitudes B = 16.6
and V = 16.4. The supernova is offset 9".2 east and 12".1 north
from the nucleus of NGC 4704. Spectroscopic and photometric
observations of this unusual supernova are encouraged."
AX J0051-722
J. C. Lochner, Goddard Space Flight Center and Universities
Space Research Association, reports: "After fading steadily from
its appearance in late Nov. 1997, the transient x-ray system AX
J0051-722 (IAUC 6803) was observed to have rebrightened in an
observation by RXTE on 1998 Mar. 25. Weak pulsations at 59 s from
XTE J0055-724 = 1SAX J0054.9-7226 (IAUC 6818) are also evident in
these data. The estimated 2-10-keV flux of AX J0051-722 for this
observation is 5.7 x 10E-11 erg sE-1 cmE-2. An observation by RXTE
on Mar. 31 showed very strong pulsations at 91.0 +/- 0.1 s, and a
decrease in the flux to 4.0 x 10E-11 erg sE-1 cmE-2. The spectrum
can be described by a cutoff power law with photon index of 0.80
and cutoff energy of 14.0 keV. This reappearance suggests a
possible orbital period of this Be/neutron-star system of about 110
days. Continued optical monitoring of the system is strongly urged."
(C) Copyright 1998 CBAT
1998 April 3 (6858) Daniel W. E. Green
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