Central Bureau for Astronomical Telegrams
IAUC 6891: XTE J1806-246; 1998bp; SNe
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Circular No. 6891
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
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XTE J1806-246
F. E. Marshall and T. Strohmayer, Goddard Space Flight Center;
and R. Remillard, Massachusetts Institute of Technology, on behalf
of the RXTE Science Operations Center, report the detection with
the Rosssi X-ray Timing Explorer of a bright, soft x-ray transient
(designated XTE J1806-246) at a position consistent with that of
the SAS source 2S 1803-245 and a possibly related source of
isolated bursts, SAX J1806.8-2435 (IAUC 6867): "The 2-12-keV flux
measured with the All-Sky Monitor increased as follows: Apr. 16.66
UT, 31 mCrab; 18.27, 60; 22.42, 131; 24.45, 356; 28.93, 417. The
3-20-keV spectrum measured with the Proportional Counter Array
(PCA) on Apr. 28.81 is well described as thermal bremsstrahlung
emission with kT = 4.3 keV. The source position determined with
the PCA is R.A. = 18h06m51s, Decl. = -24o35'.1 (equinox 2000.0)
with an estimated uncertainty of 1'.5. Observations at other
wavelengths are encouraged."
SUPERNOVA 1998bp IN NGC 6495
S. Jha, P. Garnavich, P. Challis, and R. Kirshner, Harvard-
Smithsonian Center for Astrophysics, communicate: "A spectrum
(range 360-750 nm) of SN 1998bp was taken by M. Calkins with the
Whipple Observatory 1.5-m telescope (+ FAST spectrograph) on Apr.
30.4 UT. The spectrum confirms this object (cf. IAUC 6890) to be a
type-Ia supernova near maximum light. In addition to a strong Si
II 615-nm absorption, there is a very deep Si II 580-nm feature,
typical of subluminous, fast-declining type-Ia supernovae. The Si
line-depth ratio [R(Si); Nugent et al. 1995, Ap.J. 455, L147] is
0.62, similar to that of SN 1991bg near maximum. However, the
spectrum does not resemble that of SN 1991bg in the blue; it is
more similar to that of SN 1992A. The catalogue recession velocity
for NGC 6945 is 3127 km/s (Di Nella et al. 1995, A.Ap. Suppl. 113,
151), which yields an expansion velocity from the most prominent
Si II feature (rest 635.5 nm) of -10~400 km/s."
SUPERNOVAE
Unfiltered CCD measurements by K. Sarneczky and L. Kiss,
Szeged, Hungary, with a 0.90-m Schmidt telescope (comparison-star R
magnitudes from USNO A1.0 catalogue): SN 1998V in NGC 6627, Apr.
4.05 UT, 16.2; SN 1998ab in NGC 4704, Apr. 5.11, 15.9.
(C) Copyright 1998 CBAT
1998 April 30 (6891) Daniel W. E. Green
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