Central Bureau for Astronomical Telegrams
IAUC 7039: 1998el; XTE J1946+274 = 1SAX J1945.6+2721
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Circular No. 7039
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
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SUPERNOVA 1998el IN ANONYMOUS GALAXY
L. Germany reports the discovery by the Mount Stromlo Abell
Cluster Supernova Search Team (cf. IAUC 6639) of an apparent
supernova (V = 19.6) on V and R CCD images (limiting mag V = 20.5)
taken on Oct. 22 by M. MacDonald with the Mount Stromlo 1.27-m
telescope (+ Macho Camera). SN 1998el is located near Abell 3122
at R.A. = 3h21m01s.21, Decl. = -41o33'06".6 (equinox 2000.0), which
is 0".9 east of the center of its host galaxy. A nearby star has
position end figures 07s.77, 03".6. SN 1998el was not visible on
similar images taken on Oct. 3 (limiting mag V = 20.0) but was
confirmed by M. MacDonald with the same telescope on Oct. 23
(limiting mag V = 22.0). Finding charts are available at
http://msowww.anu.edu.au/~reiss/Abell_SNSearch/.
XTE J1946+274 = 1SAX J1945.6+2721
S. Campana, Brera Astronomical Observatory; G. L. Israel and
L. Stella, Rome Astronomical Observatory; and A. Santangelo,
Istituto di Fisica Cosmica e Applicazioni all'Informatica, CNR,
Palermo, report on two BeppoSAX observations performed on Oct.
4.13-4.65 and 10.94-11.53 UT of the transient 15.8-s x-ray pulsar
XTE J1946+274 (cf. IAUC 7014): "On Oct. 4 the BeppoSAX pointing was
inaccurate, and the source straddled the edge of the MECS detectors,
preventing reliable position and flux measurements. On Oct. 10-11,
the source was observed on-axis at a flux of about 44 mCrab (1-10
keV); the position was determined to be R.A. = 19h45m38s, Decl. =
+27o21'.5 (equinox 2000.0; error radius 1' at 95-percent confidence
level). Pulsations at periods of 15.825(1) and 15.8230(1) s were
detected during the first and second observations, respectively,
implying a spin-up of about -0.18 s/yr. The pulse profile is
complex in the MECS (energy band 1-10 keV), and considerably
smoother in the PDS (20-100 keV), with a pulse fraction of about 26
percent. The source was clearly detected over the range 0.5-100
keV, showing a complex continuum spectrum, with an iron line at 6.6
keV (EW = 75 eV). The inferred column density of about 1.6 x 10E22
cmE-2 translates to A(V) about 8 magnitudes. The Be star proposed
as the optical counterpart of the x-ray source (IAUC 7021, 7022)
lies some 10" outside the BeppoSAX error circle. Slitless
spectroscopy obtained on Sept. 16 for the brightest (V < 15) stars
within the BeppoSAX error circle shows no evidence for H-alpha
emission lines."
(C) Copyright 1998 CBAT
1998 October 26 (7039) Daniel W. E. Green
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