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IAUC 6536: 1997C; GX 1+4

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                                                 Circular No. 6536
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/cfa/ps/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)

     W. Li, Q. Qiao, Y. Qiu, D. Lu, and J. Hu, Beijing Astronomical
Observatory (BAO), on behalf of the BAO Supernova Survey, report
the discovery of an apparent supernova (mag about 17.5) on
unfiltered CCD images taken on Jan. 13.74, 13.85, and 13.93 UT with
the 0.60-m BAO reflector.  SN 1997C is located at R.A. =
10h13m56s.18, Decl. = +38o49'00".5 (equinox 2000.0), which is 17".7
east and 96".1 south of the nucleus of NGC 3160.  Nothing is
present on images of NGC 3160 taken on 1996 Dec. 18 (limiting mag
about 19.0).  A spectrum (range 380-900 nm, resolution 40 nm/mm)
obtained with the BAO 2.16-m telescope at Xinglong station shows
broad emission and absorption lines typical of a type-Ic supernova,
about 3-4 weeks after maximum.  The spectrum is very similar to
that of SN 1987M, about 29 days after maximum (Wheeler and Benetti
1995, preprint).  Strong spectral lines include the Ca II infrared
triplet and H and K lines; O I at 760 nm; Na I D at 585 nm; Si II
at 636 nm; and Fe II at 424, 448, 490, and 502 nm.  There is no
distinct evidence of H Balmer lines.  The expansion velocity of the
supernova envelope is about 12 300 km/s when measured from the Ca
II triplet, 15 000 km/s when measured from O I 760-nm, and 15 900
km/s when measured from the Ca II H and K lines.  CCD frames taken
on Jan. 14 give an unfiltered magnitude of about 17.4.

GX 1+4
     R. B. Wilson, Marshall Space Flight Center, NASA; and D.
Chakrabarty, Massachusetts Institute of Technology, report for the
Compton Observatory BATSE Team:  "Pulsations from the accreting x-
ray pulsar GX 1+4, undetected (15-mCrab upper limit) in the energy
range 20-50 keV since 1996 Aug. 18 (IAUC 6478), are once again
being observed.  The source first reappeared in data summed over
Nov. 29.0-Dec. 4.0 UT, at a barycentric pulse frequency of 8.00122
+/- 0.00037 mHz.  The pulsations have continued through 1997 Jan.
12.5, with a frequency on that date of 7.9736 +/- 0.0005 mHz and a
pulsed flux of 23 +/- 3 mCrab (20-50 keV).  The mean pulse
frequency derivative since redetection is (-7.7 +/- 0.1) x 10E-12
Hz sE-1, about twice the spindown rate observed in 1996 May-June;
such values have previously been observed from the source.  The
inferred mean spindown rate during the undetected interval from
Aug. 18 to Dec. 1.5 is (-3.35 +/- 0.07) x 10E-12 Hz sE-1.  Follow-
up optical and infrared observations of the mass donor V2116 Oph
are strongly encouraged."

                      (C) Copyright 1997 CBAT
1997 January 14                (6536)            Daniel W. E. Green

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