Central Bureau for Astronomical Telegrams

Central Bureau for Astronomical Telegrams -- Image credits

IAUC 6705: 1997 O1; BL Lac

The following International Astronomical Union Circular may be linked-to from your own Web pages, but must not otherwise be redistributed (see these notes on the conditions under which circulars are made available on our WWW site).

Read IAUC 6704 SEARCH Read IAUC 6706

View IAUC 6705 in .dvi or .ps format.
IAUC number 

                                                 Circular No. 6705
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)
BMARSDEN@CFA.HARVARD.EDU or DGREEN@CFA.HARVARD.EDU (science)
URL http://cfa-www.harvard.edu/cfa/ps/cbat.html
Phone 617-495-7244/7440/7444 (for emergency use only)


COMET 1997 O1
     A. Beresford, Myrtle Bank, South Australia, reports the visual
discovery by Justin Tillbrook of a comet.  The following
observations are available:

     1997 UT             R.A. (2000) Decl.        m1    Observer
     July 22.43      12 28.4       -18 59         10    Tillbrook
          23.37432   12 20 36.23   -18 09 19.0          Garradd
          23.37542   12 20 36.35   -18 09 15.2            "
          23.37651   12 20 36.52   -18 09 11.4            "
          23.39653   12 20 39.27   -18 08 06.9            "
          23.46318   12 20 48.67   -18 04 32.2            "
          23.46596   12 20 49.02   -18 04 23.5            "
          23.46876   12 20 49.36   -18 04 12.9            "

J. Tillbrook (Clare, S. Australia).  0.20-m reflector.  Coma
  diameter 60"-70"; motion about 3'/hr northward.
G. J. Garradd (Loomberah, N.S.W.).  0.25-m f/4.1 reflector + CCD.
  30-s CCD image shows 2' coma, no tail.


BL LACERTAE
     J. E. Grove and W. N. Johnson, Naval Research Laboratory, on
behalf of the OSSE team, report: "We have detected emission from BL
Lac between 50 and 300 keV with the OSSE instrument on the Compton
Gamma Ray Observatory.  For the period July 15.7-21.0 UT, the flux
in this energy band is (9.0 +/- 1.4) x 10E-4 photons cmE-2 sE-1.
There is no evidence for variability.  The power-law spectrum is
hard, with energy index 0.5 (+/- 0.7, 95-percent confidence).
Although OSSE has not previously observed BL Lac, objects in this
class are not generally detected in this energy range."
     G. Madejski, Goddard Space Flight Center (GSFC) and University
of Maryland; T. Jaffe, GSFC and Hughes/STX; and M. Sikora,
Copernicus Center, Warsaw, report the detection of strong x-ray
flux from BL Lac, which is undergoing an outburst in the radio,
optical, and GeV bands:  "The x-ray flux, measured with the
Proportinal Counter Array aboard the Rossi X-ray Timing Explorer
about every two days between July 16 and 20, increased from about 2
to about 3.6 x 10E-11 erg sE-1 cmE-2 in the band 2-10 keV, with a
very hard energy spectrum, well described as a power law with an
energy index of 0.4 +/- 0.1.  This is an increase of flux by about
a factor of three, and a very significant hardening (from an energy
index of 0.9 +/- 0.1) of the x-ray spectrum as compared with the
Nov. 1995 ASCA observation."

                      (C) Copyright 1997 CBAT
1997 July 23                   (6705)            Daniel W. E. Green

Read IAUC 6704 SEARCH Read IAUC 6706

View IAUC 6705 in .dvi or .ps format.

Our Web policy. Index to the CBAT/MPC/ICQ pages.

Valid HTML 4.01!