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IAUC 6639: 1997by; 2EG J0432+2910, 2EG J0744+5438, 2EG J0852-1237

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                                                 Circular No. 6639
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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     The Mount Stromlo Abell Cluster Supernova Search Team (cf.
IAUC 6418) reports the discovery of an apparent supernova (mag V =
16.2) on V and R CCD images taken on Apr. 27 by S. Chan on the
Mount Stromlo 1.27-m telescope (+ Macho Camera).  SN 1997by is
located near Abell 1736 at R.A. = 13h27m27s.54, Decl. = -27o19'21".7
(equinox 2000.0).  A nearby star has position end figures 18s.62,
18'54".0.  SN 1997by was not detected on frames taken on Apr. 4,
but it is clearly visible on CCD images taken with the Mount Stromlo
0.76-m telescope on Apr. 28.  Finding charts are available at

2EG J0432+2910, 2EG J0744+5438, 2EG J0852-1237
     J. P. Halpern and M. Eracleous, University of California at
Berkeley, report optical identifications based on spectrophotometry
with the Kitt Peak 2.1-m telescope of flat-spectrum radio sources
that have been suggested as EGRET blazar counterparts:  "The radio
and optical object in the error box of 2EG J0432+2910 (located at
R.A. = 4h33m37s.8, Decl. = +29o05'56", equinox 2000.0), described
by Lundgren et al. (IAUC 6258), and Condon et al. (1983, A.J. 88,
20) has a very red BL Lac-type continuum spectrum with slope -4.0
and no emission or absorption features in the range 390-750 nm to
an upper limit of 0.2 nm equivalent width (EW); from the spectrum
obtained on 1997 Feb. 6, it has V = 17.8, which is about 2 mag
brighter than on the Palomar Sky Survey.  The radio source
candidate for 2EG J0744+5438 (located at R.A. = 7h42m39s.8, Decl. =
+55o44'25") proposed by Mukherjee et al. (1995, Ap.J. 445, 189) is
also highly variable in the optical, having declined from V = 16.9
on 1996 Feb. 16 to V = 18.4 on 1997 Feb. 6; it has z = 0.723, based
on weak emission lines in the low-state spectrum that we identify
with Mg II 280 nm (EW = 2.0 nm), H-gamma, and H-beta, and its slope
is -1.0 in the low state and -1.3 in the high state.  If this
identification is correct, it would be the weakest radio counterpart
of an EGRET blazar, with a 5-GHz flux density of 0.27 Jy.  The
candidate for 2EG J0852-1237 (located at R.A. = 8h50m09s.6, Decl. =
-12o13'34") described by Mattox et al. (1997, Ap.J., May 20 issue)
is also highly variable, having brightened from V = 18.9 on 1996
Feb. 16 to V = 16.8 on 1997 Feb. 6.  Its redshift is z = 0.566 from
the same emission lines as above, plus [O III] 500.7-nm.  In the
high-state spectrum, Mg II 280-nm has EW = 1.0 nm and the continuum
slope is -1.2."

                      (C) Copyright 1997 CBAT
1997 April 29                  (6639)            Daniel W. E. Green

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