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IAUC 7943: 2002ef; V838 Mon; 2002ed

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IAUC number

                                                  Circular No. 7943
Central Bureau for Astronomical Telegrams
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
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SUPERNOVA 2002ef IN NGC 7761
     B. Beutler and W. D. Li, University of California at Berkeley,
report the LOTOSS (cf. IAUC 7906) discovery of an apparent supernova
on unfiltered KAIT CCD images taken on July 30.4 (mag about 16.5)
and 31.4 UT (mag about 16.2). SN 2002ef is located at R.A. =
23h51m29s.54, Decl. = -13o22'46".4 (equinox 2000.0), which is
10".0 east and 7".0 north of the nucleus of NGC 7761. A KAIT image
of the same field on July 16.4 UT showed nothing at this position
(limiting mag about 18.0).

     H. E. Bond, N. Panagia, and W. B. Sparks, Space Telescope
Science Institute; S. G. Starrfield, Arizona State University;
R. M. Wagner, University of Arizona; and A. Henden, Universities
Space Research Association and U.S. Naval Observatory, report that
the light echo around V838 Mon was imaged with the Hubble Space
Telescope and Advanced Camera for Surveys on May 20.  An empty hole
in the center of the light echo has grown slightly in size since
the previous ACS observation on Apr. 30 (cf. IAUC 7892). Preliminary
analysis of images taken in the V band plus polarizing filters
reveals a narrow ring of highly (about 20%) linearly polarized light,
centered on the star and lying just outside the inner edge of this
hole at a radius of about 4".8. The high polarization indicates that
the light scattering occurs at an angle of nearly 90 deg, and thus
the material producing it lies close to the distance of the star
itself. This implies a purely geometric lower limit to the stellar
distance of 2.5 kpc, if the polarized ring is illuminated by light
emitted at the March 11 peak of the star's V band outburst. The
outermost rings in the light echo are at a radius of 20", corresponding
to material lying about 0.5 pc in front of the star, and are expanding
as the square root of the time since outburst.  The central hole
suggests that there is a cavity in the dust surrounding the star,
with a radius of about 2 light-months. If this cavity is spherical,
we predict that light from the outburst will soon reach the back
side of the cavity, thus converting the hole into a bright, filled
center. Continued observations are urged when V838 Mon emerges from
conjunction with the Sun.

SUPERNOVA 2002ed IN NGC 5468
     H. Yamaoka, Kyushu University, Japan, reports the following
position for SN 2002ed from the discovery images (cf. IAUC 7940):
R.A. = 14h06m38s.22, Decl. = -5o27'28".0 (equinox 2000.0).

                      (C) Copyright 2002 CBAT
2002 July 31                   (7943)          Carl W. Hergenrother

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