Central Bureau for Astronomical Telegrams
IAUC 6068: Poss. GRAVITATIONAL MICROLENSING EVENT; 1994X
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Circular No. 6068
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
Telephone 617-495-7244/7440/7444 (for emergency use only)
TWX 710-320-6842 ASTROGRAM CAM EASYLINK 62794505
MARSDEN@CFA or GREEN@CFA (.SPAN, .BITNET or .HARVARD.EDU)
POSSIBLE GRAVITATIONAL MICROLENSING EVENT
The MACHO collaboration (A. Alcock, T. Axelrod, R. Allsman, D.
Bennett, K. Cook, K. Freeman, K. Griest, S. Marshall, B. Peterson,
M. Pratt, P. Quinn, D. Reynolds, A. Rodgers, C. Stubbs, and W.
Sutherland; Lawrence Livermore National Laboratory, Center for
Particle Astrophysics, and Mount Stromlo Observatory) report: "We
have discovered a possible gravitational microlensing event in
progress toward the galactic bulge. The star in question is located
at R.A. = 17h59m49s.6, Decl. = -28o10'56" (equinox 2000.0); it was
constant at R = 17.8, V = 18.8 during 1993 and mid-1994, and has
brightened by 0.85 mag during the week ending Aug. 31; the color
appears unchanged. Magnitude estimates from the 1.27-m Mt. Stromlo
telescope (+ CCD): Aug. 29.39 UT. R = 17.24; 30.43, 17.08; 31.43,
16.97 (errors typically 0.05 mag). If this event is due to
gravitational microlensing, a preliminary fit predicts that the
star should reach a peak of R < 16.6 between Sept. 3 and 9 and then
decline symmetrically. As the light curve is currently incomplete,
it is not possible to confirm that this is definitely a microlensing
event, so it should be emphasized that the microlensing
interpretation is still tentative. Accurate multicolor photometry
and especially spectroscopy of this star at regular intervals during
the next 14 days will be very valuable to test the microlensing
interpretation. Light curves and a finding chart are available by
anonymous FTP to lensing.physics.ucsb.edu in the directory
macho/alert/event2. This directory will be periodically updated
with new light curves and microlensing fits as the data come in.
Potential observers are requested to contact D. Bennett (telephone
USA 510-423-0656; e-mail bennett@sunlight.llnl.gov) to coordinate
observations."
SUPERNOVA 1994X IN ANONYMOUS GALAXY
S. Benetti, European Southern Observatory (ESO), writes: "I
obtained a spectrum (450-710 nm, resolution 1.1 nm) of SN 1994X (cf.
IAUC 6056) on Aug. 29.35 UT with the ESO 2.2-m telescope (+ EFOSC2)
at La Silla. The full reduction shows the broad features of a
typical type-Ia supernova spectrum about 3 weeks after maximum. By
comparing the wavelength of the sharper emissions with those of
other well-studied type-Ia supernovae at the same phase, a redshift
of z about 0.056 is deduced for the parent galaxy. Assuming this
redshift, an expansion velocity of about 8900 km/s is derived from
the minimum of the Si II 635.5-nm multiplet; this is a typical
expansion velocity for a type-Ia supernova three weeks after maximum."
1994 September 1 (6068) Daniel W. E. Green
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