Central Bureau for Astronomical Telegrams
IAUC 6312: Prob. GRAVITATIONAL MICROLENSING EVENT; C/1995 O1
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Circular No. 6312
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Postal Address: Central Bureau for Astronomical Telegrams
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)
Phone 617-495-7244/7440/7444 (for emergency use only)
PROBABLE GRAVITATIONAL MICROLENSING EVENT
The MACHO collaboration (C. Alcock, T. Axelrod, R. Allsman, D.
Alves, A. Becker, D. Bennett, K. Cook, K. Freeman, K. Griest, J.
Guern, M. Lehner, S. Marshall, B. Peterson, M. Pratt, P. Quinn, A.
Rodgers, C. Stubbs, W. Sutherland, and D. Welch; Lawrence Livermore
National Lab., Center for Particle Astrophysics, and Mount Stromlo
Observatory) reports the discovery of a likely gravitational
microlensing event in progress toward the Large Magellanic Cloud:
"The star in question is located at R.A. = 5h24m03s.2, Decl. =
-68o49'12" (equinox 2000.0). The star was constant at R = 20.9, V
= 21.1 during 1993--1995 and brightened by 0.9 mag during the month
prior to 1996 Feb. 14. The color appears unchanged. The current
microlensing fit predicts that the star should reach a peak of V <
19.9 between Feb. 22 and Mar. 31 and then decline symmetrically.
Accurate photometry and low-resolution spectroscopy of this star at
regular intervals over the next few weeks will be valuable to test
the microlensing interpretation. Photometric measurements may
possibly detect lightcurve deviations that are due to a breakdown
of the usual point-source, point-lens, or constant-velocity
assumptions. If these exotic effects can be detected, it is
usually possible to estimate the distance to the lensing object. A
finding chart and additional information are available by anonymous
FTP at darkstar.astro.washington.edu:/macho/Alerts/96-LMC-1 or on
the WWW at http://darkstar.astro.washington.edu/. Potential
observers are requested to contact macho@astro.washington.edu, D.
Bennett at telephone 510-423-0656, or S. Marshall at 510-422-4872,
to coordinate observations."
COMET C/1995 O1 (HALE-BOPP)
M. C. Senay, Institute for Astronomy (IfA), University of
Hawaii; H.~E. Matthews, Joint Astronomy Centre, Hilo; and D. Jewitt,
IfA, write: "We observed C/1995 O1 using the 15-m James Clerk
Maxwell Telescope on Feb. 10 UT. The 345-GHz J = 3-2 transition of
carbon monoxide was detected with peak antenna temperature 0.22 K,
area 0.09 +/- 0.01 K km/s, and central velocity -33.06 +/- 0.02
km/s. The preliminary CO production rate computed using coma
temperature(s) 10 K (50 K) is 3.7 (1.2) x 10E28, corresponding to
the mass-loss rate(s) 1700 (560) kg/s. Continuous CO outgassing
has now been observed for 5 months (cf. IAUC 6234). We estimate
the total loss to date at 2 x 10E35 molecules (1 x 10E10 kg)."
(C) Copyright 1996 CBAT
1996 February 14 (6312) Daniel W. E. Green
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