Central Bureau for Astronomical Telegrams
IAUC 6361: Prob. BINARY MICROLENSING EVENT; C/1995 O1
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Circular No. 6361
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 BINARY MICROLENSING EVENT
The MACHO collaboration (cf. IAUC 6312) reports a likely
binary gravitational microlensing event in progress towards the
galactic bulge: "This event was initially reported on Mar. 12 as
MACHO Alert 96-BLG-3, via e-mail and our WWW page
(http://darkstar.astro.washington.edu/). During the last few days,
it has shown large deviations from a single-lens microlensing fit,
which are well fit by a binary lens. The star in question is
located at R.A. = 18h01m45s.5, Decl. = -29o49'47" (equinox 2000.0);
it was constant at R = 18.1, V = 19.0 during 1993-1995 and has
shown a complex lightcurve since 1996 Mar. 12. The star appears to
have undergone a caustic crossing (see Udalski et al. 1994, Ap.J.
436, L103, for an example of this) on Mar. 25, and it is currently
at 2.5 mag above normal brightness and rising. The binary-lens fit
predicts that a second caustic crossing will occur in the next few
days, most probably near Mar. 29.5 UT; this will consist of a sharp
drop in brightness by > 1.5 mag within a few hours. Very frequent
photometry and spectroscopy (hourly or more often) during the
caustic crossing can provide valuable information about the
location of the lens and the limb-darkening of the source star. A
finding chart and additional information are available by anonymous
FTP at darkstar.astro.washington.edu:/macho/Alerts/96-BLG-3 or at
the above WWW site. 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)
A. Fitzsimmons and I. M. Cartwright, Queen's University of
Belfast; and D. Pollacco, Royal Greenwich Observatory, communicate:
"An optical spectrum (range 360-520 nm) of comet C/1995 O1 was
obtained using the 2.5-m Isaac Newton Telescope on La Palma on Mar.
19.264 UT. CN(0-0) 388-nm emission was observed extending to 45"
from the nucleus, equivalent to 1.7 x 10E5 km at the comet.
Assuming HCN as a parent, the preliminary CN production rate is 1.1
x 10E26, indicating an increase by a factor of 2 from earlier
observations (cf. IAUC 6252), and similar to the increase in the
CO-production rate reported on IAUC 6312. No other emission
features were observed."
(C) Copyright 1996 CBAT
1996 March 28 (6361) Daniel W. E. Green
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