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IAUC 8325: C/2004 H1; GRAVITATIONAL MICROLENSING EVENT

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                                                  Circular No. 8325
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
Mailstop 18, Smithsonian Astrophysical Observatory, Cambridge, MA 02138, U.S.A.
IAUSUBS@CFA.HARVARD.EDU or FAX 617-495-7231 (subscriptions)
CBAT@CFA.HARVARD.EDU (science)
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Phone 617-495-7440/7244/7444 (for emergency use only)


COMET C/2004 H1 (LINEAR)
     An apparently asteroidal object reported by LINEAR (discovery
observation below), and posted on the NEO Confirmation Page, has
been found to be diffuse by at least two different CCD observing
groups, including M. Kocer at Klet (1.06-m KLENOT telescope on Apr.
16.8 UT) and A. Gilmore and P. Kilmartin at Mt. John (0.6-m
reflector on Apr. 18.4).

     2004 UT             R.A. (2000) Decl.       Mag.
     Apr. 16.13007    7 42 04.72   + 0 13 25.2   19.2

The available astrometry, the following preliminary parabolic
orbital elements, and an ephemeris appear on MPEC 2004-H26.

     T = 2004 Jan. 13.329 TT          Peri. = 288.723
                                      Node  = 119.801   2000.0
     q = 2.04920 AU                   Incl. = 141.155


GRAVITATIONAL MICROLENSING EVENT
     G. Richards, D. Johnston, and J. Hennawi, Princeton University
Observatory, report that an emission-line enhancement has been
observed for the second time in component A of the wide-separation,
quadruply imaged quasar SDSS J100434.82+411239.5 (component A, R.A.
= 10h04m34s.82, Decl. = +41o12'39".5, equinox 2000.0; magnitude i =
18.4; Inada et al. 2003, Nature 426, 810).  Specifically, the blue
wings of several high ionization emission lines were enhanced in
component A on Mar. 26 and Apr. 10 with respect to observations
made in 2003 Nov./Dec., based on data taken with the ARC 3.5-m
telescope at Apache Point Observatory.  This second epoch of
enhancement follows that of 2003 May, confirming the time-dependent
nature of this possible microlensing event as reported by Richards
et al. (2004, Ap.J., in press;
http://xxx.lanl.gov/abs/astro-ph/?0402345).  No enhancement has
been seen in component B (position end figures 34s.94, 43".0),
despite the short A-B time delay (< 30 days) and good time sampling.
Follow-up observations of components A and B are needed to confirm
the microlensing nature of the event and to probe both the
microlens distribution and the structure of the broad emission-line
region.

                      (C) Copyright 2004 CBAT
2004 April 18                  (8325)            Daniel W. E. Green

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