From spencer Tue Aug 15 10:02:58 1995
From spencer Tue Aug 15 10:02:58 1995
To: oleroemer
Subject: Io Volcano News
Content-Length: 2151
X-Lines: 49
Status: RO

Murray Silverstone reports on recent 2.1 micron photometry of Io in
eclipse at UCLA, including the August 12th event, in a DPS abstract
just submitted.  The photometry suggests that the eruption noted at the
IRTF on July 25th began between July 11th and 20th is still continuing,
and may be increasing in brightness.  Observations on July 18th by
Goguen et al at the IRTF showed "normal" 4.8 micron brightness in
eclipse, so the eruption was either too small and hot at that stage
to greatly affect 4.8 micron magnitudes, or it switched on between
the 18th and 20th of July.

Further analysis of my July 25th IRTF observations of this eruption
suggests a likely location at an unnamed caldera visible in Voyager
images at 351 W, 22 N.

Here is Murray's abstract in its entirety.

---------------------------------

K' Photometry of Io in Eclipse During 1995

Murray D. Silverstone, E. E. Becklin, (UCLA)
Karen I. Tsetsenekos (Boston University)

The broad-band K' (1.9-2.3 micron) emission of Io while in eclipse by
Jupiter is presented for 7 eclipses. Emission from Io within this band,
during eclipse, comes from high temperature volcanic activity. The K'
magnitudes listed were obtained at the UCLA 24-inch telescope located
on the campus in Los Angeles, CA. Observations were made with a
near-infrared camera (K-Cam) which has a 256x256 NICMOS-III array and a
fixed filter. The magnitudes were calibrated relative to several
standard stars of Elias et al. (1982, AJ 87, 1029). The average UT
times of the the observations, the K' magnitudes for Io in eclipse,
and the one-sigma statistical and calibration errors are as follows:

 Universal Time   K' Magnitude   Error

 March  7 12:53        11.89     0.17  
 March 30 13:09         8.99     0.16
 April 15 11:37        10.27     0.11
  July 11  6:24        11.12     0.11
  July 20  2:40         9.65     0.12
  July 27  4:41         9.71     0.10 
August 12  2:50         9.41     0.10 

It is seen that outbursts were evident on March 30, July 20 & 27, and
August 12, 1995. We thank Frank Henriquez, Brant Nelson, and Ian
McLean for their support of this project.

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