[IAUC] CBET 2769: 20110720 : NEW SATELLITE OF (134340) PLUTO: S/2011 (134340) 1

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                                                  Electronic Telegram No. 2769
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
CBAT Director:  Daniel W. E. Green; Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau en eps.harvard.edu (alternate cbat en iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


NEW SATELLITE OF (134340) PLUTO:  S/2011 (134340) 1
     M. R. Showalter, SETI Institute; and D. P. Hamilton, University of
Maryland -- on behalf of a team that includes S. A. Stern (Southwest
Research Institute), H. A. Weaver (Applied Physics Laboratory, Johns
Hopkins University), and A. J. Steffl and L. A. Young (Southwest Research
Institute)) -- report the discovery of a new satellite of Pluto.  The object,
provisionally designated S/2011 (134340) 1, was detected in five separate
sets of images taken by the Hubble Space Telescope WFC3/UVIS:  two sets on
2011 June 28.6 UT, two on July 3.4, and one on July 18.92.  The body is
visible in individual 8-minute exposures, and S/N > 5 when the five images
of each set are co-added.  On June 28, the satellite was 2".48 from the center
of Pluto in p.a. 335 deg; on July 3, it was 2".01 from Pluto at p.a. 27 deg;
on July 18, it was 2".035 from Pluto at p.a. 198.1 degrees.  The satellite's
magnitude is V = 26.1 +/- 0.3, making the object about 10 percent as bright
as Pluto II (Nix).  The diameter depends on the assumed geometric albedo:
14 km if p_v = 0.35, or 40 km if p_v = 0.04.  The motion is consistent with a
body traveling on a circular, equatorial orbit.  The inferred mean motion is
11.2 +/- 0.1 degrees per day (P = 32.1 +/- 0.3 days), and the projected radial
distance from Pluto is 59000 +/- 2000 km, placing the satellite between the
orbits of Pluto II (Nix) and III (Hydra).

     Subsequent to the discovery of S/2011 (134340) 1 by Showalter et al.,
A. J. Steffl and S. A. Stern, Southwest Research Institute (SwRI); M. R.
Showalter, SETI Institute; H. A. Weaver, Applied Physics Laboratory, Johns
Hopkins University; D. P. Hamilton, University of Maryland; and L. A. Young,
SwRI, report the probable detection of S/2011 (134340) 1 in archival Hubble
Space Telescope ACS/HRC images taken on 2006 Feb. 15.  The object has a S/N
of 2.5-3.0 in each of four images and V = 26.0 +/- 0.3.  It appears at a
distance of 2".26 from Pluto at position angle 1.7 deg on 2006 Feb 15.63 UT
and at 2".26 from Pluto in position angle 2.7 deg on 2006 Feb 15.69.

     Subsequent to the discovery of S/2011 (134340) 1 by Showalter et al. and
its possible identification in the Hubble archival images taken on 2006 Feb. 15
by Steffl et al. (see above), H. A. Weaver, Applied Physics Laboratory, Johns
Hopkins University; D. P. Hamilton, University of Maryland; M. R. Showalter,
SETI Institute; and A. J. Steffl, S. A. Stern, and L. A. Young, Southwest
Research Institute, report the probable detection of S/2011 (134340) 1 in
archival Hubble Space Telescope WF3/UVIS images taken on 2010 June 25.  The
object has S/N approximately 3 in each of four 180-s images taken through the
F350LP filter.  From a two-image composite taken on June 25.3014 UT, the
object has V = 25.71 +/- 0.3 and appears at a distance of 2".38 from Pluto at
position angle 172.0 deg.  From a two-image composite taken on June 25.3153,
the object has V = 25.96 +/- 0.3 and appears at a distance of 2".32 from Pluto
at position angle 172.2 deg.


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                         (C) Copyright 2011 CBAT
2011 July 20                     (CBET 2769)              Daniel W. E. Green