[IAUC] IAUC 9221: NEW Sat OF (134340) [25139-2012/04-R1]

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                                                  Circular No. 9221
Central Bureau for Astronomical Telegrams
INTERNATIONAL ASTRONOMICAL UNION
New postal address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
CBATIAU en EPS.HARVARD.EDU           ISSN 0081-0304
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
     As first announced on CBET 2769, 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 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 deg.  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 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
(APL), Johns Hopkins University (JHU); 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 p.a. 1.7 deg on 2006 Feb. 15.63 UT and at
2".26 from Pluto in p.a. 2.7 deg on 2006 Feb. 15.69.

     Subsequent to the above findings, H. A. Weaver, APL, JHU; D. P.
Hamilton, University of Maryland; M. R. Showalter, SETI Institute;
and A. J. Steffl, S. A. Stern, and L. A. Young, SwRI, 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 p.a. 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 p.a. 172.2 deg.

                      (C) Copyright 2011 CBAT
2011 September 10              (9221)            Daniel W. E. Green