Electronic Telegram No. 4348
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau@eps.harvard.edu (alternate cbat@iau.org)
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Prepared using the Tamkin Foundation Computer Network


COMET P/2017 B1 = 2010 EY_90 (LEMMON)
     R. Wainscoat, R. Weryk, and E. Lilly report the discovery of another
comet in images obtained with the 1.8-m Ritchey-Chretien Pan-STARRS1
telescope at Haleakala on Jan. 26 (discovery observations tabulated below),
the object showing a soft appearance, with full-width-at-half-maximum of
approximately 1".7, compared to adjacent stars that had FWHM 1".3; there is
some evidence of a very faint tail extending for a few arcseconds to the
northwest.

     2017 UT             R.A. (2000) Decl.       Mag.
     Jan. 26.59058   12 33 28.39   - 6 10 50.8   21.0
          26.61580   12 33 28.77   - 6 10 57.5   21.3
          26.62837   12 33 28.97   - 6 11 00.7   21.1

A. Fitzsimmons, Queen's University, Belfast; and M. Knight, University of
Maryland, obtained three 5-min SDSS r-band images on Jan. 27.23 UT with the
2.5-m Isaac Newton Telescope (+ Wide Field Camera) on La Palma, showing a
cometary tail extending 5" from the object's nuclear condensation toward p.a.
305 degrees.
     G. V. Williams identified this comet with an apparently asteroidal
object discovered in the course of the Mount Lemmon Survey with the 1.5-m
reflector on CCD images taken by R. A. Kowalski in March 2010 (discovery
observations tabulated below), which was then given the minor-planet
designation on 2010 EY_90 on MPS 318165.  The comet's name reflects the fact
that there was a well-established orbit for 2010 EY_90 from a good spread of
observations spanning 2010 Mar. 14-May 19.

     2010 UT             R.A. (2000) Decl.       Mag.   Observer
     Mar. 14.23752   10 22 46.52   + 8 45 32.8   19.9   Kowalski
          14.24586   10 22 46.16   + 8 45 33.6   20.0     "
          14.25428   10 22 45.76   + 8 45 35.4   20.1     "
          14.26266   10 22 45.40   + 8 45 36.2   20.2     "
          15.25493   10 22 02.49   + 8 47 59.4   20.4     "
          15.26327   10 22 02.13   + 8 48 00.5   20.1     "
          15.27163   10 22 01.77   + 8 48 01.3   21.0     "
          15.27998   10 22 01.38   + 8 48 03.1   20.6     "

     The available astrometry for both returns (including some from apparently
asteroidal Mt. Lemmon images taken on 2017 Jan. 7, when the magnitude was
given as 20.3-20.7), the following linked orbital elements by Williams (from
41 observations spanning 2010-2017), and an ephemeris appear on MPEC 2017-B83.

                    Epoch = 2010 Nov. 20.0 TT
     T = 2010 Dec.  3.62587 TT        Peri. = 256.49376
     e = 0.3010679                    Node  = 331.82677 2000.0
     q = 2.4959560 AU                 Incl. =   5.49792
       a =  3.5710995 AU   n = 0.14604986   P =   6.75 years

                    Epoch = 2017 Sept. 4.0 TT
     T = 2017 Aug. 26.73606 TT        Peri. = 255.97792
     e = 0.3005927                    Node  = 331.78243 2000.0
     q = 2.4985654 AU                 Incl. =   5.49236
       a =  3.5724041 AU   n = 0.14596986   P =   6.75 years


NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
      superseded by text appearing later in the printed IAU Circulars.

                         (C) Copyright 2017 CBAT
2017 January 28                  (CBET 4348)              Daniel W. E. Green