[Iaude] CBET 4438: 20171008 : COMET C/2017 S7 (LEMMON)

[quai at eps.harvard.edu]

                                                  Electronic Telegram No. 4438
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
 20 Oxford St.; Cambridge, MA  02138; U.S.A.
e-mail:  cbatiau at eps.harvard.edu (alternate cbat at iau.org)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET C/2017 S7 (LEMMON)
     An apparently asteroidal object discovered on Mount Lemmon survey CCD
images taken by R. G. Matheny with the 1.5-m reflector on Sept. 26 (discovery
observations tabulated below) has been found to show cometary appearance by
CCD astrometrists elsewhere, after the object was posted on the Minor Planet
Center's NEOCP and PCCP webpages.

     2017 UT             R.A. (2000) Decl.       Mag.   Observer
     Sept.26.46499    5 25 42.49   + 9 42 09.9   19.6   Matheny
          26.47107    5 25 42.40   + 9 42 07.8   19.7     "
          26.47717    5 25 42.31   + 9 42 05.8   19.9     "
          26.48326    5 25 42.22   + 9 42 03.6            "

K. Sarneczky and O. Hanyecz, Konkoly Observatory, write that three stacked
120-s unfiltered images taken with the 0.60-m Schmidt telescope at Piszkesteto,
Hungary, on Sept. 29.0 UT show the object to be softer than nearby stars, with
a small asymmetry towards p.a. 300 deg; the coma was 8" in diameter with no
tail, and the red magnitude was 20.1 as measured within a circular aperture of
radius 4".0.  Sarneczky adds that nine stacked 120-s exposures taken on Sept.
30.1 show an elongated shape in p.a. 320 deg (with FWHM = 3".8), while the
images of nearby stars (FWHM = 2".8) are circular; the red magnitudes was 19.5
as measured within a circular aperture of radius 4".0.  H. Sato, Tokyo, Japan,
finds that ten stacked 60-s exposures taken on Sept. 29.52 with a 0.61-m f/6.5
astrograph at the Sierra Remote Observatory near Auberry, CA, USA, show a
moderately condensed 10" in diameter with a suspected tail 30" long toward
p.a. 330 degrees; the total w-band magnitude was 20.1 as measured within a
circular aperture of radius 5".0.
     Earlier images taken on three nights in late 2016 at Mount Lemmon were
subsequently identified, including on 2016 Dec. 18, 27, and 30 (when the
object's brightness was measured to be 18.9-19.2, 19.3-19.4, and 19.6-20.6,
respectively).  The available astrometry, the following hyperbolic orbital
elements by G. V. Williams, and an ephemeris appear on MPEC 2017-T38.

                    Epoch = 2017 June 16.0 TT
     T = 2017 May  27.92836 TT        Peri. = 187.74976
     e = 1.0020955                    Node  = 262.78691 2000.0
     q = 7.6141487 AU                 Incl. = 124.22083


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

                         (C) Copyright 2017 CBAT
2017 October 8                   (CBET 4438)              Daniel W. E. Green