[Iaude] CBET 4434: 20170929 : COMET P/2017 S5 (ATLAS)

[quai at eps.harvard.edu]

                                                  Electronic Telegram No. 4434
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 P/2017 S5 (ATLAS)
     Aren Heinze, University of Hawaii, reports the discovery of a comet on
CCD exposures taken on Sept. 27.5 UT with the ATLAS 0.5-m f/2.0 Schmidt
telescope at Haleakala in the course of the "Asteroid Terrestrial-impact Last
Alert System" (ATLAS) search program.  Heinze writes that the object shows
clear cometary features with a tail about 20" long toward position angle
approximately 235 degrees, adding that the head of the comet also seems
elongated in the corresponding northeast-southwest direction (with full-width-
at-half-maximum = 6".1), while the images of nearby stars (FWHM = 5".2) are
circular, suggesting that the coma diameter is 3".1.  The discovery
observations are tabulated below, together with pre-discovery ATLAS
observations identified from exposures taken with the discovery telescope and
with the ATLAS 0.5-m f/2.0 Schmidt telescope at Mauna Loa.

     2017 UT             R.A. (2000) Decl.       Mag.   Observatory
     Sept.11.52132    1 02 06.39   +25 59 41.1   18.5   Haleakala
          11.52656    1 02 06.20   +25 59 41.2   18.6     "
          11.53416    1 02 06.13   +25 59 40.7   18.5     "
          11.54034    1 02 06.00   +25 59 40.6   18.6     "
          13.48509    1 01 24.50   +25 58 33.9   18.3   Mauna Loa
          13.49649    1 01 24.19   +25 58 34.3   18.0     "
          13.50967    1 01 23.83   +25 58 33.0   17.6     "
          13.51013    1 01 23.83   +25 58 33.1   18.6     "
          17.47521    0 59 42.59   +25 52 23.8   17.9     "
          17.48426    0 59 42.33   +25 52 23.4   18.1     "
          17.49045    0 59 42.14   +25 52 21.9   18.2     "
          17.50457    0 59 41.69   +25 52 20.5   18.4     "
          23.46751    0 56 33.78   +25 33 11.4   18.4   Haleakala
          23.47773    0 56 33.37   +25 33 08.5   18.3     "
          23.49300    0 56 32.78   +25 33 04.3   17.9     "
          23.49925    0 56 32.54   +25 33 03.1   17.8     "
          27.48330    0 54 08.80   +25 13 42.5   18.2     "
          27.49072    0 54 08.49   +25 13 39.8   18.2     "
          27.49293    0 54 08.40   +25 13 39.2   17.8     "
          27.49771    0 54 08.21   +25 13 37.4   18.2     "

After the object was posted at the Minor Planet Center's PCCP webpage, other
CCD astrometrists have also commented on the object's cometary appearance.
H. Sato, Tokyo, Japan, writes that ten stacked 60-s exposures taken on Sept.
28.2 UT with a 0.61-m f/6.5 astrograph located at the Sierra Remote
Observatory near Auberry, CA, USA, show a strongly condensed coma 10" in
diameter with a straight tail 40" long toward p.a. 230 degrees; the total
w-band magnitude was 17.6 as measured within a circular aperture of radius
5".0.  Images taken by R. A. Kowalski with the Steward Observatory 1.0-m
reflector at Mount Lemmon on Sept. 28.24-28.26 in good seeing show a thin
tail 20" long in p.a. 235 deg.  K. Sarneczky and O. Hanyecz, Konkoly
Observatory, write that three stacked 120-s unfiltered CCD images taken with
the 0.60-m Schmidt telescope at Piszkesteto, Hungary, on Sept. 28.8 show a
nearly stellar coma with a tail 18"-20" long in p.a. 230 deg; the coma had
red magnitude 17.7 as measured within a circular aperture of radius 4".0.
J.-F. Soulier obtained sixty 60-s unfiltered exposures with a 0.20-m f/4
Newtonian reflector at the Observatoire Chante-Perdrix near Dauban, France,
on Sept. 28.92-28.96, which show a 14" coma and a 30" tail in p.a. 220 deg;
he measured red mag 18.0 in an aperture of radius 6".6.  S. Foglia and L.
Buzzi measured eight stacked images obtained on Sept. 29.6 0.4-m f/8
reflector at Haleakala (by a team that included also P. Miller, E. Gomez,
and R. Holmes), which reveal an elongated shape of size 8" x 12" and a 30"
tail in p.a. 235 degrees.
     The available astrometry, the following elliptical orbital elements by
G. V. Williams (from 87 observations spanning Sept. 11-29), and an ephemeris
appear on MPEC 2017.S213.

                    Epoch = 2017 July 26.0 TT
     T = 2017 July 28.0582 TT         Peri. =  99.9742
     e = 0.312971                     Node  = 252.3863  2000.0
     q = 2.178983 AU                  Incl. =  11.8532
       a =  3.171603 AU    n = 0.1744961    P =   5.65 years


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

                         (C) Copyright 2017 CBAT
2017 September 29                (CBET 4434)              Daniel W. E. Green