[Iaude] CBET 4340: 20170106 : COMET C/2017 A1 (PANSTARRS)

quai at eps.harvard.edu quai at eps.harvard.edu
Fri Jan 6 14:20:37 EST 2017

                                                  Electronic Telegram No. 4340
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

     Richard Wainscoat, Eva Lilly, Rob Weryk, and Marco Micheli report the
discovery of another apparent comet in w-band exposures obtained with the
1.8-m Ritchey-Chretien Pan-STARRS1 telescope at Haleakala on Jan. 2 (discovery
observations tabulated below).  While the comet has significant interference
from background objects in the discovery images, it shows a brighter, more
diffuse nuclear condensation with a tail extending to the north for
approximately 8".

     2017 UT             R.A. (2000) Decl.       Mag.
     Jan.  2.33300    5 22 43.32   -24 40 38.4   19.6
           2.34334    5 22 42.77   -24 40 27.0   19.6

The comet was also detected at mag 18.9-19.3 on images obtained on Jan. 2.38-
2.43 UT with the ATLAS 0.5-m f/2.0 Schmidt telescope at Haleakala.  Three 60-s
follow-up exposures (with g-, r-, and i-band filters) were obtained
by R. J. Wainscoat, M. Micheli, and P. Forshay with the 3.6-m Canada-France-
Hawaii Telescope on Mauna Kea on Jan. 3.4 UT, showing the new object to be
clearly cometary with an obvious broad tail to the north, approximately 20"
long; the g-band magnitude was measured as 19.5.
     After the comet was posted on the Minor Planet Center's PCCP webpage,
other CCD astrometrists have also commented on the object's cometary
appearance.  Six stacked exposures taken on Jan. 3.6 UT by L. Buzzi, P.
Concari, C. Cremaschini, S. Foglia, G. Galli, and M. Tombelli with an
iTelescope 0.15-m f/7 refractor at Siding Spring reveal an object of size
10" x 15", elongated in p.a. 310, with red mag 17.9-18.0; they have posted
their image at website URL http://asteroidi.uai.it/neocp/P10yz57/P10yz57.htm.
Buzzi et al. obtained additional exposures in the same manner on Jan. 5.45-
5.47 that show similar details (but with red mag 19.0-19.1).  E. Bryssinck,
Kruibeke, Belgium, writes that seven co-added images taken remotely on Jan.
3.62 with a 0.7-m f/6.6 telescope (+ Luminance filter) at Siding Spring, NSW,
reveals a starlike object with a condensed coma of size 12" and a hint of a
tail 19" long towards p.a. 8 deg.  Fifteen stacked 15-s images taken by T.
Linder and R. Holmes with an 0.61-m f/6.5 Dall-Kirkham Astrograph at Cerro
Tololo on Jan. 5.2 (measured with S. Foglia) show a large coma of size 10"
with a tail 10" long in position angle 350 deg.  J.-F. Soulier, Dauban, Banon,
France, note that unfiltered stacked 60-s exposures taken on Jan. 3.9 with a
0.20-m f/4 Newtonian reflector at the Observatoire Chante-Perdrix shows a coma
of size about 20" and a tail about 22" long in p.a. 350 deg; the red magnitude
was measured as 18.8-19.4 in an aperture of radius 6".6.  Unfiltered exposures
taken by A. Maury, J.-B. de Vanssay, and J.-F. Soulier on Jan. 4.03-4.12 with
a 0.4-m f/5.4 Ritchey-Chretien reflector at San Pedro de Atacama, Chile, show
a coma of size about 17" and a tail about 23" long in p.a. about 10 degrees,
the red magnitude being 18.6-18.9 in an aperture of radius 6".2.  Soulier also
obtained unfiltered stacked images on Jan. 5.9 with a 0.30-m f/3.8 Newtonian
reflector at Maisoncelles, France, that show a coma of size about 17" and a
tail about 20" long in p.a. about 20 deg; the red magnitude was measured as
19.0-19.3 in an aperture of radius 4".9.  H. Sato, Tokyo, Japan, reports that
ten stacked 60-s exposures taken on Jan. 5.45-5.46 with a 0.51-m f/6.8
astrograph (+ luminance filter) at Siding Spring show the comet to be strongly
condensed with a coma 12" in diameter and a tail 25" long toward p.a. 355
degrees; the w-band magnitude was 17.7 as measured within a circular aperture
of radius 6".5.

     The available astrometry, the following preliminary parabolic orbital
elements by G. V. Williams (from 53 observations spanning Jan. 2-6), and an
ephemeris appear on MPEC 2017-A31.

     T = 2017 May  17.6770 TT         Peri. =   1.7923
                                      Node  = 120.1429  2000.0
     q = 2.329691 AU                  Incl. =  50.6445

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

                         (C) Copyright 2017 CBAT
2017 January 6                   (CBET 4340)              Daniel W. E. Green

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