Electronic Telegram No. 4372
Central Bureau for Astronomical Telegrams
Mailing address:  Hoffman Lab 209; Harvard University;
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Prepared using the Tamkin Foundation Computer Network


COMET C/2017 E3 (PANSTARRS)
     Eva Lilly, Rob Weryk, and Richard Wainscoat, Institute for Astronomy,
University of Hawaii, report the discovery of another comet on i-band images
obtained with the 1.8-m Pan-STARRS1 telescope at Haleakala on Mar. 7
(discovery observations tabulated below), the object showing a broad tail
extending for approximately 8" to the south-southwest; the coma shows a
full-width-at-half-maximum of approximately 1".8 (vs. 1".1 for nearby stars).

     2017 UT             R.A. (2000) Decl.       Mag.
     Mar.  7.52715   13 10 09.95   -47 17 37.3   19.2
           7.54009   13 10 09.62   -47 17 34.9   19.2
           7.54655   13 10 09.41   -47 17 33.2   18.9

After the object was posted on the Minor Planet Center's PCCP webpage, other
CCD astrometrists also reported on its cometary appearance.  H. Sato, Tokyo,
Japan, writes that stacked 60-s exposures taken on Mar. 8.7 UT with a 0.51-m
f/6.8 astrograph (+ luminance filter) at Siding Spring reveals a strongly
condensed round coma 15" in diameter with no apparent tail; the w-band
magnitude was 16.1-16.4 as measured within a circular aperture of radius
8".8.  Images obtained by S. Foglia, L. Buzzi, P. Concari, C. Cremaschini, G.
Galli, and M. Tombelli with a 0.15-m f/7 refractor at Siding Spring on Mar.
8.7 of the comet in a crowded star field show a softened aspect with a coma
10" in diameter (red mag 16.9-17.0); follow-up images taken on Mar. 9.5 show
a similar appearance (red mag 17.4-17.5).  E. Bryssinck, Kruibeke, Belgium,
relates that stacked images taken remotely with an iTelescope 0.4-m f/3.6
reflector at Siding Spring on Mar. 9.76 show a central condensation with a
coma of size 16" x  21" that is elongated towards the southwest (p.a. about
189 degrees); the red magnitude was measured as 17.1 in a photometric
aperture of radius 5".  Images taken by A. Maury, B. Sandness, and T. Noel
with a 0.38-m f/4.6 Newtonian reflector at San Pedro de Atacama, Chile, on
Mar. 10.32-10.36 reveal a diffuse coma of diameter 12" +/- 2" and red mag
17.0-17.1 in an aperture of radius 6".5.  C. Jacques reports that three
stacked 60-s images taken by E. Pimentel, J. Barros, and himself on Mar.
13.2 with a 0.45-m f/2.9 reflector at the SONEAR Observatory, near Oliveira,
Brazil, show a diffuse coma 12" in diameter.
     The available astrometry, the following preliminary parabolic orbital
elements by G. V. Williams, and an ephemeris appear on MPEC 2017-E85.

     T = 2016 Sept. 5.4237 TT         Peri. = 306.4315
                                      Node  = 222.3413  2000.0
     q = 5.690650 AU                  Incl. =  68.2761


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

                         (C) Copyright 2017 CBAT
2017 March 13                    (CBET 4372)              Daniel W. E. Green