Electronic Telegram No. 5273
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)
URL http://www.cbat.eps.harvard.edu/index.html
Prepared using the Tamkin Foundation Computer Network


COMET P/2023 M1 (PANSTARRS)
     R. Weryk, Department of Physics and Astronomy, University of Western
Ontario, reports the discovery of another comet in images obtained on June 16
with the Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala (discovery
astrometry tabulated below).  He notes that four stacked 45-s w-band survey
images show a very condensed head of size 1".9 (full-width-at-half-maximum)
in 1".5 seeing, with a point-spread-function asymmetry toward p.a. 130 deg.

     2023 UT             R.A. (2000) Decl.       Mag.
     June 16.40850   16 23 59.43   -11 07 10.8   20.4
          16.42034   16 23 59.04   -11 07 08.3   20.4
          16.43214   16 23 58.66   -11 07 05.7   20.4
          16.44396   16 23 58.28   -11 07 03.1   20.4
          16.51683   16 23 55.93   -11 06 47.4   20.0
          16.51764   16 23 55.90   -11 06 47.2   19.9

Weryk adds that three 60-s gri-band follow-up images obtained with the 3.6-m
Canada-France-Hawaii Telescope at Mauna Kea (via R. Wainscoat, A. Acohido, and
T. Burdullis) on June 19.4 UT show this object to be clearly a comet, with a
very condensed head of size 1".1 (FWHM) in 0".75 seeing and a broad tail 3"
long spanning p.a. 130-245 degrees.  Single night pre-discovery observations
were identified in the Minor Planet Center's "isolated tracklet file" (which
is accessible publicly) with the Pan-STARRS2 1.8-m Ritchey-Chretien reflector
at Haleakala on May 12.5 UT (at mag 21.6-21.7) and with the 1.5-m Mt. Lemmon
survey reflector on May 24.35-24.36 (mag 20.5-20.8).  Weryk also identified
additional pre-discovery images of the comet on Apr. 24.6 (mag 22.2-22.6) and
May 12.5 (mag 21.6-21.7) with the Pan-STARRS2 telescope and on Apr. 30.6 (mag
22.2-22.3) and May 15.44-15.46 (mag 21.2-21.6) with the Pan-STARRS1 telescope.
     After the comet was posted on the Minor Planet Center's PCCP webpage,
H. Sato (Bunkyo-ku, Tokyo, Japan) reported that eight stacked 120-s CCD
exposures taken on June 16.66 UT with a 0.51-m f/6.8 astrograph at Siding
Spring, NSW, shows a strongly condensed coma 8" in diameter with no tail;
the magnitude was 19.9 as measured within a circular aperture of radius 4".9.
    The available astrometry appears on MPEC 2023-M65.  The following
elliptical orbital elements by S. Nakano (Central Bureau) are from 30
observations spanning 2023 Apr. 24-June 19 (mean residual 0".3).  There is no
close approach to any major planets.

     T = 2023 Dec. 14.49682 TT        Peri. =  79.71956
     e = 0.5880760                    Node  = 216.86608 2000.0
     q = 2.8255901 AU                 Incl. =  12.28981
       a =  6.8594939 AU   n = 0.05486128   P =  17.965 years

The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 13.0 and 2.5n = 10 for the
magnitudes.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2023 05 16    16 41.23   -13 33.2    2.286    3.262   161.8     5.5  19.9
2023 05 26    16 36.02   -12 41.5    2.225    3.226   169.5     3.3  19.8
2023 06 05    16 30.30   -11 53.6    2.191    3.191   168.5     3.6  19.7
2023 06 15    16 24.73   -11 12.3    2.183    3.157   160.1     6.3  19.7
2023 06 25    16 19.97   -10 40.2    2.201    3.124   150.3     9.3  19.7
2023 07 05    16 16.60   -10 19.0    2.241    3.093   140.4    12.1  19.7
2023 07 15    16 15.00   -10 09.0    2.301    3.063   130.8    14.6  19.7
2023 07 25    16 15.42   -10 09.9    2.376    3.035   121.6    16.6  19.7
2023 08 04    16 17.93   -10 20.3    2.464    3.008   112.9    18.1  19.7
2023 08 14    16 22.50   -10 38.5    2.560    2.982   104.7    19.2  19.8
2023 08 24    16 29.03   -11 02.4    2.662    2.959    96.9    19.8  19.8
2023 09 03    16 37.38   -11 29.9    2.767    2.937    89.5    20.1  19.9
2023 09 13    16 47.39   -11 59.1    2.873    2.917    82.4    20.0  19.9
2023 09 23    16 58.90   -12 28.0    2.978    2.898    75.7    19.6  20.0
2023 10 03    17 11.74   -12 54.7    3.081    2.882    69.2    18.9  20.0
2023 10 13    17 25.75   -13 17.8    3.181    2.868    62.9    18.1  20.1
2023 10 23    17 40.80   -13 35.7    3.276    2.855    56.8    17.0  20.1


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

                         (C) Copyright 2023 CBAT
2023 June 20                     (CBET 5273)              Daniel W. E. Green