[Iaude] CBET 5296: COMET P/2023 S1

[quai at eps.harvard.edu]

                                                  Electronic Telegram No. 5296
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/2023 S1
     Y. Ramanjooloo, Institute for Astronomy, University of Hawaii, reports
the discovery of a comet in images obtained with the Pan-STARRS2 1.8-m
Ritchey-Chretien reflector at Haleakala on Sept. 20 (discovery observations
tabulated below); three 45-s w-band exposures show a condensed head of size
2".1 (full-width-at-half-maximum) in 1".3 seeing with a faint, straight tail
11".5 long and about 5" wide spanning p.a. 223-237 degrees.

     2023 UT             R.A. (2000) Decl.       Mag.
     Sept.20.60443    2 28 54.43   +26 21 00.3   20.3
          20.61228    2 28 54.25   +26 21 01.2   20.5
          20.62011    2 28 54.11   +26 21 01.8   20.5

Pre-discovery observations were subsequently reported to the Minor Planet
Center that had been obtained on Sept. 15.4 UT (Mt. Lemmon, mag 19.5-19.7),
on Sept. 17.5 (Pan-STARRS2, mag 20.3-20.4), and on Sept. 19.5 (Pan-STARRS1
1.8-m Ritchey-Chretien reflector at Haleakala, mag 20.2-20.5).  Also, three
observations made by T. Maroti with a 0.28-m f/2.2 reflector on Sept. 20.0 at
Csokako, Hungary, were found in the MPC's "isolated tracklet file"; Maroti
gave the magnitude as 18.4-19.4.  After the object was posted on the MPC's
PCCP webpage, H. Sato (Bunkyo-ku, Tokyo, Japan) reported that eight stacked
120-s CCD exposures taken remotely on Sept. 21.32 with a 0.51-m f/6.8
astrograph located at the Utah Desert Remote Observatory (near Beryl Junction,
UT, USA) showed a strongly condensed coma 6" in diameter with no tail; the
magnitude was 19.5 as measured within a circular aperture of radius 4".9.
T. Prystavski (Lviv, Ukraine) reports total mag 19.7 and a 0'.2 tail in p.a.
229 degrees on Sept. 25.44 from five 120-s CCD exposures obtained remotely
with an iTelescope 0.51-m reflector at Beryl Junction (image posted on the
"ICQ Comet Observations" Facebook forum).
     The available astrometry appears on MPEC 2023-S264.  The following
orbital elements by S. Nakano (Central Bureau) are from 81 observations
spanning 2023 Sept. 15-29 (mean residual 0".4) and still have much uncertainty
due to the comet having passed only 0.0017 AU from Jupiter (whose radius is
0.00048 AU) around 2021 June 8 UT.  Prior to the 2021 encounter, the comet's
previous orbital elements were T = 1998 Jan. 16 TT, q = 4.994 AU, e = 0.429,
Peri. = 205.2 deg, Node = 143.7 deg, i = 10.3 deg, a = 8.748 AU, P = 25.9
years.  These suggest that the comet also passed 0.81 AU from Jupiter around
1916.

                    Epoch = 2025 Feb. 14.0 TT
     T = 2025 Feb. 26.77752 TT        Peri. = 180.20696
     e = 0.3132301                    Node  = 317.30430 2000.0
     q = 2.6345674 AU                 Incl. =   9.15771
       a =  3.8361718 AU   n = 0.13117679   P =   7.514 years

The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 11.0 and 2.5n = 10 for the
magnitudes.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2023 09 13    02 30.81   +26 06.5    3.124    3.795   125.2    12.5  19.3
2023 09 23    02 28.08   +26 24.3    2.989    3.767   135.1    10.8  19.1
2023 10 03    02 23.55   +26 31.1    2.873    3.738   145.2     8.8  19.0
2023 10 13    02 17.46   +26 25.4    2.780    3.710   155.2     6.5  18.9
2023 10 23    02 10.24   +26 07.0    2.714    3.681   164.1     4.2  18.8
2023 11 02    02 02.54   +25 36.8    2.677    3.653   167.6     3.4  18.8
2023 11 12    01 55.06   +24 57.3    2.670    3.624   161.8     4.9  18.7
2023 11 22    01 48.51   +24 12.6    2.692    3.595   152.2     7.4  18.7
2023 12 02    01 43.46   +23 27.4    2.740    3.566   141.7     9.9  18.7
2023 12 12    01 40.30   +22 46.0    2.810    3.537   131.1    12.1  18.7
2023 12 22    01 39.22   +22 12.0    2.899    3.508   120.9    13.9  18.8
2024 01 01    01 40.25   +21 47.7    3.002    3.478   111.1    15.3  18.8
2024 01 11    01 43.30   +21 34.1    3.113    3.449   101.7    16.2  18.8
2024 01 21    01 48.24   +21 31.3    3.230    3.420    92.7    16.7  18.9
2024 01 31    01 54.89   +21 38.6    3.347    3.391    84.1    16.8  18.9
2024 02 10    02 03.06   +21 55.1    3.462    3.362    76.0    16.5  19.0
2024 02 20    02 12.61   +22 19.4    3.571    3.333    68.2    16.0  19.0


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

                         (C) Copyright 2023 CBAT
2023 September 30                (CBET 5296)              Daniel W. E. Green