[Iaude] COMET C/2023 X2

quai at eps.harvard.edu quai at eps.harvard.edu
Mon Dec 11 22:30:32 EST 2023


                                                  Electronic Telegram No. 5323
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 C/2023 X2 (LEMMON)
     R. Weryk, Department of Physics and Astronomy, University of Western
Ontario, reports the discovery of another comet in images obtained with the
Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala on Dec. 4.3 UT, in
which four 45-s w-band survey images taken in 1".0 seeing show a condensed
head of size 1".7 (full-width-at-half-maximum) with a tail about 6" long
toward p.a. 210 degrees.  The object was reported independently as an
apparently asteroidal object on images obtained shortly thereafter (Dec. 4.4)
with the 1.5-m Mt. Lemmon Survey reflector, but the Mt. Lemmon observations
were posted to the Minor Planet Center's NEOCP website before the Pan-STARRS1
observations arrived, and Weryk immediately noticed the identity.  The
discovery observations are tabulated below.

     2023 UT             R.A. (2000) Decl.       Mag.   Observer
     Dec.  4.31664    4 13 21.52   +16 02 18.3   20.5   Pan-STARRS1
           4.33254    4 13 20.94   +16 02 20.6   20.8     "
           4.34673    4 13 20.41   +16 02 22.5   20.6     "
           4.35197    4 13 20.17   +16 02 22.6   19.7   Mt. Lemmon Survey
           4.35709    4 13 19.97   +16 02 23.2   20.2     "
           4.36088    4 13 19.89   +16 02 24.2   20.5   Pan-STARRS1
           4.36221    4 13 19.78   +16 02 24.1   20.1   Mt. Lemmon Survey
           4.36733    4 13 19.60   +16 02 24.4   19.8     "

Pan-STARRS1 observations made in Oct. 12.5 UT (when the comet was at mag
21.3-21.6) were subsequently identified in MPC's "isolated tracklet file",
together with observations on Oct. 17.5 (mag 21.5-21.8) made with the
Pan-STARRS2 1.8-m Ritchey-Chretien reflector at Haleakala.  Weryk then found
additional Pan-STARRS2 observations on Aug. 18.6 (mag 21.7-22.1), Sept. 20.6
(mag 21.4-21.8), and Oct. 7.5 (mag 21.1-21.5).  Y. Ramanjooloo (Institute for
Astronomy, University of Hawaii) writes that four 45-s w-band Pan-STARRS2
images obtained on Dec. 7.33-7.37 show a diffuse and faint 2".2 tail towards
p.a. 227 degrees, with a condensed coma of size 2".1.
     After the comet was posted to the MPC's PCCP webpage, other CCD
astrometrists commented on the object's appearance.  Ten stacked 120-s
exposures taken remotely by H. Sato (Bunkyo-ku, Tokyo, Japan) with a 0.43-m
f/6.8 astrograph located at the Utah Desert Remote Observatory (near Beryl
Junction, UT, USA) on Dec. 6.2 UT show only a stellar appearance; the
magnitude was 20.2 as measured within a circular aperture of radius 3".8.
Ninety-nine stacked 30-s exposures taken by L. Buzzi and G. Galli at Varese,
Italy, with a 0.84-m f/3.5 reflector on Dec. 7.0 (measured by A. Aletti,
Buzzi, and Galli) show a condensed coma 7" wide (mag 20.5) with a faint,
straight tail 12" long in p.a. 265 degrees.
     The available astrometry appears on MPEC 2023-X226.  The following
orbital elements by S. Nakano (Central Bureau) are from 75 observations
spanning 2023 Aug. 18-Dec. 11 (mean residual 0".3).  The corresponding
"original" and "future" values of 1/a are +0.000333 and +0.000712 (+/-
0.000044) AU**-1, respectively.  The comet will pass 1.82 AU from Jupiter
on 2024 Aug. 9 UT.

                    Epoch = 2025 Dec. 31.0 TT
     T = 2025 Dec. 28.47605 TT        Peri. =  64.79176
     e = 0.9997663                    Node  =  66.30112 2000.0
     q = 5.0889123 AU                 Incl. =  76.97848

The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 8.5 and 2.5n = 8 for the
magnitudes.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2023 12 02    04 14.78   +15 57.0    6.541    7.521   173.1     0.9  19.6
2023 12 12    04 08.69   +16 20.2    6.522    7.471   163.3     2.2  19.6
2023 12 22    04 02.86   +16 44.9    6.536    7.421   152.2     3.5  19.5
2024 01 01    03 57.55   +17 11.1    6.581    7.371   141.0     4.8  19.5
2024 01 11    03 52.97   +17 39.0    6.651    7.321   129.9     5.9  19.5
2024 01 21    03 49.29   +18 08.9    6.744    7.272   119.0     6.8  19.5
2024 01 31    03 46.61   +18 40.9    6.852    7.223   108.4     7.4  19.5
2024 02 10    03 44.98   +19 14.9    6.970    7.174    98.0     7.8  19.6
2024 02 20    03 44.39   +19 50.9    7.093    7.125    87.9     8.0  19.6
2024 03 01    03 44.81   +20 28.9    7.215    7.077    78.0     7.9  19.6
2024 03 11    03 46.18   +21 08.7    7.332    7.029    68.5     7.6  19.6
2024 03 21    03 48.42   +21 50.1    7.438    6.981    59.2     7.0  19.6
2024 03 31    03 51.44   +22 33.1    7.530    6.933    50.2     6.4  19.6

2024 07 29    04 54.21   +32 34.2    6.980    6.386    50.8     7.1  19.2
2024 08 08    04 58.67   +33 34.6    6.802    6.343    59.2     7.9  19.1
2024 08 18    05 02.45   +34 37.8    6.613    6.301    67.8     8.6  19.0
2024 08 28    05 05.41   +35 44.2    6.416    6.258    76.5     9.0  18.9
2024 09 07    05 07.34   +36 54.0    6.214    6.217    85.5     9.3  18.8
2024 09 17    05 08.08   +38 07.3    6.012    6.175    94.6     9.3  18.7
2024 09 27    05 07.43   +39 23.5    5.815    6.135   104.0     9.1  18.6
2024 10 07    05 05.21   +40 42.1    5.627    6.094   113.5     8.7  18.5
2024 10 17    05 01.25   +42 01.4    5.453    6.055   123.1     7.9  18.4
2024 10 27    04 55.49   +43 19.6    5.299    6.016   132.5     7.0  18.4
2024 11 06    04 47.93   +44 33.9    5.170    5.977   141.4     5.9  18.3
2024 11 16    04 38.75   +45 41.5    5.069    5.939   149.1     4.9  18.2
2024 11 26    04 28.31   +46 39.5    4.999    5.901   153.9     4.2  18.2
2024 12 06    04 17.10   +47 25.9    4.962    5.865   154.2     4.2  18.1
2024 12 16    04 05.81   +47 59.8    4.958    5.828   149.7     4.9  18.1
2024 12 26    03 55.08   +48 21.9    4.985    5.793   142.2     6.0  18.1
2025 01 05    03 45.54   +48 34.3    5.039    5.758   133.3     7.1  18.1


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

                         (C) Copyright 2023 CBAT
2023 December 12                 (CBET 5323)              Daniel W. E. Green



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