[Iaude] COMET C/2023 X4

[quai at eps.harvard.edu]

                                                  Electronic Telegram No. 5327
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 X4 (HOGAN)
     Joshua K. Hogan, Lunar and Planetary Laboratory (LPL), University of
Arizona, reports his discovery of a comet on CCD images obtained with the
Mt. Lemmon Survey's 1.5-m reflector on Dec. 13 (discovery observations
tabulated below).  Hogan noted condensed coma of diameter 5".1 with a
prominent tail visible in 30-s exposures; four stacked 30-s exposures show
a possible second tail.  The tail length was given as 10".9, with p.a. 2.5
and 337.3 degrees also provided without elaboration.

     2023 UT             R.A. (2000) Decl.       Mag.   Observer
     Dec. 13.33238    7 23 30.24   +36 35 45.2   19.8   Hogan
          13.33765    7 23 30.08   +36 35 46.3   19.8     "
          13.34293    7 23 29.98   +36 35 47.0   19.8     "
          13.34820    7 23 29.85   +36 35 48.6   19.8     "
          13.41358    7 23 28.17   +36 36 02.7   20.0     "
          13.42704    7 23 27.82   +36 36 05.2   19.7     "
          13.44044    7 23 27.51   +36 36 08.1   19.8     "
          13.45373    7 23 27.17   +36 36 10.9   20.1     "

K. Wierzchos, LPL, writes that four 30-s unfiltered exposures obtained with
the Steward Observatory 1.0-m reflector at Mt. Lemmon on Dec. 13.43-13.47 UT
show a condensed coma of diameter 5" with a straight 13" tail in p.a. 260
degrees.  After the comet was posted to the Minor Planet Center's PCCP
webpage, R. Weryk (Department of Physics and Astronomy, University of Western
Ontario) found single-night images of this comet over three nights in the
MPC's "isolated tracklet file":  Sept. 20.6 (Pan-STARRS1 1.8-m reflector at
Haleakala; mag 22.1-22.2), Oct. 16.6 (Pan-STARRS2 1.8-m Ritchey-Chretien
reflector at Haleakala; mag 21.5-22.0), and Oct. 22.4 (Mt. Lemmon Survey; mag
21.2-21.6).  Weryk adds that four 45-s w-band survey images on Sept. 20 in
1".1 or better seeing show a very condensed head of size 1".5 (full-width-at-
half-maximum) with a short tail about 1" long in p.a. 270 degrees.  Four 45-s
Pan-STARRS2 w-band survey images on Oct. 16 in 1".2 or better seeing show a
very condensed head of size 1".4 (FWHM) and a short tail about 3" long
towards p.a. 270 degrees.
     The available astrometry appears on MPEC 2023-X272.  The following
orbital elements by S. Nakano (Central Bureau) are from 24 observations
spanning 2023 Sept. 20-Dec. 13 (mean residual 0".2).  There are no close
approaches to major planets.

                    Epoch = 2024 May  10.0 TT
     T = 2024 May  24.85539 TT        Peri. = 100.56415
     e = 0.6308741                    Node  =  28.76244 2000.0
     q = 3.6576079 AU                 Incl. =  11.59447
       a =  9.9088347 AU   n = 0.03159877   P =  31.19 years

                    Epoch = 2055 July 27.0 TT
     T = 2055 Aug.  2.32123 TT        Peri. = 100.79380
     e = 0.6299574                    Node  =  28.69909 2000.0
     q = 3.6520001 AU                 Incl. =  11.60081
       a =  9.8691349 AU   n = 0.03178963   P =  31.00 years

The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 13.0 and 2.5n = 8 for the
magnitudes.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2023 12 02    07 26.93   +35 53.8    3.062    3.862   139.2     9.6  20.1
2023 12 12    07 24.03   +36 31.0    2.963    3.840   148.9     7.6  20.0
2023 12 22    07 19.42   +37 04.7    2.890    3.819   157.8     5.6  20.0
2024 01 01    07 13.60   +37 31.6    2.845    3.800   164.1     4.1  19.9
2024 01 11    07 07.20   +37 49.0    2.827    3.781   163.6     4.2  19.9
2024 01 21    07 00.98   +37 55.4    2.839    3.764   156.9     5.9  19.9
2024 01 31    06 55.70   +37 50.5    2.878    3.748   147.8     8.1  19.9
2024 02 10    06 51.97   +37 35.7    2.941    3.733   138.0    10.2  19.9
2024 02 20    06 50.21   +37 12.8    3.025    3.720   128.3    12.0  20.0
2024 03 01    06 50.61   +36 43.9    3.125    3.707   118.9    13.5  20.0
2024 03 11    06 53.17   +36 10.6    3.239    3.696   109.9    14.6  20.1
2024 03 21    06 57.81   +35 34.2    3.362    3.687   101.2    15.4  20.2
2024 03 31    07 04.30   +34 55.4    3.490    3.679    92.9    15.7  20.2
2024 04 10    07 12.44   +34 14.3    3.620    3.672    85.0    15.8  20.3
2024 04 20    07 21.98   +33 30.8    3.750    3.666    77.5    15.5  20.4
2024 04 30    07 32.69   +32 44.9    3.877    3.662    70.3    15.0  20.5
2024 05 10    07 44.36   +31 56.0    4.000    3.659    63.3    14.3  20.5


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

                         (C) Copyright 2023 CBAT
2023 December 14                 (CBET 5327)              Daniel W. E. Green