[Iaude] CBET 4968: COMET C/2021 K1 (ATLAS)

quai at eps.harvard.edu quai at eps.harvard.edu
Fri May 28 00:14:52 EDT 2021


                                                  Electronic Telegram No. 4968
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/2021 K1 (ATLAS)
     Peter Veres, Minor Planet Center, found that images of an object that
were obtained on May 14 and 24 with 0.5-m f/2 Schmidt reflectors at Mauna Loa,
Hawaii, and at Haleakala, Hawaii, respectively, in the course of the "Asteroid
Terrestrial-Impact Last Alert System" (ATLAS) search program show cometary
appearance.  The ATLAS team had submitted the observations without comment or
flagging, and they went into the MPC's "isolated tracklet file" (ITF) with
separate designations.  Veres was using software to search for potential
interesting objects based upon brightness and motion, and he noticed the May
24 observations first, from whence he sought additional identifications and
found linkages to the May 14 ATLAS observations and also to May 22 Pan-STARRS1
ITF astrometry.  Veres has access to the actual ATLAS images.  The ATLAS
observations are tabulated below.  L. Denneau of the ATLAS team subsequently
notes a condensed 6" coma and a straight tail about 10" long extending to the
west (p.a. 265-275 deg) on both nights.

     2021 UT             R.A. (2000) Decl.       Mag.
     May  14.59378   23 24 49.83   - 5 53 35.1   16.5
          14.59793   23 24 50.24   - 5 53 33.8   16.5
          14.60809   23 24 51.31   - 5 53 30.7   17.2
          14.62053   23 24 52.59   - 5 53 27.3   17.2
          24.60613   23 41 41.47   - 5 06 54.3   16.3
          24.61025   23 41 41.85   - 5 06 53.2   16.3
          24.61942   23 41 42.76   - 5 06 51.0   16.2

As with the ATLAS observations, this object was reported without comment or
flagging initially in regular survey observations obtained with the
Pan-STARRS1 1.8-m Ritchey-Chretien reflector at Haleakala on May 22.6 UT (mag
17.6-18.0), submitted as two separate objects on the same night.  After the
comet was posted on the MPC's PCCP webpage, R. Weryk (Department of Physics
and Astronomy, University of Western Ontario) noted that the 45-s w-band
Pan-STARRS1 survey images taken on May 22 show a broad tail extending > 50"
towards p.a. 250 degrees; the comet's diffuse head showed a size of about
2".7 (full-width-at-half-maximum) in 1".6 seeing.  Weryk also has identified
many pre-discovery Pan-STARRS1 and Pan-STARRS2 observations of this comet
back to 2020 April, when the comet was fainter and it was not possible to
determine any cometary appearance; following are selected dates and
magnitudes:  2020 Apr. 20.6, 21.2-22.8; May 2.55, 22.1; June 15.4, 21.4-22.3;
22.4, 21.1-21.9; July 20.3, 21.7-21.9; Aug. 12.3, 21.3-22.4.
     A. Hale, Cloudcroft, NM, USA, finds a relatively condensed coma 9" in
diameter with V magnitude 17.2-17.3 in three 240-s exposures taken in bright
moonlight on May 26.4 with a 0.4-m f/10 Schmidt-Cassegrain telescope of the
Las Cumbres Observatory at Cerro Tololo; there was a straight, somewhat broad
tail 16" long in approximate p.a. 285 degrees.  E. Guido, Castellammare di
Stabia, Italy, writes that forty-four stacked 60-s unfiltered exposures taken
remotely by a large group of observers with a "Telescope Live" 0.61-m f/6.5
astrograph located at El Sauce, Chile, on May 27.4 show a compact coma about
20" in diameter of mag 16.8-17.0 with a tail 30" long in p.a. 245 deg.
     The available astrometry appears on MPEC 2021-K89.  The following
orbital elements by S. Nakano (CBAT) are from 63 observations spanning
2020 Apr. 20-2021 May 26 (mean residual 0".2); they indicate that the comet
passed 2.04 AU from Uranus in 1965 March and 2.55 AU from Jupiter on 2021
Mar. 22 UT.

                    Epoch = 2021 Apr. 16.0 TT
     T = 2021 May   4.66515 TT        Peri. = 184.33248
     e = 0.8043530                    Node  = 140.90560 2000.0
     q = 2.4979656 AU                 Incl. =  16.27563
       a = 12.7677189 AU   n = 0.02160400   P =  45.62 years

                    Epoch = 2065 Aug. 23.0 TT
     T = 2065 Aug. 18.58421 TT        Peri. = 184.07244
     e = 0.8021749                    Node  = 140.73611 2000.0
     q = 2.4880805 AU                 Incl. =  16.27506
       a = 12.5771713 AU   n = 0.02209681   P =  44.60 years

The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 10.0 and 2.5n = 10 for the
magnitudes.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2021 05 26    23 43.97   -05 01.0    2.658    2.507    70.4    22.4  16.1
2021 05 31    23 52.04   -04 41.5    2.609    2.511    73.2    22.7  16.1
2021 06 05    23 59.89   -04 24.5    2.560    2.517    76.1    23.0  16.0
2021 06 10    00 07.49   -04 10.2    2.511    2.523    79.0    23.3  16.0
2021 06 15    00 14.83   -03 58.9    2.462    2.530    82.1    23.4  16.0
2021 06 20    00 21.88   -03 50.7    2.414    2.538    85.1    23.5  16.0
2021 06 25    00 28.63   -03 46.0    2.366    2.548    88.3    23.5  15.9
2021 06 30    00 35.04   -03 44.8    2.319    2.558    91.6    23.4  15.9
2021 07 05    00 41.10   -03 47.4    2.273    2.568    94.9    23.2  15.9
2021 07 10    00 46.76   -03 53.9    2.228    2.580    98.4    22.9  15.9
2021 07 15    00 52.01   -04 04.5    2.184    2.593   101.9    22.6  15.8
2021 07 20    00 56.82   -04 19.2    2.141    2.606   105.6    22.1  15.8
2021 07 25    01 01.15   -04 38.0    2.101    2.620   109.4    21.4  15.8
2021 07 30    01 04.99   -05 01.0    2.063    2.635   113.3    20.7  15.8
2021 08 04    01 08.30   -05 28.0    2.027    2.650   117.3    19.9  15.8
2021 08 09    01 11.06   -05 58.8    1.994    2.667   121.4    18.9  15.8
2021 08 14    01 13.25   -06 33.3    1.964    2.684   125.7    17.9  15.8
2021 08 19    01 14.87   -07 11.0    1.938    2.702   130.0    16.7  15.8
2021 08 24    01 15.92   -07 51.3    1.915    2.720   134.4    15.4  15.8
2021 08 29    01 16.40   -08 33.7    1.897    2.739   138.8    14.0  15.8
2021 09 03    01 16.34   -09 17.5    1.884    2.759   143.2    12.6  15.8
2021 09 08    01 15.76   -10 01.9    1.876    2.780   147.6    11.2  15.8
2021 09 13    01 14.70   -10 45.9    1.874    2.800   151.7     9.8  15.8
2021 09 18    01 13.25   -11 28.5    1.877    2.822   155.4     8.5  15.9
2021 09 23    01 11.46   -12 09.0    1.887    2.844   158.5     7.4  15.9
2021 09 28    01 09.42   -12 46.3    1.903    2.867   160.5     6.7  16.0
2021 10 03    01 07.22   -13 19.7    1.925    2.890   161.1     6.4  16.0
2021 10 08    01 04.94   -13 48.6    1.954    2.914   160.2     6.7  16.1
2021 10 13    01 02.69   -14 12.3    1.989    2.938   158.0     7.3  16.2
2021 10 18    01 00.55   -14 30.5    2.030    2.962   154.8     8.2  16.3
2021 10 23    00 58.61   -14 43.1    2.077    2.987   151.1     9.3  16.3
2021 10 28    00 56.93   -14 50.1    2.131    3.013   146.9    10.4  16.4
2021 11 02    00 55.57   -14 51.5    2.190    3.039   142.6    11.4  16.5
2021 11 07    00 54.57   -14 47.6    2.254    3.065   138.2    12.4  16.6
2021 11 12    00 53.97   -14 38.6    2.323    3.091   133.8    13.4  16.7
2021 11 17    00 53.79   -14 25.0    2.396    3.118   129.3    14.2  16.8
2021 11 22    00 54.04   -14 07.2    2.474    3.146   124.9    14.9  16.9
2021 11 27    00 54.70   -13 45.6    2.555    3.173   120.6    15.5  17.1
2021 12 02    00 55.79   -13 20.6    2.640    3.201   116.3    16.0  17.2
2021 12 07    00 57.28   -12 52.6    2.727    3.229   112.1    16.4  17.3
2021 12 12    00 59.16   -12 22.0    2.817    3.258   107.9    16.7  17.4
2021 12 17    01 01.42   -11 49.1    2.910    3.287   103.8    16.9  17.5
2021 12 22    01 04.02   -11 14.3    3.004    3.316    99.8    17.0  17.6
2021 12 27    01 06.94   -10 38.0    3.099    3.345    95.8    17.0  17.7
2022 01 01    01 10.16   -10 00.3    3.195    3.374    91.9    16.9  17.8
2022 01 06    01 13.67   -09 21.6    3.293    3.404    88.1    16.8  17.9
2022 01 11    01 17.44   -08 42.1    3.390    3.434    84.3    16.6  18.0
2022 01 16    01 21.44   -08 02.0    3.488    3.464    80.5    16.3  18.1
2022 01 21    01 25.65   -07 21.4    3.585    3.494    76.8    15.9  18.2


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

                         (C) Copyright 2021 CBAT
2021 May 27                      (CBET 4968)              Daniel W. E. Green



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