[Iaude] CBET 4894: COMET P/2020 W2

quai at eps.harvard.edu quai at eps.harvard.edu
Thu Dec 3 22:42:56 EST 2020


                                                  Electronic Telegram No. 4894
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/2020 W2 = P/2003 WR_168 = P/2005 CR_16 (NEAT-LINEAR)
     D. Rankin reported the discovery of a comet with a condensed coma of size
9" on CCD images obtained on Nov. 16 with the Mount Lemmon 1.5-m reflector
(discovery observations tabulated below).  Rankin notes that this comet and
his new comet P/2020 W1 were both in the same field-of-view.

     2020 UT             R.A. (2000) Decl.       Mag.   Observer
     Nov. 16.34502    3 20 35.20   + 5 00 45.5   20.1   Rankin
          16.35015    3 20 35.01   + 5 00 44.7   19.7     "
          16.35529    3 20 34.85   + 5 00 44.1   19.8     "
          16.36043    3 20 34.65   + 5 00 43.6   19.8     "

After the comet was posted on the Minor Planet Center's PCCP webpage, other
CCD astrometrists also noted the cometary appearance, and H. Sato (Tokyo,
Japan) noted on Nov. 17 that this appears to be a recovery of an apparently
asteroidal minor planet with a 17-year orbital period that carried the
multiple designations 2003 WR_168 and 2005 CR_16.  Others have also noted
the apparent recovery, and it was confirmed by calculations made by S.
Nakano (CBAT) and at the Minor Planet Center.  The object was first found
as an apparently asteroidal object on NEAT survey images taken at Palomar
on 2003 Nov. 19 (discovery observations tabulated below), when it was given
the minor-planet designation 2003 WR_168 (cf. MPS 92901).

     2003 UT             R.A. (2000) Decl.       Mag.
     Nov. 19.35795    3 16 44.84   + 4 45 23.5   19.4
          19.37422    3 16 44.26   + 4 45 21.4   19.6
          19.37866    3 16 44.10   + 4 45 20.8   19.4
          19.39494    3 16 43.51   + 4 45 19.9   19.6
          19.39927    3 16 43.38   + 4 45 18.7   19.4
          19.41971    3 16 42.64   + 4 45 16.1   19.3

The object was only observed on a second night in Nov. 2003 before being
re-discovered as an apparently asteroidal object in 2005 in the course of the
LINEAR survey (discovery observations tabulated below), when it was given the
minor-planet designation 2005 CR_16 (cf. MPS 126428).

     2005 UT             R.A. (2000) Decl.       Mag.
     Feb.  2.28845    9 18 07.51   +14 46 18.1   19.4
           2.30126    9 18 07.06   +14 46 21.1   20.0
           2.32682    9 18 06.18   +14 46 30.2   20.0

In light of the recovery, C. Hergenrother has now re-examined images that he
had taken on 2005 Mar. 8 and Apr. 4 with the University of Arizona's Kuiper
1.55-m reflector and notes that co-added images from Mar. 8 (producing an
equivalent 900-s R-band image) show what appears to be a diffuseness about 20"
in size surrounding the image of 2005 CR_16, indicating possible cometary
activity at that time; he measured mag 19.5-19.7 from those images on 2005
Mar. 8.2 and adds that the Apr. 4 images of 2005 CR_16 were involved with
stars (with any activity being thus uncertain).  Also, S. Deen, Simi Valley,
CA, USA, has identified three 180-s i-band CCD images taken with the 3.6-m
Canada-France-Hawaii Telescope on 2005 Apr. 11.3 as part of the CFHT Legacy
Survey, finding a very condensed, virtually starlike coma of size about
1" (full-width-at-half-maximum) with an apparent very faint 5"-long tail
extending toward p.a. 150-125 degrees.
     With an earlier Spacewatch observation on 2005 Jan. 17, the 2005 arc of
available astrometry now spans 2005 Jan. 17-Apr. 11.  The identification 2005
CR_16 = 2003 WR_168 was made by T. Spahr in 2008 (MPO 132989).
     Nine stacked 120-s exposures taken remotely by Sato on 2020 Nov. 17.2 UT
with a 0.43-m f/6.8 astrograph located near Mayhill, NM, USA, show a stellar
head with a hint of tail extending 10" westwards; the magnitude was 19.5 as
measured within a circular aperture of radius 5".7.  Sixty 60-s stacked
exposures taken on Nov. 19.0 by L. Buzzi, Varese, Italy, with a 0.84-m f/3.5
reflector (measured by A. Aletti and Buzzi) show a stellar apperance, but
Buzzi also noted the apparent recovery of 2005 CR_16 = 2003 WR_168.
     The available astrometry for this comet appear on MPEC 2020-X10 and
include pre-discovery observations at the current apparition spanning 2020
Aug. 29-Nov. 5 (which are a combination of several single-night, previously
unlinked sets of observations reported earlier and sitting in the MPC's
"isolated tracklet file" plus observations submitted subsequent to Rankin's
posted discovery report).  Mt. Lemmon pre-discovery observations on 2020 Aug.
29.5 UT gave mag 21.8-22.5, on Sept. 21.4 gave mag 21.3-21.5, on Oct. 16.3
gave mag 20.1-20.6, and on Nov. 5.45-5.47 gave mag 19.9-20.4.
     The following linked orbital elements by Nakano are from 134 observations
spanning 2003-2020 (mean residual 0".5).  He notes that the residuals for the
recovery observations on 2020 Nov. 16 were +17'.6 in R.A. and +4'.4 in Decl.
from the linked 2003-2005 orbit on MPO 132989, with a correspondng Delta(T)
correction of -1.29 days.  The comet passed 0.85 AU from Jupiter on 1951
Sept. 3 UT.  Nakano was unable to identify other observations in a search of
archival astrometry.

                    Epoch = 2004 July 14.0 TT
     T = 2004 June 25.94298 TT        Peri. = 312.96177
     e = 0.5095397                    Node  = 140.22636 2000.0
     q = 3.2406357 AU                 Incl. =   9.40419
       a =  6.6073353 AU   n = 0.05803160   P =  16.98 years

                    Epoch = 2021 July  5.0 TT
     T = 2021 June 23.56532 TT        Peri. = 313.09618
     e = 0.5103851                    Node  = 139.98041 2000.0
     q = 3.2469880 AU                 Incl. =   9.39376
       a =  6.6317181 AU   n = 0.05771185   P =  17.08 years

                    Epoch = 2038 Sept.14.0 TT
     T = 2038 Aug. 25.90582 TT        Peri. = 313.16742
     e = 0.5123187                    Node  = 139.93084 2000.0
     q = 3.2614361 AU                 Incl. =   9.39453
       a =  6.6876379 AU   n = 0.05698951   P =  17.30 years

The following ephemeris by the undersigned from the above orbital elements
uses photometric power-law parameters H = 12.5 and 2.5n = 8 (which
reasonably satisfy all three years of observation) for the magnitudes.

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2020 11 07    03 25.90   +05 23.8    2.621    3.590   165.9     3.9  19.0
2020 11 12    03 23.09   +05 10.7    2.605    3.576   167.1     3.6  19.0
2020 11 17    03 20.21   +04 59.4    2.596    3.563   165.8     3.9  19.0
2020 11 22    03 17.35   +04 50.5    2.594    3.550   162.7     4.7  19.0
2020 11 27    03 14.59   +04 44.2    2.600    3.537   158.5     5.9  19.0
2020 12 02    03 12.00   +04 40.6    2.612    3.524   153.8     7.1  19.0
2020 12 07    03 09.64   +04 40.0    2.631    3.511   148.8     8.3  19.0
2020 12 12    03 07.59   +04 42.3    2.656    3.499   143.8     9.6  19.0
2020 12 17    03 05.89   +04 47.8    2.687    3.487   138.7    10.7  19.0
2020 12 22    03 04.60   +04 56.2    2.723    3.475   133.6    11.8  19.0
2020 12 27    03 03.74   +05 07.6    2.763    3.463   128.6    12.8  19.0
2021 01 01    03 03.34   +05 21.8    2.808    3.452   123.7    13.7  19.0
2021 01 06    03 03.40   +05 38.5    2.857    3.441   118.8    14.5  19.1
2021 01 11    03 03.94   +05 57.6    2.909    3.430   114.1    15.2  19.1
2021 01 16    03 04.96   +06 18.9    2.963    3.419   109.5    15.7  19.1
2021 01 21    03 06.44   +06 42.2    3.020    3.409   105.0    16.2  19.2
2021 01 26    03 08.39   +07 07.2    3.078    3.399   100.5    16.5  19.2
2021 01 31    03 10.77   +07 33.7    3.138    3.389    96.2    16.8  19.2
2021 02 05    03 13.58   +08 01.4    3.198    3.380    92.0    16.9  19.3
2021 02 10    03 16.80   +08 30.1    3.259    3.371    87.9    17.0  19.3
2021 02 15    03 20.42   +08 59.7    3.320    3.362    83.9    17.0  19.3
2021 02 20    03 24.40   +09 29.8    3.380    3.353    80.0    16.9  19.3
2021 02 25    03 28.73   +10 00.4    3.440    3.345    76.2    16.7  19.4
2021 03 02    03 33.39   +10 31.2    3.499    3.337    72.5    16.4  19.4
2021 03 07    03 38.37   +11 02.0    3.557    3.330    68.8    16.1  19.4
2021 03 12    03 43.63   +11 32.6    3.614    3.322    65.2    15.8  19.5
2021 03 17    03 49.18   +12 03.0    3.669    3.315    61.7    15.3  19.5
2021 03 22    03 54.98   +12 32.9    3.722    3.309    58.3    14.8  19.5
2021 03 27    04 01.02   +13 02.2    3.773    3.302    54.9    14.3  19.5
2021 04 01    04 07.29   +13 30.8    3.823    3.296    51.6    13.7  19.6
2021 04 06    04 13.77   +13 58.5    3.870    3.291    48.3    13.1  19.6
2021 04 11    04 20.45   +14 25.2    3.915    3.285    45.1    12.5  19.6
2021 04 16    04 27.31   +14 50.9    3.957    3.280    42.0    11.8  19.6


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

                         (C) Copyright 2020 CBAT
2020 December 3                  (CBET 4894)              Daniel W. E. Green



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