COMET C/2019 Q4 (BORISOV)
[Editor's note:  this text replaces that on CBET 4669 (author list).]
     A. Fitzsimmons, Queen's University, Belfast; O. Hainaut, Bin Yang and
C. Opitom, European Southern Observatory; K. Meech, J. Kleyna, and J. Keane,
University of Hawaii; C. Snodgrass, University of Edinburgh; M. Micheli,
Near-Earth-Object Coordination Centre, European Space Agency; and E. Jehin,
Universite de Liege, report that comet C/2019 Q4 was observed with the 4.2-m
William Herschel Telescope (+ ISIS spectrograph) on Sept. 20.2 UT.  Analysis
of a 1200-s exposure obtained through a 2"-wide slit reveals a 12-sigma
detection of CN emission at 388.0 nm.  No other gas species are immediately
apparent in this spectrum (range 350-600 nm).  Integration over a slit length
of 8" centered on the nuclear condensation gives a total emission band flux
of 8 x 10E-15 erg/s/cm^2 and a CN-production rate of 4 x 10E24 molecules/s,
assuming a standard Haser model, a molecular velocity of 0.5 km/s, and
nominal Schleicher and A'Hearn scalelengths.  However, the authors caution
that these data were obtained at high airmass and through thin cloud -- and
hence may not be reliable to within a factor of 2.
     Further to CBET 4668, D. T. Durig, Sewanee, TN, USA, writes that 150
stacked 10-s V-band CCD exposures taken with a 0.3 m f/5.0 Schmidt-Cassegrain
reflector on Sept. 18.4 UT show a 100" tail in p.a. 309 degrees.  J.-F.
Soulier reports that forty-five 60-s unfiltered CCD exposures taken with a
0.30-m f/3.8 Newtonian reflector at Maisoncelles, France, during Sept.
19.15-19.17 show a coma of size about 18" and a tail about 30" long in p.a.
about 290 degrees; the magnitude was 17.4 in an aperture of radius 6".5.
S. Nakano, Sumoto, Japan, communicates that M. Okuda, (Yao, Osaka, Japan)
found magnitude 16.6 and a short possible tail toward the northwest on CCD
images obtained on Sept. 19.789 using a 0.28-m reflector, and that Y. Mizuno
(Kani, Aichi-ken, Japan) found mag 16.7 on CCD images taken on Sept. 19.800
using a 0.32-m reflector.
     Additional astrometry for this comet have been published on MPECs
2019-R113, 2019-S03, 2019-S09, and 2019-S25.  The following revised hyperbolic
orbital elements by S. Nakano are from 404 observations spanning 2019 Aug.
30-Sept. 20 (mean residual 0".63), and they indicate an "original" value of
1/a = -1.191897 AU**-1 and a "future" 1/a value of -1.191435 (+/- 0.012877);
the respective solar-system barycentric eccentricities are 3.4150 (at r =
929 AU pre-perihelion in the year AD 1885) and 3.4114 (at r = 1003 AU post-
perihelion in the year 2165).

                    Epoch = 2019 Dec. 23.0 TT
     T = 2019 Dec.  8.27750 TT        Peri. = 208.86344
     e = 3.4045258                    Node  = 308.24843 2000.0
     q = 2.0179520 AU                 Incl. =  43.95012

     The following updated ephemeris from the above orbital elements
uses power-law magnitudes from photometric parameters H = 11.0, 2.5n =
8.0 (thus, Mag. = 11.0 + 5 log Delta + 8 log r).

Date    TT    R. A. (2000) Decl.     Delta      r     Elong.  Phase  Mag.
2019 08 05    07 39.93   +39 18.2    4.279    3.415    27.9     8.0  18.4
2019 08 10    07 49.18   +38 19.2    4.172    3.329    29.7     8.7  18.3
2019 08 15    07 58.48   +37 16.2    4.063    3.244    31.6     9.4  18.1
2019 08 20    08 07.81   +36 09.0    3.954    3.160    33.6    10.2  18.0
2019 08 25    08 17.17   +34 57.2    3.843    3.078    35.6    11.0  17.8
2019 08 30    08 26.55   +33 40.6    3.732    2.997    37.7    11.9  17.7
2019 09 04    08 35.93   +32 18.7    3.621    2.917    39.7    12.8  17.5
2019 09 09    08 45.31   +30 51.3    3.510    2.840    41.8    13.7  17.4
2019 09 14    08 54.68   +29 17.8    3.399    2.764    43.9    14.6  17.2
2019 09 19    09 04.03   +27 37.9    3.289    2.691    46.0    15.6  17.0
2019 09 24    09 13.37   +25 51.2    3.180    2.620    48.1    16.6  16.9
2019 09 29    09 22.68   +23 57.2    3.073    2.551    50.2    17.6  16.7
2019 10 04    09 31.95   +21 55.5    2.968    2.485    52.3    18.6  16.5
2019 10 09    09 41.18   +19 45.7    2.866    2.423    54.3    19.6  16.4
2019 10 14    09 50.37   +17 27.2    2.766    2.363    56.3    20.6  16.2
2019 10 19    09 59.50   +14 59.8    2.670    2.308    58.3    21.6  16.0
2019 10 24    10 08.59   +12 23.0    2.577    2.256    60.3    22.5  15.9
2019 10 29    10 17.62   +09 36.7    2.490    2.209    62.2    23.4  15.7
2019 11 03    10 26.59   +06 40.7    2.407    2.166    64.1    24.3  15.6
2019 11 08    10 35.48   +03 35.1    2.330    2.128    66.0    25.2  15.5
2019 11 13    10 44.31   +00 20.1    2.258    2.095    67.8    25.9  15.3
2019 11 18    10 53.07   -03 03.7    2.194    2.068    69.6    26.6  15.2
2019 11 23    11 01.74   -06 35.6    2.136    2.047    71.3    27.2  15.1
2019 11 28    11 10.32   -10 14.5    2.086    2.031    73.1    27.7  15.1
2019 12 03    11 18.80   -13 58.9    2.043    2.021    74.7    28.1  15.0
2019 12 08    11 27.17   -17 47.1    2.009    2.018    76.4    28.3  15.0
2019 12 13    11 35.41   -21 37.2    1.982    2.021    78.0    28.5  14.9
2019 12 18    11 43.50   -25 27.1    1.963    2.030    79.5    28.5  14.9
2019 12 23    11 51.42   -29 14.7    1.952    2.045    81.0    28.4  14.9
2019 12 28    11 59.13   -32 58.0    1.948    2.065    82.5    28.2  15.0
2020 01 02    12 06.60   -36 34.9    1.951    2.092    84.0    27.9  15.0
2020 01 07    12 13.79   -40 03.7    1.961    2.124    85.5    27.5  15.1
2020 01 12    12 20.64   -43 23.1    1.977    2.161    87.0    27.0  15.2
2020 01 17    12 27.11   -46 31.8    1.998    2.204    88.5    26.5  15.2
2020 01 22    12 33.12   -49 29.2    2.024    2.250    90.0    25.9  15.3
2020 01 27    12 38.60   -52 14.5    2.054    2.302    91.6    25.3  15.5
2020 02 01    12 43.46   -54 47.3    2.088    2.357    93.1    24.7  15.6
2020 02 06    12 47.65   -57 07.6    2.125    2.416    94.8    24.0  15.7
2020 02 11    12 51.08   -59 15.3    2.165    2.478    96.4    23.3  15.8
2020 02 16    12 53.69   -61 10.6    2.208    2.543    98.2    22.6  16.0
2020 02 21    12 55.40   -62 53.5    2.252    2.611    99.9    21.9  16.1
2020 02 26    12 56.17   -64 24.1    2.299    2.682   101.8    21.2  16.2
2020 03 02    12 56.02   -65 42.7    2.348    2.755   103.6    20.5  16.4
2020 03 07    12 54.97   -66 49.5    2.399    2.831   105.5    19.7  16.5
2020 03 12    12 53.11   -67 44.8    2.452    2.908   107.4    19.0  16.7
2020 03 17    12 50.56   -68 28.9    2.507    2.987   109.3    18.3  16.8
2020 03 22    12 47.48   -69 02.3    2.564    3.068   111.2    17.6  16.9
2020 03 27    12 44.08   -69 25.2    2.622    3.150   113.1    16.9  17.1
2020 04 01    12 40.59   -69 38.5    2.684    3.234   114.9    16.3  17.2
2020 04 06    12 37.23   -69 42.7    2.748    3.319   116.6    15.6  17.4
2020 04 11    12 34.20   -69 38.8    2.814    3.405   118.2    15.0  17.5
2020 04 16    12 31.65   -69 27.5    2.884    3.492   119.7    14.5  17.6
2020 04 21    12 29.70   -69 09.9    2.956    3.580   121.0    13.9  17.8
2020 04 26    12 28.44   -68 46.6    3.032    3.669   122.2    13.4  17.9
2020 05 01    12 27.92   -68 18.8    3.112    3.758   123.1    13.0  18.1
2020 05 06    12 28.13   -67 47.3    3.195    3.849   123.8    12.6  18.2
2020 05 11    12 29.04   -67 12.8    3.282    3.940   124.2    12.2  18.3
2020 05 16    12 30.62   -66 36.2    3.373    4.031   124.3    12.0  18.5
2020 05 21    12 32.81   -65 58.1    3.469    4.123   124.2    11.7  18.6
2020 05 26    12 35.57   -65 19.0    3.568    4.216   123.8    11.5  18.8
2020 05 31    12 38.84   -64 39.6    3.671    4.309   123.1    11.4  18.9
2020 06 05    12 42.55   -64 00.2    3.779    4.402   122.1    11.3  19.0
2020 06 10    12 46.66   -63 21.4    3.891    4.496   120.8    11.2  19.2
2020 06 15    12 51.11   -62 43.4    4.006    4.591   119.4    11.1  19.3
2020 06 20    12 55.86   -62 06.5    4.126    4.685   117.6    11.1  19.4
2020 06 25    13 00.88   -61 30.9    4.250    4.780   115.7    11.0  19.6
2020 06 30    13 06.12   -60 56.8    4.377    4.875   113.7    11.0  19.7
2020 07 05    13 11.56   -60 24.4    4.508    4.971   111.4    11.0  19.8


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

                         (C) Copyright 2019 CBAT
2019 September 21                (CBET 4670)              Daniel W. E. Green