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