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CBET 4675: COMET C/2018 DO_4
An apparently asteroidal object discovered on CCD images taken last
year
by G. J. Leonard with the Mount Lemmon Survey's 1.5-m reflector (and
announced
with minor-planet designation on MPEC 2018-F13) has been found to show
cometary activity now near perihelion. The discovery astrometry is
tabulated
below; follow-up observations appeared on MPEC 2018-Y11.
2018 UT R.A. (2000) Decl. Mag. Observer
Feb. 25.31328 12 43 55.51 +19 42 43.9 20.6 Leonard
25.31843 12 43 55.22 +19 42 46.7 21.3 "
25.32358 12 43 54.90 +19 42 50.0 21.3 "
25.32874 12 43 54.62 +19 42 53.7 21.0 "
CCD astrometrists elsewhere have reported cometary appearance in 2018 DO4.
L. Buzzi, Varese, Italy, reports that stacked images taken with his 0.60-m
f/4.6 reflector on Aug. 30.1 UT show a 15" coma and a tail at least 30" long
in p.a. 282 degrees; the magnitude was measured as 16.6. Buzzi adds that he
measured ninety stacked 15-s images obtained by R. Holmes with a 0.76-m f/3
astrograph at Westfield, IL, USA, on Sept. 4.4, which show an elongated coma
and a broad, curved tail 50" long in p.a. 285 deg; the magnitude was given
as
17.2-17.8. Buzzi further comments on images taken with his 0.60-m reflector
on Sept. 17.1 that show a strongly condensed coma 10" wide (red mag 16.8)
with a broad, fan-shaped tail at least 45" long centered in p.a. 294 deg.
M. Micheli reports that images taken on Sept. 2.63 and 3.63 by K. J. Meech
and J. Kleyna with the 3.6-m Canada-France-Hawaii Telescope at Mauna Kea
show a broad tail about 25" long in p.a. about 300 degrees. W. Ryan notes
that his images taken on Sept. 3.4 with the Magdalena Ridge Observatory
2.4-m reflector show a bright coma with distinct tail in p.a. about 290
degrees. H. Sato, Tokyo, Japan, writes that six stacked 60-s exposures
taken
on Sept. 4.47 with a 0.43-m f/6.8 astrograph near Mayhill, NM, USA, show a
condensed coma 20" in diameter with a fan-like tail 40" long toward p.a.
260-300 degrees; the magnitude was 16.1 as measured within a circular
aperture of radius 11".5.
Twelve co-added 40-s unfiltered exposures taken by T. Chen with a 0.3-m
f/7.2 reflector at Ngari, Tibet, China, in the course of the BIST survey
(cf. CBET 4629) around Sept. 4.89 (and measured by D. W. E. Green) show a
well-condensed coma of size about 7" in 3" seeing, with a faint tail perhaps
15" long in p.a. 267 degrees; the total magnitude was 17.4 in an aperture of
diameter 10". Twenty-four stacked 40-s BIST exposures on Sept. 5.9 show a
well-condensed coma of size 8"-10" in 2".6 seeing, with a faint tail perhaps
15" long fanned in p.a. 251-314 degrees; the total magnitude was 17.0 in an
aperture of diameter 12". Fifteen stacked BIST exposures taken on Sept. 6.9
show a well-condensed coma of size about 7" in 3" seeing, with a faint but
obvious fan tail up to 25" long centered at p.a. about 275 degrees; the
total
unfiltered magnitude was 17.0 in an aperture of diameter 30". Thirty-one
stacked BIST exposures taken on Sept. 7.9 show a well-condensed coma of size
about 8", with a faint but obvious fan tail up to 15" long centered at p.a.
about 275 degrees (fan perhaps 80 degrees wide); the total unfiltered
magnitude was 17.1 in an aperture of diameter 20". Nine stacked BIST
exposures taken on Sept. 8.8 show a condensed coma of size about 9" that is
elongated along p.a. 345/175 degrees, with a faint-but-obvious diffuse tail
up perhaps 20" long centered at p.a. about 280 degrees; the total magnitude
was 16.4 in an aperture of diameter 20". Thirty-three stacked BIST
exposures taken on Sept. 9.9 show a condensed coma of diameter about 10" (in
2".6 seeing) with a faint-but-obvious, diffuse fan tail perhaps 22" long
centered at p.a. about 270 degrees; the total magnitude was 17.3 in an
aperture of diameter 14".
R. Haver writes that twenty-four 90-s exposures taken on Sept. 8.11
with
a 0.37-m f/7 Cassegrain reflector at Frasso Sabino, Italy, shows a coma of
diameter 6".5 and magnitude 16.0; there was a slightly curved fan tail about
45" long in p.a. 287 degrees. Haver's follow-up images on Oct. 6.16 show
total red mag 16.5 with a coma diamete of 10".7 and a curved tail 44" long
in p.a. 292 degrees. S. Nakano, Sumoto, Japan, forwards a report by Y.
Mizuno (Kani, Japan) whose CCD images taken on Sept. 9.73 show magnitude
16.8 and a tail 0.5 degree long in p.a. 270 degrees. F. Kugel reports that
unfiltered CCD images taken on Sept. 12.15 by C. Rinner and himself with a
0.4-m f/2.8 reflector at Dauban, France, show a condensed coma and a broad
tail in p.a. 276 deg. Unfiltered images taken by J.-F. Soulier taken on
Sept. 16.1 with a 0.30-m f/3.8 Newtonian reflector at Maisoncelles, France,
show a coma about 15" in size and a tail about 25" long in p.a. 270-300 deg;
the magnitude was 16.7 in an aperture of radius 6".5. Soulier adds that
exposures taken on Sept. 19.1 show a coma of size about 19" and a tail about
25" long in p.a. 210-300 degrees; the magnitude was about 16.7 in an
aperture
of radius 6".5. Twenty stacked 30-s unfiltered exposures taken remotely on
Sept. 29.34 by E. Guido, Castellammare di Stabia, Italy, with a 0.6-m f/6.5
astrograph at El Sauce Observatory in Chile show a coma nearly 20" in
diameter with a central condensation and a diffuse fan-shaped tail about 45"
long toward p.a. 275 degrees. V. Rumyantsev reports that images taken on
Oct. 2.035 UT with the 2.6-m Shajn telescope of Crimean Astrophysical
Observatory at Nauchny, Crimea, show a bright 14" coma of red mag 17.3 and a
60" tail toward p.a. about 290 deg. Sixty stacked 60-s exposures taken by
P. Bacci, M. Maestripieri, and M. Facchini with a 0.60-m f/4 reflector at
San Marcello Pistoiese, Italy, on Oct. 6.1 show a coma with red mag 15.8 and
a tail 1'10" long in p.a. 302 degrees; they have posted a stacked image of
the comet at URL http://backman.altervista.org/Aimg/2018DO4_01_sm.jpg.
Additional astrometry has been published on MPEC 2019-T99. The
following
orbital elements by S. Nakano, Sumoto, Japan, are from 374 observations
spanning 2016 Apr. 5-2019 Oct. 2 (mean residual 0".39). The comet passed
2.87 AU from Jupiter on 2017 May 28 UT; its next return to perihelion is
predicted to be on 2147 October 10. No additional observations have been
identified in archival astrometry.
Epoch = 2019 Aug. 25.0 TT
T = 2019 Aug. 18.40490 TT Peri. = 175.97274
e = 0.9069557 Node = 251.13292 2000.0
q = 2.4059613 AU Incl. = 160.47470
a = 25.8582318 AU n = 0.00749559 P = 131.5 years
The following ephemeris by the undersigned from the above orbital elements
uses power-law photometric parameters H = 12.5 and 2.5n = 6 for the
predicted
magnitudes.
