[Iaude] CBET 4524: 20180611 : COMET C/2018 EN_4 (NEOWISE)
quai at eps.harvard.edu
quai at eps.harvard.edu
Mon Jun 11 10:33:07 EDT 2018
Electronic Telegram No. 4524
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)
Prepared using the Tamkin Foundation Computer Network
COMET C/2018 EN_4 (NEOWISE)
An apparently asteroidal object with a comet-like orbit that was found
on infrared images taken on Mar. 9 with the Near-Earth Object Wide-field
Infrared Survey Explorer (or NEOWISE; formerly the WISE earth-orbiting
satellite; cf. CBET 4225) has been found to show cometary activity by ground-
based CCD astrometrists. The discovery observations are tabulated below as
published first on MPEC 2018-F12, in which the listed optical-wavelength
magnitude was roughly estimated based on past WISE and NEOWISE cometary
2018 UT R.A. (2000) Decl. Mag.
Mar. 9.08775 6 34 15.16 -11 44 43.0 20
9.15320 6 34 12.44 -11 40 59.7
9.21865 6 34 09.78 -11 37 16.2
9.41552 6 34 02.04 -11 26 04.1
9.67733 6 33 51.52 -11 11 10.5
H. Sato, Tokyo, Japan, found a 10" coma on four stacked 60-s exposures taken
on May 13.18 UT with an iTelescope 0.61-m f/6.5 astrograph at the Sierra
Remote Observatory near Auberry, CA, USA; the w-band magnitude was 18.5 as
measured within a circular aperture of radius 5".0. Twelve stacked 60-s
exposures taken by Sato with an iTelescope 0.43-m f/6.8 astrograph near
Mayhill, NM, USA, on May 14.1 showed a round coma 10" in diameter with a
fan-like tail 20" long spanning p.a. 90-135 degrees; the w-band magnitude was
18.0 as measured within a circular aperture of radius 5".7. Exposures taken
as on May 14.1 by Sato on May 17.1 showed a strongly condensed coma 15" in
diameter with a fan-like tail 15" long spanning p.a. 90-170 degrees; the
w-band magnitude was 18.5 as measured within a circular aperture of radius
7".6. Sato obtained additional observations and stacked ten 60-s exposures
on June 1.15 and 3.15 (same instrumentation near Mayhill) that showed a
strongly condensed coma 30" in diameter (clearly larger than in May); the
w-band magnitude was 17.8 on June 1.15 and 17.4 on June 3.15 as measured
within a circular aperture of radius 15".3.
M. Micheli, J. Kleyna, K. Meech, and J. Keane obtained two 120-s r-band
exposures EN4 using the Canada-France-Hawaii Telescope at Mauna Kea on May
17.2 UT (queue observer L. Wells) that show a broadm faint tail about 10"
long toward the southeast; the coma is only marginally extended (full-width-
at-half-maximum of about 1".0, compared to 0".8 for nearby stars). M. Jaeger,
Vienna, Austria, writes that images taken by E. Prosperi, S. Prosperi, W.
Vollmann, and himself with a 0.3-m f/4 reflector at Stixendorf on June 4.9
show a 15" coma of mag 18.5, with a central condensation visible that was a
little softer than stars of the same brightness. L. Buzzi, Varese, Italy,
reports that stacked images obtained with a 0.84-m f/3.5 reflector in good
seeing on June 9.9 show a 10" round coma with no tail; he adds that his
images taken on Mar. 13.8 with the same telescope (and a total exposure time
of 50 minutes in moderate seeing) show only a stellar appearance.
Additional astrometry, the following revised orbital elements by G. V.
Williams, and an ephemeris appear on MPEC 2018-L53.
Epoch = 2018 June 11.0 TT
T = 2018 June 7.78136 TT Peri. = 35.01391
e = 0.9213777 Node = 136.16554 2000.0
q = 1.4479234 AU Incl. = 81.56186
a = 18.4161880 AU n = 0.01247109 P = 79.03 years
NOTE: These 'Central Bureau Electronic Telegrams' are sometimes
superseded by text appearing later in the printed IAU Circulars.
(C) Copyright 2018 CBAT
2018 June 11 (CBET 4524) Daniel W. E. Green
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