06478 GAULT     



Cometary appearance activity 06478, without filter, 50x60s, sampling of 1.12"/pixel,
Coma : 15", Tail : +/-4' long, structure direction the tail of PA : +/-300°,
m2 : 17.4 (+/-0.3), aperture radius for measures : 6.7"

(6478) GAULT
    K. W. Smith, Queen's University, Belfast; and L. Denneau, University of
Hawaii, on behalf of the "Asteroid Terrestrial-Impact Last Alert System"
(ATLAS) team, report the serendipitous discovery of unusual activity
associated with the inner main-belt minor planet (6478), which appears to have
developed a lengthening tail or trail that was first identified in individual
ATLAS exposures by taken by Smith.  A median combination of seven 30-s
exposures on 2019 Jan. 5 shows a tail or trail 135" long in p.a. 290 degrees.
The tail/trail first appears in individual ATLAS exposures on 2018 Dec. 8, as
identified by Denneau, with a median combined 120-s exposure showing a tail
30" long in p.a. 290 degrees.  There is no evidence of a tail in previous
ATLAS imaging in January 2018.  An initial analysis using a cometary Finson-
Probstein model (cf. website URL http://comet-toolbox.com/FP.html, as per
J.-B. Vincent) shows that both the Dec. 2018 and Jan. 2019 data are consistent
with the ejection of material or commencement of activity in early Nov. 2018.
Recent observations in Pan-STARRS1 imagery obtained by R. Weryk show a tail or
trail consistent with the ATLAS observations and confirm no prior activity as
far back as 2010.  Further observations of this object are highly encouraged.
    A. Hale, Cloudcroft, NM, USA, writes that (after seeing an image posted
on Facebook by R. Berry, via H. Weiland) he obtained 5-min CCD unfiltered
exposures of (6478) around 2019 Jan. 8.02 UT with the 1.0-m telescope of the
Las Cumbres Observatory facility at the South African Astronomical
Observatory.  These images show a straight, narrow, high-surface-brightness
tail 4'.1 long in p.a. approximately 295 degrees.
    Minor planet (6478) has predicted ephemeris V magnitude 18.7 currently.

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     superseded by text appearing later in the printed IAU Circulars.

                        (C) Copyright 2019 CBAT
2019 January 8                   (CBET 4594)              Daniel W. E. Green

(6478) GAULT
    Further to CBET 4594, A. Hale writes that he has posted two images at
website URL http://earthriseinstitute.org/gault.html.  The upper image is an
image taken with the Canada-France-Hawaii telescope as provided by H. Weiland
to R. Berry.  The lower image was the one taken by Hale on Jan. 8.0 UT.
    Fifty 60-s unfiltered CCD exposures taken by A. Maury, J.-B. de Vanssay,
and J.-F. Soulier with a 0.4-m f/5 Ritchey-Chretien reflector at San Pedro de
Atacama, Chile, on Jan. 8.32 UT show a 15" tail and a tail about 4' long in
p.a. about 300 degrees; Soulier notes that the red magnitude of the object's
head was about 17.4 as measured in a photometric aperture of radius 6".7.
Soulier adds that he obtained seventy-five 60-s unfiltered exposures with a
0.20-m f/4 Newtonian reflector at Dauban, France, on Jan. 9.15-9.20 that show
a coma about 19" across and a tail about 3'.5 long in p.a. about 310 deg; the
red mag was 17.5-17.6 as measured in an aperture of radius 6".6.
    T. Yusa, Osaki, Japan, reports that eight stacked 90-s CCD exposures
taken on Jan. 8.7 UT with an iTelescope 0.50-m f/6.8 astrograph at Siding
Spring, NSW, show the object's head to be completely stellar in appearance
and of mag 17.8 (luminance filter, compared to V-band magnitudes of stars in
the USNO-A2.0 catalogue) but with a straight 180" tail toward p.a. 292 deg;
Yusa has posted an image at the following website URL:
    K. Kadota, Ageo, Japan, found a stellar head of mag 17.4 with a straight,
narrow tail 2'.7 long in p.a. 293 deg on CCD exposures taken on Jan. 8.7 UT
with a 0.25-m f/5 reflector.
    M. Micheli writes that CCD images taken by P. Ruiz with a 1.0-m f/4.4
reflector at the European Space Agency's Optical Ground Station at Tenerife
on Jan. 9.1 UT (measured by Micheli, D. Koschny, A. Knoefel, M. Busch, and
E. Schwab) show a very thin tail 4' long at p.a. 291.5 degrees; the magnitude
of the object's head was measured as 17.6.
    L. Buzzi, Varese, Italy, writes that stacked CCD images taken with a
0.84-m f/3.5 reflector in good transparency but mediocre seeing on Jan. 9.2
UT show a stellar head with a dust trail at least 135" long in p.a. 292 deg;
the magnitude was measured as 17.7.

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

                        (C) Copyright 2019 CBAT
2019 January 9                   (CBET 4597)              Daniel W. E. Green

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