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COMET 17P/HOLMES: CONTRAST IN ACTIVITY BETWEEN BEFORE AND AFTER THE 2007 OUTBURST
Ishiguro, Masateru,Kim, Yoonyoung,Kim, Junhan,Usui, Fumihiko,Vaubaillon, Jeremie J.,Ishihara, Daisuke,Hanayama, Hidekazu,Sarugaku, Yuki,Hasegawa, Sunao,Kasuga, Toshihiro,Warjurkar, Dhanraj S.,Ham, Ji- IOP Publishing 2013 The Astrophysical journal Vol.778 No.1
<P>A Jupiter-family comet, 17P/Holmes, underwent outbursts in 1892 and 2007. In particular, the 2007 outburst is known as the greatest outburst over the past century. However, little is known about the activity before the outburst because it was unpredicted. In addition, the time evolution of the nuclear physical status has not been systematically studied. Here, we study the activity of 17P/Holmes before and after the 2007 outburst through optical and mid-infrared observations. We found that the nucleus was highly depleted in its near-surface icy component before the outburst but that it became activated after the 2007 outburst. Assuming a conventional 1 mu m sized grain model, we derived a surface fractional active area of 0.58% +/- 0.14% before the outburst whereas the area was enlarged by a factor of similar to 50 after the 2007 outburst. We also found that large (>= 1 mm) particles could be dominant in the dust tail observed around aphelion. Based on the size of the particles, the dust production rate was >= 170 kg s(-1) at a heliocentric distance of r(h) = 4.1 AU, suggesting that the nucleus was still active around the aphelion passage. The nucleus color was similar to that of the dust particles and average for a Jupiter-family comet but different from that of most Kuiper Belt objects, implying that color may be inherent to icy bodies in the solar system. On the basis of these results, we concluded that more than 76 m of surface material was blown off by the 2007 outburst.</P>
OBSERVATIONAL EVIDENCE FOR AN IMPACT ON THE MAIN-BELT ASTEROID (596) SCHEILA
Ishiguro, Masateru,Hanayama, Hidekazu,Hasegawa, Sunao,Sarugaku, Yuki,Watanabe, Jun-ichi,Fujiwara, Hideaki,Terada, Hiroshi,Hsieh, Henry H.,Vaubaillon, Jeremie J.,Kawai, Nobuyuki,Yanagisawa, Kenshi,Kuro IOP Publishing 2011 ASTROPHYSICAL JOURNAL LETTERS - Vol.740 No.1
<P>An unexpected outburst was observed around (596) Scheila in 2010 December. We observed (596) Scheila soon after the impact using ground-based telescopes. We succeeded in the detection of a faint linear tail after 2011 February, which provides a clue to determine the dust ejection date. It is found that the dust particles ranging from 0.1-1 mu m to 100 mu m were ejected into the interplanetary space impulsively on December 3.5 +/- 1.0 day. The ejecta mass was estimated to be (1.5-4.9) x 10(8) kg, suggesting that an equivalent mass of a 500-800 m diameter crater was excavated by the event. We also found that the shape of the light curve changed after the impact event probably because fresh material was excavated around the impact site. We conclude that a decameter-sized asteroid collided with (596) Scheila only eight days before the discovery.</P>
INTERPRETATION OF (596) SCHEILA'S TRIPLE DUST TAILS
Ishiguro, Masateru,Hanayama, Hidekazu,Hasegawa, Sunao,Sarugaku, Yuki,Watanabe, Jun-ichi,Fujiwara, Hideaki,Terada, Hiroshi,Hsieh, Henry H.,Vaubaillon, Jeremie J.,Kawai, Nobuyuki,Yanagisawa, Kenshi,Kuro IOP Publishing 2011 ASTROPHYSICAL JOURNAL LETTERS - Vol.741 No.1
<P>Strange-looking dust cloud around asteroid (596) Scheila was discovered on 2010 December 11.44-11.47. Unlike normal cometary tails, it consisted of three tails and faded within two months. We constructed a model to reproduce the morphology of the dust cloud based on the laboratory measurement of high-velocity impacts and the dust dynamics. As a result, we succeeded in reproducing the peculiar dust cloud by an impact-driven ejecta plume consisting of an impact cone and downrange plume. Assuming an impact angle of 45 degrees, our model suggests that a decameter-sized asteroid collided with (596) Scheila from the direction of (alpha(im), delta(im)) = (60 degrees, -40 degrees) in J2000 coordinates on 2010 December 3. The maximum ejection velocity of the dust particles exceeded 100 m s(-1). Our results suggest that the surface of (596) Scheila consists of materials with low tensile strength.</P>
KISO/KWFC Observation of the Dust Ejecta Associated with the 2007 Outburst of 17P/Holmes
Masateru Ishiguro,Yuki Sarugaku,Daisuke Kuroda,Hidekazu Hanayama,Yoonyoung Kim,Yuna Kwon,Hiroyuki Maehara,Jun Takahashi,Tsuyoshi Terai,Fumihiko Usui,Jeremie J.Vaubaillon,Tomoki Morokuma,Naoto Kobayash 한국천문학회 2015 天文學會報 Vol.40 No.2
MONITORING OBSERVATIONS OF THE JUPITER-FAMILY COMET 17P/HOLMES DURING ITS 2014 PERIHELION PASSAGE
Kwon, Yuna Grace,Ishiguro, Masateru,Hanayama, Hidekazu,Kuroda, Daisuke,Honda, Satoshi,Takahashi, Jun,Kim, Yoonyoung,Lee, Myung Gyoon,Choi, Young-Jun,Kim, Myung-Jin,Vaubaillon, Jeremie J.,Miyaji, Takes American Astronomical Society 2016 The Astrophysical journal Vol.818 No.1
<P>We performed a monitoring observation of a Jupiter-family comet, 17P/Holmes, during its 2014 perihelion passage to investigate its secular change in activity. The comet has drawn the attention of astronomers since its historic outburst in 2007, and this occasion was its first perihelion passage since then. We analyzed the obtained data using an aperture photometry package and derived the Af rho parameter, a proxy for the dust-production rate. We found that Af rho showed asymmetric properties with respect to the perihelion passage: it increased moderately from 100 cm at the heliocentric distance of r(h) = 2.6-3.1 AU to a maximal value of 185 cm at r(h) = 2.2 AU (near the perihelion) during the inbound orbit, while dropping rapidly to 35 cm at r(h) = 3.2 AU during the outbound orbit. We applied a model for characterizing dust-production rates as a function of r(h) and found that the fractional active area of the cometary nucleus had dropped from 20%-40% in 2008-2011 (around the aphelion) to 0.1%-0.3% in 2014-2015 (around the perihelion). This result suggests that a dust mantle would have developed rapidly in only one orbital revolution around the Sun. Although a minor eruption was observed on UT 2015 January 26 at r(h) = 3.0 AU, the areas excavated by the 2007 outburst would be covered with a layer of dust (less than or similar to 10 cm depth) which would be enough to insulate the subsurface ice and to keep the nucleus in a state of low activity.</P>
DETECTION OF REMNANT DUST CLOUD ASSOCIATED WITH THE 2007 OUTBURST OF 17P/HOLMES
Ishiguro, Masateru,Sarugaku, Yuki,Kuroda, Daisuke,Hanayama, Hidekazu,Kim, Yoonyoung,Kwon, Yuna G.,Maehara, Hiroyuki,Takahashi, Jun,Terai, Tsuyoshi,Usui, Fumihiko,Vaubaillon, Jeremie J.,Morokuma, Tomok American Astronomical Society 2016 The Astrophysical journal Vol.817 No.1
<P>This article reports a new optical observation of 17P/Holmes one orbital period after the historical outburst event in 2007. We detected not only a common dust tail near the nucleus. but also a long narrow structure that extended along the position angle 274 degrees.6 +/- 0 degrees.1 beyond the field of view (FOV) of the Kiso Wide Field Camera, i.e., >0 degrees.2 eastward and >2 degrees.0 westward from the nuclear position. The width of the structure decreased westward with increasing distance from the nucleus. We obtained the total cross section of the long extended structure in the FOV, C-FOV = (2.3 +/- 0.5) x 10(10) m(2). From the position angle, morphology, and mass, we concluded that the long. narrow structure consists of materials ejected during the 2007 outburst. On the basis of the dynamical behavior of dust grains in the solar radiation field, we estimated that the long. narrow structure would be composed of 1 mm(-1) cm grains having an ejection velocity of >50 m s(-1). The velocity was more than one order of magnitude faster than that of millimeter-centimeter grains from typical comets around a heliocentric distance r(h) of 2.5 AU. We considered that sudden sublimation of a large amount of water-ice (approximate to 10(30) mol s(-1)) would be responsible for the high ejection velocity. We finally estimated a total mass of M-TOT = (4-8) x 10(11) kg and a total kinetic energy of E-TOT = (1-6) x 10(15) J for the 2007 outburst ejecta, which are consistent with those of previous studies that were conducted soon after the outburst.</P>