2006 Fragmentation of Comet 73P/Schwassmann-Wachmann 3B Observed with Subaru/Suprime-Cam

We analyzed the Subaru/Suprime-Cam images of 73P/Schwassmann-Wachmann 3B and detected no fewer than 154 mini-comets. We applied synchrone-syndyne analysis, modified for rocket effect analysis, to the mini-fragment spatial distribution. We found that most of these mini-comets were ejected from fragment B by an outburst occurring around 1 April 2006. The ratio of the rocket force to solar gravity was 7 to 23 times larger than that exerted on fragment B. No significant color variation was found. We examined the surface brightness profiles of all detected fragments and estimated the sizes of 154 fragments. We found that the radius of these mini-fragments was in the 5- to 108-m range (equivalent size of Tunguska impactor). The power-law index of the differential size distribution was q = -3.34 +/- 0.05. Based on this size distribution, we found that about 1-10% of the mass of fragment B was lost in the April 2006 outbursts. Modeling the cometary fragment dynamics revealed that it is likely that mini-fragments smaller than ~10-20 m could be depleted in water ice and become inactive, implying that decameter-sized comet fragments could survive against melting and remain as near-Earth objects. We attempted to detect the dust trail, which was clearly found in infrared wavelengths by Spitzer. No brightness enhancement brighter than 30.0 mag arcsec^-2 (3sigma) was detected in the orbit of fragment B.Comment: Total pages: 46 Figures: 12 Tables: 1 To appear ICARU

A Comparative Study of Infrared Asteroid Surveys: IRAS, AKARI, and WISE

We present a comparative study of three infrared asteroid surveys based on the size and albedo data from the Infrared Astronomical Satellite (IRAS), the Japanese infrared satellite AKARI, and the Wide-field Infrared Survey Explorer (WISE). Our study showed that: (i) the total number of asteroids detected with diameter and albedo information with these three surveyors is 138,285, which is largely contributed by WISE; (ii) the diameters and albedos measured by the three surveyors for 1,993 commonly detected asteroids are in good agreement, and within +/-10% in diameter and +/-22% in albedo at 1sigma deviation level. It is true that WISE offers size and albedo of a large fraction (>20%) of known asteroids down to a few km bodies, but we would suggest that the IRAS and AKARI catalogs compensate for larger asteroids up to several hundred km, especially in the main belt region. We discuss the complementarity of these three catalogs in order to facilitate the use of these data sets for characterizing the physical properties of minor planets.Comment: 21 pages, 19 figures, and 2 tables, accepted for publication in PAS

Emission line profiles from self-gravitating toroids around black holes

We have computed line profiles from self-gravitating toroids around black holes. The specific angular momentum of the toroids is assumed to be constant in space. The images of the toroids show peculiar feature in the rear side of the black holes. Concerning the line profiles, the red wing extends to the very small frequency region because the location of the inner edge is rather near the event horizon of the black hole and consequently the velocity of the inner edge of toroids can be faster than that of the Kepler disks.Comment: 9 pages including 6 figures and 2 tables, submitted to MNRA