On Oct. 13, 2003 the LINEAR-project reported the discovery of an asteroidal object of magnitude 19.5 near the border between Ursa Major and Camelopardalis. Observations on Oct. 14/15 showed a 6" coma of total magnitude 18.0. Comet C/2003 T4 (LINEAR) will reach perihelion in April 2005 (IAUC 8224, MPEC 2003-V13). It should become visible in midsized instruments during fall 2004, reaching magnitude 10 (then in Lyra) at the end of 2004. Until it disappears for mid-European observers in mid-March 2005 (then in Aquarius) it should reach magnitude 6.
According to 5 observations by 4 members of the German Comet Section and 130 international observations the comet showed an acitivity parameter n well below average. The brightness evolution can be described by the formula
m = 7.8m + 5×log D + 6.5×log r
meaning a maximum brightness of 7.6 mag around Apr. 15.
Total Brightness and Coma diameter
The apparent coma diameter increased continuously from 0.7' at the end of July to a maximum short of 4' at the beginning of April 2005. Thereafter it decreased, reaching about 2' at the end of May. The absolute coma diameter showed only a slow increase from 150.000 km to 180.000 km between the end of July 2004 and mid-January 2005. Thereafter the increase accelerated toward maximum of 225.000 km, which was reached at the end of March. Since then the coma is shrinking, measuring 125.000 km at the end of May. The degree of condensation showed an unusual evolution: at DC 4-5 at the start of the apparition it decreased towards DC 3 until mid-December. Thereafter the coma eventually began to condense with the degree of condensation peaking at DC 6 around the date of perihelion. Visually a tail could be discerned in March and April. The observers reported lengths between 0.2° and 0.4°, corresponding to an absolute length of about 1 Mio. km.
Andreas Kammerer
