We report observations of (CO)-C-13(J = 1-0) emission from L1551-IRS5
carried out with the Nobeyama Millimeter Array. We detected a strong a
nd compact condensation associated with L1551-IRS5, and weaker extende
d components with ''U''-like features with a spatial resolution of 5.'
' 1 x 3.'' 9 (P.A. = 159 degrees). The U-like features delineate the e
dges of the molecular outflow as well as the 2.2 mu infrared reflectio
n nebula. This suggests that the extended component may be a dense she
ll swept up by the molecular outflow. The compact component was margin
ally resolved with the present angular resolution. The estimated decon
volved size is similar to 1200 x 670 AU with a position angle perpendi
cular to the optical jet. This elongated structure is very similar to
the compact gaseous disk observed in (CO)-O-18 (J = 1-0). The (CO)-C-1
3 elongated structure may be more extended than the actually measured
size, suggesting that the compact (CO)-C-13 gas is most probably the i
nner part of the gaseous disk around L1551-IRS5. The (CO)-C-13 disk ha
s a velocity gradient along its minor axis, which can be explained in
terms of infalling motion in the plane of the disk with a central mass
of 0.5 M.. We estimate the mass accretion rate at 600 AU in radius to
be 1.3-2.6 x 10(-5) M. yr(-1). The derived accretion rate might be la
rger than the accretion rate onto the star estimated from the bolometr
ic luminosity of L1551-IRS5 on the assumption of steady accretion, whi
ch suggests that the accretion around L1551-IRS5 may also be nonsteady
as was the case for HL Tau.