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   PR #    28
   The 11-minute orbital period of X1820-30 is the shortest known of
   anybinary system implying that it consists of a neutron star witha
   white dwarf companion. The period appears to be decreasing on a
   timescale of ~10^7 yr, contrary to expectations. X1820-30 is situated
   in the core of a globular cluster, and also displays luminous bursts
   and QPO.An ASCA observation would enable us to: study the
   low-amplitude (3%) orbital modulation, which may result from
   obscuration of the central neutron star/ADC by material in the disk;
   obtain further information on the orbital period change, which may
   have an important evolutionary implications; study the QPO, if
   possible; search for iron K-line emission and low-energy line
   features; look for transient spectral features in bursts.
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