The Sloan Digital Sky Survey ( SDSS ) source J102347.6 + 003841 was recently revealed to be a binary 1.69 millisecond radio pulsar with a 4.75 hr orbital period and a \sim 0.2 M _ { \sun } companion .
Here we analyze the SDSS spectrum of the source in detail .
The spectrum was taken on 2001 February 1 , when the source was in a bright state and showed broad , double-peaked hydrogen and helium lines — dramatically different from the G-type absorption spectrum seen from 2002 May onward .
The lines are consistent with emission from a disk around the compact primary .
We derive properties of the disk by fitting the SDSS continuum with a simple disk model , and find a temperature range of 2000–34000 K from the outer to inner edge of the disk .
The disk inner and outer radii were approximately 10 ^ { 9 } and 5.7 \times 10 ^ { 10 } cm , respectively .
These results further emphasize the unique feature of the source : it is a system likely at the end of its transition from an X-ray binary to a recycled radio pulsar .
The disk mass is estimated to have been \sim 10 ^ { 23 } g , most of which would have been lost due to pulsar wind ablation ( or due to the propeller effect if the disk had extended inside the light cylinder of the pulsar ) before the final disk disruption event .
The system could undergo repeated episodes of disk formation .
Close monitoring of the source is needed to catch the system in its bright state again , so that this unusual example of a pulsar-disk interaction can be studied in much finer detail .