Kavli Affiliate: Kejia Lee
| First 5 Authors: Jinchen Jiang, Shunshun Cao, Kejia Lee, Bojun Wang, Heng Xu
| Summary:
We use the Five-hundred-meter Aperture Spherical radio Telescope (FAST) to
observe the bright millisecond pulsar (MSP) PSR B1937+21 (J1939+2134) and
record the data in the band from 1.0 GHz to 1.5 GHz. We measure the neutral
hydrogen (HI) emission and absorption lines near 1420 MHz ($lambda simeq 21$
cm). We derive the kinematic distance of the pulsar with the HI observation,
and update the upper bound of kinematic distance from the previous $14.8pm
0.9$ npc in the Outer Arm to the nearer $9.4pm 0.5$ kpc in the Perseus Arm. By
comparing with the archival absorption spectra observed decades ago, we notice
possible variations in the absorption spectra towards this pulsar, which
corresponds to a possible tiny-scale atomic structure (TSAS) of a few AU in
size. We also verify the apparent faster-than-light anomalous dispersion at the
HI absorption line of this pulsar previously reported.
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