Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The intrinsic intensity modulation of PSR B1937+21 at 1410 MHz   The single-pulse properties of the millisecond radio pulsar PSR B1937+21 are
studied in the 1410 MHz radio band. Aside from occasional ``giant pulses''
occurring in restricted regions of pulse phase, the emission appears to be
remarkably stable, showing no pulse-to-pulse fluctuations other then those
induced by propagation through the interstellar medium. This type of behavior
has not been seen in any other pulsar although it was seen in previous 430 MHz
observations of this source.
  The stability of PSR B1937+21 can be understood in the context of the
sparking gap model of radio pulsar emission. Given the emission properties of
this source at 430 MHz, this model predicts that the emission at all higher
frequencies will be just as stable. Since the stability depends on the outflow
velocity of the emitting plasma, an upper bound may be placed on its Lorentz
factor.

20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
18
The categories of this paper are: econ
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
32
The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
19
The categories of this paper are: eess
21
The categories of this paper are: adap-org
23
The categories of this paper are: solv-int
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom