

Since 1990, several new massive binary pulsars similar to PSR
1913+16 were discovered, leading to the possibility of new or
improved tests of GR.
Table 7:
Parameters of other binary pulsars. From [156,
118
,
119
] and from an online catalogue of pulsars maintained by Stephen
Thorsett of the University of California, Santa Cruz, see [128].
-
PSR 1534+12.
- This is a binary pulsar system in our galaxy. Its pulses
are significantly stronger and narrower than those of PSR
1913+16, so timing measurements are more precise, reaching
3
s accuracy. Its parameters are listed in Table
7
[118,
119]. The orbital plane appears to be almost edge-on relative to
the line of sight (
); as a result the Shapiro delay is substantial, and separate
values of the parameters
r
and
s
have been obtained with interesting accuracy. Assuming general
relativity, one infers that the two masses are
and
. The rate of orbit decay
agrees with GR to about 15 percent, the precision limited by
the poorly known distance to the pulsar, which introduces a
significant uncertainty into the subtraction of galactic
acceleration. Independently of
, measurement of the four other post-Keplerian parameters gives
two tests of strong-field gravity in the non-radiative
regime [124].
-
PSR 2127+11C.
- This system appears to be a clone of the Hulse-Taylor
binary pulsar, with very similar values for orbital period and
eccentricity (see Table
7). The inferred total mass of the system is
. Because the system is in the globular cluster M15 (NGC 7078),
it suffers Doppler shifts resulting from local accelerations,
either by the mean cluster gravitational field or by nearby
stars, that are more difficult to estimate than was the case
with the galactic system PSR 1913+16. This may make a separate,
precision measurement of the relativistic contribution to
impossible.
-
PSR 1855+09.
- This binary pulsar system is not particularly relativistic,
with a long period (12 days) and highly circular orbit.
However, because we observe the orbit nearly edge on, the
Shapiro delay is large and measurable, as reflected in the
post-Keplerian parameters
r
and
s
.
-
PSR 0655+64.
- This system consists of a pulsar and a white dwarf
companion in a nearly circular orbit. Only an upper limit on
has been placed.


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The Confrontation between General Relativity and
Experiment
Clifford M. Will
http://www.livingreviews.org/lrr-2001-4
© Max-Planck-Gesellschaft. ISSN 1433-8351
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