Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: PSR J2222--0137. I. Improved physical parameters for the system   The PSR J2222-0137 binary system is a unique laboratory for testing gravity
theories. To fully exploit its potential for the tests, we aim to improve the
measurements of its physical parameters: spin, orbital orientation, and
post-Keplerian parameters which quantify the observed relativistic effects. We
present improved analysis of archival VLBI data, using a coordinate convention
in full agreement with that used in timing. We also obtain much improved
polarimetry with FAST. We provide an analysis of significantly extended timing
data taken with Effelsberg, Nancay, Lovell and Green Bank telescopes. From VLBI
analysis we obtain a new estimate of the position angle of ascending node,
Omega=189(19) deg, and a new position of the pulsar with more conservative
uncertainty. The FAST polarimetry and in particular the detection of an
interpulse, yield much improved estimate for the spin geometry of the pulsar,
in particular an inclination of the spin axis of 84 deg. From the timing we
obtain a new 1% test of general relativity (GR) from the agreement of the
Shapiro delay and the advance rate of periastron. Assuming GR in a
self-consistent analysis of all effects, we obtain much improved mass:
1.831(10) M_sun for the pulsar and 1.319(4) M_sun for the companion; the total
mass, 3.150(14) M_sun confirms it as the most massive double degenerate binary
known in the Galaxy. This analysis also yields the orbital orientation: the
orbital inclination is 85.27(4) deg, indicating a close alignment between the
spin of the pulsar and the orbital angular momentum; Omega = 188(6) deg,
matching our VLBI result. We also obtain precise value of the orbital period
derivative, 0.251(8)e-12 s s^-1, consistent with the expected variation of
Doppler factor plus the orbital decay caused by emission of gravitational wave
(GW) predicted by GR. This agreement introduces stringent constraint on the
emission of dipolar GW.

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The categories of this paper are: hep-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: ao-sci
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The categories of this paper are: funct-an
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The categories of this paper are: eess
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The categories of this paper are: physics
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The categories of this paper are: gr-qc
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The categories of this paper are: hep-ex
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The categories of this paper are: econ
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The categories of this paper are: stat
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The categories of this paper are: comp-gas
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The categories of this paper are: chem-ph
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The categories of this paper are: cond-mat
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The categories of this paper are: quant-ph
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The categories of this paper are: solv-int
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The categories of this paper are: nlin