13,336 research outputs found
Tests of gravity theories with pulsar timing
Over the last few years, a set of new results from pulsar timing has
introduced much tighter constraints on violations of the strong equivalence
principle (SEP), either via a direct verification of the universality of free
fall for a pulsar in a triple star system, or from tests of the nature of
gravitational waves, in particular a search for dipolar gravitational wave
emission in a variety of binary pulsars with different masses. No deviations
from the SEP have been detected in our experiments. These results introduce
some of the most stringent constraints on several classes of alternative
theories of gravity and complement recent results from the ground-based
gravitational wave detectors.Comment: 5 pages, 3 figures, contribution to the 2022 Gravitation session of
the 56th Rencontres de Morion
Distribuição, coleta, uso e preservação das espécies silvestres de algodão no Brasil.
bitstream/CNPA/14839/1/DOC78.pd
The Timing of Nine Globular Cluster Pulsars
We have used the Robert C. Byrd Green Bank Telescope to time nine previously
known pulsars without published timing solutions in the globular clusters M62,
NGC 6544, and NGC 6624. We have full timing solutions that measure the spin,
astrometric, and (where applicable) binary parameters for six of these pulsars.
The remaining three pulsars (reported here for the first time) were not
detected enough to establish solutions. We also report our timing solutions for
five pulsars with previously published solutions, and find good agreement with
past authors, except for PSR J1701-3006B in M62. Gas in this system is probably
responsible for the discrepancy in orbital parameters, and we have been able to
measure a change in the orbital period over the course of our observations.
Among the pulsars with new solutions we find several binary pulsars with very
low mass companions (members of the so-called "black widow" class) and we are
able to place constraints on the mass-to-light ratio in two clusters. We
confirm that one of the pulsars in NGC 6624 is indeed a member of the rare
class of non-recycled pulsars found in globular clusters. We also have measured
the orbital precession and Shapiro delay for a relativistic binary in NGC 6544.
If we assume that the orbital precession can be described entirely by general
relativity, which is likely, we are able to measure the total system mass
(2.57190(73) M_sun) and companion mass (1.2064(20) M_sun), from which we derive
the orbital inclination [sin(i) = 0.9956(14)] and the pulsar mass (1.3655(21)
M_sun), the most precise such measurement ever obtained for a millisecond
pulsar. The companion is the most massive known around a fully recycled pulsar.Comment: Published in ApJ; 33 pages, 5 figures, 7 table
Embrapa algodĂŁo - tecnologia de impacto e principais desafios-2001 a 2003.
bitstream/CNPA-2009-09/14613/1/DOC73.pd
A Massive Neutron Star in the Globular Cluster M5
We report the results of 19 years of Arecibo timing for two pulsars in the
globular cluster NGC 5904 (M5), PSR B1516+02A (M5A) and PSR B1516+02B (M5B).
This has resulted in the measurement of the proper motions of these pulsars
and, by extension, that of the cluster itself. M5B is a 7.95-ms pulsar in a
binary system with a > 0.13 solar mass companion and an orbital period of 6.86
days. In deep HST images, no optical counterpart is detected within ~2.5 sigma
of the position of the pulsar, implying that the companion is either a white
dwarf or a low-mass main-sequence star. The eccentricity of the orbit (e =
0.14) has allowed a measurement of the rate of advance of periastron: (0.0142
+/-0.0007) degrees per year. We argue that it is very likely that this
periastron advance is due to the effects of general relativity, the total mass
of the binary system then being 2.29 +/-0.17 solar masses. The small measured
mass function implies, in a statistical sense, that a very large fraction of
this total mass is contained in the pulsar: 2.08 +/- 0.19 solar masses (1
sigma); there is a 5% probability that the mass of this object is < 1.72 solar
masses and a 0.77% probability that is is between 1.2 and 1.44 solar masses.
Confirmation of the median mass for this neutron star would exclude most
``soft'' equations of state for dense neutron matter. Millisecond pulsars
(MSPs) appear to have a much wider mass distribution than is found in double
neutron star systems; about half of these objects are significantly more
massive than 1.44 solar masses. A possible cause is the much longer episode of
mass accretion necessary to recycle a MSP, which in some cases corresponds to a
much larger mass transfer.Comment: 10 pages in ApJ emulate format, 2 tables, 6 figures. Added February
2008 data, slightly revised mass limits. Accepted for publication in Ap
- …