分类： 天文学 >> 天体物理学 提交时间： 2023-02-21
H. Hu
M. Kramer
D. J. Champion
N. Wex
A. Parthasarathy
T. T. Pennucci
N. K. Porayko
W. van Straten
V. Venkatraman Krishnan
M. Burgay
P. C. C. Freire
R. N. Manchester
A. Possenti
I. H. Stairs
M. Bailes
S. Buchner
A. D. Cameron
F. Camilo
M. Serylak
摘要： The Double Pulsar, PSR J0737-3039A/B, has offered a wealth of gravitational experiments in the strong-field regime, all of which GR has passed with flying colours. In particular, among current gravity experiments that test photon propagation, the Double Pulsar probes the strongest spacetime curvature. Observations with MeerKAT and, in future, the SKA can greatly improve the accuracy of current tests and facilitate tests of NLO contributions in both orbital motion and signal propagation. We present our timing analysis of new observations of PSR J0737-3039A, made using the MeerKAT telescope over the last 3 years. The increased timing precision offered by MeerKAT yields a 2 times better measurement of Shapiro delay parameter s and improved mass measurements compared to previous studies. In addition, our results provide an independent confirmation of the NLO signal propagation effects and already surpass the previous measurement from 16-yr data by a factor of 1.65. These effects include the retardation effect due to the movement of B and the deflection of the signal by the gravitational field of B. We also investigate novel effects which are expected. For instance, we search for potential profile variations near superior conjunctions caused by shifts of the line-of-sight due to latitudinal signal deflection and find insignificant evidence with our current data. With simulations, we find that the latitudinal deflection delay is unlikely to be measured with timing because of its correlation with Shapiro delay. Furthermore, although it is currently not possible to detect the expected lensing correction to the Shapiro delay, our simulations suggest that this effect may be measured with the full SKA. Finally, we provide an improved analytical description for the signal propagation in the Double Pulsar system that meets the timing precision expected from future instruments such as the full SKA.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
A. Batrakov
H. Hu
N. Wex
P. C. C. Freire
V. Venkatraman Krishnan
M. Kramer
Y. J. Guo
L. Guillemot
J. W. McKee
I. Cognard
G. Theureau
摘要： Context. Scalar-tensor gravity (STG) theories are well-motivated alternatives to general relativity (GR). One class of STG theories, the Damour-Esposito-Farese (DEF) gravity, has a massless scalar field with two arbitrary coupling parameters. We are interested in this theory because, despite its simplicity, it predicts a wealth of different phenomena, such as dipolar gravitational wave emission and spontaneous scalarization of neutron stars (NSs). These phenomena of DEF gravity can be tested by timing binary radio pulsars. Aims. We aim to develop a new binary pulsar timing model DDSTG to enable more precise tests of STG theories based on a minimal set of binary parameters. The expressions for post-Keplerian (PK) parameters in DEF gravity are self-consistently incorporated into the model. The new technique takes into account all possible correlations between PK parameters naturally. Methods. Grids of physical parameters of NSs are calculated in the framework of DEF gravity for a set of 11 equations of state. The automatic Differentiation (AutoDiff) technique is employed, which aids in the calculation of gravitational form factors of NSs with higher precision than in previous works. The pulsar timing program TEMPO is selected as a framework for the realization of the DDSTG model. The implemented model is applicable to any type of pulsar companions. Results. We apply the DDSTG model to the most recently published observational data for PSR J2222-0137. The obtained limits on DEF gravity parameters for this system confirm and improve previous results. New limits are also the most reliable because DEF gravity is directly fitted to the data. We argue that future observations of PSR J2222-0137 can significantly improve the limits and that PSR-BH systems have the potential to place the tightest limits in certain areas of the DEF gravity parameter space.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
H. Hu
M. Kramer
D. J. Champion
N. Wex
A. Parthasarathy
T. T. Pennucci
N. K. Porayko
W. van Straten
V. Venkatraman Krishnan
M. Burgay
P. C. C. Freire
R. N. Manchester
A. Possenti
I. H. Stairs
M. Bailes
S. Buchner
A. D. Cameron
F. Camilo
M. Serylak
摘要： The Double Pulsar, PSR J0737-3039A/B, has offered a wealth of gravitational experiments in the strong-field regime, all of which GR has passed with flying colours. In particular, among current gravity experiments that test photon propagation, the Double Pulsar probes the strongest spacetime curvature. Observations with MeerKAT and, in future, the SKA can greatly improve the accuracy of current tests and facilitate tests of NLO contributions in both orbital motion and signal propagation. We present our timing analysis of new observations of PSR J0737-3039A, made using the MeerKAT telescope over the last 3 years. The increased timing precision offered by MeerKAT yields a 2 times better measurement of Shapiro delay parameter s and improved mass measurements compared to previous studies. In addition, our results provide an independent confirmation of the NLO signal propagation effects and already surpass the previous measurement from 16-yr data by a factor of 1.65. These effects include the retardation effect due to the movement of B and the deflection of the signal by the gravitational field of B. We also investigate novel effects which are expected. For instance, we search for potential profile variations near superior conjunctions caused by shifts of the line-of-sight due to latitudinal signal deflection and find insignificant evidence with our current data. With simulations, we find that the latitudinal deflection delay is unlikely to be measured with timing because of its correlation with Shapiro delay. Furthermore, although it is currently not possible to detect the expected lensing correction to the Shapiro delay, our simulations suggest that this effect may be measured with the full SKA. Finally, we provide an improved analytical description for the signal propagation in the Double Pulsar system that meets the timing precision expected from future instruments such as the full SKA.
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