Kavli Affiliate: Deepto Chakrabarty
| First 5 Authors: Tuomo Salmi, Devarshi Choudhury, Yves Kini, Thomas E. Riley, Serena Vinciguerra
| Summary:
We report an updated analysis of the radius, mass, and heated surface regions
of the massive pulsar PSR J0740+6620 using NICER data from 2018 September 21 to
2022 April 21, a substantial increase in data set size compared to previous
analyses. Using a tight mass prior from radio timing measurements and jointly
modeling the new NICER data with XMM-Newton data, the inferred equatorial
radius and gravitational mass are $12.49_{-0.88}^{+1.28}$ km and
$2.073_{-0.069}^{+0.069}$ $M_odot$ respectively, each reported as the
posterior credible interval bounded by the $16,%$ and $84,%$ quantiles,
with an estimated systematic error $lesssim 0.1$ km. This result was obtained
using the best computationally feasible sampler settings providing a strong
radius lower limit but a slightly more uncertain radius upper limit. The
inferred radius interval is also close to the $R=12.76_{-1.02}^{+1.49}$ km
obtained by Dittmann et al. 2024, when they require the radius to be less than
$16$ km as we do. The results continue to disfavor very soft equations of state
for dense matter, with $R<11.15$ km for this high mass pulsar excluded at the
$95,%$ probability. The results do not depend significantly on the assumed
cross-calibration uncertainty between NICER and XMM-Newton. Using simulated
data that resemble the actual observations, we also show that our pipeline is
capable of recovering parameters for the inferred models reported in this
paper.
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