Kavli Affiliate: Deepto Chakrabarty
| First 5 Authors: Serena Vinciguerra, Tuomo Salmi, Anna L. Watts, Devarshi Choudhury, Thomas E. Riley
| Summary:
In 2019 the NICER collaboration published the first mass and radius inferred
for PSR J0030+0451, thanks to NICER observations, and consequent constraints on
the equation of state characterising dense matter. Two independent analyses
found a mass of $sim 1.3-1.4,mathrm{M_odot}$ and a radius of $sim 13,$km.
They also both found that the hot spots were all located on the same
hemisphere, opposite to the observer, and that at least one of them had a
significantly elongated shape. Here we reanalyse, in greater detail, the same
NICER data set, incorporating the effects of an updated NICER response matrix
and using an upgraded analysis framework. We expand the adopted models and
jointly analyse also XMM-Newton data, which enables us to better constrain the
fraction of observed counts coming from PSR J0030+0451. Adopting the same
models used in previous publications, we find consistent results, although with
more stringent inference requirements. We also find a multi-modal structure in
the posterior surface. This becomes crucial when XMM-Newton data is accounted
for. Including the corresponding constraints disfavors the main solutions found
previously, in favor of the new and more complex models. These have inferred
masses and radii of $sim [1.4 mathrm{M_odot}, 11.5$ km] and $sim [1.7
mathrm{M_odot}, 14.5$ km], depending on the assumed model. They display
configurations that do not require the two hot spots generating the observed
X-rays to be on the same hemisphere, nor to show very elongated features, and
point instead to the presence of temperature gradients and the need to account
for them.
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