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Promotionskolloquium |
Miquel Colom i Bernadich
| SCHEDULED |
Max Planck Institut für Radioastronomie
Pulsars are highly magnetised, rapidly spinning neutron stars. Using
the technique of pulsar timing, we can model their rotational slowdown
with
microsecond precision, tracking every single rotation. When found in
compact binary systems, pulsar timing enables measurements of
relativistic
post-Keplerian corrections to the orbit, allowing tests of fundamental
physics and precise stellar mass determinations. Despite the discovery
of over 4,000 pulsars, many questions remain open, ranging from stellar
mass distributions to the physics of dense matter, tests of theories of
gravity and binary evolution, questions that can only be addressed
through
pulsar timing.
In this PhD defence, I present new results on southern Galactic pulsars
based on observations from two radio observatories with a privileged
view of
the southern Galactic plane: the Murriyang telescope in Parkes,
Australia,
and the SKA pathfinder MeerKAT in South Africa. Murriyang is a 64-metre
single-dish telescope with wide instantaneous bandwidth coverage, while
the 64 antennas of MeerKAT form the most sensitive radio interferometer
in
the Southern Hemisphere. Their combined use, and especially the high
sensitivity of MeerKAT, has opened new scientific opportunities for
studying
southern Galactic pulsars.
I will present discoveries from the MPIfR–MeerKAT Galactic Plane
Survey, the first wide-field interferometric pulsar survey, which has
led to over
80 new detections. Thanks to MeerKAT’s interferometric capabilities,
the sky
localisation of new pulsars is instantaneous, significantly
accelerating the
derivation of timing solutions. Among these discoveries is PSR
J1208–5936, a
double neutron star system that will merge within a Hubble time due to
gravitational-wave emission. This system and the performance of the
survey
provide valuable constraints on the neutron star merger rate in the
Milky
Way. Newly discovered pulsar–white dwarf systems also offer promising
insights into mass distributions and binary evolution pathways.
I will also present precise stellar mass measurements of the massive
pulsar–white dwarf binary PSR J1227–6208, based on joint timing
with
MeerKAT
and Murriyang. Its companion is an oxygen–neon–magnesium white
dwarf
potentially near the Chandrasekhar limit. Using Bayesian inference to
model
dispersion-measure-induced timing noise, we constrain the companion’s
mass to
lie between 1.2 and 1.5 solar masses, confirming its massive nature.
This is
only the third such mass measurement for this type of system, made
possible
by the combined sensitivity and frequency coverage of both telescopes.
These results demonstrate the complementary strengths of MeerKAT and
Murriyang, and they highlight the scientific potential of future
facilities
such as MeerKAT+ and the SKA. In particular, MeerKAT’s surveys offer
a
valuable blueprint for the next generation of pulsar searches and
timing
experiments with the SKA.