2024-03-28T19:40:20Zhttps://www.tdx.cat/oai/requestoai:www.tdx.cat:10803/5654092022-12-14T07:09:31Zcom_10803_381col_10803_395
00925njm 22002777a 4500
dc
Jiménez Forteza, Francisco
author
2017-09-05
[eng]Throughout history, human beings have received and interpreted information from distant
stars and galaxies through electromagnetic waves (light). Until 2015 this was the
dominant way for observing astrophysical events happening in our cosmos. However, on
September 14'th 2015 a new window to the universe was opened thanks to the rst direct
gravitational wave detection, a goal pursued for several decades by the LIGO/Virgo
scienti c collaboration.
Gravitational waves are tiny space-time oscillations propagating at the speed of light.
They are a prediction of the Einstein theory of gravity and we need the most catastrophic
astrophysical events to detect them. The rst observation of gravitational waves
described the inspiral, merger and ringdown of two black holes with 36 and 29 solar
masses located at 1300 billion light-years, where about the 5% of the total mass was
radiated as gravitational waves and becoming the most powerful astrophysical event ever
observed. The event was called GW150914, consistently with its the arrival date and
was publicly announced on February 11'th 2016 by the LIGO Virgo collaboration. This
has not been the only event observed during this thesis project. Relying on statistical
criteria arguments, we can certify the observation of one additional event also compatible
with the coalescense of a pair of black holes tagged as GW151226 plus a third one
called LVT151012 likely from astrophysical origin but that did not reach the statistical
signi cance required to be con rmed.
The coalescense of binary black hole systems are an optimal candidate for the observation
and study of gravitational waves. The current observations suggest that these
kind of events could dominate the future ground based detections. Then, we need to
optimise the theoretical waveform models to characterise the future observations. In
this thesis we have given the rst steps towards a new upgrading of the nonprecessing
gravitational waves models. These models result from the matching of the well known
post-Newtonian (PN) and e ective-one-body (EOB) analytic formulations to the computationally
expensive numerical solutions of the Einstein equations. They are de ned in
the frequency domain and depend on the ratio of the two black hole masses (mass-ratio)
and some e ective spin e that results from the combination of the components of the
spins orthogonal to the orbital plane thus reducing the physical parameter space to only
two dimensions. Then, although this current prescription have been demonstrated to be
su cient for the searches of the gravitational waves in the data, they are not so optimal
for the statistical inference of the spins of each BH, which is partially caused by the
inherent degeneracy introduced by the e ective spin. The focus of this work has been the extension of the one-spin phenomenological models
to its two-spin version by adding the subdominant e ects carried by the spin di erence
terms = 1 � 2. To that end, we have employed the data of more than 400 simulations
of binary black hole systems generated by four di erent codes (BAM, SpEC, LAZEV,
MAYA), 23 of them generated throughout this thesis by means of the BAM code. This
involved the di cult task of evolving, extracting the waves and the data postprocessing
of each case. Then, we have rede ned the strategy for building higher than two dimensional
ansaetze to add subdominant e ects and where we have also included the results
of the extreme mass ratio limit. All this analysis has resulted in the prescription of new
phenomenological models for the nal mass, nal spin and peak luminosity. The new
models have been shown to improve the old descriptions of these quantities while they
have clearly revealed the possible impact of the subdominant e ects in the near future
phenomenological models.
http://hdl.handle.net/10803/565409
Forats negres binaris
Ones gravitacionals
Models fenomenològics
Hierarchical data-driven modelling of binary black hole mergers