@MastersThesis{Sousa:2019:MeGeOn,
author = "Sousa, Manoel Felipe",
title = "Mecanismos de gera{\c{c}}{\~a}o de ondas gravitacionais em
an{\~a}s brancas de alta rota{\c{c}}{\~a}o",
school = "Instituto Nacional de Pesquisas Espaciais (INPE)",
year = "2019",
address = "S{\~a}o Jos{\'e} dos Campos",
month = "2019-02-27",
keywords = "An{\~a} Branca, acre{\c{c}}{\~a}o de mat{\'e}ria, campo
magn{\'e}tico, ondas gravitacionais, SGRs/AXPs, white dwarf,
accretion of matter, magnetic field, gravitational waves,
SGRs/AXPs.",
abstract = "A detec{\c{c}}{\~a}o direta de Ondas Gravitacionais (OGs) tem
proporcionado novos ramos de estudos cient{\'{\i}}ficos e
levantado novos questionamentos sobre o comportamento dos sistemas
astrof{\'{\i}}sicos. Devido a esses grandes avan{\c{c}}os e a
busca pelo entendimento de fontes astrof{\'{\i}}sicas que emitem
OGs na faixa de frequ{\^e}ncias de 10\−4 a 10\−1
Hz, esfor{\c{c}}os t{\^e}m sido feitos para o desenvolvimento de
detectores espaciais, tais como, o LISA (Laser Interferometer
Space Antenna), o BBO (Big Bang Observer) e o DECIGO (DECi-hertz
Interferometer Gravitational wave Observatory), com o intuito de
observar essas fontes que n{\~a}o podem ser medidas com
detectores terrestres. Uma das classes candidatas a serem
detectadas por esses instrumentos espaciais s{\~a}o as an{\~a}s
brancas (ABs) de alta rota{\c{c}}{\~a}o. Essas ABs s{\~a}o
remanescentes peculiares que emitem pulsos de energia apresentando
per{\'{\i}}odos de rota{\c{c}}{\~a}o da ordem de segundos a
poucos minutos e possuem intensos campos magn{\'e}ticos (106 G a
109 G). Essa classe estelar tem dado suporte a um modelo
alternativo para descrever uma classe de pulsares conhecida como
Soft Gamma Repeaters (SGRs) e Anomalous X \− Ray Pulsars
(AXPs), onde esses s{\~a}o caracterizados como pulsares de ABs
alimentados pela rota{\c{c}}{\~a}o. Nessa
disserta{\c{c}}{\~a}o, analisamos dois mecanismos de
gera{\c{c}}{\~a}o de OGs em ABs de alta rota{\c{c}}{\~a}o:
acre{\c{c}}{\~a}o de mat{\'e}ria quando essas se encontram em
um sistema bin{\'a}rio, e deforma{\c{c}}{\~a}o na estrutura da
estrela em raz{\~a}o do intenso campo magn{\'e}tico. Para isso,
calculamos a amplitude e a energia gravitacional para 3 sistemas
bin{\'a}rios: AE Aquarii, AR Scorpii e RX J0648.0-4418
considerando os dois processos de emiss{\~a}o de OGs. Ainda,
investigamos, pela primeira vez na literatura, a contrapartida
gravitacional dos SGRs/AXPs considerando o formalismo de ABs. Para
essa an{\'a}lise, aplicamos apenas o mecanismo de
deforma{\c{c}}{\~a}o magn{\'e}tica. Ap{\'o}s o c{\'a}lculo,
conclu{\'{\i}}mos que, para o primeiro mecanismo, os sistemas AE
Aquarii e RX J0648.0-4418 s{\~a}o bons candidatos a serem
observados pelo BBO e DECIGO se possu{\'{\i}}rem um amontoado de
massa em um dos polos magn{\'e}ticos (delta)m \≥
10\−5M. para 1 ano de observa{\c{c}}{\~a}o, enquanto que
para o segundo mecanismo, os 3 sistemas analisados necessitam que
a AB tenha um campo magn{\'e}tico em torno de 2 ordens de
magnitude maiores do que s{\~a}o inferidos pela emiss{\~a}o
eletromagn{\'e}tica (107 G a 108 G). Al{\'e}m disso, com o
segundo mecanismo, foi encontrado que alguns SGRs/AXPs podem ser
observados pelo BBO e DECIGO: 1E 1547.0-5408 e SGR 1806-20
s{\~a}o fontes que podem ser observadas para todo o intervalo de
massa considerado (0, 6M. \≤ MAB \≤ 1, 4M.) em 1 ano
de observa{\c{c}}{\~a}o, j{\'a} as fontes SGR 1900+14, CXOU
J171405.7-381031, Swift J1834.9-0846 e SGR1627-41 ser{\~a}o
detectadas com um tempo de observa{\c{c}}{\~a}o de 5 anos para o
mesmo intervalo de massa. Com isso, uma poss{\'{\i}}vel
detec{\c{c}}{\~a}o de OGs cont{\'{\i}}nuas provindas desses
objetos corroboraria com o modelo de pulsares de ABs, pois notamos
que os SGRs e AXPs, no modelo de magnetar (estrelas de
n{\^e}utrons altamente magnetizadas), est{\~a}o muito abaixo das
curvas de sensibilidade do BBO e DECIGO e n{\~a}o ser{\~a}o
detectados por esses instrumentos com esse mecanismo. ABSTRACT:
The direct detection of gravitational waves (GWs) provided new
branches of scientific studies and raised new questions about the
behavior of astrophysical systems. Due to these great advances and
the search for understanding of astrophysical sources that emit
GWs in the frequency range of 10\−4 to 10\−1 Hz,
efforts have been made for the development of space detectors such
as, LISA (Laser Interferometer Space Antenna), BBO (Big Bang
Observer) and DECIGO (DECi-hertz Interferometer Gravitational wave
Observatory), in order to observe these sources that cannot be
measured with terrestrial detectors. One of the candidate classes
to be detected by these spatial instruments are the fast-rotating
white dwarf (fast-rotating WDs). These WDs are peculiar remnants
that emit pulses of energy presenting rotation periods of the
order of seconds to a few minutes and have intense magnetic fields
(106 G to 109 G). This stellar class supports an alternative model
to describe a class of pulsar known as Soft Gamma Repeaters (SGRs)
and Anomalous X-Ray Pulsars (AXPs), where, in this model, these
objects are characterized as WD pulsars powered by rotation. In
this work, we analyzed two mechanisms of GWs emission in
fast-rotating WDs: acrection of matter when these ones are in a
binary system, and deformation of the structure of the star due to
the strong magnetic field. For this, we calculated the
gravitational amplitude and energy for 3 binary systems: AE
Aquarii, AR Scorpii and RX J0648.0-4418, considering the two
processes of GW emission. We also investigated, for the first time
in the literature, the gravitational counterpart of the SGRs/AXPs
considering the formalism of WDs. For this analysis, we applied
only the magnetic deformation mechanism. After the calculation, we
concluded that, for the first mechanism, the systems AE Aquarii
and RX J 0648.0- 4418 are good candidates to be observed by BBO
and DECIGO if they have an amount of accumulated mass on one of
the magnetic poles of (delta)m \≥ 10\−5M. for 1 year
of observation, while, for the second mechanism , the 3 analyzed
systems require that WD has a magnetic field around 2 orders of
magnitude higher than that is inferred by electromagnetic emission
(107 G a 108 G). In addition, using the second mechanism, it was
found that some SGRs/AXPs can be observed by BBO and DECIGO: 1E
1547.0-5408 and SGR 1806-20 are sources that can be observed for
the entire considered mass range (0, 6M. \≤ MAB \≤
1, 4M.) in 1 year of observation, for the sources SGR 1900+14,
CXOU J171405.7-381031, Swift J1834.9-0846 and SGR 1627-41 will be
detected with a 5-year observation time for the same mass range.
Thereby, a possible detection of continuous GWs originated from
these objects is a good indication that corroborates with the WD
pulsar model because we noted that the SGRs and AXPs, in the
Magnetar model (highly magnetized neutron stars), are far below
the sensitivity curves of BBO and DECIGO and will not be detected
by these instruments using this mechanism.",
committee = "Rodrigues, Cl{\'a}udia Vilega (presidente) and Ara{\'u}jo,
Jos{\'e} Carlos Neves de (orientador) and Coelho, Jaziel Goulart
(orientador) and Aguiar, Odylio Denys de and Alves, M{\'a}rcio
Eduardo da Silva",
englishtitle = "Gravitational wave emission mechanisms in fast-rotating white
dwarfs",
language = "pt",
pages = "107",
ibi = "8JMKD3MGP3W34R/3SNU748",
url = "http://urlib.net/ibi/8JMKD3MGP3W34R/3SNU748",
targetfile = "publicacao.pdf",
urlaccessdate = "19 abr. 2024"
}