7 research outputs found
Measuring Neutron Star Radius with second and third generation Gravitational Wave Detector Networks
The next generation of ground-based interferometric gravitational wave
detectors will observe mergers of black holes and neutron stars throughout
cosmic time. A large number of the binary neutron star merger events will be
observed with extreme high fidelity, and will provide stringent constraints on
the equation of state of nuclear matter. In this paper, we investigate the
systematic improvement in the measurability of the equation of state with
increase in detector sensitivity by combining constraints obtained on the
radius of a neutron star from a simulated source
population. Since the measurability of the equation of state depends on its
stiffness, we consider a range of realistic equations of state that span the
current observational constraints. We show that a single 40km Cosmic Explorer
detector can pin down the neutron star radius for a soft, medium and stiff
equation of state to an accuracy of 10m within a decade, whereas the current
generation of ground-based detectors like the Advanced LIGO-Virgo network would
take years to do so for a soft equation of state.Comment: 14 pages, 3 figures, 1 table, supplemental materials at
https://github.com/sugwg/bns-eos-ngg
The Peak of the Fallback Rate from Tidal Disruption Events: Dependence on Stellar Type
A star completely destroyed in a tidal disruption event (TDE) ignites a
luminous flare that is powered by the fallback of tidally stripped debris to a
supermassive black hole (SMBH) of mass . We analyze two estimates
for the peak fallback rate in a TDE, one being the "frozen-in" model, which
predicts a strong dependence of the time to peak fallback rate, ,
on both stellar mass and age, with yr for main sequence stars with masses and . The second estimate, which postulates
that the star is completely destroyed when tides dominate the maximum stellar
self-gravity, predicts that is very weakly dependent on stellar
type, with for , while for a Kroupa initial
mass function truncated at . This second estimate also agrees
closely with hydrodynamical simulations, while the frozen-in model is
discrepant by orders of magnitude. We conclude that (1) the time to peak
luminosity in complete TDEs is almost exclusively determined by SMBH mass, and
(2) massive-star TDEs power the largest accretion luminosities. Consequently,
(a) decades-long extra-galactic outbursts cannot be powered by complete TDEs,
including massive-star disruptions, and (b) the most highly super-Eddington
TDEs are powered by the complete disruption of massive stars, which -- if
responsible for producing jetted TDEs -- would explain the rarity of jetted
TDEs and their preference for young and star-forming host galaxies.Comment: 10 pages, 4 figures, ApJL accepte
Characterizing Gravitational Wave Detector Networks: From A to Cosmic Explorer
Gravitational-wave observations by the Laser Interferometer
Gravitational-Wave Observatory (LIGO) and Virgo have provided us a new tool to
explore the universe on all scales from nuclear physics to the cosmos and have
the massive potential to further impact fundamental physics, astrophysics, and
cosmology for decades to come. In this paper we have studied the science
capabilities of a network of LIGO detectors when they reach their best possible
sensitivity, called A#, and a new generation of observatories that are factor
of 10 to 100 times more sensitive (depending on the frequency), in particular a
pair of L-shaped Cosmic Explorer observatories (one 40 km and one 20 km arm
length) in the US and the triangular Einstein Telescope with 10 km arms in
Europe. We use a set of science metrics derived from the top priorities of
several funding agencies to characterize the science capabilities of different
networks. The presence of one or two A# observatories in a network containing
two or one next generation observatories, respectively, will provide good
localization capabilities for facilitating multimessenger astronomy and
precision measurement of the Hubble parameter. A network of two Cosmic Explorer
observatories and the Einstein Telescope is critical for accomplishing all the
identified science metrics including the nuclear equation of state,
cosmological parameters, growth of black holes through cosmic history, and make
new discoveries such as the presence of dark matter within or around neutron
stars and black holes, continuous gravitational waves from rotating neutron
stars, transient signals from supernovae, and the production of stellar-mass
black holes in the early universe. For most metrics the triple network of next
generation terrestrial observatories are a factor 100 better than what can be
accomplished by a network of three A# observatories.Comment: 45 pages, 20 figure
Detectability of Sub-Solar Mass Neutron Stars Through a Template Bank Search
We study the detectability of gravitational-wave signals from sub-solar mass
binary neutron star systems by the current generation of ground-based
gravitational-wave detectors. We find that finite size effects from large tidal
deformabilities of the neutron stars and lower merger frequencies can
significantly impact the sensitivity of the detectors to these sources. By
simulating a matched-filter based search using injected binary neutron star
signals with tidal deformabilities derived from physically motivated equations
of state, we calculate the reduction in sensitivity of the detectors. We
conclude that the loss in sensitive volume can be as high as for an
equal mass binary system of chirp mass , in a
search conducted using binary black hole template banks. We use this loss in
sensitive volume, in combination with the results from the search for sub-solar
mass binaries conducted on data collected by the LIGO-Virgo observatories
during their first three observing runs, to obtain a conservative upper limit
on the merger rate of sub-solar mass binary neutron stars. Since the discovery
of a low-mass neutron star would provide new insight into formation mechanisms
of neutron stars and further constrain the equation of state of dense nuclear
matter, our result merits a dedicated search for sub-solar mass binary neutron
star signals.Comment: 12 pages, 7 figures, supplemental materials at
https://github.com/sugwg/sub-solar-ns-detectabilit