309 research outputs found
Towards asteroseismology of core-collapse supernovae with gravitational-wave observations - I. Cowling approximation
Gravitational waves from core-collapse supernovae are produced by the
excitation of different oscillation modes in the proto-neutron star (PNS) and
its surroundings, including the shock. In this work we study the relationship
between the post-bounce oscillation spectrum of the PNS-shock system and the
characteristic frequencies observed in gravitational-wave signals from
core-collapse simulations. This is a fundamental first step in order to develop
a procedure to infer astrophysical parameters of the PNS formed in
core-collapse supernovae. Our method combines information from the oscillation
spectrum of the PNS, obtained through linear-perturbation analysis in general
relativity of a background physical system, with information from the
gravitational-wave spectrum of the corresponding non-linear, core-collapse
simulation. Using results from the simulation of the collapse of a 35
presupernova progenitor we show that both types of spectra are
indeed related and we are able to identify the modes of oscillation of the PNS,
namely g-modes, p-modes, hybrid modes, and standing-accretion-shock-instability
(SASI) modes, obtaining a remarkably close correspondence with the
time-frequency distribution of the gravitational-wave modes. The analysis
presented in this paper provides a proof-of-concept that asteroseismology is
indeed possible in the core-collapse scenario, and it may serve as a basis for
future work on PNS parameter inference based on gravitational-wave
observations
Are pulsars born with a hidden magnetic field?
The observation of several neutron stars in the centre of supernova remnants and with significantly lower values of the dipolar magnetic field than the average radio-pulsar population has motivated a lively debate about their formation and origin, with controversial interpretations. A possible explanation requires the slow rotation of the protoneutron star at birth, which is unable to amplify its magnetic field to typical pulsar levels. An alternative possibility, the hidden magnetic field scenario, considers the accretion of the fallback of the supernova debris on to the neutron star as responsible for the submergence (or screening) of the field and its apparently low value. In this paper, we study under which conditions the magnetic field of a neutron star can be buried into the crust due to an accreting, conducting fluid. For this purpose, we consider a spherically symmetric calculation in general relativity to estimate the balance between the incoming accretion flow and the magnetosphere. Our study analyses several models with different specific entropy, composition, and neutron star masses. The main conclusion of our work is that typical magnetic fields of a few times 1012 G can be buried by accreting only 10−3–10−2 M⊙, a relatively modest amount of mass. In view of this result, the central compact object scenario should not be considered unusual, and we predict that anomalously weak magnetic fields should be common in very young (< few kyr) neutron stars.This work has been supported by the Spanish MINECO grants AYA2013-40979-P and AYA2013-42184-P and by the Generalitat Valenciana (PROMETEOII-2014-069)
Classification methods for noise transients in advanced gravitational-wave detectors II: performance tests on Advanced LIGO data
The data taken by the advanced LIGO and Virgo gravitational-wave detectors contains short duration noise transients that limit the significance of astrophysical detections and reduce the duty cycle of the instruments. As the advanced detectors are reaching sensitivity levels that allow for multiple detections of astrophysical gravitational-wave sources it is crucial to achieve a fast and accurate characterization of non-astrophysical transient noise shortly after it occurs in the detectors. Previously we presented three methods for the classification of transient noise sources. They are Principal Component Analysis for Transients (PCAT), Principal Component LALInference Burst (PC-LIB) and Wavelet Detection Filter with Machine Learning (WDF-ML). In this study we carry out the first performance tests of these algorithms on gravitational-wave data from the Advanced LIGO detectors. We use the data taken between the 3rd of June 2015 and the 14th of June 2015 during the 7th engineering run (ER7), and outline the improvements made to increase the performance and lower the latency of the algorithms on real data. This work provides an important test for understanding the performance of these methods on real, non stationary data in preparation for the second advanced gravitational-wave detector observation run, planned for later this year. We show that all methods can classify transients in non stationary data with a high level of accuracy and show the benefits of using multiple classifiers
Solving the Teukolsky equation with physics-informed neural networks
We use physics-informed neural networks (PINNs) to compute the first
quasi-normal modes of the Kerr geometry via the Teukolsky equation. This
technique allows us to extract the complex frequencies and separation constants
of the equation without the need for sophisticated numerical techniques, and
with an almost immediate implementation under the \texttt{PyTorch} framework.
We are able to compute the oscillation frequencies and damping times for
arbitrary black hole spins and masses, with accuracy typically below the
percentual level as compared to the accepted values in the literature. We find
that PINN-computed quasi-normal modes are indistinguishable from those obtained
through existing methods at signal-to-noise ratios (SNRs) larger than 100,
making the former reliable for gravitational-wave data analysis in the mid
term, before the arrival of third-generation detectors like LISA or the
Einstein Telescope, where SNRs of might be achieved.Comment: 12 pages, 7 figure
Convolutional Neural Networks for the classification of glitches in gravitational-wave data streams
We investigate the use of Convolutional Neural Networks (including the modern
ConvNeXt network family) to classify transient noise signals (i.e.~glitches)
and gravitational waves in data from the Advanced LIGO detectors. First, we use
models with a supervised learning approach, both trained from scratch using the
Gravity Spy dataset and employing transfer learning by fine-tuning pre-trained
models in this dataset. Second, we also explore a self-supervised approach,
pre-training models with automatically generated pseudo-labels. Our findings
are very close to existing results for the same dataset, reaching values for
the F1 score of 97.18% (94.15%) for the best supervised (self-supervised)
model. We further test the models using actual gravitational-wave signals from
LIGO-Virgo's O3 run. Although trained using data from previous runs (O1 and
O2), the models show good performance, in particular when using transfer
learning. We find that transfer learning improves the scores without the need
for any training on real signals apart from the less than 50 chirp examples
from hardware injections present in the Gravity Spy dataset. This motivates the
use of transfer learning not only for glitch classification but also for signal
classification.Comment: 15 pages, 14 figure
Inference of proto-neutron star properties in core-collapse supernovae from a gravitational-wave detector network
The next Galactic core-collapse supernova (CCSN) will be a unique opportunity
to study within a fully multi-messenger approach the explosion mechanism
responsible for the formation of neutron stars and stellar-mass black holes.
State-of-the-art numerical simulations of those events reveal the complexity of
the gravitational-wave emission which is highly stochastic. This challenges the
possibility to infer the properties of the compact remnant and of its
progenitor using the information encoded in the waveforms. In this paper we
take further steps in a program we recently initiated to overcome those
difficulties. In particular we show how oscillation modes of the proto-neutron
star, highly visible in the gravitational-wave signal, can be used to
reconstruct the time evolution of their physical properties. Extending our
previous work where only the information from a single detector was used we
here describe a new data-analysis pipeline that coherently combines
gravitational-wave detectors' data and infers the time evolution of a
combination of the mass and radius of the compact remnant. The performance of
the method is estimated employing waveforms from 2D and 3D CCSN simulations
covering a progenitor mass range between 11\, and
40\, and different equations of state for both a network of
up to five second-generation detectors and the proposed third-generation
detectors Einstein Telescope and Cosmic Explorer. Our study shows that it will
be possible to infer PNS properties for CCSN events occurring in the vicinity
of the Milky Way, up to the Large Magellanic Cloud, with the current generation
of gravitational-wave detectors
- …