The next breakthrough in gravitational wave astronomy may be the first discovery of continuous gravitational waves. I will review the data analysis methods used to search for continuous gravitational waves since the early days of LIGO and Virgo. I will present an overview of continuous gravitational wave search results that have been achieved to date, and show how they illustrate the various...
Continuous gravitational wave atlas is a way to distribute data from a wide parameter continuous wave search. We will show the latest atlas produced by Falcon pipeline, with examples of how to use the atlas data in new searches.
The atlas data is provided in a new MVL file format that allows analysis on small computers, such as your notebook. There is also an MVL version of Gaia DR3 data,...
Started in May 2023 and planned to last 20 months, the fourth observing run (O4) of the advanced ground-based interferometric detector network LIGO-Virgo-KAGRA provides the deepest yet reach into the gravitational-wave side of our Universe. I will give a status update on the run's progress and results obtained so far, as well as a brief overview of the science scope of planned O4 searches for...
I will describe the latest results on the modelling of gravitational wave emission from neutron stars, discussing both mountains and stellar oscillations. In the case of mountains, I review the latest results on both maximum mountains, and the mechanisms by which mountains might form in the first place. I will end by discussing the inverse problem, i.e. what we learn following a detection.
The spin of pulsars can be timed with exquisite precision. They are observed to spin-down steadily over long periods but once in a while, they can undergo a rapid and sudden increase in their spin, which is known as a glitch. For some cases, the glitch is followed by a post-glitch recovery. There are several models that predict the emission of continuous gravitational waves from glitches and...
In the next few decades a number of space-based gravitational wave detectors sensitive in the deci-Hertz band should be operational.
Among the main goals of such detectors are a number of "first detections" such as primordial gravitational waves, compact stellar mass inspirals and intermediate mass black hole mergers.
Interestingly enough we find no mention of Continuous Gravitational...
The Einstein Telescope (ET) is a proposed third-generation, wide-band gravitational wave (GW) detector which will have an improved detection sensitivity for low frequencies, leading to a longer observation time in the detection band and higher detection rate for binary neutron stars (BNSs). GWTC-3 detections have already constrained the merger rates of BNS with just two events, assuming that...
In the past decades, several neutron stars (NSs), particularly pulsars, with mass $M>2M_\odot$ have been observed. On the other hand, the existence of massive white dwarfs (WDs), even violating the Chandrasekhar mass limit, was inferred from the peak luminosities of type Ia supernovae. Hence, there is a generic question of the origin of massive compact objects. Here we explore the existence of...
Analysis of the polarization of electromagnetic radiation, or polarimetry, is a unique tool that allows us to obtain information about astrophysical objects that cannot be obtained in other ways, for example, regarding their geometry. With the launch of the IXPE (Imaging X-ray Polarimetry Explorer) mission at the end of 2021, this instrument became available in the X-ray range as well. In my...
Globular clusters have historically been a prime target for radio pulsar searching owing to their old stellar population and dense environment. The Terzan 5 globular cluster is one such source that houses numerous pulsars and has been extensively studied at multiple wavelengths. In this talk, I will be presenting 9 new binary pulsars discovered in Terzan 5 using the MeerKAT radio telescope....
Radio searches of unidentified Fermi-LAT gamma-ray sources have discovered more than a hundred new millisecond pulsars. The two types of data, radio and gamma-ray, have very different properties. For example, the radio data provides extremely precise pulse arrival times, but often has gaps and typically only covers the time span between detection and the most recent observation. The gamma-ray...
Neutron stars in compact binary systems are potential sources of continuous gravitational waves. While those containing another degenerate object should provide the "cleanest" signals, double neutron stars are rare, and neutron star-white dwarfs tend to be found at wider orbital periods. On the other hand, another type of neutron star binary, colloquially called spiders due to the strongly...
Since its launch in 2008, the Fermi Large Area Telescope (Fermi-LAT) has aided to discover more than half of the known millisecond pulsars (MSPs). Among these are Spider pulsars, which are MSP binaries with main sequence or semi-degenerate stars in tight orbit (orbital periods ≲ 1day). These Spider pulsars are among the fastest-spinning and heaviest pulsars due to the recycling scenario....
Millisecond pulsars are ideal targets to probe the strong interaction at supranuclear densities and search for continuous gravitational wave (CW) sources. Either the rotation of their magnetic field or the infall of matter lost by a companion star is assumed to power their electromagnetic emission. Recently, we exploited the fast optical photometer SiFAP2 at 3.6m INAF’s Telescopio Nazionale...
Pulsar timing noise is the stochastic deviation of the pulse arrival times of a pulsar away from their long term trend. In the standard two-component crust-superfluid neutron-star model, timing noise can be explained as the perturbation of the two components by irregular torques. Interactions between the crust and superfluid cause these perturbations to decay exponentially with a...
Over ten years ago, Fermi observed an excess of GeV gamma rays from
the Galactic Center whose origin is still under debate. One
explanation for this excess involves annihilating dark matter; another
requires an unresolved population of millisecond pulsars concentrated
at the Galactic Center. We use the results from LIGO/Virgo/KAGRA's most
recent all-sky search for quasi-monochromatic,...
The Band-Sampled-Data (BSD) framework has emerged as a powerful tool in the search for GW signals. With its versatile capabilities and adaptability, BSD has been instrumental in various searches for both standard CW signals and dark matter candidates. Over the past five years, the BSD framework has evolved significantly, offering a comprehensive suite of functions for analysing GW data. Its...
The accurate modeling of rotating neutron stars and their observational signatures is fundamental to exploring the nuclear equation of state at high densities. However, modeling rapidly rotating neutron stars, especially their dynamical properties, becomes increasingly involved with rotation rate. This talk presents a set of novel universal relations that are valid even with high rotation...
To detect quasi-monochromatic gravitational wave radiation emitted by the non-symmetric rotating neutron stars requires a long observation time to distinguish it from the detector's noise. If, in addition, the signal is microlensed, the mass of the lens magnifies the signal amplitude, which aids in detection of these signals and in probing the physical nature of the lens as well as the source....
The observed spin frequency distribution of millisecond (ms) pulsars is a result of their current or previous spin evolution in the low-mass X-ray binary phase. Such a spin evolution depends on various physical aspects, such as binary evolution, disk-magnetosphere interaction, continuous gravitational wave emission, transient accretion, neutron star equations of state, etc. Thus, the...
The maximum-likelihood F-statistic, a classical tool in continuous-gravitational-wave (CW) analysis, can be represented as a Bayes-factor analytically marginalized over unphysical priors on the four signal amplitude parameters (h0, cosi, psi, phi0).
This makes the F-statistic Neyman-Pearson sub-optimal but computationally attractive, because four search parameters have been eliminated...
Searches for continuous gravitational waves targeted at known pulsars use pulsar timing observations to infer the phase evolution parameters of the CW signals they emit. We present a new method and implementation to obtain Bayesian posteriors on the amplitude parameters of the CW signal, combining modern Bayesian parameter estimation techniques with the well-established F-statistic framework....
Spinning neutron stars are sources of long-duration continuous waves that may be detected by interferometric detectors. We focus on long, but not infinite duration continuous wave signals when there are no electromagnetic observations to inform on the time of occurrence of the signal. We propose a search scheme to identify the signal duration and location of the signal in the data.
Dark compact objects, like primordial black holes, can span a large range of masses depending on their time and mechanism of formation. In particular, they can have subsolar masses and form binary systems with an inspiral phase that can last for long periods of time. Additionally, these signals have a slow increase of frequency, and, therefore, are well suited to be searched with continuous...
I will discuss the mini-EMRI systems that can be detected at LIGO,
which are ideal systems for detecting very light subsolar exotic compact
objects. The detection strategy and method are both similar to those
currently being used in CW searches. This talk is based on the paper
https://arxiv.org/abs/2205.10359.
In this talk, I will review the main properties of the galactic population of neutron stars, the so-called neutron star zoo. I will focus in particular on the subgroup of isolated stars, such as magnetars, X-ray dim isolated neutron stars (XDINS), and central compact objects in supernova remnants (CCOs).
I will also discuss how different neutron star populations are thought to be...
In the era of multi-messenger astrophysics, we are on the precipice of observing binary systems within our galaxy using gravitational waves in addition to traditional electromagnetism, in the advent of third generation gravitational wave detectors such as LISA. The joint messenger observations can bolster our detection ability of systems throughout our galaxy, providing an unprecedented...
The r-mode instability is among the most promising sources for continuous gravitational-wave emission from rotating neutron stars. However, our present understanding of these purely axial perturbations rely on Newtonian gravity and assume simplistic models of the nuclear matter. Moreover, calculations in general relativity suggest a continuous spectrum, posing challenges for...
Neutron stars provide a unique opportunity to study strongly interacting matter under extreme density conditions. The intricacies of matter inside neutron stars and their equation of state are not directly visible, but determine bulk properties, such as mass and radius, which affect the star's thermal X-ray emissions. However, the telescope spectra of these emissions are also affected by the...
Second-generation ground-based detectors, Advanced-LIGO and Advanced-Virgo, opened the window of gravitational wave astronomy. Over the past seven years, we witnessed GW astronomy begin with the first detection and rapidly emerge as a well-established field of transient astronomy. However, we have not detected any persistent gravitational wave (GW) signal. Scorpius X-1, the brightest low-mass...
All-sky searches for continuous gravitational waves (CWs) emitted by yet-unknown neutron stars pose high computational costs and are typically optimized for signal sensitivity through hierarchical pipelines. Initial search stages reduce the required accuracy in estimated signal parameters by accepting high false alarm rates. All recorded alarms are then analyzed for signal consistency in...
Continuous gravitational waves (CWs) are long-lasting gravitational waves emitted by rapidly spinning neutron stars that can be seen in the LIGO band. The most sensitive classical search method, the coherent matched filter search for continuous waves is not computationally feasible. Instead, a semi-coherent method is used for the search because it has a higher senesitivity than the coherent...
Convolutional neural networks (CNN) have an advantage in computational cost for the search of continuous gravitational waves (CGWs). We are developing a deep learning method for CGW searches. In our previous work, we proposed a method in which the doubly Fourier transformed strain data are used as inputs of CNN and assessed the effects of non-Gaussian artifacts. In this talk, we will talk...
The detection of gravitational waves (GWs) has opened new avenues for studying the universe and testing fundamental physics. As LIGO, Virgo and KAGRA undertake another observation run (O4) with an improved sensitivity, non-axisymmetric neutron stars emitting quasi monochromatic, long-standing GWs are expected to be within the detectors' sensitivity band. However, their detection in the...
I will present various ways in which our group is searching for dark matter using GW detectors.
-
Searching for GW signals from mergers of ultralight primordial black holes using LIGO data.
-
Searching for direct interaction between dilatonic DM and LIGO.
-
Searching for GWs from axion clouds around spinning black holes using a network of radio-frequency GW detectors.
4....
Gravitational waves can probe the existence of primordial black holes (PBHs). If PBHs form in binary systems, they will inspiral and eventually merge, just as stellar-mass black holes do, emitting gravitational waves in the process. Here, we describe multiple methods to probe the existence of planetary-mass PBHs, and focus on one, the generalized frequency-Hough, that we used to run a search...
The existence of massive white dwarfs (WDs), violating the Chandrasekhar mass limit, was inferred from the peak luminosities of type Ia supernovae. On the other hand, independent observations have suggested that WDs can have surface magnetic field upto 10^9 Gauss, which can be even more intense in the center. One of the interesting models to explain the existence of such massive WDs is to...
