GEMMA 2

16 Sept 2024, 07:20 → 19 Sept 2024, 20:00 Europe/Rome

Aula Cabibbo (CU033 FISICA E. FERMI - ground floor) (Rome, Italy)

Paola Leaci (Sapienza and Rome INFN)

 

[Sorry for those of you who could not be in the picture due to time constraints]

 

The aim of the GEMMA2 workshop is to discuss on Gravitational waves, ElectroMagnetic and dark MAtter physics, bringing together the experimental, theoretical and data analysis aspects of these apparently heterogeneous fields.

The details of the first GEMMA workshop can be found here.

REGISTRATION is now open and ABSTRACT SUBMISSION is welcome on these topics (please see below).
The workshop will be held, from 16 to 19 September 2024, at the "aula Cabibbo” of the Sapienza University in Rome.

WiFi access will be available through the eduroam network for those with an active eduroam account.

KEYNOTE SPEAKERS
MICHAL BEJGER, ISTITUTO NAZIONALE DI FISICA NUCLEARE
GIANFRANCO BERTONE, UNIVERSITY OF AMSTERDAM
GIANCARLO GHIRLANDA, OSSERVATORIO ASTRONOMICO DI BRERA
PAULO FREIRE, MAX-PLANCK-INSTITUT FUER RADIOASTRONOMIE 
GIOVANNI LOSURDO, INFN, PISA
PATRICIA SCHMIDT, UNIVERSITY OF BIRMINGHAM

 

IMPORTANT DEADLINES

• Registration is open until August 31st, 2024
• Registration fee amounts to 250 EUR until June 28th, and 300 after this date
• Abstract submission is open until June 16th, 2024

 

       

Flyer_GEMMA2.pdf

Monday, 16 September

Registration

Gravitational Waves

1 LIGO-Virgo-KAGRA gravitational-wave sources and observational results

The talk will summarise main observational results obtained by the current network of gravitational wave detectors, including the ongoing O4 run which started May 2023. First half of O4 - O4a - ended January 2024, providing 81 new high-confidence gravitational wave candidates. I will also discuss challenges and outlook related to searches for transient signals emitted by tight binaries composed of compact objects, other transient signals, such as supernovae, as well as long-duration (persistent) signals, and their diverse astrophysics.

Speaker: Michal Stanislaw Bejger (INFN)

LIGO-Virgo-KAGRA gravitational-wave sources and observational results (3).pdf

2 Recent continuous wave searches and their astrophysical implications

The direct detection of gravitational waves from highly energetic collisions of compact binary systems comprising black holes and/or neutron stars has inaugurated
an exciting new era in astrophysical science. In recent years, searches have been designed to look for other types of gravitational radiation, including the much fainter long-duration, persistent emission known as continuous waves. Potential sources of continuous waves include spinning neutron stars with some non-axisymmetries, conjectured ultralight boson clouds around rotating black holes, etc. In this talk, I will give an overview of continuous wave sources and the latest search results from LIGO-Virgo-KAGRA’s third observing run and discuss the astrophysical implications in the absence of a confident detection.

Speaker: Dr Dana Jones

Jones_GEMMA2_talk.pdf

3 Exploring the Gravitational Wave Background and its Implications

The gravitational wave background (GWB) is a superposition of weak, independent and unresolved gravitational wave (GW) sources. It can be sourced by both astrophysical and cosmological sources, among which we find unresolved compact binary coalescences, supernovae, first order cosmological phase transitions and cosmic strings. Since the beginning of its observational runs, the LIGO-Virgo-KAGRA (LVK) collaboration has been searching for the GWB, utilizing a cross-correlation technique. We have not made a GWB detection thus far. However, we have succeeded in establishing upper limits on the GWB's amplitude, providing invaluable insights into the model parameters governing its various sources. In this presentation, I will provide an encompassing overview of the GWB, shedding light on the search techniques employed by the LVK collaboration and the multitude of data analysis challenges we encounter. Furthermore, I will delve into the implications of our searches for cosmological sources. Finally, I will explore the exciting prospects for future detection with third generation detectors, paving the way for groundbreaking discoveries in gravitational wave astronomy.

Speaker: Alba Romero-Rodríguez (Vrije Universiteit Brussels (VUB))

GEMMA2-3.pdf

Coffee Break

Gravitational Waves

4 The low-frequency gravitational sky: Pulsar Timing Arrays

Pulsar Timing Arrays (PTAs) exploit the extreme rotational stability of pulsars to chase the direct detection of nanoHertz-frequency gravitational waves (GWs), hence expanding the accessible windows of the GW spectrum.
In 2023, the European together with the Indian PTA (EPTA, InPTA), the North American PTA and the Australian PTA presented three series of articles reporting the first convincing evidence for a GW signature in the pulsar data collected to date.
This groundbreaking result is not a confirmed discovery yet, as its signal-to-noise does not reach the safe 5 threshold requested for a robust detection. This is mainly because of the numerous other signals that are present in pulsar data, such as intrinsic instabilities of the pulsars and the plasma-induced noise.
In this talk I will revise the current status of PTA experiments and their most significant results, as well as their future perspectives.

Speaker: Caterina Tiburzi (INAF-OAC)

GEMMA2_Caterina.pdf

5 Searching for generic gravitational waves transients in the data of current ground based detectors

Solving for exact and analytical solutions in general relativity to extract gravitational waves is a challenging task and for most of the known astrophysical systems it is not realised. In addition to this the understanding of gravitational waves transient universe is in early stages and hence searching for all possible transient events in all sky direction and with gravitational waveform of all morphologies is an important and necessary task. In this talk I will provide discuss the methodologies which are in place for detecting gravitational waves transients without any assumptions on their morphology, sky direction, time of arrival or polarisation. I will also give an update of the current results obtained with the LIGO-Virgo-KAGRA detectors.

Speaker: Shubhanshu Tiwari (University Of Zurich, Swtizerland)

Tiwari-gemma2 .pdf

6 Progresses on targeted searches for gravitational waves emitted by Core-Collapse Supernovae

We present a case study on archival open GW data to test new methodological improvements in targeted searches for gravitational-wave transients associated with core-collapse supernovae.
The study involves core-collapse supernovae optically observed within 30 Mpc during the third observing run of Advanced LIGO and Advanced Virgo. We report the detection efficiency and the distance range for various models of gravitational-wave emissions.

Speaker: Dr Francesco Salemi (University of Rome, "La Sapienza" and INFN Roma)

GEMMA2_Salemi_v3.pdf

Lunch

MultiMessenger

7 Multi messenger view of transients

Over the last two decades astronomy has established the first informative connections between different cosmic messengers, exemplified by the association of electromagnetic emission and the gravitational wave signal produced by the binary neutron star merger GW170817. Milt-messenger astronomy provides crucial insights into the physics of these sources by combining independent messengers. GW170817 demonstrated the potential of this approach to constrain the properties of progenitor neutron stars and of the ejecta and relativistic jets they produce when they merge, and to use these sources to constrain cosmological parameters. Future events and currently undetected sources may significantly advance this research field. I will review the current advancements and future perspectives in multi-messenger observations.

Speaker: Giancarlo Ghirlanda (Istituto Nazionale di Astrofisica - Osservatorio di Brera & INFN sezione di Milano Bicocca)

Gemma2_Ghirlanda.pdf

8 Constraints on the merging binary neutron star mass distribution and equation of state based on the incidence of jets in the population

The fact that a successful jet has been produced in the single well-localised binary neutron star (BNS) merger detected to date in gravitational waves suggests that this is not a rare outcome of this type of mergers. We back this intuitive conclusion with quantitative arguments that constrain the fraction of BNS mergers that produce a successful jet to be larger than about 1/3 at 90% confidence, and larger than 3-5% at the 3-sigma level. When combined with the physically motivated assumption that such a jet can only be produced by a black hole remnant surrounded by an accretion disc, this can be used to place a joint constraint on the space of BNS component mass distributions and neutron star matter equations of state. The result disfavours narrow neutron star mass distributions unless they are centered around some specific, equation-of-state-dependent values. This in turn can be used to shed light on the processes that determine the component masses in binary neutron stars.

Speaker: Alberto Colombo (Istituto Nazionale di Fisica Nucleare)

gemma2_colombo.pdf

9 Gamma-ray bursts and gravitational waves

Gamma-ray bursts arise from at least two distinct progenitor channels, the collapse of massive stars, and the merger of two compact objects. While both may plausibly yield detectable gravitational wave emission, compact object mergers represent the best prospects for joint electromagnetic and gravitational wave detections in the near-term future. I will review the evidence linking both short- and some long-duration gamma-ray bursts to compact object mergers, discuss how joint GW-EM searches for GRBs may be optimized, and look at additional routes for enhancing the detectability of both GRBs and their multiwavelength counterparts in coincidence with gravitational wave events.

Speaker: Andrew Levan

gemma2_rome_levan.pptx

gemma2_rome_levan_v2.pdf

Coffee Break

MultiMessenger

10 Joint analysis of electromagnetic and gravitational-wave data

On August 17, 2017, the first joint detection of gravitational waves (GWs) and electromagnetic (EM) waves from a binary neutron star (BNS) merger marked the beginning of multi-messenger astronomy with GWs and clearly demonstrated the huge informative power of joint EM and GW observations. In addition to BNS mergers, there is a wide range of highly energetic astrophysical sources expected to emit both GW and EM radiation, and in the future multi-messenger astronomy will be key to further probe the rich physics of transient phenomena in the Universe.
This talk will give an overview of the results of joint searches for GW and EM waves during past and current observing runs of Advanced LIGO, Advanced Virgo and KAGRA, and it will discuss the prospects and challenges for the upcoming years.

Speaker: Barbara Patricelli (Istituto Nazionale di Fisica Nucleare)

GEMMA2_Barbara.pdf

11 Fast optical photometry as a tool for CW counterpart searches

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 Galileo to discover optical pulsations from two millisecond pulsars surrounded by an accretion disk. Thanks to the much higher photon counting statistics of an optical telescope compared to high energy instruments, this has opened the intriguing possibility of searching for weak pulsed signals from accreting neutron stars at an unprecedented sensitivity. I will discuss the properties of the optical millisecond pulsars discovered so far and new search efforts carried out in our group to pin down the spin frequency and orbital parameters of strong candidates for CW emission.

Speaker: Riccardo La Placa

12 Acceleration and plunge from a quasi-spherical orbit near a rotating black hole

We explore cases of off-equatorial motion of a matter following inclined, almost spherical, relativistically precessing trajectories around a supermassive black hole with the aim of understanding the boundaries between the regions of stable, plunging, and escaping motion. As a generalisation of the Innermost Stable Circular Orbit (ISCO), the concept of the radius of the Innermost Stable Spherical Orbit (ISSO) determines the inner rim of inclined accretion/ejection process. We demonstrate that the region of bound orbits has a complicated structure due to enhanced precession in strong gravity. We also explore the fate of particles launched below the radius of the marginally bound spherical orbit: these may either plunge into the event horizon or accelerate to very high energy towards radial infinity (cf. The Astrophysical Journal, Volume 966, id.226, 2024; https://arxiv.org/abs/2404.04501).

Speaker: Vladimir Karas (Astronomical Institute, Czech Academy of Sciences)

karas-GEMMA2-2024.pdf

13 3D magnetothermal evolution of neutron stars with the new finite volume code MATINS

The study of the thermal and magnetic evolution of neutron stars in time is fundamental to understand the spectral and temporal properties of these sources, shed light on the origin of the different neutron star populations, and constraining the dense matter equation of state. To this aim, a numerical study of the heat diffusion and magnetic evolution equation is required, coupled with a detailed calculation of the microphysical property of the star, such as neutrino emissivity and heat and electric conductivity. Moreover, in order to account for non-axisymmetric effects, which are expected to lead to the formation of a non axisymmetric temperature distribution on the stellar surface, a solution of the equation in 3D is required. In this talk, I present our new code, MATINS, which aims to solve the magneto-thermal evolution of neutron star in 3D incorporating the most detailed microphysical description currently available.

Speaker: Dr Stefano Ascenzi (GSSI)

14 Multi-Messenger Astrophysics and cosmology with next-generation GRB space missions

The huge luminosity, the redshift distribution extending at least up to z~10 and the association with the explosive death of very massive stars make long GRBs extremely powerful probes for investigating the early Universe (pop-III stars, cosmic re-ionization, SFR and metallicity evolution up to the “cosmic dawn”) and measuring cosmological parameters. At the same time, as demonstrated by the GW170817 event, GRBs are a key electromagnetic counterpart of gravitational waves produced by NS-NS and NS-BH merging events. GRB space mission projects for the next decade aim at fully exploiting these unique potentialities of the GRB phenomenon, thus providing an ideal synergy with the very large astronomical facilities of the future (e.g., ELT, CTA, SKA, Athena) and, in particular, with the Einstein Telescope (ET). For instance, the THESEUS mission, under study by ESA as candidate M7 for a launch in 2037, by providing an unprecedented combination of X-/gamma-ray monitors, on-board IR telescope and spacecraft autonomous fast slewing capabilities, would be a wonderful machine for the detection, multi-wavelength characterization and redshift measurement of any kind of GRBs and many classes of X-ray transients. Thanks to these unprecedented capabilities and a perfectly matched timeline with ET, this mission would thus provide at least several tens, and likely more than one hundred, EM counterparts to GW detections, thus greatly enhancing the scientific return of ET for multi-messenger astrophysics and cosmology, as well as extreme and fundamental physics with GRBs.

Speaker: Lorenzo Amati (INAF - IASF Bologna)

amati-gemma2.pdf

Tuesday, 17 September

Registration

Dark Matter

15 Gravitational wave probes of dark matter

I discuss the interplay between dark matter, black holes, and gravitational waves, and the prospects for characterizing and identifying dark matter using gravitational waves. I will present some new results on the detectability of dark matter overdensities around black holes in binary systems, and argue that future interferometers may enable precision studies of the dark matter distribution and particle properties.

Speaker: Gianfranco Bertone (University of Amsterdam)

Bertone2.pdf

16 Searching for particle dark matter with gravitational waves

LISA, the space-based gravitational wave detector which was recently adopted, is due to fly in the mid 2030s. An entire new frequency range will be opened up for discovering gravitational wave sources, including intermediate and extreme mass ratio black hole binaries which will remain in band for up to weeks, months or even years. This offers an exciting new avenue for fundamental physics discoveries because the environment of the binaries will have an effect on the gravitational waveform over this long period of time, and we will be able to measure the properties of the environments from the gravitational wave observations alone.

I will demonstrate that we can distinguish the presence of different dark matter environments with a Bayesian model comparison approach and argue the importance of including environmental effects in the data analysis pipelines. I will address some ongoing challenges with modelling both the signals and the noise for these types of systems, and how simulation-based inference methods may help to overcome some barriers that traditional parameter estimation techniques may face.

Speaker: Philippa Cole (Istituto Nazionale di Fisica Nucleare)

Cole_GEMMA2.pdf

17 Primordial Black Holes as Dark Matter

Primordial black holes are black holes that may have formed in the early Universe. Their masses potentially span a range from as low as the Planck mass up to many orders of magnitude above the solar mass. This, in particular, includes those black holes recently discovered by LIGO/Virgo, and these may conceivably be primordial in origin. Furthermore, there are now numerous recent hints for compact bodies constituting (part of) the dark matter. After a general introduction of the topic, I will talk about those, their connection and future detection possibilities.

Speaker: Florian Kühnel (LMU & MPP Munich)

Kuhnel, Florian - GEMMA2 - Rome - Spetember 2024.pdf

Coffee Break

Dark Matter

18 Gravitational Waves from Superradiance Boson Clouds

Black hole superradiance is a mechanism that allows a large cloud of ultralight bosons to grow around spinning black holes, simply through their gravitational interaction. The large amount of energy stored in these clouds is then typically dissipated through the emission of detectable monochromatic gravitational waves. I will focus on superradiance of vector fields that also couple electromagnetically, which results in very luminous boson clouds, emitting across the whole electromagnetic spectrum. The existence of these particles can therefore be revealed through unique multimessanger searches, targeting the combined electromagnetic and gravitational wave emissions.

Speaker: Cristina Mondino (Perimeter Institute for Theoretical Physics)

CMondino_GEMMA2_Sept2024.pdf

19 Direct Searches for Ultralight Dark Matter Using Gravitational-Wave Detectors

An ultralight boson, with a mass smaller than 1 eV, emerges as an intriguing candidate for dark matter (DM). It behaves as classical waves within the Galaxy due to its large occupation number, and its frequency is determined by the boson's mass. Notably, these waves can induce oscillations in mirrors of gravitational-wave interferometers, and hence this type of dark matter can be searched for using detectors like LIGO, Virgo, and KAGRA. In the first half of the talk, I will review recent studies in this direction including our works on searches for dark photon and axion using LIGO and KAGRA. In the latter portion, I will elucidate the statistical properties of the signal and propose an optimal detection strategy.

Speaker: Soichiro Morisaki

GEMMA2.pdf

20 Gravitational-wave event rates as a new probe for dark matter microphysics

Next-generation gravitational-wave (GW) observatories will provide exquisite measurements of the merger rate of high-redshift binary black holes (BBHs), detecting many thousands of these systems every year. The abundance of these binaries is a direct tracer of the early stages of star formation, and therefore of cosmic structure formation. This raises the possibility of using GW observations to probe the microphysical properties of dark matter (DM), particularly warm, fuzzy, or interacting DM models which suppress the matter power spectrum on small scales, and therefore suppress the BBH merger rate.
I will describe recent work to model this suppression using a full end-to-end pipeline from DM model parameters to synthetic populations of BBHs. I will present forecasts for the third-generation GW observatories Einstein Telescope and Cosmic Explorer, showing that these will probe DM-neutrino interactions 100 times weaker than the most stringent present constraints.

Speaker: Alex Jenkins (University College London)

jenkins-gemma2.pdf

Lunch

Gravitational Waves

21 LIGO-VIRGO-KAGRA NETWORK: THE O4 RUN AND BEYOND

The LVK O4 observing run resumed in April. In this talk we will discuss the main public results so far, along with the perspectives for the upgrades of the detectors and the next observation periods.

Speaker: Giovanni Losurdo (Istituto Nazionale di Fisica Nucleare)

GEMMA2_Losurdo_240917.pdf

22 Einstein Telescope, a 3G gravitational wave observatory

The Einstein Telescope (ET) is the planned third-generation gravitational wave (GW) observatory in Europe, expected to start operating in the late 2030s. It will be an underground and cryogenic GW detector, aiming to push the observation horizon to the primordial high-redshift universe, with huge impact on multimessenger astronomy, cosmology, and fundamental physics.
In this talk I will give an overview of ET in the framework of the 3G GW detectors network, with a focus on the technological and engineering challeges of the project, and the environmental noise characterization of the candidate sites.

Speaker: Dr Luca Naticchioni (INFN Roma)

LNat_ET_gemma2024_p.pdf

23 Quantum Noise Reduction with Squeezing in Gravitational Wave Detectors, and upgraded technologies

Quantum Noise (QN) represents one of the main limitations to the Gravitational Wave (GW) interferometers’ sensitivity in all the frequency bandwidth (10Hz - 10kHz) [1, 2, 3]. During the run O3, the implementation of frequency-independent squeezing (FIS) demonstrated powerful quantum shot noise reduction in the high-frequency region above 50 Hz in Virgo and LIGO [4, 5]. Nevertheless, FIS at high frequencies has the drawback effect of increasing the quantum radiation pressure noise in the low frequencies, as also observed in O3 [4, 5, 6], thus demonstrating that from O4 run ahead, to reach a broadband QN Reduction (QNR), GW detectors should implement frequency-dependent squeezing (FDS) [7, 8]. The QNR system of Virgo provides FDS via an upgrade of the existing FIS source used in O3, coupled to a 285m-long detuned filter cavity (FC) [7, 9, 10]. The implementation of the FC required huge infrastructure work in Virgo. Hence, looking forward to post-O5 and the 3rd generation of GW detectors such as the Einstein Telescope (ET), the development of new more compact technologies allowing broadband QNR, without needing external FC could be of great benefit. This is the case of a novel and promising technology based on Einstein Podolsky Rosen (EPR) quantum entanglement. For this aim, we are setting up a compact experiment in the R&D squeezing laboratories of Virgo to measure the effect of EPR-FDS in the audio band region of interest of ground-based GW detectors [15]. After an introduction to QNR in GW detectors, I will focus on the squeezing techniques implemented in O3, the newly introduced for O4. I will conclude by mentioning a new and highly promising alternative FDS technique in view of post-O5 and ET.

References
[1] F. Acernese et al., Class. Quantum Grav., 32, 024001 (2015) AdV
[2] J. Asii et al., Class. Quantum Grav., 32, 074001 (2015) AdLIGO
[3] Y. Aso et al., Phys. Rev. D 88 043007 (2013)
[4] F. Acernese et al., Phys. Rev. Lett. 123, 231108 (2019)
[5] M. Tse et al., preceding Letter, Phys. Rev. Lett. 123, 231107 (2019) FIS in O3 LIGO
[6] F. Acernese et al., Phys. Rev. Lett. 125, 131101 (2020)
[7] F. Acernese et al., Phys. Rev. Lett. 131, 041403 (2023)
[8] L. McCuller et al. Phys. Rev. Lett. 124, 171102 (2020)
[9] S. Di Pace, and on behalf of the Virgo Collaboration, Phys. Scr. 96 124054 (2021)
[10] V. Sequino, Phys. Scr. 96 104014 (2021)
[11] V. Sequino, et al. Proc. of the GRavitational-waves Science&technology Symposium (GRASS) 2019, zenodo, (2020) DOI: https://zenodo.org/records/3554320

Speaker: Sibilla Di Pace (Istituto Nazionale di Fisica Nucleare)

VIR-0512B-24-QNRinGWdetectorsAndUpgradedTechnologies_DIPACES-GEMMA2.pdf

Coffee Break

Gravitational Waves

24 Time-delay interferometry as a coronagraph

The Laser Interferometer Space Antenna (LISA) will be a space-borne gravitational wave (GW) detector to be launched in the next decade. Central to LISA data analysis is time-delay interferometry (TDI), a numerical procedure which drastically reduces otherwise overwhelming laser frequency noise. LISA data analysis is usually performed on sets of TDI variables, e.g. Michelson variables (X, Y, Z) or quasiorthogonal variables (A, E, T ). We investigate a less standard TDI variable denoted κ which depends on time, or frequency, and two parameters (β, λ). This so-called coronagraphic TDI variable has the singular property of canceling GW signal when (β, λ) tend to the sky position of the GW source. Thanks to this property, coronagraphic TDI has the potential to be an efficient model-agnostic method for sky localization of GW sources with LISA. Those characteristics make it relevant for low-latency searches and a possible glitch veto. Although briefly discussed in the literature, coronagraphic TDI has only been tested on theoretical grounds. We validate the applicability of κ to sky localization of typical LISA sources, namely Galactic binaries (GBs) and massive black hole binaries (MBHBs), when considering a simplified LISA instrument. The goal is to pave the way for applications of coronagraphic TDI to practical LISA data analysis problems. In fact, within the context of low-latency searches coronagraphic TDI can, in principle, be used to send alerts to other observatories thus enhancing the chance of detection of electromagnetic counterparts.

Speaker: Raissa Costa Barroso

RaissaCostaBarroso_gemma2.pdf

25 Deep learning methods for the analysis of gravitational wave data

Gravitational waves have opened a new window on the cosmos and revolutionized our view of astrophysical phenomena. Current ground-based interferometers such as Advanced LIGO, Virgo and KAGRA are currently the most sensitive detectors and form a worldwide network capable of rapid detection and localization of gravitational wave signals of coalescence of compact binary systems. Nearly real-time analysis of transient sources is a key requirement to issue alerts for gravitational wave signals and trigger electromagnetic follow-up campaigns. The large amount of data produced by interferometers and the need for fast analysis pose several challenges from the data analysis point of view. Machine learning is a promising approach to tackle this challenge and offers viable solutions to boost our capabilities of analyzing gravitational wave data. In particular, deep learning-based architectures have been shown to be effective in various fields of data analysis, from noise studies to source detection. I will review the main applications of deep learning to gravitational wave data analysis, encompassing studies on detector noise and detection of transient and persistent sources.

Speaker: Massimiliano Razzano (University of Pisa and INFN-Pisa)

2024_09_16_deeplearning_gemma2-razzano-v5.pdf

26 Astrophysical implications of compact binary observations with gravitational waves

The first half of LIGO-Virgo-KAGRA's (LVK) fourth observing run (O4) concluded earlier this year. During the eight-month observation period, the number of gravitational-wave candidates has almost doubled compared to the total number of events reported from the first three observing runs combined (O1, O2, and O3) and includes the gravitational-wave event GW230529; a gravitational-wave signal from the merger of a neutron star and a ~3.6 compact object located in the region between neutron star and black hole masses. The properties we infer from these observations have broad implications for the physics and evolution of massive stars, supernova mechanisms, our understanding of different subpopulations of compact binary systems and more. In this talk, I will discuss some of the open questions in gravitational-wave astronomy following O3 and the prospects for improving our understanding of these questions with O4 and beyond.

Speaker: Shanika Galaudage (Observatoire de la Côte d'Azur)

Galaudage_GEMMA2.pdf

27 Impact of coalescence signals on continuous gravitational waves searches

This study investigates the influence of a spectrum of gravitational wave signals from coalescing binaries on the search for continuous waves (CWs) in the Einstein Telescope and during Virgo O5.
With the forthcoming upgrades to current detectors and the advent of third-generation detectors, an increased number of inspiral compact object cycles in the frequency band will be detected, leading to potential signal superpositions. We simulate the spectrum of coalescence signals, focusing on the low-frequency range of 1-10 Hz, where these signals are expected to be prevalent.
Coalescence signals, especially at low frequencies, act as noise and must be accounted for in the construction of the background for CW detection and analysis. This work aims to quantify the impact of these signals on CW searches, enhancing our understanding and improving detection methods.

Speaker: Elena Codazzo (Università di Cagliari)

GEMMA_Codazzo.pdf

Wednesday, 18 September

MultiMessenger

28 NGC 1851E: A millisecond pulsar in a binary system with a compact companion in the mass gap between neutron stars and black holes

Since March 2019, a large international collaboration (known as “Transients and Pulsars with MeerKAT”, or “TRAPUM”) has been using the 64-antenna MeerKAT radio telescope array in South Africa to search for pulsars in globular clusters. These surveys have been exceptionally successful, with the discovery of almost 100 new pulsars in globular clusters, which represent one third of the current pulsar population in globular clusters.
Among these discoveries is a set of 14 new pulsars in the globular cluster NGC 1851, where only one pulsar was previously known (NGC 1851A). One of the newly discovered pulsars (NGC 1851E) is quite extraordinary: it is in an usually eccentric orbit with a very unusual companion. The latter has a mass that is intermediate between the most massive neutron stars known and the lightest known black holes. From considerations on stellar evolution, we can conclude that this system formed in a binary exchange, which is only likely to happen in the dense environment of a globular cluster.
Similarly massive objects have been discovered in merging binaries with the LIGO and Virgo interferometers; but were until now undetected in our Galaxy. The discovery of a millisecond pulsar orbiting one of these objects implies that we will be able to study its properties in some detail in the near future by measuring relativistic effects in the orbit of the millisecond pulsar. A particularly exciting possibility is that this massive companion is a black hole that formed in the merger of two neutron stars, in which case it will be spinning very fast. This will cause an observable relativistic precession of the orbital plane, an effect known as Lense-Thirring precession. Measuring this effect we will be able to gain some insight into the origin of the companion and possibly test the cosmic censorship hypothesis of general relativity.

Speaker: Paulo Freire (Max Planck Institute for Radio Astronomy)

29 Searching for Radio and Gamma-ray Millisecond Pulsars with MeerKAT

TRAnsients and PUlsars with MeerKAT (TRAPUM) is a large survey project using the new MeerKAT radio interferometer to search for pulsars in the southern sky. TRAPUM's targeted searches of globular clusters, nearby galaxies, Galactic nebulae, and gamma-ray sources have led to the discovery of around 150 new pulsars, the majority of which are millisecond pulsars (MSPs) in binary systems. In this talk, I will focus on 35 of these new MSPs that were found in TRAPUM's survey of unidentified Fermi-LAT gamma-ray sources, and on the multi-wavelength and multi-messenger follow-up science that can be performed with them. Many of these new MSPs are in "spider" binary systems, where optical light-curve modelling allows us to probe the upper limits of the pulsar mass distribution to help constrain the neutron star equation-of-state. I will also describe how joint radio and gamma-ray timing of these new MSPs provides 16-year ephemerides that enable searches for continuous gravitational waves in archival LIGO data, and allows these pulsars to join ongoing pulsar timing array projects searching for the stochastic gravitational wave background.

Speaker: Colin Clark (Max Planck Institute for Gravitational Physics / Leibniz Universität Hannover)

CJC_TRAPUM_Fermi_GEMMA2.pdf

30 X-ray pulse profile modeling

X-ray pulses of rapidly rotating neutron stars (NSs) can be used to probe both the properties of heated surface regions of a NS and the equation of state (EoS) of high-density matter inside a NS. Constraints on the EoS are obtained by measuring the mass and radius of the NS based on the relativistic effects when photons travel from the stellar surface to the observer. During the last few years, NICER telescope has been used to study several rotation-powered millisecond pulsars using this technique. I will review our latest analysis for the first published pulsar PSR J0030+0451, the massive pulsar PSR J0740+6620, and the brightest pulsar PSR J0437−4715. In addition, I will discuss our recent progress in applying the pulse profile modeling method to accretion and thermonuclear-powered millisecond pulsars.

Speaker: Tuomo Salmi (University of Helsinki)

PP_tsalmi_GEMMA2_rome_2024_v3.pdf

Coffee Break

MultiMessenger

31 Rapid prediction of kilonova light curves from gravitational wave signals for observed binary neutron star coalescences

Kilonovae are the optical counterparts to gravitational wave emissions, which are produced by the radioactive decay of heavy elements formed through rapid neutron captures following neutron star mergers. Combining the gravitational wave and kilonova information reveals the characteristics of dense matter, as well as the physical properties of neutron stars such as the equation of state. To effectively observe and study these electromagnetic transients, predictions of kilonova light curves are required for neutron star coalescences with gravitational wave detections. However, generating large amounts of light curves using current theoretical models is time-consuming and computationally expensive. In this study, we use a normalised flow machine learning model trained on light-curve data from theoretical kilonova models, which can rapidly predict consistent kilonova light curves based on only the mass and tidal deformability information of neutron stars. This machine-learning model can then be used as a tool to inform follow-up strategies in the optical and near-infrared bands for the following gravitational wave observation run.

Speaker: Xiaofei Dong (University of Glasgow)

GEMMA2_XiaofeiD.pdf

32 Determination of microscopic dynamics of dense matter from gravitational and electromagnetic observations

The availability of accurate astronomical data collected by electromagnetic observatories and gravitational-wave (GW) interferometers, supplemented by the information obtained from Earth-based laboratory experiments, has opened a new era for the investigation of nuclear dynamics in dense matter. Besides being a valuable source of information on average properties, such as the Equation of State (EOS), the new data will provide an unprecedented opportunity to constrain the underlying dynamical models at supranuclear density. I will report the results of a recent analysis, suggesting that the advent third-generation GW interferometers will allow a reliable determination of the strength of
irreducible repulsvive interactions involving three nucleons, which are know to drive the stiffness of the EOS at large density.

Speaker: Omar Benhar (Istituto Nazionale di Fisica Nucleare)

benhar_GEMMA2.pdf

33 Numerical Simulations of Dark Matter Admixed Binary Neutron Star Mergers Using the BAM Code

We present the first application of the BAM code for numerical-relativity simulations of neutron stars (NS) admixed with fermionic dark matter (DM). Employing the Sly4 Equation of State (Sly4) for baryonic matter and treating dark matter as a non-interacting fluid, we investigate the impact of a varying dark matter fraction (0%, 3%, and 15% of the gravitational mass) on the merger dynamics, ejecta mass, post-merger remnant properties, and emitted gravitational waves. Our findings reveal significant alterations in the merger process due to the presence of dark matter. The simulations predict a decrease in the remnant’s lifetime with increasing dark matter content for DM core configurations, potentially favoring a prompt collapse to a black hole. Additionally, the ejected material and the emitted gravitational wave signature exhibit deviations from their DM-free counterparts. These unprecedented results pave the way for a deeper understanding of DM influence on BNS mergers and offer crucial benchmarks for future observations from advanced gravitational-wave detectors and multi-messenger astronomy.

Speaker: Edoardo Giangrandi (University of Coimbra, University of Potsdam)

Lunch

Gravitational Waves

34 A non-template-based data analysis approach to detect continuous gravitational waves from targeted neutron stars at dual harmonics

A biaxial or triaxial neutron star rotating about a non-principal axis of inertia emits a dual harmonic gravitational wave. i.e., gravitational wave at its rotational frequency and twice its rotational frequency. Those signals undergo modulations due to Earth's rotation and orbital motion, which create frequency shifts and side bands in the signal when they reach the gravitational wave detectors at Earth. We implemented high-order statistics such as bispectrum and bicoherence (a normalization of bispectrum) to search for the dual harmonics signal of targeted neutron stars and study them with the simulations. We show our detection results from the simulation and compare them with template-based analysis.

Speaker: Sudhagar Suyamprakasam (Nicolaus Copernicus Astronomical Center Polish Academy of Sciences, Poland)

sudhagar_GEMMA2-2024.pdf

35 LongFT: making exact computation of very long Fourier transforms accessible to everyone

This work discusses the implementation of LongFT: a procedure to enable the exact computation of very long Fourier transforms without the need of expensive supercomputers with TeraBytes of RAM.

Our software tool will let independent researchers and/or small research groups worldwide to perform uncompromised spectral analyses, even when low in budget or computing resources.

LongFT has its perfect application in the analysis of persistent narrowband signals, such as the still-to-be-detected Continuous Gravitational Waves.

To showcase its strength, we tailor LongFT to Continuous Gravitational Wave searches, applying the algorithm to the most recent (time-domain) O3b public dataset released by the LVK Collaboration via the Gravitational Wave Open Science Center (GWOSC).
Using just a regular workstation, we compute a single exact Fourier transform of approximately 6 months of 4 kHz Float64 data.
With the results, we create the (frequency-domain) O3b-FD dataset and release it to the public under a Creative Common license.

This O3b-FD open dataset will allow for easy, fast and lightweight handling of exact frequency-domain data. It will thus enhance the sensitivity of existing computing-bounded search algorithms.

The LongFT software and the O3b-FD dataset will let researchers worldwide to more easily contribute to the search for Continuous Gravitational Waves, thus accelerating their (hopefully upcoming) discovery.

Speaker: Federico Muciaccia (Istituto Nazionale di Fisica Nucleare)

36 Follow-up a signal deepened into noise: the challenge of blind continous gravitational wave searches

The impressive computational cost required to probe a vast parameter space forces blind searches for Continuous Gravitational Waves (CW) to undertake a semi-coherent approach. On top of that, the sensitivity to CW depends on the coherent segment's length and obviously on the total observation time. Hence, searches have to be supported by follow-up pipelines where this baseline is gradually increased. Since follow-ups have to deal with $O(10^{5-6}$) outliers, their tuning is of crucial importance towards the first detection. In fact, just by accepting more candidates, searches can achieve better sensitivities at the price of higher false alarm probabilities.
Starting from a brief introduction to blind searches, this talk will focus on follow-up pipelines. Lastly, implications on sensitivities will be discussed.

Speaker: Lorenzo Mirasola (Istituto Nazionale di Fisica Nucleare)

GEMMA2 talk.pdf

GEMMA2 talk.pptx

37 Chemically-Homogeneous Evolution: Impacts on Stellar Populations and Compact Binary Mergers

Compact binary mergers mark the final stage of a complex journey that begins with massive star binaries. Within the isolated channel, binaries undergo intricate processes, including mass transfer and tidal interactions, ultimately giving rise to neutron stars or black holes. Notably, chemically-homogeneous evolution, prevalent in metal-poor binary systems, significantly influences this process by triggering rapid spin increases and subsequent changes in stellar properties.
In my talk, I will present the effects of chemically-homogeneous evolution both on observable stellar populations and the detectability of compact binary mergers using gravitational wave interferometers. My population-synthesis simulations reveal how chemically-homogeneous evolution alters the ratio of red supergiants to Wolf-Rayet stars, dramatically affecting stellar populations potentially observable through electromagnetic observations. Notably, Wolf-Rayet stars produced by chemically-homogeneous evolution are, on average, more massive, more numerous, and more luminous than Wolf-Rayet produced either via single or common binary evolution. The effects of chemically-homogeneous evolution are eventually inherited by the compact objects produced by these stellar progenitors: neutron star production is suppressed in favor of black holes, leading to an increased ratio of binaries composed of neutron stars and black holes or massive black holes. Conversely, chemically-homogeneous evolution strongly suppresses the production of compact binary mergers. These findings emphasize the intricate interplay between chemically-homogeneous evolution, stellar populations, and compact binary mergers.

Speaker: Marco Dall'Amico (Istituto Nazionale di Fisica Nucleare)

DallAmico.pdf

Coffee Break

Poster Session

Free hours

Social Dinner: Please note that the Cialone Bus will depart at 19:15 from Piazzale Aldo Moro 2

Thursday, 19 September

Gravitational Waves

38 The Future of Gravitational-Wave Astronomy

Since the groundbreaking first detection of gravitational waves (GWs) from merging black holes and neutron stars in 2015, current ground-based GW detectors have identified around 100 such events. These discoveries have unveiled the mass and spin distributions of stellar-mass black holes, provided new insights into the behavior of superdense matter, and offered an independent measurement of the Universe’s expansion rate.

The next-generation ground-based GW detectors will achieve a tenfold increase in sensitivity, extending our reach to far greater cosmological distances. Complementing this, the European Space Agency’s adoption of the proposed space-based mission LISA will allow us to explore a broader range of frequencies and uncover entirely new GW sources. Together, these instruments will enable some of the most precise tests of the laws of physics across various scales.

In this talk, I will explore the scientific potential of upcoming GW detectors like the Einstein Telescope and Cosmic Explorer, while also touching on space-based detectors and specialised high-frequency detectors.

Speaker: Patricia Schmidt (University of Birminham)

Schmidt.pdf

MultiMessenger

39 Envisioning Tomorrow: INAF prospects and challenges for multi-messenger astronomy in the era of Einstein Telescope

INAF will play a key role in the newborn multi-messenger astronomy field allowing us to study and identify the likely faint and rapidly fading electromagnetic counterparts of the hundreds gravitational wave (GW) events expected by the 2nd generation GW detectors network at full sensitivity together with upcoming electromagnetic facilities like Rubin telescope.
In this talk, I will present all the activities we are carrying out to optimize the response of the Italian and European network of facilities to expected GW triggers, and how the team is working in the context of the search for electromagnetic counterparts of GW sources and their spectroscopic characterization, also in anticipation of the arrival of the Einstein Telescope, in which our large community is involved.
All the activities are expected to provide means and opportunities to the Italian and European astronomical communities to have a leading role in the GW and Time Domain Astronomy.

Speaker: Silvia Piranomonte (INAF - Osservatorio Astronomico di Roma)

Envisioning Tomorrow INAF prospects and challenges for multi-messenger astronomy in the era of Einstein Telescope (4).pdf

Gravitational Waves

40 Tests of general relativity with LIGO-Virgo-KAGRA data

The first three observing runs of the Advanced LIGO-Virgo-KAGRA detector network have led to the detection of about 90 compact binary coalescences, mergers of binaries of black holes or neutron stars. These observations have given us access to an otherwise uncharted regime of dynamical strong-field gravity. In this talk we briefly review the many tests of general relativity performed with these detections and the search for exotic behaviour which can be demonstrated by compact objects mimicking black holes.

Speaker: Archisman Ghosh (Ghent University)

ag_gemma_v2.pdf

Coffee Break

Gravitational Waves

41 Cosmology with gravitational waves

Gravitational wave signals from compact binary mergers are excellent cosmological probes due to their ability to act as standard sirens: objects with measured luminosity distance which is independent of the cosmic distance ladder. This opens up new ways of measuring cosmological parameters, which is particularly relevant in the era of the so-called "Hubble tension". However, in order for this measurement to be made, additional redshift information is required. In the scenario where the merger is observed without a confirmed electromagnetic counterpart - true for all but one of the detections from the LIGO-Virgo-KAGRA collaborations to date - galaxy surveys, and the population of gravitational waves themselves, can be used to provide this missing information. I will introduce the latest developments to this method, which allow both sources of redshift information to be used simultaneously to measure cosmological parameters and compact binary population parameters, and discuss what this means for the field moving forwards.

Speaker: Rachel Gray (University of Glasgow)

Gray_GEMMA2.pdf

42 Synergies between gravitational-wave and dark-matter detection

Dark matter could compose ~80% of all matter in the universe, and yet it is completely invisible to us. Despite decades of experiments designed to detect dark matter, and numerous models for potential dark matter particles, no concrete evidence has been put forward to support the existence of beyond standard-model physics. Because of this, it is worth asking whether approaching the detection of dark matter from a different point of view, that is, via gravitational waves, could provide some insight into explaining the origin of dark matter. In this talk, I discuss the prospects for using gravitational-wave interferometers to search for dark matter in two forms: ultralight particle dark matter and sub-solar mass primordial black holes. While not designed to search for dark matter, gravitational-wave detectors can robustly probe a variety of dark-matter models simultaneously, without affecting their sensitivity to canonical gravitational-wave sources, and put competitive and sometimes even stronger constraints than those from other experiments designed to search for dark matter.

Speaker: Andrew Miller (Nikhef / Utrecht University)

gemma2_talk.pdf

Dark Matter

43 Ultralight dark matter search with KAGRA -O3GK result and what's next?-

Among various dark matter (DM) candidates, ultralight bosonic fields can be explored by using gravitational wave laser interferometers. For example, massive vector fields weakly coupled to the standard model particles yield oscillating forces acting on the test masses. In this context, KAGRA has a unique feature due to differing compositions of its mirrors, enhancing the signal of vector DM in the length change in the auxiliary channels. Here I present the first result of $U(1)_{B−L}$ gauge boson DM search using the KAGRA data from O3GK run. The result is derived from a newly developed pipeline, which properly takes into account the stochastic nature of ultralight DM. I'll also discuss the application of our pipeline to the planned axion DM search.

Speaker: Jun'ya Kume (University of Padova, Istituto Nazionale di Fisica Nucleare Sezione di Padova)

DM_KAGRA_GEMMA2_JK.pdf

Lunch

Dark Matter

44 Atom interferometer searches for spin-2 ultra-light dark matter

Atom interferometers are a new class of quantum sensors capable of making precision measurements in many areas of fundamental physics including gravitational wave and ultra-light dark matter (ULDM) searches. While the sensitivity of atom interferometers to scalar ULDM has been established [arXiv: 1911.11755; arXiv: 2308.10731], spin-2 ULDM models are also well motivated but have yet to be fully explored. In this talk I will outline the phenomenology of spin-2 ULDM in atom interferometers and discuss how best to optimise searches by operating multiple experiments in a network. Existing laser interferometer searches for spin-2 ULDM will be complemented by atom interferometers by probing different mass parameter space and offering a distinct method of detection. Not only will spin-2 ULDM induce a change in the laser phase measured in the interferometer but will additionally couple directly to the internal energy states of the atoms. Atom interferometers are uniquely sensitive to both effects, which will enhance the limits these experiments will place on spin-2 ULDM and help distinguish these signals from scalar candidates. Work in collaboration with Diego Blas and Christopher McCabe.

Speaker: John Carlton (King's College London)

GEMMA2_Carlton_spin-2.pdf

45 Analytical gravitational waveforms with dark matter calibrated to N-body simulations

Dark matter overdensities, called 'spikes', can be present around intermediate-mass black holes [1]. It has been suggested that these can be detected in the GW signal of an intermediate mass ratio inspiral (IMRI) composed of secondary black hole or neutron star orbiting the primary black hole, and interacting with the spike via dynamical friction. However, the standard treatment [2] does not account for the feedback of dynamical friction onto the spike itself --- but energy conservation arguments [3] show that the energy transferred from the binary to the spike is much larger that the binding energy of the spike itself, so cannot be neglected. Thanks to the HaloFeedback code [3], it was found that the spike in fact dramatically depletes, thus reducing the observed effect by orders of magnitude, but still being detectable by LISA. Subsequent N-body simulations [4,5] showed that HaloFeedback is qualitatively correct, but does not correctly capture the precise dynamics of the depletion, in particular due to the neglect of three-body interactions. However, N-body simulations are extremely long to run and are not adapted for data-analysis oriented waveform templates. Here, we present preliminary work on the construction of a simple semianalytical "effective density" model, calibrated on the N-body simulations. This will yield a fast waveform template for circular orbits, which will account for this effect with the correct order of magnitude [contrary to all previous analytical models].

[1] P. Gondolo and J. Silk, Phys.Rev.Lett. 83, 1719 (1999), astro-ph/9906391
[2] K. Eda, Y. Itoh, S. Kuroyanagi, and J. Silk, Phys.Rev.Lett. 110, 221101 (2013), 1301.5971
[3] B. Kavanagh, D. Nichols, G. Bertone, and D. Gaggero, Phys.Rev.D 102, 083006 (2020), 2002.12811
[4] D. Mukherjee, A. Miguel Holgado, G. Ogiya, and H. Trac (2023), arXiv:2312.02275
[5] B. Kavanagh, T. Karydas, G. Bertone, P. Di Cintio and M. Pasquato (2024), 2402.13762

Speaker: David Trestini (FZU (Institute of Physics of the Czech Academy of Sciences))

david_trestini_GEMMA2.pdf

46 Bayesian inference on dark matter admixed neutron star mergers with gravitational-wave data

Dark matter makes up a large portion of matter in the Universe and, thus, could be present inside compact objects such as neutron stars. Until today, little is known about its composition, fraction and particle mass. However, multi-messenger data, such as gravitational-wave as well as electromagnetic radiation, can in principle be used to study dark matter admixed neutron stars, which would pave a new way to constrain the properties of dark matter. In this study, we present a new feature of the nuclear physics multi-messenger framework "NMMA" to sample over the dark matter mass and fraction in addition to the usual sampling on the neutron star equation of state. We present our analysis of GW170817 under the assumption that dark matter is present as non-interacting Fermi gas as well as first results for synthetic data assuming the Einstein telescope as gravitational-wave detector.

Speaker: Nina Kunert (Institute for Physics and Astronomy, University of Potsdam, D-14476 Potsdam, Germany)

GEMMA2_NK.pdf

47 Searching for dark matter signatures in the 21cm signal

The 21cm signal is a promising observable that has the potential to probe uncharted regions of our Universe, thereby presenting an opportunity to challenge the standard model and perhaps discover new physics. In this talk I will discuss how we can exploit the spatial fluctuations in the signal to study exotic models of dark matter. I will focus on two popular dark matter candidates, fuzzy dark matter (FDM) and scattering dark matter (SDM). Despite the high uncertainty in the astrophysics that control the signal, our analysis shows that 21cm interferometers, such as HERA, will be sensitive enough to probe FDM and SDM in regions in the parameter space that haven’t been ruled out by other observations. With the new cosmological tool we have developed, 21cmFirstCLASS, a merger of the well known codes 21cmFAST and CLASS, I will demonstrate how a joint analysis of 21cm and CMB can relax degeneracies between the cosmological parameters and improve their constraints considerably.

Speaker: Jordan Flitter (Ben-Gurion University)

21cm DM constraints - GEMMAII 2024.pdf

Coffee Break

MultiMessenger

48 Multimessenger signals from axion star mergers

Axion dark matter can form stable, self-gravitating objects called axion stars, which are made unstable above a critical mass by their coupling to electromagnetism. In this talk, using numerical relativity, I will demonstrate how two sub-critical axion stars can merge and form a more massive, excited and critical star, which consequently decays through electromagnetic radiation. The whole process gives out a rich multimessenger signal including gravitational waves, electromagnetic radiation, and axion radiation, providing a new avenue for dark matter detection efforts.

Speaker: Liina Chung-Jukko (King's College London)

Pacmans at GEMMA2 - PDF.pdf

49 Magnetars and Fast Radio Bursts: a new connection?

Over 15 years since their discovery, the origin of fast radio bursts (FRBs) still eludes us, despite outstanding progress both observationally and theoretically. The huge FRB luminosities, the apparent dichotomy between one-offs and repeaters, and the lack of bright FRB sources in the local Universe, are just some of the theoretical challenges still facing us. Among the countless theoretical interpretations, many authors proposed that (at least some) FRB sources be related to the cosmic population of magnetars. Observations lend support to this hypothesis, as the galactic magnetar SGR 1935+215 is the only known astrophysical source from which FRB-like radio emission has been detected. I will summarize the main advantages, and some shortcomings, of magnetar-based FRB models and will introduce a new paradigm that holds the potential to overcome the main hurdles, to explain at once the rare repeaters and the numerous one-off sources, and to even bridge the gap between the apparent paucity of FRBs from local magnetars and their comparatively large all-sky rate.

Speaker: Simone Dall'Osso

50 Fast optical variability in the sky: millisecond pulsars and more

Millisecond pulsars are the fastest-spinning compact stars in the Universe. They are prime targets to probe the strong interaction at supranuclear densities and search for continuous gravitational wave sources. A long-standing paradigm assumes that a millisecond pulsar in a binary system, during its evolution, can be powered either by the rotation of the pulsar's magnetic field or by the accretion of plasma from a companion star. The discovery of optical pulsations from a pair of millisecond pulsars by the fast optical photometer SiFAP2 at the INAF/TNG has recently challenged this standard scenario. The high optical pulsed luminosity cannot be explained by emission mechanisms commonly operating in binary pulsars, such as accretion-powered emission. The coherent variability observed at optical and X-ray energies suggests that the acceleration of charged particles to extremely high speeds can occur in the magnetosphere of a neutron star even when it is engulfed with accreting matter. Thanks to the much higher sensitivity granted by the throughput of optical photons compared to higher energies, fast optical astronomy also has the potential to open a discovery window on continuous gravitational wave sources, magnetars, and fast radio bursts. In this presentation, I will present the first results obtained with SiFAP2 and prospects for the near future.

Speaker: Arianna Miraval Zanon (Agenzia Spaziale Italiana)

GEMMA2_2024.pdf