LOFAR 144-MHz follow-up observations of GW170817

ABSTRACT We present low-radio-frequency follow-up observations of AT 2017gfo, the electromagnetic counterpart of GW170817, which was the first binary neutron star merger to be detected by Advanced LIGO–Virgo. These data, with a central frequency of 144 MHz, were obtained with LOFAR, the Low-Frequency Array. The maximum elevation of the target is just 13${_{.}^{\circ}}$7 when observed with LOFAR, making our observations particularly challenging to calibrate and significantly limiting the achievable sensitivity. On time-scales of 130–138 and 371–374 d after the merger event, we obtain 3σ upper limits for the afterglow component of 6.6 and 19.5 mJy beam−1, respectively. Using our best upper limit and previously published, contemporaneous higher frequency radio data, we place a limit on any potential steepening of the radio spectrum between 610 and 144 MHz: the two-point spectral index $\alpha ^{610}_{144} \gtrsim$ −2.5. We also show that LOFAR can detect the afterglows of future binary neutron star merger events occurring at more favourable elevations.

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Using negative-latency gravitational wave alerts to detect prompt radio bursts from binary neutron star mergers with the Murchison Widefield Array

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slz129 ◽

2019 ◽

Vol 489 (1) ◽

pp. L75-L79 ◽

Cited By ~ 5

Author(s):

Clancy W James ◽

Gemma E Anderson ◽

Linqing Wen ◽

Joel Bosveld ◽

Qi Chu ◽

...

Keyword(s):

Neutron Star ◽

Gravitational Wave ◽

Radio Signal ◽

Low Frequency ◽

Positional Accuracy ◽

Binary Neutron Star ◽

Observational Mode ◽

Fast Radio Burst ◽

Murchison Widefield Array

ABSTRACT We examine how fast radio burst (FRB)-like signals predicted to be generated during the merger of a binary neutron star (BNS) may be detected in low-frequency radio observations triggered by the aLIGO/Virgo gravitational-wave detectors. The rapidity, directional accuracy, and sensitivity of follow-up observations with the Murchison Widefield Array (MWA) are considered. We show that with current methodology, the rapidity criterion fails for triggered MWA observations above 136 MHz for BNS mergers within the aLIGO/Virgo horizon, for which little dispersive delay is expected. A calculation of the expected reduction in response time by triggering on ‘negative latency’ alerts from aLIGO/Virgo observations of gravitational waves generated by the BNS inspiral is presented. This allows for observations up to 300 MHz where the radio signal is expected to be stronger. To compensate for the poor positional accuracy expected from these alerts, we propose a new MWA observational mode that is capable of viewing one-quarter of the sky. We show the sensitivity of this mode is sufficient to detect an FRB-like burst from an event similar to GW 170817 if it occurred during the ongoing aLIGO/Virgo third science run (O3).

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Gamma-Ray Bursts and Binary Neutron Star Mergers

Symposium - International Astronomical Union ◽

10.1017/s0074180900055959 ◽

1996 ◽

Vol 165 ◽

pp. 489-502

Author(s):

Tsvi Piran

Keyword(s):

Neutron Star ◽

Gravitational Radiation ◽

Gamma Ray ◽

Indirect Evidence ◽

Gamma Ray Bursts ◽

Binary Neutron Star ◽

Merger Event ◽

Γ Rays ◽

Γ Ray ◽

The One

Neutron star binaries, such as the one observed in the famous binary pulsar PSR 1913+16, end their life in a catastrophic merger event (denoted here NS2M). The merger releases ∼5 1053 ergs, mostly as neutrinos and gravitational radiation. A small fraction of this energy suffices to power γ-ray bursts (GRBs) at cosmological distances. Cosmological GRBs must pass, however, an optically thick fireball phase and the observed γ rays emerge only at the end of this phase. Hence, it is difficult to determine the nature of the source from present observations (the agreement between the rates of GRBs and NS2Ms providing only indirect evidence for this model). In the future a coinciding detection of a GRB and a gravitational-radiation signal could confirm this model.

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Identifying Quark Matter in Hybrid Stars through Relativistic Tidal Deformations

Universe ◽

10.3390/universe5090193 ◽

2019 ◽

Vol 5 (9) ◽

pp. 193

Author(s):

Bryen Irving ◽

Thomas Klähn ◽

Prashanth Jaikumar ◽

Marc Salinas ◽

Wei Wei

Keyword(s):

Neutron Star ◽

Parameter Space ◽

Quark Matter ◽

Specific Model ◽

Nuclear Model ◽

Hartree Fock ◽

Binary Neutron Star ◽

Merger Event ◽

Hybrid Stars ◽

Parameter Ranges

We study a specific model of neutron star matter that supports a phase transition to quark matter at high density and examine parameter ranges for consistency with the mass-weighted tidal deformability of Λ ˜ = 300 − 230 + 420 for a mass ratio of q ∈ [ 0.73 , 1.0 ] , as inferred from observations of gravitational waves from the binary neutron star merger event GW170817. By using this observation to restrict the parameter space for the equation of state (EoS) model used throughout this study, we aim to assess the possibility of a potential solution to the masquerade and flavor camouflage problems for hybrid EoS models. Assuming the two stars have the same EoS, in which the Dirac-Brueckner-Hartree Fock (DBHF) nuclear model transitions to the vBag quark model, we see if the parameter space of these hybrid model stars are restricted due to the adherence to the reported Λ 1.4 ∈ 70 , 580 and M m a x ∈ [ 2.01 , 2.16 ] M ⊙ constraints. Upon completion, we find that, while the parameter space for our model does get restricted, it does not ultimately resolve the masquerade and flavor camouflage problems.

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Variability in extragalactic class I methanol masers: new maser components towards NGC 4945 and NGC 253

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz3098 ◽

2019 ◽

Vol 491 (4) ◽

pp. 4642-4655

Author(s):

T P McCarthy ◽

S P Ellingsen ◽

S L Breen ◽

M A Voronkov ◽

X Chen ◽

...

Keyword(s):

Class I ◽

Continuum Emission ◽

Imaging Procedures ◽

Upper Limit ◽

Upper Limits ◽

Maser Line ◽

Density Values ◽

Methanol Masers ◽

Compact Array

ABSTRACT We have used the Australia Telescope Compact Array (ATCA) to make new observations of the 36.2-GHz (4−1 → 30E) methanol transition towards NGC 4945 and NGC 253. These observations have revealed the presence of new maser components towards these galaxies, and have provided the first clear evidence for variability in extragalactic class I methanol masers. Alongside the new observations of NGC 4945 and NGC 253, we present the results of recent 36.2-GHz methanol maser searches towards 12 galaxies, placing upper limits on the emission from the 36.2-GHz class I transition and the 37.7-GHz (72 → 81E) class II maser line towards these sources. Flux density values for the 7-mm continuum emission towards these sources are also reported where applicable. A re-analysis of the published 36.2-GHz methanol observations of Arp 220 undertaken as part of the search revealed some issues with previous imaging procedures. The re-analysis, combined with non-detections in independent follow-up observations, suggests that there is no 36.2-GHz methanol emission towards Arp 220 stronger than 3.5 mJy in a 10 km s−1 channel (5σ upper limit).

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Probing binary neutron star mergers in dense environments using afterglow counterparts

Astronomy and Astrophysics ◽

10.1051/0004-6361/201937115 ◽

2020 ◽

Vol 639 ◽

pp. A15

Author(s):

Raphaël Duque ◽

Paz Beniamini ◽

Frédéric Daigne ◽

Robert Mochkovitch

Keyword(s):

Neutron Star ◽

Gravitational Wave ◽

Indirect Evidence ◽

High Sensitivity ◽

Small Sample ◽

High Density ◽

Binary Neutron Star ◽

Delay Times ◽

Wave Event

The only binary neutron star merger gravitational wave event with detected electromagnetic counterparts recorded to date is GRB170817A. This merger occurred in a rarefied medium with a density smaller than 10−3 − 10−2 cm−3. Since kicks are imparted to neutron star binaries upon formation, and due to their long delay times before merger, such low-density circum-merger media are generally expected. However, there is some indirect evidence for fast-merging or low-kick binaries, which would coalesce in denser environments. Nonetheless, present astronomical data are largely inconclusive on the possibility of these high-density mergers. We describe a method to directly probe this hypothetical population of high-density mergers through multi-messenger observations of binary neutron star merger afterglows, exploiting the high sensitivity of these signals to the density of the merger environment. This method is based on a sample of merger afterglows that has yet to be collected. Its constraining power is large, even with a small sample of events. We discuss the method’s limitations and applicability. In the upcoming era of third-generation gravitational wave detectors, this method’s potential will be fully realized as it will allow us to probe mergers that occurred soon after the peak of cosmic star formation, provided the follow-up campaigns are able to locate the sources.

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Radio astronomical measurements from earth satellites

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1959.0212 ◽

1959 ◽

Vol 253 (1275) ◽

pp. 494-500 ◽

Cited By ~ 3

Keyword(s):

Low Frequency ◽

Radio Spectrum ◽

Absorption Bands ◽

Frequency Limit ◽

Low Frequencies ◽

Earth’S Atmosphere ◽

Upper Limit ◽

The Earth ◽

Earth's Atmosphere

It may be thought that radio astronomical measurements made on the earth are not subject to the influence of the atmosphere and ionosphere to any great extent and that consequently there is no demand for measurements from earth satellites or other space stations. Unfortunately this is not the case and certain measurements from outside the earth’s atmosphere are very much desired. The radio spectrum so far explored extends from a low frequency limit in the 10 to 20 Mc/s band, to an upper limit in the millimetre waveband. In the millimetre band the limitation to the extension of the spectrum arises from absorption bands in the atmosphere, whereas at low frequencies the extension is limited by absorption and disturbances in the ionosphere. In this paper some examples will be given of the need to overcome these obstacles.

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Data-driven Expectations for Electromagnetic Counterpart Searches Based on LIGO/Virgo Public Alerts

The Astrophysical Journal ◽

10.3847/1538-4357/ac366d ◽

2022 ◽

Vol 924 (2) ◽

pp. 54

Author(s):

Polina Petrov ◽

Leo P. Singer ◽

Michael W. Coughlin ◽

Vishwesh Kumar ◽

Mouza Almualla ◽

...

Keyword(s):

Data Analysis ◽

Neutron Star ◽

Gravitational Wave ◽

Gamma Ray ◽

Data Driven ◽

Wave Localization ◽

Localization Accuracy ◽

Binary Neutron Star ◽

Data Release

Abstract Searches for electromagnetic counterparts of gravitational-wave signals have redoubled since the first detection in 2017 of a binary neutron star merger with a gamma-ray burst, optical/infrared kilonova, and panchromatic afterglow. Yet, one LIGO/Virgo observing run later, there has not yet been a second, secure identification of an electromagnetic counterpart. This is not surprising given that the localization uncertainties of events in LIGO and Virgo’s third observing run, O3, were much larger than predicted. We explain this by showing that improvements in data analysis that now allow LIGO/Virgo to detect weaker and hence more poorly localized events have increased the overall number of detections, of which well-localized, gold-plated events make up a smaller proportion overall. We present simulations of the next two LIGO/Virgo/KAGRA observing runs, O4 and O5, that are grounded in the statistics of O3 public alerts. To illustrate the significant impact that the updated predictions can have, we study the follow-up strategy for the Zwicky Transient Facility. Realistic and timely forecasting of gravitational-wave localization accuracy is paramount given the large commitments of telescope time and the need to prioritize which events are followed up. We include a data release of our simulated localizations as a public proposal planning resource for astronomers.

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Collimated outflows from long-lived binary neutron star merger remnants

Monthly Notices of the Royal Astronomical Society Letters ◽

10.1093/mnrasl/slaa062 ◽

2020 ◽

Vol 495 (1) ◽

pp. L66-L70 ◽

Cited By ~ 7

Author(s):

Riccardo Ciolfi

Keyword(s):

Black Hole ◽

Neutron Star ◽

Gamma Ray ◽

Gamma Ray Bursts ◽

Spin Axis ◽

Binary Neutron Star ◽

Physical Conditions ◽

Massive Neutron Star ◽

Merger Event ◽

First Time

ABSTRACT The connection between short gamma-ray bursts (SGRBs) and binary neutron star (BNS) mergers was recently confirmed by the association of GRB 170817A with the merger event GW170817. However, no conclusive indications were obtained on whether the merger remnant that powered the SGRB jet was an accreting black hole (BH) or a long-lived massive neutron star (NS). Here, we explore the latter case via BNS merger simulations covering up to 250 ms after merger. We report, for the first time in a full merger simulation, the formation of a magnetically driven collimated outflow along the spin axis of the NS remnant. For the system at hand, the properties of such an outflow are found largely incompatible with an SGRB jet. With due consideration of the limitations and caveats of our present investigation, our results favour a BH origin for GRB 170817A and SGRBs in general. Even though this conclusion needs to be confirmed by exploring a larger variety of physical conditions, we briefly discuss possible consequences of all SGRB jets being powered by accreting BHs.

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Detecting the Hadron-Quark Phase Transition with Gravitational Waves

Universe ◽

10.3390/universe5060156 ◽

2019 ◽

Vol 5 (6) ◽

pp. 156 ◽

Cited By ~ 5

Author(s):

Matthias Hanauske ◽

Luke Bovard ◽

Elias Most ◽

Jens Papenfort ◽

Jan Steinheimer ◽

...

Keyword(s):

Phase Transition ◽

Neutron Star ◽

Equation Of State ◽

Gravitational Wave ◽

Compact Star ◽

Binary Neutron Star ◽

Interesting Part ◽

Merger Event ◽

Tidal Deformations ◽

Quark Phase

The long-awaited detection of a gravitational wave from the merger of a binary neutron star in August 2017 (GW170817) marks the beginning of the new field of multi-messenger gravitational wave astronomy. By exploiting the extracted tidal deformations of the two neutron stars from the late inspiral phase of GW170817, it is now possible to constrain several global properties of the equation of state of neutron star matter. However, the most interesting part of the high density and temperature regime of the equation of state is solely imprinted in the post-merger gravitational wave emission from the remnant hypermassive/supramassive neutron star. This regime was not observed in GW170817, but will possibly be detected in forthcoming events within the current observing run of the LIGO/VIRGO collaboration. Numerous numerical-relativity simulations of merging neutron star binaries have been performed during the last decades, and the emitted gravitational wave profiles and the interior structure of the generated remnants have been analysed in detail. The consequences of a potential appearance of a hadron-quark phase transition in the interior region of the produced hypermassive neutron star and the evolution of its underlying matter in the phase diagram of quantum cromo dynamics will be in the focus of this article. It will be shown that the different density/temperature regions of the equation of state can be severely constrained by a measurement of the spectral properties of the emitted post-merger gravitational wave signal from a future binary compact star merger event.

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