arXiv subjects

Peter Mészáros

Publications and source records attributed to Peter Mészáros.

At least 55 records · Page 3Linked to original sources

arXiv2016

A New Test of Lorentz Invariance Violation: the Spectral Lag Transition of GRB 160625B

Possible violations of Lorentz invariance (LIV) have been investigated for a long time using the observed spectral lags of gamma-ray bursts (GRBs). However, these generally have relied on using a single photon in the highest energy range. Furthermore, the search for LIV lags has been hindered by our ignorance concerning the intrinsic time lag in different energy bands. GRB 160625B, the only burst so far with a well-defined transition from $positive$ lags to $negative$ lags provides a unique opportunity to put new constraints on LIV. Using multi-photon energy bands we consider the contributions to the observed spectral lag from both the intrinsic time lag and the lag by LIV effects, and assuming the intrinsic time lag to have a positive dependence on the photon energy, we obtain robust limits on LIV by directly fitting the spectral lag data of GRB 160625B. Here we show that these robust limits on the quantum gravity energy scales are $E_{\rm QG,1}\geq0.5\times10^{16}$ GeV for the linear, and $E_{\rm QG,2}\geq1.4\times10^{7}$ GeV for the quadratic LIV effects, respectively. In addition, we give for the first time a reasonable formulation of the intrinsic energy-dependent time lag.

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arXiv2016

High-Energy Neutrino Emission from White Dwarf Mergers

The merger of two white dwarfs is expected to result in a central fast rotating core surrounded by a debris disk, in which magnetorotational instabilities give rise to a hot magnetized corona and a magnetized outflow. The dissipation of magnetic energy via reconnection could lead to the acceleration of cosmic-rays in the expanding material, which would result in high energy neutrinos. We discuss the possibility of using these neutrino signals as probes of the outflow dynamics, magnetic energy dissipation rate and cosmic-ray acceleration efficiency. Importantly, the accompanying high-energy gamma-rays are absorbed within these sources because of the large optical depth, so these neutrino sources can be regarded as hidden cosmic-ray accelerators that are consistent with the non-detection of gamma-rays with Fermi-LAT. While the cosmic-ray generation rate is highly uncertain, if it reaches $\sim10^{45}\,\rm erg\,Mpc^{-3}\,yr^{-1}$, the diffuse neutrino flux could contribute a substantial fraction of the IceCube observations. We also evaluate the prospect of observing individual merger events, which provides a means for testing such sources in the future.

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arXiv2016

Limits on the Neutrino Velocity, Lorentz Invariance, and the Weak Equivalence Principle with TeV Neutrinos from Gamma-Ray Bursts

Five TeV neutrino events weakly correlated with five gamma-ray bursts (GRBs) were detected recently by IceCube. This work is an attempt to show that if the GRB identifications are verified, the observed time delays between the TeV neutrinos and gamma-ray photons from GRBs provide attractive candidates for testing fundamental physics with high accuracy. Based on the assumed associations between the TeV neutrinos and GRBs, we find that the limiting velocity of the neutrinos is equal to that of photons to an accuracy of $\sim1.9\times10^{-15}-2.5\times10^{-18}$, which is about $10^{4}-10^{7}$ times better than the constraint obtained with the neutrino possibly from a blazar flare. In addition, we set the most stringent limits up to date on the energy scale of quantum gravity for both the linear and quadratic violations of Lorentz invariance, namely $E_{\rm QG, 1}>6.3\times10^{18}-1.5\times10^{21}$ GeV and $E_{\rm QG, 2}>2.0\times10^{11}-4.2\times10^{12}$ GeV, which are essentially as good as or are an improvement of one order of magnitude over the results previously obtained by the GeV photons of GRB 090510 and the PeV neutrino from a blazar flare. Assuming that the Shapiro time delay is caused by the gravitational potential of the Laniakea supercluster of galaxies, we also place the tightest limits to date on Einstein's weak equivalence principle through the relative differential variations of the parameterized post-Newtonian parameter $γ$ values for two different species of particles (i.e., neutrinos and photons), yielding $Δγ\sim 10^{-11}-10^{-13}$. However, it should be emphasized again that these limits here obtained are at best forecast of what could be achieved if the GRB/neutrino correlations would be finally confirmed.

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arXiv2016

Testing Einstein's Weak Equivalence Principle With Gravitational Waves

A conservative constraint on the Einstein Weak Equivalence Principle (WEP) can be obtained under the assumption that the observed time delay between correlated particles from astronomical sources is dominated by the gravitational fields through which they move. Current limits on the WEP are mainly based on the observed time delays of photons with different energies. It is highly desirable to develop more accurate tests that include the gravitational wave (GW) sector. The detection by the advanced LIGO/VIRGO systems of gravitational waves will provide attractive candidates for constraining the WEP, extending the tests to gravitational interactions, with potentially higher accuracy. Considering the capabilities of the advanced LIGO/VIRGO network and the source direction uncertainty, we show that the joint detection of GWs and electromagnetic signals could probe the WEP to an accuracy down to $10^{-10}$, which is one order of magnitude tighter than previous limits, and seven orders of magnitude tighter than the multi-messenger (photons and neutrinos) results by supernova 1987A.

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arXiv2016

Revisiting the Contributions of Supernova and Hypernova Remnants to the Diffuse High-Energy Backgrounds: Constraints on Very-High-Redshift Injections

Star-forming and starburst galaxies are considered as one of the viable candidate sources of the high-energy cosmic neutrino background detected in IceCube. We revisit contributions of supernova remnants (SNRs) and hypernova remnants (HNRs) in such galaxies to the diffuse high-energy neutrino and gamma-ray backgrounds, in light of the latest Fermi data above 50GeV. We also take into account possible time dependent effects of the cosmic-ray (CR) acceleration during the SNR evolution. CRs accelerated by the SNR shocks can produce high-energy neutrinos up to $\sim100$ TeV energies, but CRs from HNRs can extend the spectrum up to PeV energies. We show that, only if HNRs are dominant over SNRs, the diffuse neutrino background above 100 TeV can be explained without contradicting the gamma-ray data. However, the neutrino data around 30 TeV remain unexplained, which might suggest a different population of gamma-ray dark CR sources. Alternatively, we consider possible contributions of Pop-III HNRs up to $z\lesssim10$, and show that they are not constrained by the gamma-ray data, and thus could contribute to the diffuse high-energy backgrounds if their explosion energy reaches ${\mathcal E}_{\rm POP-III}\sim{\rm a~few}\times10^{53}$erg. More conservatively, our results suggest that the explosion energy of POP-III HNRs is ${\mathcal E}_{\rm POP-III}\lesssim7\times{10}^{53}$erg.

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arXiv2016

Constraints on the Photon Mass with Fast Radio Bursts

Fast radio bursts (FRBs) are radio bursts characterized by millisecond durations, high Galactic latitude positions, and high dispersion measures. Very recently, the cosmological origin of FRB 150418 has been confirmed by \cite{kea16}, and FRBs are now strong competitors as cosmological probes. The simple sharp feature of the FRB signal is ideal for them to probe some of the fundamental laws of physics. Here we show that by analyzing the delay time between different frequencies, the FRB data can place stringent upper limits on the rest mass of the photon. For FRB 150418 at $z=0.492$, one can potentially reach $m_γ \leq 5.2 \times 10^{-47}$ g, which is $10^{20}$ times smaller than the rest mass of electron, and is about $10^3$ times smaller than that obtained using other astrophysical sources with the same method.

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arXiv2015

Testing Einstein's Equivalence Principle with Fast Radio Bursts

The accuracy of Einstein's Equivalence Principle (EEP) can be tested with the observed time delays between correlated particles or photons that are emitted from astronomical sources. Assuming as a lower limit that the time delays are caused mainly by the gravitational potential of the Milky Way, we prove that fast radio bursts (FRBs) of cosmological origin can be used to constrain the EEP with high accuracy. Taking FRB 110220 and two possible FRB/gamma-ray burst (GRB) association systems (FRB/GRB 101011A and FRB/GRB 100704A) as examples, we obtain a strict upper limit on the differences of the parametrized post-Newtonian parameter $γ$ values as low as $\left[γ(1.23\; \rm GHz)-γ(1.45\; \rm GHz)\right]<4.36\times10^{-9}$. This provides the most stringent limit up to date on the EEP through the relative differential variations of the $γ$ parameter at radio energies, improving by 1 to 2 orders of magnitude the previous results at other energies based on supernova 1987A and GRBs.

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arXiv2015

Cosmic Transients Test Einstein's Equivalence Principle out to GeV Energies

The Einstein Equivalence Principle (EEP) can be probed with astrophysical sources emitting simultaneously different types of neutral particles, or particles with varying energies, by testing their time of flight through the same gravitational field. Here we use the time delays between correlated photons from cosmological transients to constrain the accuracy of the EEP. We take data from two gamma-ray bursts as an example, and use, as a lower limit to the theoretical time delays between different energies, delays arising from only the gravitational field of our own galaxy. We then show that the parameterized post-Newtonian parameter $γ$ is the same for photons over energy ranges between eV and MeV and between MeV and GeV to a part in $10^{-7}$, which is at least one order of magnitude better than previous limits. Combining this bound on the wavelength dependence of $γ$ with the absolute bound $|γ-1|<0.3\%$ from light-deflection measurements at optical (eV) wavelengths, we thus extend this absolute bound on $γ$ to GeV energies.

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arXiv2015

Reverse Shock Emission in Gamma-ray Bursts Revisited

A generic synchrotron external shock model is the widely preferred paradigm used to interpret the broad-band afterglow data of gamma-ray bursts (GRBs), including predicted observable signatures from a reverse shock which have been confirmed by observations. Investigations of the nature of the reverse shock emission can provide valuable insights into the intrinsic properties of the GRB ejecta. Here we briefly review the standard and the extended models of the reverse shock emission, discussing the connection between the theory and observations, including the implications of the latest observational advances.

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arXiv2015

A morphological analysis of gamma-ray burst early optical afterglows

Within the framework of the external shock model of gamma-ray bursts (GRBs) afterglows, we perform a morphological analysis of the early optical lightcurves to directly constrain model parameters. We define four morphological types, i.e. the reverse shock dominated cases with/without the emergence of the forward shock peak (Type I/ Type II), and the forward shock dominated cases without/with $ν_m$ crossing the band (Type III/IV). We systematically investigate all the Swift GRBs that have optical detection earlier than 500 s and find 3/63 Type I bursts (4.8%), 12/63 Type II bursts (19.0%), 30/63 Type III bursts (47.6%), 8/63 Type IV bursts (12.7%) and 10/63 Type III/IV bursts (15.9%). We perform Monte Carlo simulations to constrain model parameters in order to reproduce the observations. We find that the favored value of the magnetic equipartition parameter in the forward shock ($ε_B^f$) ranges from $10^{-6}$ to $10^{-2}$, and the reverse-to-forward ratio of $ε_B$ ($R_B$) is about 100. The preferred electron equipartition parameter $ε_e^{r,f}$ value is 0.01, which is smaller than the commonly assumed value, e.g., 0.1. This could mitigate the so- called "efficiency problem" for the internal shock model, if $ε_e$ during the prompt emission phase (in the internal shocks) is large (say, $\sim 0.1$). The preferred $R_B$ value is in agreement with the results in previous works that indicates a moderately magnetized baryonic jet for GRBs.

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arXiv2015

Gamma Ray Bursts in the HAWC Era

Gamma-Ray Bursts are the most energetic explosions in the Universe, and are among the most promising for detecting multiple non-electromagnetic signals, including cosmic rays, high energy neutrinos and gravitational waves. The multi-GeV to TeV gamma-ray range of GRB could have significant contributions from hadronic interactions, mixed with more conventional leptonic contributions. This energy range is important for probing the source physics, including overall energetics, the shock parameters and the Lorentz factor. We discuss some of the latest observational and theoretical developments in the field.

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arXiv2015

Extragalactic star-forming galaxies with hypernovae and supernovae as high-energy neutrino and gamma-ray sources: the case of the 10 TeV neutrino data

In light of the latest IceCube data, we discuss the implications of the cosmic ray energy input from hypernovae and supernovae into the Universe, and their propagation in the hosting galaxy and galaxy clusters or groups. The magnetic confinement in these environments may lead to efficient $pp$ collisions, resulting in a diffuse neutrino spectrum extending from PeV down to 10 TeV energies, with a spectrum and flux level compatible with that recently reported by IceCube. If the diffuse 10 TeV neutrino background largely comes from such the CR reservoirs, the corresponding diffuse gamma-ray background should be compatible with the recent \textit{Fermi} data. In this scenario, the CR energy input from hypernovae should be dominant over that of supernovae, implying that the starburst scenario does not work if the supernova energy budget is a factor of two larger than the hypernova energy budget. Thus, this strong case scenario can be supported or ruled out in near future.

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arXiv2015

Relation between the intrinsic and observed central engine activity time: implications for ultra-long GRBs

The GRB central engine intrinsic activity time $T_{\rm ce}$ is usually described through either the $γ$-ray duration $T_{90}$ or through a generalized burst duration $t_{\rm burst}$ which includes both the $γ$-ray emission and (when present) an extended flaring X-ray plateau. Here, we define a more specific operational description of $T_{\rm ce}$, and within the framework of the internal-external shock model, we develop a numerical code to study the relationship between $T_{90}$ and $T_{\rm ce}$, as well as between $t_{\rm burst}$ and $T_{\rm ce}$, for different initial conditions. We find that when $T_{\rm ce}\lesssim 10^4$ s, late internal collisions or refreshed external collisions result in values of $T_{\rm 90}$ and $t_{\rm burst}$ larger than $T_{\rm ce}$, usually by factors of $2-3$. For $T_{\rm ce}\gtrsim 10^4$ s, the $t_{\rm burst}$ is always a good estimator for $T_{\rm ce}$, while $T_{90}$ can underpredict $T_{\rm ce}$ when the late central engine activity is moderate. We find a clear bimodal distribution for $T_{\rm ce}$, based on our simulations as well as on the observational data for $T_{90}$ and $t_{\rm burst}$. We suggest that $t_{\rm burst}$ is a reliable measure for defining "ultra-long" GRBs. Bursts with $T_{90}$ of order $10^3$ s need not belong to a special population, while bursts with $t_{\rm burst} > 10^4$ s, where the late central engine activity is more moderate and shows up in X-rays, may represent a new population. These conclusions are insensitive to the initial conditions assumed in the models.

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arXiv2014

Galaxy Mergers as a Source of Cosmic Rays, Neutrinos, and Gamma Rays

We investigate the shock acceleration of particles in massive galaxy mergers or collisions, and show that cosmic rays (CRs) can be accelerated up to the second knee energy ~0.1-1 EeV and possibly beyond, with a hard spectral index Gamma ~ 2. Such CRs lose their energy via hadronuclear interactions within a dynamical timescale of the merger shock, producing gamma rays and neutrinos as a by-product. If ~ 10 % of the shock dissipated energy goes into CR acceleration, some local merging galaxies will produce gamma-ray counterparts detectable by CTA. Also, based on the concordance cosmology, where a good fraction of the massive galaxies experience a major merger in a cosmological timescale, the neutrino counterparts can constitute ~ 20-60 % of the isotropic background detected by IceCube.

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arXiv2013

Cosmological Fast Radio Bursts from Binary White Dwarf Mergers

Recently, Thornton et al. reported the detection of four fast radio bursts (FRBs). The dispersion measures indicate that the sources of these FRBs are at cosmological distance. Given the large full sky event rate ~ 10^4 sky^-1 day^-1, the FRBs are a promising target for multi-messenger astronomy. Here we propose double degenerate, binary white-dwarf (WD) mergers as the source of FRBs, which are produced by coherent emission from the polar region of a rapidly rotating, magnetized massive WD formed after the merger. The basic characteristics of the FRBs, such as the energetics, emission duration and event rate, can be consistently explained in this scenario. As a result, we predict that some FRBs can accompany type Ia supernovae (SNe Ia) or X-ray debris disks. Simultaneous detection could test our scenario and probe the progenitors of SNe Ia, and moreover would provide a novel constraint on the cosmological parameters. We strongly encourage future SN and X-ray surveys that follow up FRBs.

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arXiv2013

Neutron-Proton-Converter Acceleration Mechanism at Subphotospheres of Relativistic Outflows

We study a type of particle acceleration that operates via neutron-proton conversion in inelastic nuclear collisions. This mechanism can be expected for relativistic shocks at subphotospheres if relativistic outflows contain neutrons. Using a test-particle approximation, we numerically calculate the energy spectrum and the efficiency of accelerated particles, and show that a good energy fraction of the nucleons can be accelerated. This mechanism may especially be relevant if the shock is radiation-mediated, and it would enhance the detectability of GeV-TeV neutrinos.

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arXiv2013

High-energy neutrino and gamma-ray transients from trans-relativistic supernova shock breakouts

Relativistic shocks that accompany supernovae (SNe) produce X-ray burst emissions as they break out in the dense circumstellar medium around the progenitors. This phenomenon is sometimes associated with peculiar low-luminosity gamma-ray bursts (LL GRBs). Here, we investigate the high energy neutrino and gamma-ray counterparts of such a class of SNe. Just beyond the shock breakout radius, particle acceleration in the collisionless shock starts to operate in the presence of breakout photons. We show that protons may be accelerated to sufficiently high energies and produce high energy neutrinos and gamma rays via the photomeson interaction. These neutrinos and gamma rays may be detectable from 10 Mpc away by IceCube/KM3Net as multi-TeV transients almost simultaneously with the X-ray burst emission, and even from 100 Mpc away with follow-up observations by CTA using a wide-field sky monitor like Swift as a trigger. A statistical technique using a stacking approach could also be possible for the detection, with the aid of the SN optical/infrared counterparts. Such multi-messenger observations offer the possibility to probe the transition of relativistic shocks from radiation-mediated to collisionless ones, and would also constrain the mechanisms of particle acceleration and emission in LL GRBs.

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arXiv2012

Gamma Ray Bursts and their links with Supernovae and Cosmology

Gamma-ray bursts are the most luminous explosions in the Universe, whose origin and mechanism is the focus of intense interest. They appear connected to supernova remnants from massive stars or the merger of their remnants, and their brightness makes them temporarily detectable out to the larges distances yet explored in the Universe. After pioneering breakthroughs from space and ground experiments, their study is entering a new phase with observations from the recently launched \fermi satellite, as well as the prospect of detections or limits from large neutrino and gravitational wave detectors. The interplay between such observations and theoretical models of gamma-ray bursts is reviewed, as well as their connections to supernovae and cosmology.

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