arXiv subjects

J. A. Rueda

Publications and source records attributed to J. A. Rueda.

At least 55 records · Page 3Linked to original sources

arXiv2021

Hinting a dark matter nature of Sgr A* via the S-stars

The motion data of the S-stars around the Galactic center gathered in the last 28 yr imply that Sgr A* hosts a supermassive compact object of about $4\times 10^6$ $M\odot$, a result awarded with the Nobel Prize in Physics 2020. A non-rotating black hole (BH) nature of Sgr A* has been uncritically adopted since the S-star orbits agree with Schwarzschild geometry geodesics. The orbit of S2 has served as a test of General Relativity predictions such as the gravitational redshift and the relativistic precession. The central BH model is, however, challenged by the G2 post-peripassage motion and by the lack of observations on event-horizon-scale distances robustly pointing to its univocal presence. We have recently shown that the S2 and G2 astrometry data are better fitted by geodesics in the spacetime of a self-gravitating dark matter (DM) core - halo distribution of 56 keV-fermions, "darkinos", which also explains the outer halo Galactic rotation curves. This Letter confirms and extends this conclusion using the astrometry data of the $17$ best-resolved S-stars, thereby strengthening the alternative nature of Sgr A* as a dense core of darkinos.

astro-ph.GA↗

arXiv2021

The Quantum Emission of an Alive Black Hole

A long march of fifty years of successive theoretical progress and new physics discovered using observations of gamma-ray bursts, has finally led to the formulation of an efficient mechanism able to extract the rotational energy of a Kerr black hole to power these most energetic astrophysical sources and active galactic nuclei. We here present the salient features of this long-sought mechanism, based on gravito-electrodynamics, and which represents an authentic shift of paradigm of black holes as forever "alive" astrophysical objects.

gr-qc↗

arXiv2021

Galactic Center constraints on self-interacting sterile neutrinos from fermionic dark matter ("ino") models

The neutrino minimal standard model ($ν$MSM) has been tightly constrained in the recent years, either from dark matter (DM) production or from X-ray and small-scale observations. However, current bounds on sterile neutrino DM can be significantly modified when considering a $ν$MSM extension, in which the DM candidates interact via a massive (axial) vector field. In particular, standard production mechanisms in the early Universe can be affected through the decay of such a massive mediator. We perform an indirect detection analysis to study how the $ν$MSM parameter-space constraints are affected by said interactions. We compute the X-ray fluxes considering a DM profile that self-consistently accounts for the particle physics model by using an updated version of the Ruffini-Argüelles-Rueda (RAR) fermionic ("ino") model, instead of phenomenological profiles such as the Navarro-Frenk-White (NFW) distribution. We show that the RAR profile accounting for interacting DM, is compatible with measurements of the Galaxy rotation curve and constraints on the DM self-interacting cross section from the Bullet cluster. A new analysis of the X-ray NuSTAR data in the central parsec of the Milky Way, is here performed to derive constraints on the self-interacting sterile neutrino parameter-space. Such constraints are stronger than those obtained with commonly used DM profiles, due to the dense DM core characteristic of the RAR profiles.

astro-ph.CO↗

arXiv2021

The newborn black hole in GRB 191014C proves that it is alive

A multi-decade theoretical effort has been devoted to finding an efficient mechanism to use the rotational and electrodynamical extractable energy of a Kerr-Newman black hole (BH), to power the most energetic astrophysical sources such as gamma-ray bursts (GRBs) and active galactic nuclei (AGN). We show an efficient general relativistic electrodynamical process which occurs in the "inner engine" of a binary driven hypernova (BdHN). The {inner engine} is composed of a rotating Kerr BH of mass $M$ and dimensionless spin parameter $α$, a magnetic field of strength $B_0$ aligned and parallel to the rotation axis, and a very low-density ionized plasma. Here, we show that the gravitomagnetic interaction between the BH and the magnetic field induces an electric field that accelerates electrons and protons from the environment to ultrarelativistic energies emitting synchrotron radiation. We show that in GRB 190114C the BH of mass $M = 4.4~M_\odot$, $α= 0.4$, and $B_0 \approx 4\times 10^{10}$ G can lead to a high-energy ($\gtrsim$GeV) luminosity of $10^{51}$ erg s$^{-1}$. The inner engine parameters are determined by requiring 1) that the BH extractable energy explains the GeV and ultrahigh-energy emission energetics, 2) that the emitted photons are not subjected to magnetic-pair production, and 3) that the synchrotron radiation timescale agrees with the observed high-energy timescale. We find for GRB 190114C a clear jetted emission of GeV energies with a semi-aperture angle of approximately $60^\circ$ with respect to the BH rotation axis.

astro-ph.HE↗

arXiv2021

X-ray and GeV afterglows and sub-TeV emission of GRB 180720B

GRB 180720B, observed by {\it Fermi}-GBM, with redshift $z=0.653$, isotropic energy $E_{\rm iso}=5.92\times 10^{53}$ erg, and X-ray afterglow observed by the XRT onboard the Neil Gehrels Swift satellite, is here classified as a Binary-driven Hypernova I (BdHN I). BdHN I are long GRBs with a binary progenitor composed of a carbon-oxygen core (CO$_{\rm core}$) and a neutron star (NS) companion with orbital period $\sim 5$ min. The gravitational collapse of the CO$_{\rm core}$ generates a supernova (SN) and a new NS ($ν$NS) at its center. The SN hypercritical accretion onto the companion NS triggers its gravitational collapse forming a black hole (BH). An electrodynamical process near the BH horizon leads to the long-lasting GeV emission with power-law luminosity $L_{\rm GeV}\propto t^{-1.19\pm0.04}$, powered by the BH rotational energy. Correspondingly, we determine the BH mass and spin. The $ν$NS via its pulsar-like emission and fallback accretion injects energy into the magnetized SN ejecta generating synchrotron radiation. This explains the \textit{long-lasting} X-ray afterglow with power-law luminosity $L_X \propto t^{-1.48\pm 0.32}$, energized by the $ν$NS rotational energy. We apply this to GRB 180720B determining the $ν$NS magnetic field and spin. We also analyze the GRB 180720B emission observed by the High-Energy Stereoscopic System (H.E.S.S.), at $100$-$440$ GeV energies, $10.1$-$12.1$ h after the Fermi-GBM trigger. We propose that this \textit{short-term} radiation of energy $2.4\times 10^{50}$ erg and duration $\sim 10^3$ s, is powered by a "glitch" event that suddenly injects relativistic electrons into the $ν$NS magnetosphere during its slowing down phase.

astro-ph.HE↗

arXiv2021

The morphology of the X-ray afterglows and of the jetted GeV emission in long GRBs

We recall evidence that long gamma-ray bursts (GRBs) have binary progenitors and give new examples. Binary-driven hypernovae (BdHNe) consist of a carbon-oxygen core (CO$_{\rm core}$) and a neutron star (NS) companion. For binary periods $\sim 5$ min, the CO$_{\rm core}$ collapse originates the subclass BdHN I characterized by: 1) an energetic supernova (the "SN-rise"); 2) a black hole (BH), born from the NS collapse by SN matter accretion, leading to a GeV emission with luminosity $L_{\rm GeV} = A_{\rm GeV}\,t^{-α_{\rm GeV}}$, observed only in some cases; 3) a new NS ($ν$NS), born from the SN, originating the X-ray afterglow with $L_X = A_{\rm X}\,t^{-α_{\rm X}}$, observed in all BdHN I. We record $378$ sources and present for four prototypes GRBs 130427A, 160509A, 180720B and 190114C: 1) spectra, luminosities, SN-rise duration; 2) $A_X$, $α_X=1.48\pm 0.32$, and 3) the $ν$NS spin time-evolution. We infer a) $A_{\rm GeV}$, $α_{\rm GeV}=1.19 \pm 0.04$; b) the BdHN I morphology from time-resolved spectral analysis, three-dimensional simulations, and the GeV emission presence/absence in $54$ sources within the Fermi-LAT boresight angle. For $25$ sources, we give the integrated and time-varying GeV emission, $29$ sources have no GeV emission detected and show X/gamma-ray flares previously inferred as observed along the binary plane. The $25/54$ ratio implies the GeV radiation is emitted within a cone of half-opening angle $\approx 60^{\circ}$ from the normal to the orbital plane. We deduce BH masses $2.3$-$8.9~M_\odot$ and spin $0.27$-$0.87$ by explaining the GeV emission from the BH energy extraction, while their time evolution validates the BH mass-energy formula.

astro-ph.HE↗

arXiv2020

Neutrino oscillations in a neutrino-dominated accretion disk around a Kerr BH

In the binary-driven hypernova model of long gamma-ray bursts, a carbon-oxygen star explodes as a supernova in presence of a neutron star binary companion in close orbit. Hypercritical (i.e. highly super-Eddington) accretion of the ejecta matter onto the neutron star sets in, making it reach the critical mass with consequent formation of a Kerr black hole. We have recently shown that, during the accretion process onto the neutron star, fast neutrino flavour oscillations occur. Numerical simulations of the above system show that a part of the ejecta keeps bound to the newborn Kerr black hole, leading to a new process of hypercritical accretion. We here address, also for this phase of the binary-driven hypernova, the occurrence of neutrino flavour oscillations given the extreme conditions of high density (up to $10^{12}$ g cm$^{-3}$) and temperatures (up to tens of MeV) inside this disk. We estimate the \textcolor{red}{behaviour} of the electronic and non-electronic neutrino content within the two-flavour formalism ($ν_{e}ν_{x}$) under the action of neutrino collective effects by neutrino self-interactions. We find that in the case of inverted mass hierarchy, neutrino oscillations inside the disk have frequencies between $\sim (10^{5}$-$10^{9})$ s$^{-1}$, leading the disk to achieve flavour equipartition. This implies that the energy deposition rate by neutrino annihilation ($ν+ \barν \to e^{-} + e^{+}$) in the vicinity of the Kerr black hole, is smaller than previous estimates in the literature not accounting by flavour oscillations inside the disk. The exact value of the reduction factor depends on the $ν_{e}$ and $ν_{x}$ optical depths but it can be as high as $\sim 5$. The results of this work are a first step toward the analysis of neutrino oscillations in a novel astrophysical context and, as such, deserve further attention.

astro-ph.HE↗

arXiv2020

On the role of the Kerr-Newman black hole in the GeV emission of long gamma-ray bursts

X-ray Flashes (XRFs), binary-driven hypernovae (BdHNe) are long GRB subclasses with progenitor a CO$_{\rm core}$, undergoing a supernova (SN) explosion and hypercritically accreting in a tight binary system onto a companion neutron star (NS) or black hole (BH). In XRFs the NS does not reach by accretion the critical mass and no BH is formed. In BdHNe I, with shorter binary periods, the NS gravitationally collapses and leads to a new born BH. In BdHNe II the accretion on an already formed BH leads to a more massive BH. We assume that the GeV emission observed by \textit{Fermi}-LAT originates from the rotational energy of the BH. Consequently, we verify that, as expected, in XRFs no GeV emission is observed. In $16$ BdHNe I and $5$ BdHNe II, within the boresight angle of LAT, the integrated GeV emission allows to estimate the initial mass and spin of the BH. In the remaining $27$ sources in the plane of the binary system no GeV emission occurs, hampered by the presence of the HN ejecta. From the ratio, $21/48$, we infer a new asymmetric morphology for the BdHNe reminiscent of the one observed in active galactic nuclei (AGN): the GeV emission occurs within a cone of half-opening angle $\approx 60^{\circ}$ from the normal to the orbital plane of the binary progenitor. The transparency condition requires a Lorentz factor $Γ\sim 1500$ on the source of GeV emission. The GeV luminosity in the rest-frame of the source follows a universal power-law with index of $-1.20 \pm 0.04$, allowing to estimate the spin-down rate of the BH

astro-ph.HE↗

arXiv2020

The geodesic motion of S2 and G2 as a test of the fermionic dark matter nature of our galactic core

[Abridged] The S-stars motion around the Galactic center (Sgr A*) implies the existence of a compact source with a mass of about $4\times 10^6 M_\odot$, traditionally assumed to be a massive black hole (BH). Important for any model is the explanation of the multiyear, accurate astrometric data of S2 and the challenging G2: its post-pericenter velocity decelerates faster than expected from a Keplerian orbit around the putative BH. This has been reconciled in the literature by acting on G2 a drag force by an accretion flow. Alternatively, we show that the S2 and G2 motion is explained by the "core-halo" fermionic dark matter (DM) profile of the fully-relativistic Ruffini-Argüelles-Rueda (RAR) model. It has been already shown that for 48-345 keV fermions, it accurately fits the rotation curves of the Milky-Way halo. We here show that, for a fermion mass of 56 keV, it explains the time-dependent data of the position (orbit) and light-of-sight radial velocity (redshift function $z$) of S2 and G2, the latter without a drag force. We find the RAR model fits better the data: the mean of reduced chi-squares of the orbit and $z$ data are, for S2, $\langle\barχ^2\rangle_{\rm S2, RAR}\approx 3.1$ and $\langle\barχ^2\rangle_{\rm S2, BH}\approx 3.3$ while, for G2, $\langle\barχ^2\rangle_{\rm G2, RAR}\approx 20$ and $\langle\barχ^2\rangle_{\rm G2, BH}\approx 41$. For S2 the fits of the $z$ data are comparable, $\barχ^2_{z,\rm RAR}\approx 1.28$ and $\barχ^2_{z,\rm BH}\approx 1.04$, for G2 only the RAR model fits, $\barχ^2_{z,\rm RAR}\approx 1.0$ and $\barχ^2_{z,\rm BH}\approx 26$. In addition, the critical mass for the gravitational collapse of a degenerate 56 keV-fermion DM core into a BH is $\sim 10^8 M_\odot$, which may be the initial seed for the formation of the observed central supermassive BH in active galaxies, such as M87.

astro-ph.GA↗

arXiv2020

The blackholic quantum

We show that the high-energy emission of GRBs originates in the "inner engine": a Kerr black hole (BH) surrounded by matter and a magnetic field $B_0$. It radiates a sequence of discrete events of particle acceleration, each of energy ${\cal E} = \hbar\,Ω_{\rm eff}$, the \textit{blackholic quantum}, where $Ω_{\rm eff} =4(m_{\rm Pl}/m_n)^8(c\,a/G\,M)(B_0^2/ρ_{\rm Pl})Ω_+$. Here $M$, $a=J/M$, $Ω_+=c^2\partial M/\partial J=(c^2/G)\,a/(2 M r_+)$ and $r_+$ are the BH mass, angular momentum per unit mass, angular velocity and horizon; $m_n$ is the neutron mass, $m_{\rm Pl}$, $λ_{\rm Pl}=\hbar/(m_{\rm Pl}c)$ and $ρ_{\rm Pl}=m_{\rm Pl}c^2/λ_{\rm Pl}^3$, are the Planck mass, length and energy density. {Here and in the following use CGS-Gaussian units}. The time\-scale of each process is $τ_{\rm el}\sim Ω_+^{-1}$, {along the rotation axis, while it is much shorter off-axis owing to energy losses such as synchrotron radiation}. We show an analogy with the Zeeman and Stark effects, properly scaled from microphysics to macrophysics, that allows us to define the "BH magneton", $μ_{\rm BH}=(m_{\rm Pl}/m_n)^4(c\,a/G\,M)e\,\hbar/(M c)$. We give quantitative estimates for GRB 130427A adopting $M=2.3~M_\odot$, $c\, a/(G\,M)= 0.47$ and $B_0= 3.5\times 10^{10}$ G. Each emitted "quantum", ${\cal E}\sim 10^{37}$ erg, extracts only $10^{-16}$ times the BH rotational energy, guaranteeing that the process can be repeated for thousands of years. The "inner engine" can also work in AGN as we here exemplified for the supermassive BH at the center of M87.

astro-ph.HE↗

arXiv2019

The photon time delay in magnetized vacuum magnetosphere

We study the transverse propagation of photons in a magnetized vacuum considering radiative corrections in the one-loop approximation. The dispersion equation is modified due to the magnetized photon self-energy in the transparency region ($0<ω<2m_e$). The aim of our study is to explore propagation of photons in a neutron star magnetosphere (described by magnetized vacuum). The solution of the dispersion equation is obtained in terms of analytic functions. The larger the magnetic field, the lower the phase velocity and the more the dispersion curve deviates from the light-cone. For fixed values of the frequency, we study the dependence of photon time delay with the magnetic field strength, as well as with distance. For the latter, we adopt a magnetic dipole configuration and obtain that -- contrary to the expectation, according to the traditional time delay of photons in the interstellar medium -- photons of higher energy experience a longer time delay. A discussion of potential causes of this behaviour is presented.

astro-ph.HE↗

arXiv2019

On the GeV emission of the type I BdHN GRB 130427A

We propose that the "inner engine" of a type I binary-driven hypernova (BdHN) is composed of a Kerr black hole (BH) in a non-stationary state, embedded in a uniform magnetic field $B_0$ aligned with the BH rotation axis, and surrounded by an ionized plasma of extremely low density of $10^{-14}$~g~cm$^{-3}$. Using GRB 130427A as a prototype we show that this "inner engine" acts in a sequence of "elementary impulses". Electrons are accelerated to ultra-relativistic energy near the BH horizon and, propagating along the polar axis, $θ=0$, they can reach energies of $\sim 10^{18}$ eV, and partially contribute to ultra-high energy cosmic rays (UHECRs). When propagating with ${θ\neq 0}$ through the magnetic field $B_0$ they give origin by synchrotron emission to GeV and TeV radiation. The mass of BH, $M=2.3 M_\odot$, its spin, $α= 0.47$, and the value of magnetic field $B_0= 3.48 \times 10^{10}$ G, are determined self-consistently in order to fulfill the energetic and the transparency requirement. The repetition time of each elementary impulse of energy ${\cal E} \sim 10^{37}$ erg, is $\sim 10^{-14}$ s at the beginning of the process, then slowly increasing with time evolution. In principle, this "\textit{inner engine}" can operate in a GRB for thousands of years. By scaling the BH mass and the magnetic field the same "inner engine" can describe active galactic nuclei (AGN).

astro-ph.HE↗

arXiv2019

Self-Similarities and Power-laws in the Time-resolved Spectra of GRB 190114C, GRB 130427A, GRB 160509A, and GRB 160625B

[Shortened] CONTEXT: [...] AIMS: To identify and verify the BdHNe I properties in the additional sources GRB160509A, GRB160625B and GRB1340427A, and compare and contrast the results with the ones of a BdHN II source GRB180728A. We have also identified in all four sources, following the analysis GRB 130427A in the companion paper, the GeV radiation during and following the UPE phase. Also in all the four sources, we describe the spectral properties of their afterglow emission, including the mass estimate of the $ν$NS, following the results presented in the companion paper. METHODS: [...] RESULTS: The results of the spectral analysis have validated the common properties in all BdHNe I: the three Episodes as well as the self-similar structures and the associated power-laws in the UPE phase. The profound similarities of the results have made a significant step forward in the taxonomy of GRBs and in evidencing a standard composition of the BdHN I. This opens the opportunity of a vaster inquire of the astrophysical nature of their components in the population synthesis approach: e.g., the BH formation in all BdHN I occurs due to accretion of the SN ejecta in a tight binary system with a neutron star companion which reaches its critical mass, leading to the formation of the BH. The SN-rise in all five BdHNe are compare and contrasted. CONCLUSIONS: The most far reaching discovery of self-similarities and power-laws here extensively confirmed, thanks also to the conclusions presented in the companion papers, leads to the existence of a discrete quantized repetitive polarized emission, both in the GeV and MeV observed by {\it Fermi}-GBM and {\it Fermi}-LAT, on a timescale as short as $10^{-14}$s. These results open new paths in the discovery of fundamental physical laws.

astro-ph.HE↗

arXiv2019

The inner engine of GeV-radiation-emitting gamma-ray bursts

We motivate how the most recent progress in the understanding the nature of the GeV radiation in most energetic gamma-ray bursts (GRBs), the binary-driven hypernovae (BdHNe), has led to the solution of a forty years unsolved problem in relativistic astrophysics: how to extract the rotational energy from a Kerr black hole for powering synchrotron emission and ultra high-energy cosmic rays. The "inner engine" is identified in the proper use of a classical solution introduced by Wald in 1974 duly extended to the most extreme conditions found around the newborn black hole in a BdHN. The energy extraction process occurs in a sequence impulsive processes each accelerating protons to $10^{21}$ eV in a timescale of $10^{-6}$ s and in presence of an external magnetic field of $10^{14}$ G. Specific example is given for a black hole of initial angular momentum $J=0.3\,M^2$ and mass $M\approx 3\,M_\odot$ leading to the GeV radiation of $10^{49}$ erg$\cdot$s$^{-1}$. The process can energetically continue for thousands of years.

astro-ph.HE↗

arXiv2019

Can fermionic dark matter mimic supermassive black holes?

We analyze the intriguing possibility to explain both dark mass components in a galaxy: the dark matter (DM) halo and the supermassive dark compact object lying at the center, by a unified approach in terms of a quasi-relaxed system of massive, neutral fermions in general relativity. The solutions to the mass distribution of such a model that fulfill realistic halo boundary conditions inferred from observations, develop a highly-density core supported by the fermion degeneracy pressure able to mimic massive black holes at the center of galaxies. Remarkably, these dense core-diluted halo configurations can explain the dynamics of the closest stars around Milky Way's center (SgrA*) all the way to the halo rotation curve, without spoiling the baryonic bulge-disk components, for a narrow particle mass range $mc^2 \sim 10$-$10^2$~keV.

astro-ph.GA↗

arXiv2019

Induced Gravitational Collapse, Binary-Driven Hypernovae, Long Gramma-ray Bursts and Their Connection with Short Gamma-ray Bursts

Short and long Gamma-ray bursts (GRBs) originate in subclasses with specific energy release, spectra, duration, etc, and have binary progenitors. We review here the binary-driven hypernovae (BdHNe) subclass whose progenitor is a CO$_\textrm{core}$-neutron star (NS). The supernova (SN) explosion of the CO$_\textrm{core}$ produces at its center a new NS ($ν$NS) and triggers a hypercritical accretion onto the NS. The NS can become a more massive NS or collapse into a black hole (BH). We summarize this topic from the first analytic estimates in 2012 to the most recent three-dimensional (3D) smoothed-particle-hydrodynamics (SPH) numerical simulations in 2018. Long GRBs are richer and more complex than previously thought. The SN and the accretion explain X-ray precursors. The NS accretion, its collapse and the BH formation produce asymmetries in the SN ejecta, implying a 3D GRB analysis. The newborn BH surrounded by the ejecta and the magnetic field inherited from the NS, are the \emph{inner engine} from which the electron-positron ($e^+e^-$) plasma and the high-energy emission initiate. The $e^+e^-$ impact on the ejecta converts the SN into a hypernova (HN). The plasma dynamics in the ejecta explains the ultrarelativistic prompt emission in the MeV domain and the mildly-relativistic flares of the early afterglow in the X-ray domain. The feedback of the $ν$NS emission on the HN explains the X-ray late afterglow and its power-law regime. All the above is in contrast with GRB models attempting to explain all the GRB phases with the kinetic energy of anultrarelativistic jet, as traditionally proposed in the "collapsar-fireball" model. In addition, BdHNe in their different flavors lead to $ν$NS-NS or $ν$NS-BH binaries. These binaries merge by gravitational wave emission producing short GRBs, establishing a connection between long and short GRBs and their occurrence rates.

astro-ph.HE↗

arXiv2019

Self-similarity and power-laws in GRB 190114C

Following Fermi and NOT observations, Ruffini et al. (2019b) soon identified GRB 190114C as BdHN I at z=0.424, it has been observed since, with unprecedented accuracy, [...] all the way to the successful optical observation of our predicted supernova (SN). This GRB is a twin of GRB 130427A. Here we take advantage of the GBM data and identify in it three different Episodes. Episode 1 represents the precursor which includes the SN breakout and the creation of the new neutron star ($ν$NS), the hypercritical accretion of the SN ejecta onto the NS binary companion, exceeding the NS critical mass at $t_{rf}=1.9$s. Episode 2 starting at $t_{rf}=1.9$s includes three major events: the formation of the BH, the onset of the GeV emission and the onset of the ultra-relativistic prompt emission (UPE), which extends all the way up to $t_{rf}=3.99$s. Episode 3 which occurs at times following $t_{rf}=3.99$s reveals the presence of a cavity carved out in the SN ejecta by the BH formation. We perform an in depth time-resolved spectral analysis on the entire UPE with the corresponding determination of the spectra best fit by a cut-off power-law and a black body (CPL+BB) model, and then we repeat the spectral analysis in 5 successive time iterations in increasingly shorter time bins: we find a similarity in the spectra in each stage of the iteration revealing clearly a self-similar structure. We find a power-law dependence of the BB temperature with index $-1.56\pm0.38$, a dependence with index $-1.20\pm0.26$ for the gamma-ray luminosity confirming a similar dependence with index $-1.20\pm0.36$ which we find as well in the GeV luminosity, both expressed in the rest-frame. We thus discover in the realm of relativistic astrophysics the existence of a self-similar physical process and power-law dependencies, extensively described in the micro-physical world by the classical works of Heisenberg-Landau-Wilson.

astro-ph.HE↗

arXiv2019

Electromagnetic emission of white dwarf binary mergers

It has been recently proposed that the ejected matter from white dwarf (WD) binary mergers can produce transient, optical and infrared emission similar to the "kilonovae" of neutron star (NS) binary mergers. To confirm this we calculate the electromagnetic emission from WD-WD mergers and compare with kilonova observations. We simulate WD-WD mergers leading to a massive, fast rotating, highly magnetized WD with an adapted version of the smoothed-particle-hydrodynamics (SPH) code Phantom. We thus obtain initial conditions for the ejecta such as escape velocity, mass and initial position and distribution. The subsequent thermal and dynamical evolution of the ejecta is obtained by integrating the energy-conservation equation accounting for expansion cooling and a heating source given by the fallback accretion onto the newly-formed WD and its magneto-dipole radiation. We show that magnetospheric processes in the merger can lead to a prompt, short gamma-ray emission of up to $\approx 10^{46}$ erg in a timescale of $0.1$-$1$ s. The bulk of the ejecta initially expands non-relativistically with velocity $0.01 c$ and then it accelerates to $0.1 c$ due to the injection of fallback accretion energy. The ejecta become transparent at optical wavelengths around $\sim 7$ days post-merger with a luminosity $10^{41}$-$10^{42}$ erg s$^{-1}$. The X-ray emission from the fallback accretion becomes visible around $\sim 150$-$200$ day post-merger with a luminosity of $10^{39}$ erg s$^{-1}$. We also predict the post-merger time at which the central WD should appear as a pulsar depending on the value of the magnetic field and rotation period.

astro-ph.HE↗