ICRANet Newsletter
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ICRANet Newsletter
December 2020/January 2021
December 2020/January 2021
SUMMARY
1. Shedding new light on sterile neutrinos from XENON1T experiment
2. New Agreement on scientific cooperation between USTC and ICRANet, December 28, 2020
3. New Cooperation Protocol between CIMPA and ICRANet, January 20, 2021
4. "The solar eclipse and the measurement of the solar diameter", online meeting, December 14, 2020
5. "Conjunction and Solstice between history and celestial mechanics", online meeting, December 21, 2020 and ICRANet press release on that event
6. Recent publications
1. Shedding new light on sterile neutrinos from XENON1T experiment
2. New Agreement on scientific cooperation between USTC and ICRANet, December 28, 2020
3. New Cooperation Protocol between CIMPA and ICRANet, January 20, 2021
4. "The solar eclipse and the measurement of the solar diameter", online meeting, December 14, 2020
5. "Conjunction and Solstice between history and celestial mechanics", online meeting, December 21, 2020 and ICRANet press release on that event
6. Recent publications
1. Shedding new light on sterile neutrinos from XENON1T experiment
A new paper co-authored by Shakeri, S., Hajkarim, F. & Xue, SS. has been published on December 30, 2020 in Journal of High Energy Physics.
Fig. 1, 2 and 3: XENON1T experiment at INFN Laboratori Nazionali del Gran Sasso.
Fig. 4 and 5: In the left panel events versus recoil energy including the error bars are shown in blue color. The solid red line is the background model computed by XENON Collaboration. The additional recoil due to the sterile neutrino DM interaction with the Xenon electrons are shown by green solid curve. Right panel shows best fit points for the coupling and mass of electron sterile neutrino.
The XENON1T collaboration recently reported the excess of events from recoil electrons which may be sign of a fundamental new discovery about our universe. The XENON1T as the world's most sensitive dark matter experiment hosted in an underground laboratory beneath a mountain at Gran Sasso National Laboratory (INFN Laboratori Nazionali del Gran Sasso) in Italy. The evidence for the existence of dark matter (DM) which makes up 85% of the matter in the universe, is implied from various astrophysical and cosmological observations, but scientists still do not know the particle nature of this exotic material.
A group of scientists She-sheng Xue from ICRANet/ICRA, Soroush Shakeri from ICRANet-Isfahan and Isfahan University of Technology (IUT) and Fazlollah Hajkarim from Università degli Studi di Padova and Goethe Universität, claimed to have found a new interpretation for XENON1T excess by considering effective interactions between the DM sterile neutrinos and the SM particles.
Sterile neutrinos as a warm DM with masses at keV scale are well motivated from astrophysical and cosmological point of view. It is shown that sterile neutrinos with masses around 90 keV and specific effective coupling can fit well with the XENON1T data where the best fit points preserving DM constraints and possibly describe the anomalies in other experiments. In addition to explain XENON1T anomaly, the scenario presented in this group has some distinctive features which can be used to distinguish between their scenario and other beyond SM proposals.
This research, as shown by the references below, has been well developed for many years in ICRANet to understand the nature of dark matter particles as a fermion with the mass in keV range. It has been individuated the window 50-350 keV for the mass of fermionic dark matter ("ino") from the analysis of the rotation curves of the Milky Way. Accurate analysis has been done by ICRANet member in the case of the S2 and G2 orbits around the Galactic center and explained them with the distribution of DM for 56 keV fermions.
The XENON1T new results attract so much attention in Physics community. Physicists will likely treat the XENON1T results as preliminary for the near future. An upcoming, larger XENON experiment called XENONnt, still under construction in Italy besides the next generation of XENON detectors may shed light on the dark matter nature and low energy neutrino physic beyond SM.
• XENON collaboration, Excess electronic recoil events in XENON1T, Phys. Rev. D 102(2020) 072004
• Soroush Shakeri, Fazlollah Hajkarim, She-Sheng Xue, Shedding New Light on Sterile Neutrinos from XENON1T Experiment, JHEP12(2020)194
• C.R. Argüelles, N.E. Mavromatos, J.A. Rueda and R. Ruffini, The role of self-interacting right-handed neutrinos in galactic structure, JCAP 04 (2016) 038
• N. E. Mavromatos, C. R. Argüelles, R. Ruffini, J. A. Rueda, Self- interacting dark matter, International Journal of Modern Physics D 26 (2017) 1730007
• R. Ruffini, C. R. Argüelles, J. A. Rueda, On the core-halo distribution of dark matter in galaxies, MNRAS 451 (2015) 622-628
• E. A. Becerra-Vergara, C. R. Argüelles, A. Krut, J. A. Rueda, R. Ruffini, The geodesic motion of S2 and G2 as a test of the fermion dark matter constituency of our galactic core, A&A 641, A34 (2020)
• R. Yunis, C. R. Argüelles, N. E. Mavromatos, A. Moliné, A. Krut, M. Carinci, J. A. Rueda, R. Ruffini, Galactic center constraints on self-interacting sterile neutrinos from fermionic dark matter ("ino") models, Physics of the Dark Universe 30 (2020) 100699
Link to the paper https://doi.org/10.1007/JHEP12(2020)194
Fig. 1, 2 and 3: XENON1T experiment at INFN Laboratori Nazionali del Gran Sasso.
Fig. 4 and 5: In the left panel events versus recoil energy including the error bars are shown in blue color. The solid red line is the background model computed by XENON Collaboration. The additional recoil due to the sterile neutrino DM interaction with the Xenon electrons are shown by green solid curve. Right panel shows best fit points for the coupling and mass of electron sterile neutrino.
The XENON1T collaboration recently reported the excess of events from recoil electrons which may be sign of a fundamental new discovery about our universe. The XENON1T as the world's most sensitive dark matter experiment hosted in an underground laboratory beneath a mountain at Gran Sasso National Laboratory (INFN Laboratori Nazionali del Gran Sasso) in Italy. The evidence for the existence of dark matter (DM) which makes up 85% of the matter in the universe, is implied from various astrophysical and cosmological observations, but scientists still do not know the particle nature of this exotic material.
A group of scientists She-sheng Xue from ICRANet/ICRA, Soroush Shakeri from ICRANet-Isfahan and Isfahan University of Technology (IUT) and Fazlollah Hajkarim from Università degli Studi di Padova and Goethe Universität, claimed to have found a new interpretation for XENON1T excess by considering effective interactions between the DM sterile neutrinos and the SM particles.
Sterile neutrinos as a warm DM with masses at keV scale are well motivated from astrophysical and cosmological point of view. It is shown that sterile neutrinos with masses around 90 keV and specific effective coupling can fit well with the XENON1T data where the best fit points preserving DM constraints and possibly describe the anomalies in other experiments. In addition to explain XENON1T anomaly, the scenario presented in this group has some distinctive features which can be used to distinguish between their scenario and other beyond SM proposals.
This research, as shown by the references below, has been well developed for many years in ICRANet to understand the nature of dark matter particles as a fermion with the mass in keV range. It has been individuated the window 50-350 keV for the mass of fermionic dark matter ("ino") from the analysis of the rotation curves of the Milky Way. Accurate analysis has been done by ICRANet member in the case of the S2 and G2 orbits around the Galactic center and explained them with the distribution of DM for 56 keV fermions.
The XENON1T new results attract so much attention in Physics community. Physicists will likely treat the XENON1T results as preliminary for the near future. An upcoming, larger XENON experiment called XENONnt, still under construction in Italy besides the next generation of XENON detectors may shed light on the dark matter nature and low energy neutrino physic beyond SM.
• XENON collaboration, Excess electronic recoil events in XENON1T, Phys. Rev. D 102(2020) 072004
• Soroush Shakeri, Fazlollah Hajkarim, She-Sheng Xue, Shedding New Light on Sterile Neutrinos from XENON1T Experiment, JHEP12(2020)194
• C.R. Argüelles, N.E. Mavromatos, J.A. Rueda and R. Ruffini, The role of self-interacting right-handed neutrinos in galactic structure, JCAP 04 (2016) 038
• N. E. Mavromatos, C. R. Argüelles, R. Ruffini, J. A. Rueda, Self- interacting dark matter, International Journal of Modern Physics D 26 (2017) 1730007
• R. Ruffini, C. R. Argüelles, J. A. Rueda, On the core-halo distribution of dark matter in galaxies, MNRAS 451 (2015) 622-628
• E. A. Becerra-Vergara, C. R. Argüelles, A. Krut, J. A. Rueda, R. Ruffini, The geodesic motion of S2 and G2 as a test of the fermion dark matter constituency of our galactic core, A&A 641, A34 (2020)
• R. Yunis, C. R. Argüelles, N. E. Mavromatos, A. Moliné, A. Krut, M. Carinci, J. A. Rueda, R. Ruffini, Galactic center constraints on self-interacting sterile neutrinos from fermionic dark matter ("ino") models, Physics of the Dark Universe 30 (2020) 100699
Link to the paper https://doi.org/10.1007/JHEP12(2020)194
2. New Agreement on scientific cooperation between USTC and ICRANet, December 28, 2020
On December 28, 2020 an agreement on scientific cooperation between ICRANet and the University of Science and Technology of China was signed by Prof. Xinhe Bao (President of the USTC) and by Prof. Remo Ruffini (Director of ICRANet). The main joint activities to be developed under the framework of this agreement include: the promotion of theoretical and observational activities within the field of Relativistic Astrophysics; the institutional exchange of faculty members, researchers, post-doctorate fellows and students; the promotion of technological developments; the development of Data Centers for Astrophysical data in all wavebands; the organization of training and teaching courses, seminars, conferences, workshops or short courses, and the development of inter-institutional research areas associated to local graduate programs; and joint publications. The agreement will be valid for 5 years.
For the text of the agreement:
http://www.icranet.org/index.php?option=com_content&task=view&id=1353
3. New Cooperation Protocol between CIMPA and ICRANet, January 20, 2021
On January 20, 2021 a new Cooperation Protocol between ICRANet and the Centre International de Mathématiques Pures et Appliquées (CIMPA) has been signed by Prof. Barry Green (President of CIMPA), Prof. Christophe Ritzenthaler (Executive Director of CIMPA), Prof. Remo Ruffini (Director of ICRANet) and Prof. Jorge A. Rueda H. (ICRANet Faculty Professor). The main joint activities to be developed under the framework of this agreement include: the promotion of theoretical and observational activities within the field of Relativistic Astrophysics; the institutional exchange of faculty members, researchers, post-doctorate fellows and students; the promotion of technological developments; the development of Data Centers for Astrophysical data in all wavebands; the organization of training and teaching courses, seminars, conferences, workshops or short courses, and the development of inter-institutional research areas associated to local graduate programs; and joint publications. The agreement will be valid for 5 years.
For the text of the agreement:
http://www.icranet.org/index.php?option=com_content&task=view&id=1354.
4. "The solar eclipse and the measurement of the solar diameter", online meeting, December 14, 2020
Fig. 6: November 19, 2020, Ostia (Italy) - Blue Baily's bead.
The event "The solar eclipse and the measurement of the solar diameter. Eclipses' hunters from 1500 to present: Cristoforo Clavio, Halley, padre Secchi, Eddington and the actual status of art" has been held virtually on December 14, 2020. Prof. Costantino Sigismondi, ICRANet collaborator and chair of the event, thanks also to the support of ICRANet and many other scientists from all over the world, organized this virtual meeting as well as a podcast meeting in order to create a nice occasion for discussion among students and researchers.
The virtual meeting started at 4:30 PM on Monday December 14, with the opening remarks made by Prof. Sigismondi and went on with presentations on "The eclipse and solar physics in Turin" by Prof. Alessandro Bemporad (INAF - Astrophysical Observatory in Turin, Italy), on "The studies on Physics and on the Sun at the University of Rome Tor Vergata" and on "The legacy of Angelo Secchi: study on the connection between Sun and Earth" by Prof. Francesco Berrilli (Department of Physics, University of Rome Tor Vergata - Accademia Nazionale dei Lincei), on "The diameter of the Sun measured by eclipse observations" by Prof. Andrea Raponi (INAF IAPS), on the Telescope Copernicus in Cima Ekar (an INFN Telescope of the Astronomical Observatory in Asiago) by Prof. Paolo Ochner and Prof. Armando Sorrenti (University of Padova), on "Halley" by Prof. Giuseppe Massara (University La Sapienza of Rome) and on "Punto nave" by Prof. Cosimo Palagiano (Accademia Nazionale dei Lincei). Then, Prof. Sigismondi showed and technically explained some live videos of solar eclipses in Argentina, Chile, Egypt and Paraguay. The last part of the event has been dedicated to the concluding remarks by Prof. Remo Ruffini, Director of ICRANet.
This theoretical section was also integrated with the podcast materials prepared by Prof. Sigismondi as well as by Prof. Berilli and Prof. Ramponi, available on the webpage of the meeting.
The program of the event and all the relevant podcast materials, can be found at the following link: http://www.icranet.org/index.php?option=com_content&task=view&id=1348
5. "Conjunction and Solstice between history and celestial mechanics", online meeting, December 21, 2020 and ICRANet press release on that event
The event "Conjunction and Solstice between history and celestial mechanics. As planetary conjunctions were sources of improved planetary theories" has been held online on December 21, 2020, on the occasion of the Jupiter and Saturn's great conjunction. This allowed to reason on the hypothesis developed by Kepler on the Star of Bethlehem: in his opinion, the similar conjunction occurred in the year 7/6 b.c. was the cause of the appearance of the Star, it was not a star.
Fig. 7: the Star of Bethlehem in the Church of the Nativity (Bethlem).
Prof. Costantino Sigismondi, ICRANet collaborator and chair of the event, thanks also to the support of ICRANet and many other scientists from all over the world, organized this virtual meeting as well as a podcast meeting in order to create a nice occasion for discussion among students and researchers.
The virtual meeting started at 4:30 PM on Monday December 21, with the opening remarks made by Prof. Sigismondi and went on with presentations on "Short history and some activity from IOTA/ES" by Prof. Konrad Guhl (IOTA), on "Conjunctions and occultation" by Prof. Paolo Ochner (University of Padova), on "Kepler and the great conjunction" by Prof. Anna Maria Lombardi (University of Milan) and on "Planetary conjunctions, Invariant inequalities and the solar-climate oscillations" by Prof. Nicola Scafetta (University of Napoli). The concluding remarks have been made by Prof. Rahim Moradi (ICRANet Faculty Professor) on behalf of Prof. Remo Ruffini (Director of ICRANet).
This theoretical session has been also integrated with a lot podcast material prepared by Prof. Sigismondi (on "Jupiter, Saturn, Uranus and Neptune 1821", on the "Meridian transit in Saint Pieter, Vatican City", on "Jupiter and Mars in 1591", on "Jupiter and Saturn" both in 1563 and 7/6 b. C. as well as on "Astronomy in the Gospels: the Star of Bethlehem and the Eclipse on the Good Fridat"), by Prof. Pascal Descamps (on the "rapprochements Jupiter-Saturn 7 b.c", on the "rapprochements Jupiter-Saturn in 1562", on the "rapprochements Mars-Jupiter in 1591" as well as on the "rapprochements Mars-Saturn in 1604"). Other materials have been prepared by Prof. Paolo Zanna (on "The conjunction within us"), by Prof. Giorgio Rossi (on the "Conjunction Jupiter-Saturn in 1563"), by Prof. Marco Di Capua and Prof. Elizabeth Stillwachs - Marina Green, San Francisco, California USA (with some photos of Jupiter and Saturn in San Francisco) as well as by Prof. Enrico Guliani and Prof. Paul Waddington (on the "Conjunction Jupiter-Saturn" and on the "Moon at the winter solstice").
The program of the event and all the relevant podcast materials, can be found on the webpage of the meeting: http://www.icranet.org/index.php?option=com_content&task=view&id=1351
On that occasion, Prof. Sigismondi and ICRANet staff have also prepared a press release, both in Italian and in English.
Fig. 7: the Star of Bethlehem in the Church of the Nativity (Bethlem).
Prof. Costantino Sigismondi, ICRANet collaborator and chair of the event, thanks also to the support of ICRANet and many other scientists from all over the world, organized this virtual meeting as well as a podcast meeting in order to create a nice occasion for discussion among students and researchers.
The virtual meeting started at 4:30 PM on Monday December 21, with the opening remarks made by Prof. Sigismondi and went on with presentations on "Short history and some activity from IOTA/ES" by Prof. Konrad Guhl (IOTA), on "Conjunctions and occultation" by Prof. Paolo Ochner (University of Padova), on "Kepler and the great conjunction" by Prof. Anna Maria Lombardi (University of Milan) and on "Planetary conjunctions, Invariant inequalities and the solar-climate oscillations" by Prof. Nicola Scafetta (University of Napoli). The concluding remarks have been made by Prof. Rahim Moradi (ICRANet Faculty Professor) on behalf of Prof. Remo Ruffini (Director of ICRANet).
This theoretical session has been also integrated with a lot podcast material prepared by Prof. Sigismondi (on "Jupiter, Saturn, Uranus and Neptune 1821", on the "Meridian transit in Saint Pieter, Vatican City", on "Jupiter and Mars in 1591", on "Jupiter and Saturn" both in 1563 and 7/6 b. C. as well as on "Astronomy in the Gospels: the Star of Bethlehem and the Eclipse on the Good Fridat"), by Prof. Pascal Descamps (on the "rapprochements Jupiter-Saturn 7 b.c", on the "rapprochements Jupiter-Saturn in 1562", on the "rapprochements Mars-Jupiter in 1591" as well as on the "rapprochements Mars-Saturn in 1604"). Other materials have been prepared by Prof. Paolo Zanna (on "The conjunction within us"), by Prof. Giorgio Rossi (on the "Conjunction Jupiter-Saturn in 1563"), by Prof. Marco Di Capua and Prof. Elizabeth Stillwachs - Marina Green, San Francisco, California USA (with some photos of Jupiter and Saturn in San Francisco) as well as by Prof. Enrico Guliani and Prof. Paul Waddington (on the "Conjunction Jupiter-Saturn" and on the "Moon at the winter solstice").
The program of the event and all the relevant podcast materials, can be found on the webpage of the meeting: http://www.icranet.org/index.php?option=com_content&task=view&id=1351
 |
 |
| Fig. 8: Jupiter and Saturn between the Cicadee, December 15, 2020 (photo by Jorge Ruiz, Paraguay) | Fig 9: the Moon, Jupiter and Saturn from Ostia (Italy), December 18, 2020 (photo by Prof. Costantino Sigismondi) |
On that occasion, Prof. Sigismondi and ICRANet staff have also prepared a press release, both in Italian and in English.
6. Recent publications
Shakeri, S., Hajkarim, F. & Xue, SS. Shedding new light on sterile neutrinos from XENON1T experiment, published in J. High Energ. Phys. 2020, 194 (2020).
The XENON1T collaboration recently reported the excess of events from recoil electrons, possibly giving an insight into new area beyond the Standard Model (SM) of particle physics. We try to explain this excess by considering effective interactions between the sterile neutrinos and the SM particles. In this paper, we present an effective model based on one-particle-irreducible interaction vertices at low energies that are induced from the SM gauge symmetric four-fermion operators at high energies. The effective interaction strength is constrained by the SM precision measurements, astrophysical and cosmological observations. We introduce a novel effective electromagnetic interaction between sterile neutrinos and SM neutrinos, which can successfully explain the XENON1T event rate through inelastic scattering of the sterile neutrino dark matter from Xenon electrons. We find that sterile neutrinos with masses around 90 keV and specific effective coupling can fit well with the XENON1T data where the best fit points preserving DM constraints and possibly describe the anomalies in other experiments.
Link: https://doi.org/10.1007/JHEP12(2020)194
R. Yunis, C. R. Argüelles, N. E. Mavromatos, A. Moliné, A. Krut, M. Carinci, J. A. Rueda, R. Ruffini, Galactic center constraints on self-interacting sterile neutrinos from fermionic dark matter ("ino") models, published in Physics of the Dark Universe, Volume 30, article id. 100699 on December 2020.
The neutrino minimal standard model (νMSM) 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 vMSM 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 vMSM 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.
Link:
https://www.sciencedirect.com/science/article/abs/pii/S221268641930370X?via%3Dihub
Link nasa-ads: https://ui.adsabs.harvard.edu/abs/2020PDU....3000699Y/abstract
J. D. Uribe, E. A. Becerra-Vergara, J. A. Rueda, Neutrino Oscillations in Neutrino-Dominated Accretion Around Rotating Black Holes, published in Universe, vol. 7, issue 1, p. 7 on January 2021.
In the binary-driven hypernova model of long gamma-ray bursts, a carbon-oxygen star explodes as a supernova in the 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 flavor oscillations occur. Numerical simulations of the above system show that a part of the ejecta stays bound to the newborn Kerr black hole, leading to a new process of hypercritical accretion. We address herein, also for this phase of the binary-driven hypernova, the occurrence of neutrino flavor oscillations given the extreme conditions of high density (up to 1012 g cm−3) and temperatures (up to tens of MeV) inside this disk. We estimate the behavior of the electronic and non-electronic neutrino content within the two-flavor formalism (νeνx) 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 ∼(105-109) s−1, leading the disk to achieve flavor equipartition. This implies that the energy deposition rate by neutrino annihilation (ν+ν¯→e−+e+) in the vicinity of the Kerr black hole is smaller than previous estimates in the literature not accounting for flavor oscillations inside the disk. The exact value of the reduction factor depends on the νe and νx optical depths but it can be as high as ∼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.
Link: https://www.mdpi.com/2218-1997/7/1/7
Link nasa-ads: https://ui.adsabs.harvard.edu/abs/2021Univ....7....7U/abstract
Sahakyan, N.; Giommi, P., The strange case of the transient HBL blazar 4FGL J1544.3-0649, published in Monthly Notices of the Royal Astronomical Society, 202, stab011.
We present a multifrequency study of the transient γ-ray source 4FGL J1544.3-0649, a blazar that exhibited a remarkable behavior raising from the state of an anonymous mid-intensity radio source, never detected at high energies, to that of one of the brightest extreme blazars in the X-ray and γ-ray sky. Our analysis shows that the averaged γ-ray spectrum is well described by a powerlaw with a photon index of 1.87 ± 0.04, while the flux above 100 MeV is (8.0 ± 0.9) × 10-9 photon cm-2 s-1, which increases during the active state of the source. The X-ray flux and spectral slope are both highly variable, with the highest 2-10 keV flux reaching (1.28 ± 0.05) × 10-10 erg cm-2 s-1. On several observations the X-ray spectrum hardened to the point implying as SED peak moving to energies larger than 10 keV. As in many extreme blazars the broadband spectral energy distribution can be described by a homogeneous one-zone synchrotron-self-Compton leptonic model. We briefly discuss the potential implications for high-energy multi-messenger astrophysics in case the dual behavior shown by 4FGL J1544.3-0649 does not represent an isolated case, but rather a manifestation of a so far unnoticed relatively common phenomenon.
DOI: https://doi.org/10.1093/mnras/stab011
Link: https://ui.adsabs.harvard.edu/abs/2021MNRAS.tmp...56S/abstract
Acciari, V. A.; Ansoldi, S.; Antonelli, L. A..... Sahakyan, N., et al., Multiwavelength variability and correlation studies of Mrk 421 during historically low X-ray and γ-ray activity in 2015-2016, published in Monthly Notices of the Royal Astronomical Society, 2020, staa3727.
We report a characterization of the multi-band flux variability and correlations of the nearby (z=0.031) blazar Markarian 421 (Mrk 421) using data from Metsähovi, Swift, Fermi-LAT, MAGIC, FACT and other collaborations and instruments from November 2014 till June 2016. Mrk 421 did not show any prominent flaring activity, but exhibited periods of historically low activity above 1 TeV (F>1TeV < 1.7× 10-12 ph cm-2 s-1) and in the 2-10 keV (X-ray) band (F2 - 10 keV < 3.6 × 10-11 erg cm-2 s-1), during which the Swift-BAT data suggests an additional spectral component beyond the regular synchrotron emission. The highest flux variability occurs in X-rays and very-high-energy (E>0.1 TeV) γ-rays, which, despite the low activity, show a significant positive correlation with no time lag. The HRkeV and HRTeV show the harder-when-brighter trend observed in many blazars, but the trend flattens at the highest fluxes, which suggests a change in the processes dominating the blazar variability. Enlarging our data set with data from years 2007 to 2014, we measured a positive correlation between the optical and the GeV emission over a range of about 60 days centered at time lag zero, and a positive correlation between the optical/GeV and the radio emission over a range of about 60 days centered at a time lag of 43+9−6 days. This observation is consistent with the radio-bright zone being located about 0.2 parsec downstream from the optical/GeV emission regions of the jet. The flux distributions are better described with a LogNormal function in most of the energy bands probed, indicating that the variability in Mrk 421 is likely produced by a multiplicative process.
DOI: https://doi.org/10.1093/mnras/staa3727
Link: https://ui.adsabs.harvard.edu/abs/2020MNRAS.tmp.3563A/abstract
The XENON1T collaboration recently reported the excess of events from recoil electrons, possibly giving an insight into new area beyond the Standard Model (SM) of particle physics. We try to explain this excess by considering effective interactions between the sterile neutrinos and the SM particles. In this paper, we present an effective model based on one-particle-irreducible interaction vertices at low energies that are induced from the SM gauge symmetric four-fermion operators at high energies. The effective interaction strength is constrained by the SM precision measurements, astrophysical and cosmological observations. We introduce a novel effective electromagnetic interaction between sterile neutrinos and SM neutrinos, which can successfully explain the XENON1T event rate through inelastic scattering of the sterile neutrino dark matter from Xenon electrons. We find that sterile neutrinos with masses around 90 keV and specific effective coupling can fit well with the XENON1T data where the best fit points preserving DM constraints and possibly describe the anomalies in other experiments.
Link: https://doi.org/10.1007/JHEP12(2020)194
R. Yunis, C. R. Argüelles, N. E. Mavromatos, A. Moliné, A. Krut, M. Carinci, J. A. Rueda, R. Ruffini, Galactic center constraints on self-interacting sterile neutrinos from fermionic dark matter ("ino") models, published in Physics of the Dark Universe, Volume 30, article id. 100699 on December 2020.
The neutrino minimal standard model (νMSM) 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 vMSM 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 vMSM 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.
Link:
https://www.sciencedirect.com/science/article/abs/pii/S221268641930370X?via%3Dihub
Link nasa-ads: https://ui.adsabs.harvard.edu/abs/2020PDU....3000699Y/abstract
J. D. Uribe, E. A. Becerra-Vergara, J. A. Rueda, Neutrino Oscillations in Neutrino-Dominated Accretion Around Rotating Black Holes, published in Universe, vol. 7, issue 1, p. 7 on January 2021.
In the binary-driven hypernova model of long gamma-ray bursts, a carbon-oxygen star explodes as a supernova in the 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 flavor oscillations occur. Numerical simulations of the above system show that a part of the ejecta stays bound to the newborn Kerr black hole, leading to a new process of hypercritical accretion. We address herein, also for this phase of the binary-driven hypernova, the occurrence of neutrino flavor oscillations given the extreme conditions of high density (up to 1012 g cm−3) and temperatures (up to tens of MeV) inside this disk. We estimate the behavior of the electronic and non-electronic neutrino content within the two-flavor formalism (νeνx) 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 ∼(105-109) s−1, leading the disk to achieve flavor equipartition. This implies that the energy deposition rate by neutrino annihilation (ν+ν¯→e−+e+) in the vicinity of the Kerr black hole is smaller than previous estimates in the literature not accounting for flavor oscillations inside the disk. The exact value of the reduction factor depends on the νe and νx optical depths but it can be as high as ∼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.
Link: https://www.mdpi.com/2218-1997/7/1/7
Link nasa-ads: https://ui.adsabs.harvard.edu/abs/2021Univ....7....7U/abstract
Sahakyan, N.; Giommi, P., The strange case of the transient HBL blazar 4FGL J1544.3-0649, published in Monthly Notices of the Royal Astronomical Society, 202, stab011.
We present a multifrequency study of the transient γ-ray source 4FGL J1544.3-0649, a blazar that exhibited a remarkable behavior raising from the state of an anonymous mid-intensity radio source, never detected at high energies, to that of one of the brightest extreme blazars in the X-ray and γ-ray sky. Our analysis shows that the averaged γ-ray spectrum is well described by a powerlaw with a photon index of 1.87 ± 0.04, while the flux above 100 MeV is (8.0 ± 0.9) × 10-9 photon cm-2 s-1, which increases during the active state of the source. The X-ray flux and spectral slope are both highly variable, with the highest 2-10 keV flux reaching (1.28 ± 0.05) × 10-10 erg cm-2 s-1. On several observations the X-ray spectrum hardened to the point implying as SED peak moving to energies larger than 10 keV. As in many extreme blazars the broadband spectral energy distribution can be described by a homogeneous one-zone synchrotron-self-Compton leptonic model. We briefly discuss the potential implications for high-energy multi-messenger astrophysics in case the dual behavior shown by 4FGL J1544.3-0649 does not represent an isolated case, but rather a manifestation of a so far unnoticed relatively common phenomenon.
DOI: https://doi.org/10.1093/mnras/stab011
Link: https://ui.adsabs.harvard.edu/abs/2021MNRAS.tmp...56S/abstract
Acciari, V. A.; Ansoldi, S.; Antonelli, L. A..... Sahakyan, N., et al., Multiwavelength variability and correlation studies of Mrk 421 during historically low X-ray and γ-ray activity in 2015-2016, published in Monthly Notices of the Royal Astronomical Society, 2020, staa3727.
We report a characterization of the multi-band flux variability and correlations of the nearby (z=0.031) blazar Markarian 421 (Mrk 421) using data from Metsähovi, Swift, Fermi-LAT, MAGIC, FACT and other collaborations and instruments from November 2014 till June 2016. Mrk 421 did not show any prominent flaring activity, but exhibited periods of historically low activity above 1 TeV (F>1TeV < 1.7× 10-12 ph cm-2 s-1) and in the 2-10 keV (X-ray) band (F2 - 10 keV < 3.6 × 10-11 erg cm-2 s-1), during which the Swift-BAT data suggests an additional spectral component beyond the regular synchrotron emission. The highest flux variability occurs in X-rays and very-high-energy (E>0.1 TeV) γ-rays, which, despite the low activity, show a significant positive correlation with no time lag. The HRkeV and HRTeV show the harder-when-brighter trend observed in many blazars, but the trend flattens at the highest fluxes, which suggests a change in the processes dominating the blazar variability. Enlarging our data set with data from years 2007 to 2014, we measured a positive correlation between the optical and the GeV emission over a range of about 60 days centered at time lag zero, and a positive correlation between the optical/GeV and the radio emission over a range of about 60 days centered at a time lag of 43+9−6 days. This observation is consistent with the radio-bright zone being located about 0.2 parsec downstream from the optical/GeV emission regions of the jet. The flux distributions are better described with a LogNormal function in most of the energy bands probed, indicating that the variability in Mrk 421 is likely produced by a multiplicative process.
DOI: https://doi.org/10.1093/mnras/staa3727
Link: https://ui.adsabs.harvard.edu/abs/2020MNRAS.tmp.3563A/abstract