ICRANet Newsletter

ICRANet Newsletter
August - September 2017

English - Italian - Portuguese - Russian

SUMMARY
1. Two new publications from the Director of ICRANet-Yerevan, prof. Narek Sahakyan, just accepted for publication in ApJ (Impact factor: 5.533) and in A&A (Impact factor: 5.014)
2. ICRANet and the European Researchers' Night
3. ICRANet – WIGNER: New cooperation agreement
4. ICRANet seminar on 8^th of September by Takahiro Hayashinaka
5. Recent publications
6. IRAP PhD 2017 call extension
7. Upcoming meetings

1.Two new publications from the Director of ICRANet-Yerevan, prof. Narek Sahakyan, just accepted for publication in ApJ (Impact factor: 5.533) and in A&A (Impact factor: 5.014)

1. D. Zargaryan, S. Gasparyan, V. Baghmanyan, N. Sahakyan, “Comparing 3C 120 jet emission at small and large scales”, arXiv:1709.05175, Accepted for publication in Astronomy & Astrophysics.

Important information on the evolution of the jet can be obtained by comparing the physical state of the plasma at its propagation through the broad-line region (where the jet is most likely formed) into the intergalactic medium, where it starts to significantly decelerate. The constraints on the physical parameters in the innermost (≤ pc) and outer (≥ kpc) regions of the 3C 120 jet, see Fig. 1., are compared by means of a detailed multiwavelength analysis and theoretical modeling of their broadband spectra. The data collected by Fermi LAT, Swift and Chandra are analyzed together and the spectral energy distributions are modeled using a leptonic synchrotron and inverse Compton model, taking into account the seed photons originating inside and outside of the jet. The model parameters are estimated using the MCMC method. The γ-ray flux from the inner jet of 3C 120 was characterized by rapid variation from MJD 56900 to MJD 57300. Two strong flares were observed on April 24, 2015 when, within 19.0 minutes and 3.15 hours the flux was as high as (7.46±1.56)×10^-6 cm⁻²s⁻¹ and (4.71±0.92)×10⁻⁶cm⁻²s⁻¹ respectively. The broadband emission in the quiet and flaring states can be described as SSC emission while IC scattering of dusty torus photons cannot be excluded for the flaring states. The X-ray emission from the knots can be well reproduced by IC scattering of CMB photons only if the jet is highly relativistic (since even when δ=10 still U_e/U_B≥80). These extreme requirements can be somewhat softened assuming the X-rays are from the synchrotron emission of a second population of very-high-energy electrons. The jet power estimated at two scales is consistent, suggesting that the jet does not suffer severe dissipation, it simply becomes radiatively inefficient.

2. V. Baghmanyan, S. Gasparyan, N. Sahakyan, “Rapid Gamma-ray variability of NGC 1275”, arXiv:1709.03755v1, Accepted for publication in ApJ.
A detailed analysis of the γ-ray light curve of NGC 1275 is reported using the Fermi large area telescope data accumulated in 2008-2017. Major γ-ray flares were observed in October 2015 and December 2016/January 2017 when the source reached a daily peak flux of (2.21±0.26)×10⁻⁶cm⁻²s⁻¹, achieving a flux of (3.48±0.87)×10⁻⁶cm⁻²s⁻¹ within 3 hours, which corresponds to an apparent isotropic γ-ray luminosity of ≃3.84×10⁴⁵erg s⁻¹. The most rapid flare had e-folding time as short as 1.21±0.22 hours which had never been previously observed for any radio galaxy in γ-ray band. Also γ-ray spectral changes were observed during these flares: in the flux versus photon index plane the spectral evolution follows correspondingly a counter clockwise and a clockwise loop inferred from the light curve generated by an adaptive binning method. On December 30, 2016 and January 01, 2017 the X-ray photon index softened (Γ_X≃1.75−1.77) and the flux increased nearly ∼3 times as compared with the quiet state. The observed hour-scale variability suggests a very compact emission region (Rγ≤5.22×10¹⁴(δ/4)cm) implying that the observed emission is most likely produced in the subparsec-scale jet if the entire jet width is responsible for the emission. During the active periods the γ-ray photon index hardened, shifting the peak of the high energy spectral component to >GeV, making it difficult to explain the observed X-ray and γ-ray data in the standard one-zone synchrotron self-Compton model.

2. ICRANet and the European Researchers' Night

Also this year ICRANet together with the Municipality of Pescara, through Europe Direct, and in collaboration with the University “G. d’Annunzio” of Chieti-Pescara, organized the “European Researchers' Night”. The event attracts a lot of people every year and offers visitors a unique opportunity to meet researchers and to take part in science activities aiming to showcase both the fascination of research as a career and its significant societal impact. The program of this event can be found here (in Italian). During the morning the ICRANet Headquarters in Pescara has hosted 200 students of high schools. On this occasion, the Director of ICRANet, Professor Remo Ruffini delivered the first "Carlo Pace Awards" in the presence of the Mayor of Pescara Marco Alessandrini and Senator Federica Chiavaroli, Undersecretary of Justice.
This award was given to:
- Francesca Allegrino from Liceo Galileo Galilei, Pescara, for student’s category
- Tiziana Pompa from Liceo Galileo Galilei, Pescara, for professor’s category
- Costantino Sigismondi from Liceo Scientifico Galileo Ferraris, Roma, for professor’s category


After the award ceremony three lectures were delivered by ICRANet scientists: Dr. Marco Muccino – Faculty at ICRANet - “Visitare l'Universo con i Gamma Ray Bursts (GRBs)“; Prof. Paolo Giommi – ASI, Agenzia Spaziale Italiana – “Osservazioni multimessenger dei nuclei galattici attivi” and Dr. Laura Becerra – Università di Roma “La Sapienza” and ICRANet “Simulando le Hypernovae all'ICRANet ed a Los Alamos”.

These morning public lectures were followed by the evening public lectures at Aurum with the following program:


21.00 - Professor Remo Ruffini - Director of ICRANet and Wang Yu - Student of IRAP Ph.D., “Esplorando l'Universo con i satelliti SWIFT e FERMI”
21.45 - Professor Jorge Rueda – ICRANet and Jose Rodriguez Ruiz - Student of IRAP Ph.D., “Simulando la emissione di onde gravitazionali”
22.30 - Professor Paolo Giommi ASI – Agenzia Spaziale Italiana and Carlos Henrique Brandt - Student of IRAP Ph.D., “Il Centro Dati dell'ICRANet in Brasile (BSDC)”.

In the evening, ICRANet center in Pescara opened its door to the public. Prof. Vereshchagin, Prof. Belinski, Prof. Xue and some PhD students showed to the visitors the ICRANet building and research activities.


During the evening, at Aurum, ICRANet has organized, for the first time, the exhibition dedicated to the birth of the Relativistic Astrophysics and its major figures such as Einstein, Heisenberg and Fermi, as well as the scientific collaboration between ICRANet and China, centered on Professor LiZhi Fang, First President of ICRANet Steering Committee. This exhibition, which is part of the project: "Of Talent and Curiosity. When the eagle and the sparrow fly together”, will be moved, in the next months, to Rome at the Marco Besso Foundation.

Video from this event is available here.

3. ICRANet – WIGNER: New cooperation agreement

New collaboration agreement has been recently signed between ICRANet, International Center for Relativistic Astrophysics Network, and WIGNER Research Centre for Physics in Budapest, Hungary. This Agreement was signed by Prof. Peter Levai, Director General of WIGNER Research Centre, and Prof. Remo Ruffini, Director of ICRANet. It will consist of joint actions including: promotion of theoretical and observational research activities within the field of Relativistic Astrophysics; the exchange of faculty members, researchers, post-doctoral fellows and students; promotion of technological developments. Special attention will be devoted to space missions and advanced experiments and observations from the ground and underground facilities and observatories. The text of the agreement can be found here.

On September 8, 2017, Takahiro Hayashinaka, of the Research Center for the Early Universe (RESCEU), Department of Physics, Graduate School of Science, of the University of Tokyo (Japan), gave a seminar at the ICRANet center in Pescara, titled: " de Sitter QED and non-perturbative renormalization approach ". This talk was dedicated to show recent activities on the topic. In the first half of the talk, it was shown how negative, i.e. unstable, electromagnetic responses have been revealed. Though this phenomenon was repeatedly reported by several groups recently, neither physical origin or interpretation of the phenomenon have been explicitly given up to the present. Inspired by a relevant negative response phenomenon in a specific ferroelectric matter, it was recognized importance of spontaneous symmetry breaking and the effective action or potential of the system. A variation of renormalization group technique, which is called non-perturbative renormalization group (NPRG), was used for evaluation of the effective action. As a result, undesirable behavior of the IR modes in de Sitter spacetime can be virtually suppressed. It was shown how the electric field can change the shape of the scalar effective potential.

5. Recent publications

B. Eslam Panah, G. H. Bordbar, S. H. Hendi, R. Ruffini, Z. Rezaei, R. Moradi, “Expansion of magnetic neutron stars in an energy (in)dependent spacetime”, arXiv:1707.06460, accepted for publication in Astrophys. J.

Regarding the strong magnetic field of neutron stars and high energy regime scenario which is based on high curvature region near the compact objects, one is motivated to study magnetic neutron stars in an energy dependent spacetime. In this paper, we show that such strong magnetic field and energy dependency of spacetime have considerable effects on the properties of neutron stars. We examine the variations of maximum mass and related radius, Schwarzschild radius, average density, gravitational redshift, Kretschmann scalar and Buchdahl theorem due to magnetic field and also energy dependency of metric. First, it will be shown that the maximum mass and radius of neutron stars are increasing function of magnetic field while average density, redshift, the strength of gravity and Kretschmann scalar are decreasing functions of it. These results are due to a repulsive-like force behavior for the magnetic field. Next, the effects of the gravity's rainbow will be studied and it will be shown that by increasing the rainbow function, the neutron stars could enjoy an expansion in their structures. Then, we obtain a new relation for the upper mass limit of a static spherical neutron star with uniform density in gravity's rainbow (Buchdahl limit) in which such upper limit is modified as M_eff<4c²R/9G. In addition, stability and energy conditions for the equation of state of neutron star matter are also investigated and a comparison with empirical results is done. It is notable that the numerical study in this paper is conducted by using the lowest order constrained variational (LOCV) approach in the presence of magnetic field employing AV18 potential.

6. IRAP PhD 2017 call extension

The International Relativistic Astrophysics Ph.D. (IRAP PhD) – Joint Doctorate Program sponsored by ICRANet.
A deadline for eight positions open internationally and directly sponsored by the participating institutions has been extended to 25th of October 2017.
Please see the poster here.
The coordinated effort of many international organizations such as the National Aeronautics and Space Administration (NASA), the European Center for Nuclear Research (CERN), the European Space Agency (ESA), the European Southern Observatory (ESO), has led to an unprecedented amount of scientific information from the microphysical world all the way to the entire Universe. To harvest the results of these scientific missions, a specific Ph. D. program has been envisaged in order to involve the students in the analysis and modeling of the above observational data within the theory of general relativity and relativistic quantum and classical field theories.

The students will also be involved in innovative experimental programs in relativistic astrophysics. The program provides expertise in the most advanced topics of experimental, mathematical and theoretical physics relevant to the context of astronomy, astrophysics and cosmology. These activities, being necessarily international, the scientific and academic institutions, indicated below, participate with their own specific scientific specialties and a joint degree is delivered, at the end of the program.
The Institutions participating in the IRAP PhD are: the international organization ICRANet as coordinating institution and the University of Nice Sophia Antipolis as the host Institution; the Albert Einstein Institute, Potsdam (Germany); Indian Centre for Space Physics, Kolkata (India); Observatoire de la Cote D’Azur, Nice (France); University of Ferrara (Italy); University of Rome, la Sapienza (Italy); University of Savoie, Annecy (France).
The Final Ph.D. degree will be jointly delivered by the Academic Institutions participating in the program.
We encourage applications from the best candidates worldwide, independent of nationality, gender or background.
The Courses are listed on the website. Each student will have to follow 180 hours of courses during the three years of the Ph.D. program. There is also a possibility to follow courses from other Physics, Mathematics, Astronomy and Astrophysics Ph.D. programs in each participating institution, after approval by the Faculty.

7. Upcoming meetings

a. Fifteenth Marcel Grossmann Meeting on General Relativity (MG15), Rome, Italy

The Fifteenth Marcel Grossmann Meeting on General Relativity and Relativistic Astrophysics will be held at the campus of the University of Rome “La Sapienza” in Rome (Italy) on July 1-7, 2018, celebrating the 50th anniversary of the first neutron star discovery marking the birth of relativistic astrophysics.

There will be four satellite meetings of MG15 in 2018:
Third Zeldovich meeting, at the National Academy of Sciences of Belarus in Minsk (Belarus), 23-27 April 2018;
First Markarian meeting, at the National Academy of Sciences in Yerevan (Armenia), 21-25 May 2018;
Second Julio Garavito Armero meeting on Relativistic Astrophysics, in Bucaramanga (Colombia), 30 July – 3 August, 2018;
Third Cesar Lattes Meeting, in Rio de Janeiro (Brazil), 6-10 August 2018.

Further information will be available at the website: http://www.icra.it/MG/mg15/

b. The Third Zeldovich meeting, Minsk, Belarus