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ICRANet Newsletter
December 2016 – January 2017

1. A first generation of young Brazilian professors, graduated from the IRAP PhD, carry on the fundamental message of Prof.s Malheiro, Ruffini and Rueda: an additional clear success of the CAPES-ICRANet joint program

A new paper "Thermal X-ray emission from massive, fast rotating, highly magnetized white dwarfs" is just published by the group of scientists from ICRANet, including: D. L. Cáceres, S. M. de Carvalho, J. G. Coelho, R. C. R. de Lima, Jorge A. Rueda, in one of the leading journals in astrophysics (Impact Factor 4.952), Monthly Notices of the Royal Astronomical Society. The publication is available here: https://doi.org/10.1093/mnras/stw3047.
There are two special types of compact objects: anomalous X‐ray pulsars (AXPs) and soft gamma repeaters (SGRs), which possess very distinct properties among pulsars, namely: lack of evidence of binary companions; narrow distribution of the spin period between 5 and 12 seconds; secular spin-down on timescales of 103-105 years; variability on very different timescales; absence of radio emission; association with supernova remnants (in some cases) [1]. Historically SGRs were discovered through the detection of repeating short bursts in the hard X-ray/soft gamma-ray range, while persistent emission from AXPs was first detected in the soft X-ray range. Subsequent observations at different wavelengths showed that both types of objects share many characteristics. They are now considered as the same class of objects.
When AXPs and SGRs are viewed as (1) neutron stars (NS) (2) with mass equal to solar mass and (3) radius 10 km, their emitted power appears to exceed by several orders of magnitude the rotational energy loss, requiring different energy source. The most unorthodox proposal in the literature was to use the magnetic energy in the bulk as the energy source powering these objects, e.g. magnetar [2]. The magnetic field estimate, based on observed period and its first derivative, exceeds many times the critical quantum value for vacuum polarization, Bc=4.4x1013 Gauss.
A very different model has been proposed by Malheiro, Ruffini and Rueda [5] following the previous works [6,7]. They critically reanalyzed the above three assumptions, understood as not necessary in the explanation of both SGRs and AXPs. The model is based on canonical physics and astrophysics and describes SGRs and AXPs as powered by rotational energy of massive highly magnetized rotating white dwarfs (WDs), in total analogy with pulsars powered by rotating neutron stars. Given its much larger moment of inertia, the WD model naturally explains the energy budget of persistent emission of AXPs and SGRs. Moreover, emission of giant flares and bursts can be explained as consequences of glitches with rotational period fractional change from 10-7 up to 10-3. It turns out that within the WD model the energetic of both the steady emission as well as that of the outbursts following the glitch can be simply explained in terms of the loss of rotational energy. This is in sharp contrast with alternative models of magnetars or quark stars, where different components are required for explanation of steady emission and outbursts, respectively. As opposed to the NS case, the magnetic fields involved in the WD model are not extreme and are of the order of the ones observed in most magnetized isolated WDs.

The group picture of the Adriatic Workshop held in Pescara in June 20-30, 2016, at the time when this new work has been carried out. In the first row is prof. Remo Ruffini (forth from left) and prof. Manuel Malheiro (third from right). In the second row prof. Jorge Rueda (fifth from left), and in the last row Diego Caceres (second from right)

The new publication by D. L. Caceres et al. [8] focuses on the thermal X‐ray emission observed in SGRs and AXPs, in particular 4U 0142+61 and 1E 2259 586, both previously considered in the literature as magnetars [9,10]. Contrary to the magnetar model, where the structure of the magnetic field is unknown, the specific WD rotation assumption, with a well established magnetic field, allows to make the new theoretical developments and further refine the theoretical analysis. Following the Malheiro, Ruffini and Rueda [5] such thermal emission is similar to the one operating in usual pulsars: the magnetic polar cap heating by back flowing electrons and positrons created in the magnetosphere. The authors of publication [8] show that the kinetic energy of particles is effectively transformed into heat in the thin layer on the surface of the WD polar cap, hence this energy is efficiently radiated in the form of thermal soft X-rays. This work by D. L. Caceres et al. confirms previous expectations by Malheiro, Ruffini and Rueda [5] that in AXPs, in addition to the blackbody component observed in the optical wavelengths and interpreted as the surface temperature of the cooling white dwarfs, the blackbody component seen in X-rays can be of magnetospheric origin. This work also adds to the theory of white dwarfs and sheds new light on the properties of magnetosphere, magnetic field structure and pulsed emission properties of rotating magnetized WDs.
Professor S.O. Kepler, the author of the most extended catalogue of white dwarfs
It is appropriate to recall that Brazil through the work of prof. Kepler has today reached a forefront position in the study of WDs. Up to about 600 magnetized WDs have been recently identified in the largest white dwarf catalogue made with the Sloan Digital Sky Survey (SDSS), published by S.O. Kepler [11,12]. This catalogue now contains dozens of thousands of spectroscopically identified white dwarfs. Such unprecedented number of known WDs had enormous impact on the study of these stars. The most recent update of the catalogue has just appeared in 2017 [13].

The work of D. L. Caceres et al. [8] inserts a new fundamental understanding of the role of rotation and magnetic fields in WDs.

[1] S. Mereghetti, Astron Astrophys Rev 15 (2008) 225; S. Mereghetti, Brazilian Journal of Physics 43 (2013) 356.
[2] R. C. Duncan and C. Thompson ApJL 392 (1992) L9; C. Thompson and R. C. Duncan, MNRAS 275 (1995) 255; C. Thompson and R. C. Duncan, ApJ 473 (1996) 322.
[3] H. Tong and R.-X. Xu, IJMPE 20 (2011) 15.
[4] N. Rea, et al., Science 330 (2010) 944.
[5] M. Malheiro, J. A. Rueda and R. Ruffini, PASJ 64 (2012) 56.
[6] B. Paczynski, ApJ 365 (1990) L9.
[7] V. Usov, ApJ 427 (1994) 984.
[8] D. L. Cáceres et al., MNRAS 465 (2017) 4434.
[9] Z. Wang, D. Chakrabarty and D. L. Kaplan, Nature 440 (2006) 772.
[10] R. F. Archibald et al, Nature 497 (2013) 591.
[11] S. O. Kepler, et al., MNRAS 446 (2015) 4078.
[12] E. Garcia-Berro, M. Kilic and S.O. Kepler, IJMPD 25 (2016) 1630005.
[13] S. O. Kepler, arXiv:1702.01134.

About the authors
foto Diego Leonardo Caceres Uribe is from Colombia, he is a student of the IRAP PhD program. At the moment in ICRANet Pescara with an Italian fellowship.
foto Sheyse Martins de Carvalho from Brazil has been the Erasmus Mundus IRAP PhD student and received her PhD degree in 2013. She was also CAPES-ICRANet Postdoc at Universidade Federal Fluminense (UFF), from 2014 to February 2016. Currently she is Professor at Universidade Federal do Tocantins (UFT).
foto Jaziel Goulart Coelho has been the CAPES-ICRANet postdoc at Sapienza University of Rome, from February 2014 to January 2015. Currently he is postdoctoral student at Instituto Nacional de Pesquisas Espaciais (INPE), Brazil.
foto Rafael de Lima has been the CAPES-ICRANet postdoc at ICRANet headquarters in Pescara from March 2014 to February 2016. Currently he is Professor at Universidade do Estado de Santa Catarina (UDESC), Brazil.
foto Jorge Rueda is Professor of ICRANet faculty. He has been CAPES-ICRANet senior visitor to Brazil in 2013-2015.

This work is performed within the collaboration between ICRANet and Brazilian universities, see:

2. A new ICRANet center in Isfahan

Prof. Remo Ruffini, Director of ICRANet, visited together Dr. Narek Sahakyan (Director of the ICRANet seat in Yerevan) different centers and institutes in Iran: the Isfahan University of Technology on December 10 and 11, 2016, the Institute for Advanced Studies in Basic Sciences (Zanjan) and the Shahid Beheshti University. During this visit it was inaugurated also the ICRANet Center at the Physics Department of IUT, Isfahan.

From left to right: Dr. Narek Sahakyan (Director of the ICRANet seat in Yerevan), Prof. Remo Ruffini (ICRANet Director), Prof. Mahmood Modarres-Hashemi (President of IUT), Prof Parviz Kameli (Head of IUT physics department) and Prof. Moslem Zarei (Deputy of Research of IUT physics Department)

On 10 and 11 December Professor Ruffini met the President of Isfahan University of Technology and other Officials. After the tour of department of Physics he had a seminar at the department of Physics and a meeting with the faculty of Physics Department. In this travel Professor Ruffini was together the Prof Sahakyan who gave a lecture at the department of Physics.

foto foto
foto foto
Prof. Ruffini visits IASBS - Institute for Advanced Studies in Basic Sciences (Zanjan)

During this travel in Iran Professor Ruffini visited also the Institute for Advanced Studies in Basic Sciences (IASBS) in Zanjan and he met Professor Yousef Sobouti, founder of this Institute. Prof. Sobouti Yousef is Iranian theoretical physicist with worldwide scientific prominence. He was a PhD student of the Nobel Laureate Subrahmanyan Chandrasekhar. The Institute for Advanced Studies in Basic Sciences (IASBS) is currently known as the University of Advanced Studies in Basic Sciences. For more information see: http://iasbs.ac.ir/~sobouti/

Prof. Ruffini visits SBU - Shahid Beheshti University, from left to right: Prof. Seyed Mohammad Sadegh Movahed, Prof. Reza Mansouri, Prof. Vahid Ahmadi, Prof. Remo Ruffini, Dr. Narek Sahakyan

1. I UT Isfahan University of Technology - Isfahan, Iran (February 21, 2016)
2. Sharif University of Technology - Teheran, Iran (March 12, 2016)
3. IASBS Institute for Advanced Studies in Basic Sciences - Zanjan, Iran (9 April 2016)
4. IPM Institute for Research in Fundamental Sciences - Teheran, Iran (May 3, 2016)
5. Shiraz University - Shiraz, Iran (March 21, 2016)
The texts of these agreements can be found here.

3. The 1st ICRANet Catalog of Binary-driven Hypernovae and the BSDC

The director of ICRANet, Professor Remo Ruffini, announces the publication of the first ICRANet catalog of binary-driven hypernovae (IBdHNe), counting 175 sources observed up to the end of 2016 [1-3].
In a series of recent publications, scientists from ICRANet led by professor Remo Ruffini have reached a novel comprehensive picture of gamma-ray bursts (GRBs) thanks to their development of a series of new theoretical approaches. Among those, the induced gravitational collapse (IGC) paradigm explains a class of energetic, long-duration GRBs associated with Ib/c supernovae (SN), recently named BdHNe (see Figure 1 and 2, and [4-7]).

foto foto
Fig. 1: Graphic representation of the IGC scenario. The Ns companion accretes material from the expanding outer layers of the SN which just exploded. If the binary system is tight enough, the accretion process becomes hypercritical, and the NS eventually collapse to a black hole, emitting a GRB. Fig. 2: This space-time diagram shows all the different physical processes and relative emissions occurring in a BdHN phenomenon.

BdHNe have a well defined set of observational features which allow to identify them:
- long duration of the GRB explosion, namely larger than 2 s in the rest frame;
- a total energy, released in all directions by the GRB explosion, larger than 1052 ergs;
- peak energy released during the GRB explosion larger than 200 keV;
- presence of a flare in the X-ray emission around 100 s in the rest-frame after the GRB explosion, visible if dominant over the underlying X-ray decaying emission [1];
- a plateau phase in the X-ray luminosity emitted between ~100 and ~104 s in the rest-frame after the GRB explosion;
- a universal late time power-law decay in the X-rays luminosity after 104 s, with typical decaying slope of ~1.5 [3, 8].
The first three features regard the prompt GRB emission observed in the gamma-rays by the GBM, BAT, Konus instruments onboard, respectively, Fermi, Swift, Wind satellites. The following three features are observed within the long lasting decaying X-ray emission, well covered by the XRT instrument onboard Swift.

Fig. 3: The first 20 rows of the 1st IBdHN Catalog showing some of the significant observed quantities. The first seven BdHNe form the so called Golden Sample, the first source which have been identified as BdHNe

Thanks to this novel theoretical and observational understanding, it was possible for ICRANet scientists to build the 1st BdHNe catalog, composed by the 175 BdHNe identified up to the end of 2016. BdHNe are named as "IBdHN", where the "I" stands for ICRANet, followed by the number identifying the correspondent GRB date of explosion.
Figure 3 shows the first 20 rows of the 1st IBdHNe catalog. The columns show some of the significant observed quantities of the BdHN. The complete list of the quantities contained in the catalog follows:
- z: the observed redshift, z, which gives us information on the distance of the source;
- r-f T90: the duration of the GRB in the rest-frame, namely the observed time during which the GRB has released 90% of its energy corrected by the redshift;
- Eiso: the total energy released by the GRB in any direction, computed between 1-104 keV;
- tstart: the beginning rest-frame time of the late X-ray power-law behaviour;
- tend: the rest-frame time of the last X-ray data observed by Swift/XRT;
- slope: decaying slope of the late X-ray power-law behaviour;
- ELT: total energy released in all directions in the X-ray band between 104 and 106 s in the rest-frame after the GRB explosion;
- angle: inferred opening angle of the late beamed X-ray emission
- flare: marks the presence of a flare around 100 s in the rest-frame, visible in the X-rays when dominant over the underlying decaying emission;
- satellite: name of the satellite which has the best observed data in the gamma-ray band;
- GCN: number of the GCN circular correspondent to the best gamma-ray data of the source.
This catalogue is currently uploaded in the BSDC.

[1] Ruffini, R., Wang, Y., Muccino, M., et al. in preparation
[2] Ruffini, R., Rueda, J. A., Muccino, M., et al. 2016, ApJ, 832, 136
[3] Pisani, G. B., Ruffini, R., Aimuratov, Y., et al. 2016, ApJ, 833, 159
[4] Fryer, C. L., Rueda, J. A., & Ruffini, R. 2014, ApJ, 793, L36
[5] Rueda, J. A., Ruffini, R., 2012, ApJ, 758, L7
[6] Ruffini, R., Wang, Y., Enderli, M., et al. 2015, ApJ, 798, 10
[7] Ruffini, R., Muccino, M., Bianco, C. L., et al. 2014, A&A, 565, L10
[8] Pisani, G. B., Izzo, L., Ruffini, R., et al. 2013, A&A, 552, L5 https://gcn.gsfc.nasa.gov/gcn3_archive.html

4. The First Brazilian ICRANet Gamma-ray Blazar catalog and BSDC

There are the following five main projects within BSDC, on which Prof. Paolo Giommi collaborates with postdoc from Brazil, Dr. Bruno Sversut Arsioli, who obtained his PhD within IRAP PhD program promoted by ICRANet.


The first one, the 1WHSP, is a sample of HSP blazars, with about 1000 objects at |b|>20˚, built based on multifrequency selection criteria including IR colours. At the time, this sample was the largest HSP catalog available, and was key to understand that the CTA sky will be full of new sources to study. This sample is a collection of HE and VHE candidates, to be observed with current and future Cherenkov Telescopes. With this sample, we also study and suggest new association with sources from the 3FGL catalog, which were then considered by the Fermi-LAT team for the 3LAC catalog (listing AGNs with gamma-ray counterparts). In addition, this work also discusses population properties for this particular blazar-family. This work is published in A&A 579, A34 (2015), and is also available online: https://arxiv.org/abs/1504.02801; and a direct link to the SED builder tool is here: http://www.asdc.asi.it/1whsp/ in collaboration with YuLing Chang (also IRAP PhD student, from Taiwan), 1WHSP catalog has been extended. The 2WHSP catalog now goes down to |b|>10˚ and is also based in multifrequency selection criteria, despite we do not use IR color-color selection this time, so we manage to be more complete. We also used updated X-ray catalog, and benefit from more than 160 new Swift XRT observations of WHSP blazars. This allowed us to have a better description of the synchrotron peak parameters, for many know and new HSP sources, so we could revisit some population studies using the 2WHSP sample. The 2WHSP cat has ~1700 objects, and is published in A&A 598, A17 (2017), also available at: https://arxiv.org/abs/1609.05808; and a direct link to the SED builder tool is here: http://www.asdc.asi.it/2whsp/
The third work of this series, is the First Brazilian ICRANet Gamma-ray Blazar catalog. Since we claim the WHSP samples are a collection of god TeV-candidates, they should also be very helpful to unveil new MeV-GeV sources in reach from Fermi-LAT satellite. So, we have used 7.5 yrs of Pass 8 Fermi-LAT data, and study about 400 bright WHSP sources which yet had no gamma-ray counterpart (bright blazar meaning: a sources with bright synchrotron peak nfn). As result, we found 150 new gamma-ray sources. This one we called 1BIGB (First Brazilian ICRANet Gamma-ray Blazar catalog). We describe their spectral parameters in the 0.3-500 GeV band, and showed that they might represent 6-8% of the extragalactic diffuse gamma-ray background around 50 GeV. Also, this work is an important "proof of concept" in the sense that the WHSP samples are really useful to unveil HE sources, and certainly very helpful to select promising TeV-targets.

5. Professor Rueda visiting Colombia

On December 12-16, 2016, Prof. Jorge Rueda visited Universidad Industrial de Santander (UIS) in Bucaramanga, Colombia, to receive the "Distinguished Former Student Award". During this visit Prof. Rueda delivered at the Physics Department of UIS a short 8 h course "Physics and Astrophysics of White Dwarfs and Neutron Stars"; as well as the invited Lecture at the "III Jornadas Científicas Escuela de Física UIS", and the Public Lecture "Vida después de la muerte: los cataclismos más potentes del Universo" at the event "Café Científico" organized by Casa del Libro Total in Bucaramanga.

Link to the video of the Public Lecture at the Casa del Libro Total in Bucaramanga: https://www.youtube.com/watch?v=Xs2rSYzwbvA

Public Lecture by Prof. Jorge Rueda at the event "Café Científico" held at Casa del Libro Total on December 15, 2016, in Bucaramanga.

6. Two meetings for the "School – Work" project with the Science High School Galileo Galilei in Pescara


The school-work project was started on December with two appointments with the 3rd class of the Scientific High School "Galileo Galilei" of Pescara. The project involves a total of 25 students and 70 hours divided between theory and practice. The focus of the first lesson with Professor Sigismondi Costantino and Dr. Alessandra Di Cecco was "The value of research and the work of the researcher". Professor Sigismondi made a video presentation, about the work of researcher that is possible to find here: https://www.youtube.com/watch?v=OOVxOlsEDoU&t=1s and another video about "Geminids and Quadrantids: guide for scientific observation" that is possible see here: https://www.youtube.com/watch?v=0xLV0BOrvdg&feature=youtu.be
Alessandra Di Cecco dedicated her lesson to the introduction at the astrophysics with this program http://www.icranet.org/scuola_lavoro/dicecco_sem.pdf


The second meeting was about the "History of Astrophysics and Relativity" and the professors were: Gregory Vereshchagin, Vladimir Belinski, and the PhD student from China Yu Wang.



7. New Ph.D Thesis discussion and Diploma

Clément Stahl, "On early and late phases of acceleration of the expansion of the universe", defended on 23rd of January, 2017 at the University of Rome "Sapienza"
Commission members: Jean Audouze (Institut d'Astrophysique de Paris, France), Paolo De Bernardis (University of Rome "Sapienza", Italy), Massimo Della Valle (Osservatorio Astronomico di Capodimonte, Italy) and Nikolaos Mavromatos (King's College London, UK).


This thesis tackles the vast question of generating accelerated periods of expansion of the universe. Models loosely related were developed in the early and late universe. In the early universe, generalizations of the Schwinger effect were developed in curved space (de Sitter) spacetime and some backreaction effects were estimated.
In the late universe, a fractal model was developed and confronted to supernovae data. This relies on the idea of an accelerated expanding universe being nothing but a mirage due to inhomogeneities disposed in a fractal (in this particular model) way. Finally a model of interacting energy based on an Einstein-Cartan gravitational theory was phenomenologically investigated.

List of publications:
E. Bavarsad, C Stahl, and S.-S Xue, Scalar current of created pairs by Schwinger mechanism in de Sitter spacetime, Phys. Rev., vol. D 94, 2016.
C. Stahl and E. Strobel, Semiclassical fermion pair creation in de Sitter spacetime, proceeding of the second Cesar Lattes meeting, 2015.
C. Stahl, E. Strobel, and S.-S. Xue, Fermionic current and Schwinger e_ect in de Sitter spacetime, Phys. Rev., vol. D 93, 2016.
C. Stahl, E. Strobel, and S.-S. Xue, Pair creation in the early universe, proceeding of MG14, 2016.
C. Stahl and S.-S. Xue, Schwinger effect and backreaction in de Sitter spacetime, Phys. Lett., vol. B760, 2016.
C. Stahl, Inhomogeneous matter distribution and supernovae, Int. J. Mod. Phys., vol. D25, 2016.
R. Ruffini, C. Stahl, Cosmological fractal matter distribution with an upper cutoff, proceeding of IK14, 2016
D. Bégué, C. Stahl, and S.-S. Xue, A model of interacting dark energy and supernovae, to appear, 2017.

8. Recent publications

a. Thermal X-ray emission from massive, fast rotating, highly magnetized white dwarfs", D. L. Cáceres, S. M. de Carvalho, J. G. Coelho, R. C. R. de Lima, Jorge A. Rued, MNRAS (2016) 465 (4): 4434-4440
There is solid observational evidence on the existence of massive, M ∼ 1 M, highly magnetized white dwarfs (WDs) with surface magnetic fields up to B ∼ 109 G. We show that, if in addition to these features, the star is fast rotating, it can become a rotation-powered pulsar-like WD and emit detectable high-energy radiation. We infer the values of the structure parameters (mass, radius, moment of inertia), magnetic field, rotation period and spin-down rates of a WD pulsar death-line. We show that WDs above the death-line emit blackbody radiation in the soft X-ray band via the magnetic polar cap heating by back flowing pair-created particle bombardment and discuss as an example the X-ray emission of soft gamma-repeaters and anomalous X-ray pulsars within the WD model.
The paper is available here: https://doi.org/10.1093/mnras/stw3047

b. "Polarization of a probe laser beam due to nonlinear QED effects", Soroush Shakeri, Seyed Zafarollah Kalantari, and She-Sheng Xue, Phys. Rev. A 95, 012108
Nonlinear QED interactions induce different polarization properties on a given probe beam. We consider the polarization effects caused by the photon-photon interaction in laser experiments, when a laser beam propagates through a constant magnetic field or collides with another laser beam. We solve the quantum Boltzmann equation within the framework of the Euler-Heisenberg Lagrangian for both time-dependent and constant background field to explore the time evolution of the Stokes parameters Q, U, and V describing polarization. Assuming an initially linearly polarized probe laser beam, we also calculate the induced ellipticity and rotation of the polarization plane.
The paper is available here: http://link.aps.org/doi/10.1103/PhysRevA.95.012108

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Figures: Comparison between dimensionless Stokes parameters U, Q, and V in both time-dependent and static background fields. In the time-dependent case we used the numerical solution of Sec. 4b to plot U [dashed (green) line] and Q [dot-dashed (red) line] in the left panel and for V [dotted (red) line] in the right panel. In the static magnetic field we have used the analytic solution of Sec. 4a to plot Q and U [solid (blue) line] in the left panel and V [solid (blue) line] in the right panel. These figures are plotted for a 10-keV linearly polarized probe laser beam interacting with a target laser beam in optical frequency ω=1eV and peak intensity I=3×1022W/cm2.
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