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Newsletter English August/September 2020 Print E-mail

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ICRANet Newsletter

ICRANet Newsletter
August/September 2020

1. Videos of recent talks given by ICRANet faculty members
Talk of Prof. Remo Ruffini at IWARA 2020 meeting Talk of Prof. Jorge Rueda at IWARA 2020 meeting
Talk of Prof. Remo Ruffini at The Fourth Zeldovich virtual meeting Talk of Prof. Gregory Vereshchagin at The Fourth Zeldovich virtual meeting
Talk of Prof. Jorge Rueda at The Fourth Zeldovich virtual meeting Talk of Prof. Remo Ruffini at the 14th International Conference on Gravitation, Astrophysics and Cosmology

2. Multiwavelength Study of High-Redshift Blazars

The new article coauthored by N. Sahakyan, D. Israyelyan, G. Harutyunyan, M. Khachatryan and S. Gasparyan “Multiwavelength Study of High-Redshift Blazars”, is published in Monthly Notices of the Royal Astronomical Society on 17 August 2020.

Figure 1. Spectra of some blazars.

Blazars harboring supermassive black holes are valuable sources for studying the relativistic outflows and formation and propagation of relativistic jets. In this context, the high redshift blazars (z>2.5) are of particular interest; they are among the most powerful non- explosive astrophysical sources in the Universe. Their study can shed light on the further understanding of the cosmological evolution of blazars and supermassive black holes and also on the evolution of relativistic jets across different cosmic epochs. Motivated by the large number of detected high redshift γ-ray emitting blazars, with the aim to characterize their multiwavelength emission properties, an intense broadband study of all the thirty-three known γ-ray blazars beyond redshift 2.5 is performed. In order to characterize the physical properties of the considered sources, Fermi Large Area Telescope γ-ray data accumulated during 2008-2018, as well as X-ray and optical/UV data from the observations with both Swift X-ray Telescope and Ultraviolet and Optical Telescope in the previous fifteen years are analyzed. This allowed collecting unprecedented data in the optical/UV, X-ray, and γ-ray bands, which is used to constrain the multiwavelength spectral energy distributions (SEDs), see Fig. 1. Then, through modeling of these SEDs within a one-zone leptonic scenario (assuming that the X-ray and γ-ray emissions are produced from inverse Compton scattering of synchrotron and dusty torus photons), the physical parameters characterizing the sources (disc luminosity, black hole mass, etc.) and their jets (e.g., the distribution of underlying electrons, magnetic field, power, etc.) are derived, allowing a quantitative discussion and investigation of the state of plasma in these powerful jets.
Time variability in different energy bands is particularly important. In the X-ray band, only the emission of PKS 0438-43, B2 0743+25 and TXS 0222+185 is found to vary in different Swift XRT observations whereas in the γ-ray band, the emission is variable for fourteen sources: the flux of B3 1343+451 and PKS 0537-286 changes in sub-day scales, that of PKS 0347-211 and PKS 0451-28 in day scales, while the γ-ray variability of the others is in week or month scales. Such rapid variability in high energy band is in agreement with recently proposed model for the inner engine of AGNs by Rueda, J.A., Ruffini, R., "The blackholic quantum", Eur. Phys. J. C 80, 300 (2020), see https://doi.org/10.1140/epjc/s10052-020-7868-z.

The article is available here: https://doi.org/10.1093/mnras/staa2477
ArXiv e-print: https://arxiv.org/abs/2008.09675

3. Geodesic motion of S2 and G2 as a test of the fermionic dark matter nature of our Galactic core

The paper “Geodesic motion of S2 and G2 as a test of the fermionic dark matter nature of our Galactic core”, co-authored by E.A. Becerra-Vergara, C.R. Argüelles, A. Krut, J.A. Rueda, and R. Ruffini has been published by Astronomy & Astrophysics on September 4, 2020. In this paper, the evidence is given on the possibility of different interpretation of observational data of the motion of S2 and G2 objects near the Galactic center. Within this interpretation, which is perfectly consistent with General Relativity, the compact object is not a black hole but a condensation of dark matter.


Link to the paper: https://www.aanda.org/articles/aa/abs/2020/09/aa35990-19/aa35990-19.html
Link to ArXiv e-print: https://arxiv.org/abs/2007.11478

4. New collaboration Agreement between University of Mazandaran and ICRANet, August 24, 2020


On August 24, a cooperation agreement between ICRANet and the University of Mazandaran (Iran) was signed by Prof. Kourosh Nozari (President of the University of Mazandaran), Prof. Mahmoud Azizi (Director of the Office of International and Scientific Cooperation – University of Mazandaran) 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:

5. The 14th International Conference on Gravitation, Astrophysics and Cosmology (ICGAC 14), August 17 – 21, 2020

4 The 2020 edition of the ICGAC 14 meeting has been held virtually from August 17 to 21 at the National Central University, Jhongli, in Taiwan. Prof. Ruffini, Director of ICRANet, gave a lecture titled “The geodesic motion of S2 and G2 as a test of the fermionic dark matter nature of our galactic core”, while Prof. Gregory Vereshchagin, ICRANet Faculty Professor, gave a lecture titled “Diffusive photospheres and thermal emission in early afterglows of gamma-ray bursts”. ICGAC14 is the series of biennial conferences on Gravitation, Astrophysics and Cosmology which take place in the Asia-Pacific region, with the goals to promote cooperation among the member countries and within an international context, high level studies on hot topics and to encourage young physicists on these fields.
The website of the meeting: https://icgac14.phy.ncu.edu.tw

6. IWARA 2020 video conference. From Quarks to Cosmo, September 6 – 12, 2020


Prof. Remo Ruffini was invited to give a plenary lecture on the occasion of the IWARA 2020 video conference, held from September 6-12 in Mexico City. On Sunday September 6, Prof. Ruffini presented his lecture on the “Discovery of energy extraction from a Kerr Black Hole by discrete Black-Holic quanta in GRB 190114C, GRB 130427A, GRB 160509A and GRB 160625B”. Abstract: Almost fifty years after the paper "Introducing the Black Hole" by Ruffini and Wheeler and the Black Hole (BH) mass energy formula by Christodoulou, Ruffini and Hawking, we can finally assert that we have been observing the moment of creation of a BH in the BdHN I in GRB 190114C, GRB 130427A, GRB 160509A and GRB 160625B, with the corresponding rotational energy extraction process. The first appearance of the Supernova, the SN-rise, triggering the BdHN has been identified. The hypercritical accretion on the SN ejecta on the new NS (νNS) created in the SN, is shown to originate the X-ray afterglow observed by the NASA Neil-Gehrels SWIFT satellite (SWIFT). The hypercritical accretion of the SN on the NS binary companion in the BdHN I model leads to the formation of the newly formed BH. The onset of the GeV radiation coinciding with the BH formation has revealed self similar structures in the time resolved spectral analysis of all sources. Consequently, we find evidence for quantized-discrete-emissions in all sources, with energy quanta of 1037 ergs with repetition time of 10-14 sec. GRBs are the most complex systems ever successfully analyzed in Physics and Astrophysics, and they may well have a role in the appearance of life in the Cosmos. These results have been made possible by a long-lasting theoretical activity, a comprehensive unprecedented high quality data analysis, an observational multi-messenger effort by the astronomical, the physical and the space research communities. This observational effort is well epitomized by the original Vela Satellites, the NASA Compton space mission (CGRO), the Italo-Dutch Beppo SAX satellite, the Russian Konus Wind Satellite, the SWIFT satellite, the Italian AGILE satellite, the NASA FERMI mission and most recently the Chinese satellite HXMT. These space missions have been assisted by radio and optical equally outstanding observational facilities from the ground.
The website of the conference: https://indico.cern.ch/event/822124/

7. The 4th Zeldovich virtual meeting, September 7 - 11, 2020

The Fourth Zeldovich virtual meeting has been organized by ICRANet and by the National Academy of Sciences of Belarus. It was held virtually from 7 to 11 of September, 2020.

Figure 2. Final greetings at the end of the meeting.

The number of registered participants, about 150, was record breaking for Zeldovich meetings. Participants from all the continents and time zones were present. Every day, three sessions were organized: two in the morning in European Central Summer Time (CEST), and one in the afternoon. In the morning sessions mostly Asian, African and European speakers were present while in the afternoon session American participants, both from the North and the South were joining the meeting. The sessions included the following topics: Gravity, Gamma-Ray Bursts, General Relativity And The Quantum, The Space Missions, Magnetic Fields, General Relativity And Alternative Theories, Early Universe, Black Hole Horizons, Multi-Messenger Astrophysics, Gravity, Astrophysics And Elementary Particles, Large Scale Structure Of The Universe, Starburst and Dark Matter in the Universe, Exoplanets and Astrobiology, Dark Matter and Dark Energy, Supernovae and Gravity. In total, 89 talks have been presented, among them 30 were invited. Many exciting observational results were discussed, in particular: the first results from SRG Orbital Observatory and HXMT mission, the ground based observations of Neutrinos by ICECube Observatory, the high energy Gamma-Rays by MAGIC telescopes, and prompt optical observations by the MASTER network, the observations of Galactic Center by GRAVITY collaboration and Black Hole Shadow in M87*, the new observations and data analysis of Gamma-Ray Bursts, Exoplanets and large scale structure of the Universe. In addition, theoretical progress in Gamma-Ray Burst theory and Supernovae mechanisms, Magnetic Dynamo in Galaxies, Quantum Gravity, alternative gravity theories, Neutrino Physics, origin of Dark Matter, CMB spectral distortions and many other topics were amply discussed.
The concluding remarks, summarizing the new and important scientific results presented along the meeting, have been made by Academician Sergei Kilin, Deputy Chairman of the National Academy of Sciences of Belarus NASB, by Prof. Remo Ruffini, Director of ICRANet and by Prof. Gregory Vereshchagin.
The proceedings of the 4th Zeldovich meeting will be published in the refereed journal Astronomy Reports, the leading Russian journal on Astronomy and Astrophysics. The website of the journal: https://www.springer.com/journal/11444.
This celebration was the forth international conference dedicated to Ya. B. Zeldovich. The previous meetings were held on April 23-27, 2018 in Minsk, on April 20-23, 2009 in Minsk (jointly organized by ICRANet and the Belarusian State University BSU, celebrating also the 2009 Year of Astronomy) and on March 11-14, 2014, celebrating 100th anniversary of Ya. B. Zeldovich.
The videos of the sessions are available on ICRANet YouTube channel:
The speakers’ presentations are available on the conference webpage: http://www.icranet.org/index.php?option=com_content&task=view&id=1339
The website of the meeting: http://www.icranet.org/zeldovich4

8. 106th SIF National Congress, September 14 – 18, 2020

From September 14 - 18, the Italian Physical Society (Società Italiana di Fisica, SIF) held its 106th National Congress (virtually). Prof. Remo Ruffini, Director of ICRANet, Prof. Jorge Rueda, ICRANet Faculty Professor, and Prof. Costantino Sigismondi, ICRANet collaborator, were invited to participate and present their talk through a video presentation reporting on their latest scientific results. Prof. Ruffini presented a talk titled "Magnetic fields and afterglows of BdHNe: Inferences from GRB 130427A, GRB 160509A, GRB 160625B, GRB 180728A and GRB 190114C", Prof. Rueda presented a talk titled "On the inner engine of the high-energy (GeV) emission of gamma-ray bursts" and Prof. Sigismondi presented a talk on "The Eclipses of Betelgeuse" (this red supergiant is now at magnitude 0.65, nearly at its maximum, after the second dimming due to dust cloud expulsions in the last few months).
For more information, please check the conference website: https://www.sif.it/attivita/congresso/106

9. “Dante e l’Astronomia” podcast meeting, September 13, 2020

C. Sigismondi, ICRA/Sapienza

The fame of Dante is international, as the Poet was at his own times. Remembering of his passage at the University of Paris are still visible. His pilgrimages, for political and professional reasons, are framed in the verses of the Divine Comedy. His poetry has been able to include all cultural, artistic, theological as well as scientific and religious aspects of his times. The podcast meeting inaugurated on September 13, 2020 is expressly dedicated Dante and Astronomy. It started the seventh centennial celebrations of the death of Dante, occurred in Ravenna on the night of September 13-14, 1321. Dante is an icon of the medieval culture, where science and faith were deeply united.

Figure 3. Dante Alighieri (1265-1321).

“e nove Muse mi dimostran l'Orse” (Par. II, 9)
is the verse chosen for the title of the event: nine muses, all arts, contribute to show the Ursae, to maintain the North, the correct direction, in the extraordinary trip that Dante (not Aeneas, a classical hero, nor St. Paul, the Apostle...as he wrote) was able to perform. But not only a figurative North, an ideal Compass in the hard sea of human life... Dante shows several pictures of genuine observations of physical phenomena, and the awe of astronomical events as himself indeed experienced.
Astronomy as codified language, astronomical observations filled by nostalgic sensations, astronomical bodies as silent testimonies of the phases of the human life, before and after the passage into the Other World, of which Dante is the cantor par excellence.
Contributions of scientists and dantists were included in this meeting dedicated especially to the young students, and to all estimators of Dante. The podcast was hosted by ICRANet in Pescara with the participation of the Astrophysical Observatory of Asiago and of the Academy of Lincei. The patrocinium to the IAU Commission III of History of Astronomy has been requested.
For more information about the meeting: http://www.icranet.org/index.php?option=com_content&task=view&id=1334
For a press release (in Italian) on regional tv channel Rete 8: https://www.rete8.it/cronaca/icranet-dante-e-lasrtronomia/

10. Recent publications

N. Sahakyan, D. Israyelyan, G. Harutyunyan, M. Khachatryan and S. Gasparyan, Multiwavelength Study of High-Redshift Blazars, accepted for publication in MNRAS.
High-redshift blazars are among the most powerful objects in the Universe. The spectral and temporal properties of thirty-three distant blazars (z > 2.5) detected in the high energy γ-ray band are investigated by analyzing the Fermi-LAT and Swift UVOT/ XRT data. The considered sources have soft time averaged γ-ray spectra (Γγ ≥ 2.2) whereas those that have been observed in the X-ray band have hard X-ray spectra (ΓX = 1.01 − 1.86). The γ-ray flux of high-redshift blazars ranges from 4.84 × 10−10 to 1.50 × 10−7 photon cm−2 s−1 and the luminosity is within (0.10 − 5.54) × 1048 erg s−1 which during the γ-ray flares increases up to (0.1 − 1) × 1050 erg s−1. In the X-ray band, only the emission of PKS 0438-43, B2 0743+25 and TXS 0222+185 is found to vary in different Swift XRT observations whereas in the γ-ray band, the emission is variable for fourteen sources: the flux of B3 1343+451 and PKS 0537-286 changes in sub-day scales, that of PKS 0347-211 and PKS 0451-28 in day scales, while the γ-ray variability of the others is in week or month scales. The properties of distant blazar jets are derived by modeling the multiwavelength spectral energy distributions within a one-zone leptonic scenario assuming that the X-ray and γ-ray emissions are produced from inverse Compton scattering of synchrotron and dusty torus photons. From the fitting, the emission region size is found to be ≤0.05 pc and the magnetic field and the Doppler factor are correspondingly within 0.10 − 1.74 G and 10.0 − 27.4. By modeling the optical-UV excess, we found that the central black hole masses and accretion disk luminosities are within Ld ≃ (1.09 − 10.94) × 1046 erg s−1 and (1.69 − 5.35) × 109 M, respectively.
DOI: https://doi.org/10.1093/mnras/staa2477
Link: https://ui.adsabs.harvard.edu/abs/2020arXiv200809675S/abstract

N. Sahakyan, G. Harutyunyan, D. Israyelyan and M. Khachatryan, Exploring the Origin of Multiwavelength Emission from High-Redshift Blazar B3 1343 + 451, published in Astrophysics, Volume 63, Issue 3, p.334-348, 2020.
B3 1343 + 451 is a distant ( z = 2.534 ) and bright flat-spectrum radio quasar observed in the γ -ray band. The results from the multiwavelength observations of B3 1343 + 451 with Fermi-LAT and Swift are reported. In the γ -ray band, strong flares were observed on 05 December 2011 and on 13 December 2009 when the flux increased up to (8.78 ± 0.83).10-7 photon cm-2 s-1. The hardest photon index Γ = 1.73 ± 0.24 has been observed on MJD 58089 which is not common for flat-spectrum radio quasars. The analysis of Swift XRT data shows that in 2014 the X-ray flux of the source increased ~2 times as compared to 2009, but in both periods the X-ray emission is characterized by a hard photon index of ΓX-ray = 1.2-1.3. During the γ -ray flares, the shortest flux halving timescale was ~2.34 days, implying the emission had been produced in a very compact region, R ≤ δ ct /(1 + z) = 3.43.1016 cm (when δ = 20). The spectral energy distribution of B3 1343 + 451 is modeled during the quiescent and flaring periods assuming a compact emitting region outside the BLR. It is found that the flares can be explained by only changing the bulk Lorentz factor of the emitting region without significant modification of the emitting electron parameters and luminosity of the jet.
DOI: https://doi.org/10.1007/s10511-020-09638-z
Link: https://ui.adsabs.harvard.edu/abs/2020Ap.....63..334S/abstract

MAGIC collaboration, Testing two-component models on very high-energy gamma-ray-emitting BL Lac objects, Astronomy & Astrophysics, Volume 640, id.A132, 29 pp., 2020.
Context. It has become evident that one-zone synchrotron self-Compton models are not always adequate for very high-energy (VHE) gamma-ray-emitting blazars. While two-component models perform better, they are difficult to constrain due to the large number of free parameters.
Aims: In this work, we make a first attempt at taking into account the observational constraints from very long baseline interferometry (VLBI) data, long-term light curves (radio, optical, and X-rays), and optical polarization to limit the parameter space for a two-component model and test whether or not it can still reproduce the observed spectral energy distribution (SED) of the blazars.
Methods: We selected five TeV BL Lac objects based on the availability of VHE gamma-ray and optical polarization data. We collected constraints for the jet parameters from VLBI observations. We evaluated the contributions of the two components to the optical flux by means of decomposition of long-term radio and optical light curves as well as modeling of the optical polarization variability of the objects. We selected eight epochs for these five objects based on the variability observed at VHE gamma rays, for which we constructed the SEDs that we then modeled with a two-component model.
Results: We found parameter sets which can reproduce the broadband SED of the sources in the framework of two-component models considering all available observational constraints from VLBI observations. Moreover, the constraints obtained from the long-term behavior of the sources in the lower energy bands could be used to determine the region where the emission in each band originates. Finally, we attempt to use optical polarization data to shed new light on the behavior of the two components in the optical band. Our observationally constrained two-component model allows explanation of the entire SED from radio to VHE with two co-located emission regions.
DOI: https://doi.org/10.1051/0004-6361/202037811
Link: https://ui.adsabs.harvard.edu/abs/2020A%26A...640A.132M/abstract

D. Maričić, B. Vršnak, A. M. Veronig, M. Dumbović, F. Šterc, D. Roša, M. Karlica, D. Hržina & I. Romštajn, Sun-to-Earth Observations and Characteristics of Isolated Earth-Impacting Interplanetary Coronal Mass Ejections During 2008-2014, published in Sol Phys 295, 91 (2020).
A sample of isolated Earth-impacting interplanetary coronal mass ejections (ICMEs) that occurred in the period January 2008 to August 2014 is analyzed to study in detail the ICME in situ signatures, with respect to the type of filament eruption related to the corresponding CME. Observations from different vantage points provided by the Solar and Heliospheric Observatory (SOHO) and the Solar Terrestrial Relations Observatory Ahead and Behind (STEREO-A and B) are used to determine whether each CME under study is Earth directed or not. For Earth-directed CMEs, a kinematical study was performed using the STEREO-A and B COR1 and COR2 coronagraphs and the Heliospheric Imagers (HI1), to estimate the CME arrival time at 1 AU and to link the CMEs with the corresponding in situ solar wind counterparts. Based on the extrapolated CME kinematics, we identified interacting CMEs, which were excluded from further analysis. Applying this approach, a set of 31 isolated Earth-impacting CMEs was unambiguously identified and related to the in situ measurements recorded by the Wind spacecraft. We classified the events into subsets with respect to the CME source location, as well as with respect to the type of the associated filament eruption. Hence, the events are divided into three subsamples: active region (AR) CMEs, disappearing filament (DSF) CMEs, and stealthy CMEs. The related three groups of ICMEs were further divided into two subsets: magnetic obstacle (MO) events (out of which four were stealthy), covering ICMEs that at least partly showed characteristics of flux ropes, and ejecta (EJ) events, not showing such characteristics. In this way, 14 MO-ICMEs and 17 EJ-ICMES were identified. The solar source regions of the non-stealthy MO-ICMEs are found to be located predominantly (9/10, 90%) within ±30∘±30∘ from the solar central meridian, whereas EJ-ICMEs originate predominantly (16/17, 94%) from source regions that are outside ±30∘±30∘. In the next step, MO-events were analyzed in more detail, considering the magnetic field strength and the plasma characteristics in three different segments, defined as the turbulent sheath (TS), the frontal region (FR), and the MO itself. The analysis revealed various well-defined correlations for AR, DSF, and stealthy ICMEs, which we interpreted considering basic physical concepts. Our results support the hypothesis that ICMEs show different signatures depending on the in situ spacecraft trajectory, in terms of apex versus flank hits.
DOI: https://doi.org/10.1007/s11207-020-01658-4
Link: https://link.springer.com/article/10.1007/s11207-020-01658-4
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