ICRANet Newsletter

ICRANet Newsletter
February-March 2020

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RÉSUMÉ
1. Statistiques sur le COVID-19
2. The "Blackholic quantum"
3. Deux articles rédigés par les chercheurs ICRANet dans la collaboration MAGIC
4. La "montée et la chute" de Betelgeuse en 2020
5. VII Leopoldo García-Colín Mexican Meeting on Mathematical and Experimental Physics, Mexico, 15-18 Février 2020
6. Ajournement du 4^ème Zeldovich meeting, Minsk, Belarus
7. Félicitations au Prof. Narek Sahakyan, Directeur d'ICRANet Arménie, inclut entre les 100 meilleurs scientifiques d'Arménie, 6 Mars 2020
8. Publications récentes

1. Statistiques sur le COVID-19

À partir du 15 Avril 2020, on offre à tous les membres ICRANet, notre rapport quotidien sur le COVID-19. Veuillez cliquer sur ce lien pour à la page web d'ICRANet: http://www.icranet.org/covid19-statistics. La fonction logistique phénoménologique est utilisée pour modéliser l'évolution de la pandémie de COVID-19 dans différents pays. Le modèle logistique est utilisé principalement en épidémiologie et offre un aperçu des dynamiques de transmission du virus. Les données proviennent de l'Université Johns Hopkins. Cependant, nous observons qu'on a besoin de modèles plus raffinés afin d'évaluer les dynamiques de transmission du COVID-19, qui prennent en compte les mesures spécifiques adoptées dans chaque pays.

Nombre total de cases confirmés, en fonction du temps: 15.04.2020

2. The "Blackholic quantum"

Summary of paper "The blackholic quantum" by J. A. Rueda and R. Ruffini

Progress is being made at ICRANet towards a change of paradigm in black hole (BH) physics that explains how they can be the most powerful sources of energy emission in the Universe. The energy that can be "extracted" from a BH was established in a short period, from September 17, 1970, to March 11, 1971, in a series of papers published by D. Christodoulou, R. Ruffini and S.W. Hawking. Up to 29% of the BH mass-energy could be in principle extracted. This means that for a few solar masses, the amount of energy that it stores is of the order of 10⁵³ erg, and up to billion times bigger for the supermassive black holes harbored in the cores of some galaxies. The former energetic could explain the most powerful astrophysical sources in the sky, the gamma-ray bursts (GRBs), while the latter might explain the active galactic nuclei (AGN). However, the determination of a physical process that efficiently extracts the BH energy, has remained elusive for decades.

The new article by J. A. Rueda and R. Ruffini, "The blackholic quantum", published in The European Physical Journal C [1], makes a step forward the identification of such a physical process: it makes use of a rotating BH in presence of a magnetic field and ionized matter, conditions which are common in astrophysical environments. The rotation and the magnetic field induces an electric field (from which it is possible to define an effective BH charge) that accelerates the charged particles toward ultra-relativistic speeds in the BH surroundings, thence emitting high-energy radiation. In the article, the amount of energy of the BH that this acceleration process is able to take off, is established. The process is shown to occur in "elementary steps", each one radiating off a part of the BH energy and angular momentum. Indeed, it is shown that, as in the case of the quantum of energy of quantum mechanics, each elementary process takes off a specific amount of the BH energy, say E, that is expressible in the "quantum" form, E = ħ*Ω_eff, where Ωeff is an effective angular frequency that depends on the BH mass, angular momentum, the magnetic field strength, and fundamental constants such as the Planck mass and length. The timescale in which the elementary process occurs leads to an estimate of the luminosity of the process, which is applicable and it is shown to be in agreement, to the observed luminosities not only for GRBs but also for AGN, by duly scaling of the BH mass (from solar mass BH to billion mass one) and the strength (from tens of giga Gauss to tens of Gauss) of the surrounding magnetic field. The table shown below, reproduced from the publication, shows the obtained astrophysical quantities derivedfrom the "energy quantum" and the characteristic time of the elementary process. This mechanism, already recently applied to the case of GRB 130427A (see Table and Ref. [2] for details), paves the way towards the explanation of the recently observed emission in GRB 190114C, which not only radiates at GeV energies but also in the most-extreme TeV energy domain, as well as to the high-emission of AGN, such as the one at the center of M87.


The analogy with the quantum world does not end here, it is also shown that, by properly introducing the concept of "BH magneton", for the energy of the accelerated particles occurs an analogy with the Zeeman and Stark effects, scaled from microphysics to macrophysics. Furthermore, the application of the derived formulas to an electron, namely replacing the BH mass with the electron mass, it is shown that the effective BH charge, which depends on the magnetic moment of the exterior field and the BH angular momentum, becomes the electron's charge. Further consequences on theoretical physics aspects of these intriguing analogies are currently under study.

For more details, we refer to the published article [1].
[1] Rueda, J.A., Ruffini, R., "The blackholic quantum", Eur. Phys. J. C 80, 300 (2020). https://doi.org/10.1140/epjc/s10052-020-7868-z / ArXiv pre-print: https://arxiv.org/abs/1907.08066
[2] Ruffini, R., Rueda, J.A., Moradi, R., et al., "On teh GeV emission of the Type I BdHN GRB 130427A", The Astrophysical Journal 886, 82 (2019).

3. Deux articles rédigés par les chercheurs ICRANet dans la collaboration MAGIC

The paper by MAGIC collaboration entitled "Monitoring of the radio galaxy M 87 during a low-emission state from 2012 to 2015 with MAGIC" has been published in Monthly Notices of the Royal Astronomical Society on 08 January 2020.


M87 is a large elliptical galaxy located at about 50 million light years from Earth. It is a very interesting source for various reasons. First, at the center of M87 we can infer the presence of an object that contains a total mass about as large as 7 billion times the mass of the Sun. We think that such an object is a super massive black hole. Second, M87 is surrounded by a disk of matter that fuels the emission of particles/radiation, which we can detect from Earth. This radiations pans a large range of energy, going from radio waves (indeed, M87, is known as a radio galaxy) to very high energy. In particular, part of this emission is concentrated in a pair of narrow jets that, indeed, do accelerate particles up to very high energy. By studying this emission we can gain a better understanding of the physics that governs the evolution of M87, and other similar objects in the universe. Moreover, we can also test our understanding of physics in such an extreme scenario. Finally, since M87 is located relatively close to Earth (it is, indeed, the closest very high energy source), it is a convenient target for such challenging observations.

Objects like M87 often show a variable emission, which means that the amount of particles/radiation that they emit changes with time. Sometimes they are in a "high state" (more particles/energy emitted), other times in a "low" one. Moreover, such a change in the emission may appear at some energies, but not at others (e.g., we could see an enhanced radio emission, but a constant emission at very high energies, and so on).

The MAGIC telescopes, a pair of Cherenkov telescopes located at the Canary Island of La Palma, are an ideal instrument to study the very high energy emission of M87. MAGIC uses the Earth's atmosphere as a huge detector: when high-energy particles reach Earth, they interact with the atmosphere, and produce fluorescence light, that is collected by MAGIC17 meters wide mirrors, and focused on a camera. The data acquired in this way is thoroughly analyzed, to extract as much information as possible about the original particle. It proves extremely effective to combine the very high energy information obtained by MAGIC, with the observations of other instruments at different energies, as different energies are usually related to different fundamental processes.

This is why, between 2012 and 2015, MAGIC joined forces with other instruments (Fermi-LAT, Chandra, HST, EVN, VERA, VLBA, and the Liverpool Telescope) to regularly monitor the emission of M87 over its entire energy spectrum (from radio to very high energy). Another goal of MAGIC observations has been to pinpoint the region where VHE are emitted. These combined observations, together with, e.g., the more recent results of the Event Horizon Telescope, give us a more complete picture of M87 and of the processes that it harbors, and helps us in developing and refining our models of this fascinating astrophysical object. More details and technical results, are reported in a paper that has been recently published in the Monthly Notices of the Royal Astronomical Society.

Links: https://arxiv.org/abs/2001.01643, https://doi.org/10.1093/mnras/staa014.


The paper "New Hard-TeV Extreme Blazars Detected with the MAGIC Telescopes" has been published in the Astrophysical Journal on 20 February 2020.

Extreme high-frequency-peaked BL Lac objects (EHBLs) are blazars that exhibit extremely energetic synchrotron emission. They also feature non thermal gamma-ray emission whose peak lies in the very high-energy (VHE, E > 100 GeV) range, and in some sources exceeds 1 TeV: this is the case for hard-TeV EHBLs such as 1ES 0229+200. With the aim of increasing the EHBL population, 10 targets were observed with the MAGIC telescopes from 2010 to 2017, for a total of 265 hr of good-quality data. The data were complemented by coordinated Swift observations. The X-ray data analysis confirms that all but two sources are EHBLs. The sources show only a modest variability and a harder-when-brighter behavior, typical for this class of objects. At VHE gamma-rays, three new sources were detected and a hint of a signal was found for another new source. In each case, the intrinsic spectrum is compatible with the hypothesis of a hard-TeV nature of these EHBLs. The broadband spectral energy distributions (SEDs) of all sources are built and modeled in the framework of a single-zone, purely leptonic model. The VHE gamma-ray-detected sources were also interpreted with a spine-layer model and a proton synchrotron model. The three models provide a good description of the SEDs. However, the resulting parameters differ substantially in the three scenarios, in particular the magnetization parameter. This work presents the first mini catalog of VHE gamma-ray and multi wave length observations of EHBLs.

Link: https://doi.org/doi:10.3847/1538-4365/ab5b98

4. La "montée" et la "chute" de Betelgeuse en 2020

C. Sigismondi, ICRA/Sapienza

Introduction
Betelgeuse, the supergiant star alpha of Orion is a semi-regular variable star, ranging normally between 0 and 0.9 magnitude. In 2019/2020 it reached a visual minimum of 1.45 mag around February 11, and by April 12, it is already at mag 0.45. The attention of the astronomical world on this phenomenon was relevant, but none of the media dedicated were able to evidence the unproper quoting of a supposed pre-supernova stage.
A meeting on January 17, 2020 in ICRANet seat in Pescara was organized in order to comment these news and the last observations show a rapid restoring of the usual luminosity of the star, please see:
http://www.icranet.org/index.php?option=com_content&task=view&id=1281.


Visual observations of Variable stars since 1997 with Mira Ceti
On December 6th 2019, after more than one month of cloudy nights over Rome, Betelgeuse was estimated by me as 1.1 visual magnitude, getting the lowest value of AAVSO records. AAVSO is the American Association of variable Stars Observers and it has thousands affiliated.
During a science visit as ICRA member in Fermilab and ESO/Chile in 1999, I had the first possibility to observe Eta Carinae, the supergiant star that had a outburst in 1843, to negative magnitude, becoming the second star of the night sky, only inferior to Sirius and Canopus. This observation was done in Santiago de Chile at ESO headquarters where I gave a talk on Fermions in the Early Universe, the subject of my first PhD, and it was the occasion to become an AAVSO contributing observer, with the code SGQ. The enrollment on the internet was done in the bureaus of prof. Teitelboim, I was visiting.
In July of the same year (1999), when the Nova Aquilae 1999 was measured from Pescara ICRANet seat, we obtained an acknowledging diploma from Janet Mattei, the former director of AAVSO, untimely dead in 2004. My research project in variable stars begun in 1997 with my history of science studies about the Bethlehem star, made for the master's degree in Theology at Lateran University (Rome, 1998). I explored the hypothesis that Mira Ceti could have been that star.
Mira is close to the position where in the year 6-7 b.C. Jupiter and Saturn had the triple conjunction calculated already from Kepler in 1611. Kepler added that this conjunction could have been the cause of the new star, which should have been the Bethlehem star. The connection between Mira and the Bethlehem star was possible because of my series of observations of Mira in 1997, made for understanding the appearance of a variable star, and the method of observing with naked eyes (Argelander's method and airmass correction). This is for presenting my 23-years experience in observing variable stars.
On the occasion of the XIV Marcel Grossmann Meeting (MG14) in 2015 and of the XV Marcel Grossmann Meeting (MG15) in 2018, I have presented two talks dedicated to 1) the first 1000 observations; and 2) Betelgeuse visual observations compared to V-band digital data realized in Wien by Wolfgang Vollmann for the same time period: from 2011.

The historical minimum
On December 8, E. Guinan of Villanova University started a series of Astronomer's Telegrams dedicated to the unusual fading of Betelgeuse. I attended it on December 29, 2019 to prepare a communication to arxiv.org appeared on January 1, 2020, dealing with the Historical minimum of Betelgeuse, about to end. The date of the minimum was predicted "by February" simply by analyzing the last 8 years of homogeneous observations made by me and Vollmann (SGQ and VOL) already published in MGM XIV and updated to the end 2019.

The ICRANet meeting on Betelgeuse dimming
Another occasion to study the behavior of Betelgeuse was created by the interaction held with Margarita Karovska of Harvard CfA who read my arxiv and commented it via e-mail: we decided to organize a virtual meeting with the most prominent italian experts of Supernovae and Observational Astronomy and the AAVSO director Stella Kafka. The Meeting was held in Pescara, ICRANet seat on January 17.
My first goal was to remind the public opinion that a Supernova is the result of a core collapse in a free-fall time, that for a 12 solar mass star does not excess some tens of minutes, not months, as the news from several media were diffusing.
Cesare Barbieri, Massimo Turatto and Paolo Ochner of Padova University and Asiago Astrophysical Observatory, the major in Italy added their contribution to that successful meeting, chaired by prof. Ruffini and me.
On February 2, on AGB newsletter of the IAU division on Red Giant Variable stars, I sent my contribution for the Question of the Month "When Betelgeuse will explode? And it has been reported in full detail, with the aforementioned goal of the ICRANet meeting of January 17.

Rapid rising of the light curve of Betelgeuse in March-April 2020
On March 31, I have published the Astronomer's Telegram #13601 regarding the rapid rising of the light curve of Betelgeuse, attaining already 0.02 magnitudes/day and 0.9 visual magnitude, with an increase of 0.55 magnitudes since February 11, 2020, when the minimum was reached, with 1.45 visual magnitude. I wrote that if this will be the fastest rate it would have been reasonable a maximum around magnitude 0.4, with a very simple kinematic model: the largest speed is found at the center of an oscillation.


Now, April 12, 2020, the magnitude is reaching already 0.45 visual magnitude with an average rising velocity of 0.45 mag/12 days or 0.0375 mag/day during the last two weeks, see Fig. 2. A simple extension of the kinematic model would consider this one as the new center of the oscillation, but it cannot be, implying a negative magnitude maximum, which would be really unprecedented.
The basic idea proposed since 1984 by Margarita Karovska and treated once again during our ICRANet meeting of January 17, is that there are dust clouds around the star which can either dim the light from the photosphere, either diffuse it through backward scattering when the cloud is behind the star. The observations to be realized in these days by the ESO VLT interferometer can confirm this hypothesis. The last published ones, available in the Astronomer's Telegram references in my #13601, show Betelgeuse at minimum, as consisting in a photosphere divided in two regions, one of which is much darker than the other, because behind the aforementioned cloud of ejecta. Now this cloud is possibly moving to the back of the stellar photosphere, contributing to a maximum even brighter than usual values and approaching to magnitude 0. We have to expect new data to complete this noteworthy cycle of Betelgeuse.

Conclusions
The last one data on which I based the ATel #13601 have been taken from Rome, near the Vatican, by using the naked eye technique developed in these last two decades to solve the problem of lack of nearby comparison stars for such bright variable star. Differential photometry is impossible and the different altitude of the comparison stars has to be measured to compute the air mass contributions for each star (Betelgeuse, compared with Pollux and Castor during the minimum phase and compared with Procyon and Aldebaran during the present phase, or Procyon and Rigel during maxima).
This technique is a basic one in photometry, but it is not mentioned in visual observations. I have done it with several high school students of Rome and Pescara and through specialized publications.

References
http://www.astronomerstelegram.org/?read=13601
http://www.astronomerstelegram.org/?read=13525
http://www.astronomerstelegram.org/?read=13512
http://www.astronomerstelegram.org/?read=13501
http://www.astronomerstelegram.org/?read=13439
http://www.astronomerstelegram.org/?read=13410
http://www.astronomerstelegram.org/?read=13365
http://www.astronomerstelegram.org/?read=13341
https://www.eso.org/public/videos/eso1121a/
https://www.youtube.com/watch?v=TWYBoIYVjkE
https://www.arxiv.org/abs/1912.12539
https://www.aavso.org/lcg with alf Ori and SGQ observing code for the last measurements.

- Karovska, M. 1987, "Stellar Pulsation; Proceedings of the Conference held as a Memorial to John P. Cox", at the Los Alamos National Laboratory, Los Alamos, NM, Aug. 11-15, 1986. Lecture Notes in Physics, Vol. 274, edited by A. N. Cox, W. M. Sparks, and S. G. Starrfield. Springer-Verlag, Berlin, 1987., p.260
- Schaefer, B. E., Yes, Aboriginal Australians Can And Did Discover The Variability Of Betelgeuse, J. of Astron. History and Heritage, 21 (1), 7-12 (2018)
- Schaefer, B.E., 2013. The thousand star magnitudes in the catalogues of Ptolemy, Al Sufi, and Tycho are all corrected for atmospheric extinction. Journal for the History of Astronomy, 44, 47‒74.
- C. Sigismondi, Betelgeuse 2020 dimming: getting the minimum (preprint, Jan 20, 2020)
- C. Sigismondi, https://www.astro.keele.ac.uk/AGBnews No. 272 (1 March, 2020)

5. VII Leopoldo García-Colín Mexican Meeting on Mathematical and Experimental Physics, Mexico, 15-18 Février 2020

Du 15 au 18 Février, le Professeur Ruffini, Directeur d'ICRANet, a visité El Colegio Nacional à Mexico (Mexique), puisque il a été invite à donner une super plenary lecture à l'occasion du VII Leopoldo García-Colín Mexican Meeting on Mathematical and Experimental Physics. Le lundi 17 Février, le Prof. Ruffini a présenté son exposé, titré "Discovery of energy extraction by discrete "Black-Holic" quanta from a Kerr Black Hole in GRB 190114C".

Voici l'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 GRB 190114C with corresponding rotational energy extraction process. The predicted properties of the BdHN I have been now observed: both in this source and in GRB 130427A, in GRB 160509A and in GRB 160625B. The first appearance of the Supernova the SN rise triggering the BdHN has been identified and followed all the way to the appearance of the optical SN. 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 NASA Niels-Gehrels 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.

Fig. 6: le Prof. Ruffini pendant sa super plenary lecture au VII Leopoldo García-Colín Mexican Meeting on Mathematical and Experimental Physics, à Mexico (Mexique), 17 Février 2020.

Fig. 7: le Prof. Alfredo Macias présente le Prof. Ruffini auprès de El Colegio Nacional.

Pour la vidéo de la présentation du Prof. Ruffini: https://www.youtube.com/watch?v=m532c7iFE60

6. Ajournement du 4^ème Zeldovich meeting, Minsk, Belarus

Compte tenu de la situation mondiale crée par le Coronavirus COVID-19, le Comité organisateur du 4^ème Zeldovich meeting a décidé d'ajourner cette conférence, précédemment organisée du 20 au 24 Avril à Minsk (Belarus). Les nouvelles dates provisoires du meeting sont du 7 à l'11 Septembre 2020. Nous souhaitons que les orateurs ainsi que les autres participants seront disponibles aussi dans ces nouvelles dates.
Plus de détails seront communiqués su la page web de la conférence:
http://www.icranet.org/zeldovich4

7. Félicitations au Prof. Narek Sahakyan, Directeur d'ICRANet Arménie, inclut entre les 100 meilleurs scientifiques d'Arménie, 6 Mars 2020

C'est un plaisir Vous informer que le Professeur Narek Sahakyan, Directeur d'ICRANet Arménie, a été nommé dans la liste des 100 meilleurs chercheurs en Arménie. Le 6 Mars 2020, le Ministère de l'Education, de la Science, de la Culture et du Sport du pays a publié, comme chaque année, la liste des 100 scientifiques arméniens plus actifs et productives dans toutes les disciplines ("Top 100"), basée sur les publications des 10 dernières années, sur les citations, etc. Le Prof. Sahakyan a été inclut dans cette liste. Pour l'annonce officiel, (en Arménien) voir le lien: http://scs.am/am/06-03-2020

8. Publications récentes

J. A. Rueda and R. Ruffini, The blackholic quantum, European Physical Journal C, 80, 300 (2020).
We show that the high-energy emission of GRBs originates in the "inner engine": a Kerr black hole (BH) surrounded by matter and a magnetic field B0. It radiates a sequence of discrete events of particle acceleration, each of energy ε=ℏΩ_eff, the "blackholic quantum", where Ω_eff=4(m_Pl/m_n)⁸(ca/GM)(B²₀/ρ_Pl)Ω₊. Here M, a=J/M, Ω₊=c²∂M/∂J=(c²/G)a/(2Mr₊) and r₊ are the BH mass, angular momentum per unit mass, angular velocity and horizon; m_n is the neutron mass, m_Pl, λ_Pl=ℏ/(m_Plc) and ρ_Pl=m_Plc²/λ³_Pl, are the Planck mass, length and energy density. The timescale of each process is τel∼Ω⁻¹₊. We show an analogy with the Zeeman and Stark effects, properly scaled from microphysics to macrophysics, that allows us to define the "BH magneton", μ_BH=(m_Pl/m_n)⁴(ca/GM)eℏ/(Mc). We give quantitative estimates for GRB 130427A adopting M=2.3M_⊙, ca/(GM)=0.3 and B₀=2.9×10¹⁴ G. Each emitted "quantum", ε∼10⁴⁴ erg, extracts only 10⁻⁹ times the BH rotational energy, guaranteeing that the process can be repeated for thousands of years. The "inner engine" can also work in AGN as we here exemplified for the supermassive BH at the center of M87.
Links: https://arxiv.org/abs/1907.08066,
https://doi.org/10.1140/epjc/s10052-020-7868-z.


J. A. Rueda, R. Ruffini, M. Karlica, R. Moradi, Y. Wang, Magnetic Fields and Afterglows of BdHNe: Inferences from GRB 130427A, GRB 160509A, GRB 160625B, GRB 180728A and GRB 190114C, accepted for publication in The Astrophysical Journal.
GRB 190114C is the first binary-driven hypernova (BdHN) fully observed from the initial supernova appearance to the final emergence of the optical SN signal. It offers an unprecedented testing ground for the BdHN theory and it is here determined and further extended to additional gamma-ray bursts (GRBs). BdHNe comprise two subclasses of long GRBs with progenitors a binary system composed of a carbon-oxygen star (CO_core) and a neutron star (NS) companion. The CO_core explodes as a SN leaving at its center a newborn NS (νNS). The SN ejecta hypercritically accretes both on the νNS and the NS companion. BdHNe I are the tightest binaries where the accretion leads the companion NS to gravitational collapse into a black hole (BH). In BdHN II the accretion onto the NS is lower, so there is no BH formation. We observe the same structure of the afterglow for GRB 190114C and other selected examples of BdHNe I (GRB 130427A, GRB 160509A, GRB 160625B) and for BdHN II (GRB 180728A). In all the cases the explanation of the afterglow is reached via the synchrotron emission powered by the νNS: their magnetic fields structures and their spin are determined. For BdHNe I, we discuss the properties of the magnetic field embedding the newborn BH, inherited from the collapsed NS and amplified during the gravitational collapse process, and surrounded by the SN ejecta.
Link: https://arxiv.org/abs/1905.11339


De Lima, Rafael C. R.; Coelho, Jaziel G.; Pereira, Jonas P.; Rodrigues, Claudia V.; Rueda, Jorge A., Evidence for a Multipolar Magnetic Field in SGR J1745-2900 from X-Ray Light-curve Analysis, published in The Astrophysical Journal, Volume 889, Issue 2, id.165, on February 4, 2020.
SGR J1745-2900 was detected from its outburst activity in April 2013 and it was the first soft gamma repeater (SGR) detected near the center of the Galaxy (Sagittarius A∗). We use 3.5-year Chandra X-ray light-curve data to constrain some neutron star (NS) geometric parameters. We assume that the flux modulation comes from hot spots on the stellar surface. Our model includes the NS mass, radius, a maximum of three spots of any size, temperature and positions, and general relativistic effects. We find that the light-curve of SGR J1745-2900 could be described by either two or three hot spots. The ambiguity is due to the small amount of data, but our analysis suggests that one should not disregard the possibility of multi-spots (due to a multipolar magnetic field) in highly magnetized stars. For the case of three hot spots, we find that they should be large and have angular semi-apertures ranging from 16-67 degrees. The large size found for the spots points to a magnetic field with a nontrivial poloidal and toroidal structure (in accordance with magnetohydrodynamics investigations and NICER's recent findings for PSR J0030+0451) and is consistent with the small characteristic age of the star. Finally, we also discuss possible constraints on the mass and radius of SGR J1745-2900 and briefly envisage possible scenarios accounting for the 3.5-year evolution of SGR J1745-2900 hot spots.
Link: https://arxiv.org/abs/1912.12336


Loppini A, Cherubini C, Bertolaso M, Filippi S., Breaking down calcium timing in heterogenous cells populations, published in BIOSYSTEMS, vol. 191-192, p. 1-7, ISSN: 0303-2647.
Calcium controls a large number of cellular processes at different scales. Decades of studies have pointed out the importance of calcium signaling in regulating differentiation, apoptosis, mitosis and functions such as secretion, muscle contraction and memory. The space-time structure of calcium signaling is central to this complex regulation. In particular, cells within organisms behave as clocks beating their own biological time, although in several cases they can synchronize across long distances leading to an emergent space-time dynamics which is central for single cell and organ functioning. We use a mathematical model built on published experimental data of hepatic non-excitable cells, analyzing emerging calcium dynamics of cells clusters composed both of normally functioning cells and pathological aggregates. Calcium oscillations are investigated by varying the severity of dysfunction and size of pathological aggregate. We show how strong and localized heterogeneity in cellular properties can profoundly alter organized calcium dynamics leading to sub-populations of cells which create their own coordinated dynamical organization. Our simulations of Ca²⁺ signals reveal how cell behaviors differ and are related to intrinsic time signals. Such different cells clusters dynamically influence each other so that non-physiological although organized calcium patterns are generated. This new reorganization of calcium activity may possibly be a precursor of cancer initiation.
Link: https://doi.org/10.1016/j.biosystems.2020.104117


MAGIC Collaboration; Acciari, V. A.; Ansoldi, S.; Antonelli, L. A.; Arbet Engels, A.; Arcaro, C.; Baack, D.; Babić, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bellizzi, L.; Bernardini, E.; Berti, A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C. Biland, A.; Blanch, O.; Bonnoli, G.; Bošnjak, Ž.; Busetto, G.; Carosi, R.; Ceribella, G.; Chai, Y.; Chilingaryan, A.; Cikota, S.; Colak, S. M.; Colin, U.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; D'Elia, V.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Lotto, B.; Delfino, M.; Delgado, J.; Depaoli, D.; di Pierro, F.; di Venere, L.; Do SoutoEspiñeira, E.; Dominis Prester, D.; Donini, A.; Dorner, D.; Doro, M.; Elsaesser, D.; Fallah Ramazani, V.; Fattorini, A.; Fernández-Barral, A.; Ferrara, G.; Fidalgo, D.; Foffano, L.; Fonseca, M. V.; Font, L.; Fruck, C.; Fukami, S.; García López, R. J.; Garczarczyk, M.; Gasparyan, S.; Gaug, M.; Giglietto, N.; Giordano, F.; Godinović, N.; Green, D.; Guberman, D.; Hadasch, D.; Hahn, A.; Herrera, J.; Hoang, J.; Hrupec, D.; Hütten, M.; Inada, T.; Inoue, S.; Ishio, K.; Iwamura, Y.; Jouvin, L.; Kerszberg, D.; Kubo, H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas, A.; Loporchio, S.; Machado de Oliveira Fraga, B.; Maggio, C.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Masuda, S.; Mazin, D.; Mićanović, S.; Miceli, D.; Minev, M.; Miranda, J. M.; Mirzoyan, R.; Molina, E.; Moralejo, A.; Morcuende, D.; Moreno, V.; Moretti, E.; Munar-Adrover, P.; Neustroev, V.; Nigro, C.; Nilsson, K.; Ninci, D.; Nishijima, K.; Noda, K.; Nogués, L.; Nöthe, M.; Nozaki, S.; Paiano, S.; Palacio, J.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Peñil, P.; Peresano, M.; Persic, M.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich, A.; Saha, L.; Sahakyan, N.; Saito, T.; Sakurai, S.; Satalecka, K.; Schmidt, K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Somero, A.; Stamerra, A.; Strom, D.; Strzys, M.; Suda, Y.; Surić, T.; Takahashi, M.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Teshima, M.; Torres-Albà, N.; Tosti, L.; Tsujimoto, S.; Vagelli, V.; van Scherpenberg, J.; Vanzo, G.; Acosta, M. Vazquez; Vigorito, C. F.; Vitale, V.; Vovk, I.; Will, M.; Zarić, D.; Asano, K.; Hada, K.; Harris, D. E.; Giroletti, M.; Jermak, H. E.; Madrid, J. P.; Massaro, F.; Richter, S.; Spanier, F.; Steele, I. A.; Walker, R. C., Monitoring of the radio galaxy M 87 during a low-emission state from 2012 to 2015 with MAGIC, published on Monthly Notices of the Royal Astronomical Society, Volume 492, Issue 4, p.5354-5365.
M 87 is one of the closest (z = 0.004 36) extragalactic sources emitting at very high energies (VHE, E > 100 GeV). The aim of this work is to locate the region of the VHE gamma-ray emission and to describe the observed broad-band spectral energy distribution (SED) during the low VHE gamma-ray state. The data from M 87 collected between 2012 and 2015 as part of a MAGIC monitoring programme are analysed and combined with multiwavelength data from Fermi-LAT, Chandra, HST, EVN, VLBA, and the Liverpool Telescope. The averaged VHE gamma-ray spectrum can be fitted from ∼100 GeV to ∼10 TeV with a simple power law with a photon index of (-2.41 ± 0.07), while the integral flux above 300 GeV is (1.44± 0.13)× 10^{-12} cm^{-2} s^{-1}. During the campaign between 2012 and 2015, M 87 is generally found in a low-emission state at all observed wavelengths. The VHE gamma-ray flux from the present 2012-2015M 87 campaign is consistent with a constant flux with some hint of variability (∼ 3 σ) on a daily time-scale in 2013. The low-state gamma-ray emission likely originates from the same region as the flare-state emission. Given the broad-band SED, both a leptonic synchrotron self-Compton and a hybrid photohadronic model reproduce the available data well, even if the latter is preferred. We note, however, that the energy stored in the magnetic field in the leptonic scenario is very low, suggesting a matter-dominated emission region.
Link: https://doi.org/10.1093/mnras/staa014


Acciari, V. A.; Ansoldi, S.; Antonelli, L. A.; Engels, A. Arbet; Asano, K.; Baack, D.; Babić, A.; Banerjee, B.; de Almeida, U. Barres; Barrio, J. A.; González, J. Becerra; Bednarek, W.; Bellizzi, L.; Bernardini, E.; Berti, A.; Besenrieder, J.; Bhattacharyya, W.; Bigongiari, C.; Biland, A.; Blanch, O. Bonnoli, G.; Bošnjak, Ž.; Busetto, G.; Carosi, R.; Ceribella, G.; Cerruti, M.; Chai, Y.; Chilingaryan, A.; Cikota, S.; Colak, S. M.; Colin, U.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; D'Elia, V.; Vela, P. Da; Dazzi, F.; Angelis, A. De; Lotto, B. De; Delfino, M.; Delgado, J.; Depaoli, D.; Pierro, F. Di; Venere, L. Di; SoutoEspiñeira, E. Do; Prester, D. Dominis; Donini, A.; Dorner, D.; Doro, M.; Elsaesser, D.; Ramazani, V. Fallah; Fattorini, A.; Ferrara, G.; Fidalgo, D.; Foffano, L.; Fonseca, M. V.; Font, L.; Fruck, C.; Fukami, S.; López, R. J. García; Garczarczyk, M.; Gasparyan, S.; Gaug, M.; Giglietto, N.; Giordano, F.; Godinović, N.; Green, D.; Guberman, D.; Hadasch, D.; Hahn, A.; Herrera, J.; Hoang, J.; Hrupec, D.; Hütten, M.; Inada, T.; Inoue, S.; Ishio, K.; Iwamura, Y.; Jouvin, L.; Kerszberg, D.; Kubo, H.; Kushida, J.; Lamastra, A.; Lelas, D.; Leone, F.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas, A.; Loporchio, S.; de Oliveira Fraga, B. Machado; Maggio, C.; Majumdar, P.; Makariev, M.; Mallamaci, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Mićanović, S.; Miceli, D.; Minev, M.; Miranda, J. M.; Mirzoyan, R.; Molina, E.; Moralejo, A.; Morcuende, D.; Moreno, V.; Moretti, E.; Munar-Adrover, P.; Neustroev, V.; Nigro, C.; Nilsson, K.; Ninci, D.; Nishijima, K.; Noda, K.; Nogués, L.; Nozaki, S.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Peñil, P.; Peresano, M.; Persic, M.; Moroni, P. G. Prada; Prandini, E.; Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Righi, C.; Rugliancich, A.; Saha, L.; Sahakyan, N.; Saito, T.; Sakurai, S.; Satalecka, K.; Schmidt, K.; Schweizer, T.; Sitarek, J.; Šnidarić, I.; Sobczynska, D.; Somero, A.; Stamerra, A.; Strom, D.; Strzys, M.; Suda, Y.; Surić, T.; Takahashi, M.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Teshima, M.; Torres-Albà, N.; Tosti, L.; Vagelli, V.; Scherpenberg, J. van; Vanzo, G.; Acosta, M. Vazquez; Vigorito, C. F.; Vitale, V.; Vovk, I.; Will, M.; Zarić, D.; Arcaro, C.; Carosi, A.; D'Ammando, F.; Tombesi, F.; Lohfink, A., New Hard-TeV Extreme Blazars Detected with the MAGIC Telescopes, published on The Astrophysical Journal Supplement Series, Volume 247, Issue 1, id.16.
Extreme high-frequency-peaked BL Lac objects (EHBLs) are blazars that exhibit extremely energetic synchrotron emission. They also feature nonthermal gamma-ray emission whose peak lies in the very high-energy (VHE, E > 100 GeV) range, and in some sources exceeds 1 TeV: this is the case for hard-TeV EHBLs such as 1ES 0229+200. With the aim of increasing the EHBL population, 10 targets were observed with the MAGIC telescopes from 2010 to 2017, for a total of 265 hr of good-quality data. The data were complemented by coordinated Swift observations. The X-ray data analysis confirms that all but two sources are EHBLs. The sources show only a modest variability and a harder-when-brighter behavior, typical for this class of objects. At VHE gamma-rays, three new sources were detected and a hint of a signal was found for another new source. In each case, the intrinsic spectrum is compatible with the hypothesis of a hard-TeV nature of these EHBLs. The broadband spectral energy distributions (SEDs) of all sources are built and modeled in the framework of a single-zone, purely leptonic model. The VHE gamma-ray-detected sources were also interpreted with a spine-layer model and a proton synchrotron model. The three models provide a good description of the SEDs. However, the resulting parameters differ substantially in the three scenarios, in particular the magnetization parameter. This work presents the first mini catalog of VHE gamma-ray and multiwavelength observations of EHBLs.
Link: https://doi.org/10.3847/1538-4365/ab5b98


Paiani et al., The redshift and the host galaxy of the neutrino candidate 4FGL J0955.1+3551 (3HSP J095507.9+355101), accepted by MNRAS.
The BL Lac object 4FGLJ0955.1+3551 has been suggested as a possible source of ultra energetic neutrinos detected by the Icecube observatory. The target was observed in January 2020 at the Large Binocular Telescope. Our spectroscopy (4100-8500 Ang) yields a firm redshift z = 0.557 as deduced by the absorption lines of the host galaxy. The upper limit of the minimum equivalent width on emission lines is 0.3 Ang. From the source image we are able to resolve the host galaxy for which we measure an absolute magnitude M(R) = -22.9 and Re = 8 kpc, that is values which are typical of the host galaxies of BL Lacs.
Link: https://arxiv.org/abs/2003.03634


She-Sheng Xue,Cosmological constant, matter, cosmic inflation and coincidence, Modern Physics Letters A (2020), 2050123 (13 pages).
We present a possible understanding to the issues of cosmological constant, inflation, dark matter and coincidence problems based only on the Einstein equation and Hawking particle production. The inflation appears and results agree to observations. The CMB large-scale anomaly can be explained and the dark-matter acoustic wave is speculated. The entropy and reheating are discussed. The cosmological term Ω_Λ tracks down the matter Ω_M until the radiation-matter equilibrium, then slowly varies, thus the cosmic coincidence problem can be avoided. The relation between Ω_Λ and Ω_M is shown and can be examined at large redshifts.
Link: https://doi.org/10.1142/S0217732320501230