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ICRANet Newsletter
Febbraio/Marzo 2021
Febbraio/Marzo 2021
SOMMARIO
1. Astronomers get their First Look at the Dynamics of the Base of a Relativistic Jet
2. Sedicesimo Marcel Grossmann Meeting virtuale (MG16), 5-9 Luglio 2021
3. Inaugurazione del centro ICRANet Mazandaran (Iran), 28 Febbraio 2021
4. Nuovo Protocollo di cooperazione ICRA-ICRANet-Alzahra University, 9 Febbraio 2021
5. Rinnovo di 3 Accordi di collaborazione ICRANet in Iran
6. Nuovo Memorandum of Understanding e Accordo di cooperazione in Astrofisica Relativistica ICRA - University of Sciences and Technology of China (USTC), 16 Marzo 2021
7. Nuovo Protocollo di cooperazione ICRANet - Ulugh Beg Astronomical Institute of Uzbekistan Academy of Sciences (UBAI), 26 Marzo 2021
8. 43° COSPAR Scientific Assembly meeting (online), 28 Gennaio - 4 Febbraio 2021
9. Seminario del Prof. Ruffini per Space Science at Drop tower, ZARM Brema (Germania), 8 Marzo 2021
10. Rencontres de Moriond on Gravitation (poster session), 9-11 Marzo 2021
11. Nuovi risultati sull'AXP 4U 01242+61 dalla collaborazione ICRANet - ITA
12. Pubblicazioni recenti
1. Astronomers get their First Look at the Dynamics of the Base of a Relativistic Jet
2. Sedicesimo Marcel Grossmann Meeting virtuale (MG16), 5-9 Luglio 2021
3. Inaugurazione del centro ICRANet Mazandaran (Iran), 28 Febbraio 2021
4. Nuovo Protocollo di cooperazione ICRA-ICRANet-Alzahra University, 9 Febbraio 2021
5. Rinnovo di 3 Accordi di collaborazione ICRANet in Iran
6. Nuovo Memorandum of Understanding e Accordo di cooperazione in Astrofisica Relativistica ICRA - University of Sciences and Technology of China (USTC), 16 Marzo 2021
7. Nuovo Protocollo di cooperazione ICRANet - Ulugh Beg Astronomical Institute of Uzbekistan Academy of Sciences (UBAI), 26 Marzo 2021
8. 43° COSPAR Scientific Assembly meeting (online), 28 Gennaio - 4 Febbraio 2021
9. Seminario del Prof. Ruffini per Space Science at Drop tower, ZARM Brema (Germania), 8 Marzo 2021
10. Rencontres de Moriond on Gravitation (poster session), 9-11 Marzo 2021
11. Nuovi risultati sull'AXP 4U 01242+61 dalla collaborazione ICRANet - ITA
12. Pubblicazioni recenti
1. Astronomers get their First Look at the Dynamics of the Base of a Relativistic Jet
Synopsis of the Astrophysical Journal paper "Observing the Time Evolution of the Multi-Component Nucleus of 3C 84" by Brian Punsly, Hiroshi Nagai, Tuomas Savolainen and Monica Orienti.
Relativistic astrophysical jets are some of the most energetic objects in the Universe. They are driven by compact objects, primarily black holes. The jets from the supermassive black holes can have powers >1040 Watts and last for a million years. They are intense pencil beams of energy that terminate in enormous plume or lobe, an order of magnitude larger than the largest galaxies. The bases of the jets, where the jets originate, are too small to be within the reach of modern telescopes. Thus, the Event Horizon Telescope (EHT) that can image the base of the jet in the nearby galaxy, M87. The observations are so difficult, that we are lucky to have one successful observation every few years. Thus, one cannot track the dynamics of the base of the jet over time scales of weeks to a year when all the significant changes occur.
Consequently, a team of astronomers looked to the nearby extragalactic radio source 3C 84 that is much brighter than M87 to glimpse the dynamics of a jet near its source for the first time. They were able to use a high efficiency global network of telescopes, the Very Long Baseline Array, that is operated by National Radio Astronomy Observatory. This telescope can efficiently observe on a regular basis, but with a resolution of only 25% of EHT. The fact that 3C 84 is the brightest extragalactic object in the sky at the observed frequency allows for very high signal to noise and the use of novel high resolution data reduction schemes invented for this purpose. ICRANet astrophysicist, Brian Punsly, patiently waited throughmany years of monthly monitoring until the base of the of the southerly directed jet started to evolve. Over twenty months, the central engine ejected a high energy plasma source to the east not the south - perpendicular to the pencil beam jet! Not only that it moved at only 9% of the speed of light, very slow by relativistic standards. Now that we can see the base of the jets, we can intelligently describe their genesis in the future.
Fig. 1: This frame shows the VLBA.
Fig. 2: This frame shows the east-west motion of the nucleus on the left contrasted with the north-south jet on the right.
Brian Mathew Punsly from Mathew California University, Los Angeles USA is a member of ICRANet Faculty Staff.
Link to the article: https://arxiv.org/abs/2102.07272
Relativistic astrophysical jets are some of the most energetic objects in the Universe. They are driven by compact objects, primarily black holes. The jets from the supermassive black holes can have powers >1040 Watts and last for a million years. They are intense pencil beams of energy that terminate in enormous plume or lobe, an order of magnitude larger than the largest galaxies. The bases of the jets, where the jets originate, are too small to be within the reach of modern telescopes. Thus, the Event Horizon Telescope (EHT) that can image the base of the jet in the nearby galaxy, M87. The observations are so difficult, that we are lucky to have one successful observation every few years. Thus, one cannot track the dynamics of the base of the jet over time scales of weeks to a year when all the significant changes occur.
Consequently, a team of astronomers looked to the nearby extragalactic radio source 3C 84 that is much brighter than M87 to glimpse the dynamics of a jet near its source for the first time. They were able to use a high efficiency global network of telescopes, the Very Long Baseline Array, that is operated by National Radio Astronomy Observatory. This telescope can efficiently observe on a regular basis, but with a resolution of only 25% of EHT. The fact that 3C 84 is the brightest extragalactic object in the sky at the observed frequency allows for very high signal to noise and the use of novel high resolution data reduction schemes invented for this purpose. ICRANet astrophysicist, Brian Punsly, patiently waited throughmany years of monthly monitoring until the base of the of the southerly directed jet started to evolve. Over twenty months, the central engine ejected a high energy plasma source to the east not the south - perpendicular to the pencil beam jet! Not only that it moved at only 9% of the speed of light, very slow by relativistic standards. Now that we can see the base of the jets, we can intelligently describe their genesis in the future.
Fig. 1: This frame shows the VLBA.
Fig. 2: This frame shows the east-west motion of the nucleus on the left contrasted with the north-south jet on the right.
Brian Mathew Punsly from Mathew California University, Los Angeles USA is a member of ICRANet Faculty Staff.
Link to the article: https://arxiv.org/abs/2102.07272
2. Sedicesimo Marcel Grossmann Meeting virtuale (MG16), 5-9 Luglio 2021
Il Sedicesimo Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Astrophysics and Relativistic Field Theories (MG16) si terrà virtualmente da lunedì 5 a venerdì 9 Luglio 2021.
Il meeting sarà organizzato dall'ICRA (Roma, Italia), dall'ICRANet (Pescara, Italia) e dai centri associati all'ICRANet compresi quello a Yerevan, Armenia; a Minsk, Bielorussia; a Rio de Janeiro, Brasile; presso l'USTC, Cina; ad Isfahan, Iran; presso la Stanford University e l'University of Arizona, USA.
Durante questa conferenza online che durerà 5 giorni, saranno discussi un'ampia varietà di tematiche nel corso di sessioni plenarie e parallele. Ogni giorno, il programma si comporrà di 3 blocchi da 3 ore ciascuno: a rotazione, uno sarà riservato alle sessioni plenarie, gli altri due alle sessioni parallele, per venire incontro ai tre principali fusi orari continentali:
Central European Summer Time (CEST):
Blocco 1: 6:30-9:30
Blocco 2: 9:30-12:30
Blocco 3: 16:30-19:30
La prima sessione plenaria inizierà alle h 9:30 del lunedì, la seconda alle h 16:30 del martedì, la terza alle h 6:30 del mercoledì e così via. Le registrazioni delle sessioni plenary saranno disponibili su YouTube il giorno seguente. Ogni blocco avrà 10 sessioni parallele che si svolgeranno in contemporanea, e in ciascuna saranno presentati 9 talks.
Il sito web del MG16 è http://www.icra.it/mg/mg16. Tutte le informazioni sui programmi delle sessioni plenarie e parallele, sulla registrazione e sulla sottomissione degli abstract sono disponibili sulla piattaforma Indico al seguente link: https://indico.icranet.org/event/1/. Chi volesse partecipare alla conferenza, deve registrarsi sia alla piattaforma Indico che alla conferenza MG16, usando i seguenti link:
Registrazione sulla piattaforma Indico: https://indico.icranet.org/register/
Registrazione alla conferenza MG16: https://indico.icranet.org/event/1/registrations/
Una volta registrati, sarete inseriti nel nostro database e riceverete tutte le comunicazioni necessarie inerenti al MG16 meeting.
Le date importanti sono:
* 15 Marzo 2021: apertura delle registrazioni
* 15 Aprile 2021: apertura della sottomissione degli abstract
* 15 Maggio 2021: chiusura delle registrazioni
* 15 Giugno 2021: chiusura della sottomissione degli abstract
Le registration fee per partecipare al meeting sono:
* Regular fee: 150 Euro (fino al 1 Aprile) - rinviata al 30 Aprile
* Late fee: 250 Euro (dopo il 30 Aprile)
* Reduced fee: 50 Euro (per studenti, pensionati e uditori fino al 30 Aprile) - rinviata al 30 Aprile
* Late Reduced fee: 80 Euro (a per studenti, pensionati e uditori dopo il 30 Aprile)
Per qualsiasi tipo di richiesta, contattare il seguente indirizzo mg16[AT]icranet.org
Il meeting sarà organizzato dall'ICRA (Roma, Italia), dall'ICRANet (Pescara, Italia) e dai centri associati all'ICRANet compresi quello a Yerevan, Armenia; a Minsk, Bielorussia; a Rio de Janeiro, Brasile; presso l'USTC, Cina; ad Isfahan, Iran; presso la Stanford University e l'University of Arizona, USA.
Durante questa conferenza online che durerà 5 giorni, saranno discussi un'ampia varietà di tematiche nel corso di sessioni plenarie e parallele. Ogni giorno, il programma si comporrà di 3 blocchi da 3 ore ciascuno: a rotazione, uno sarà riservato alle sessioni plenarie, gli altri due alle sessioni parallele, per venire incontro ai tre principali fusi orari continentali:
Central European Summer Time (CEST):
Blocco 1: 6:30-9:30
Blocco 2: 9:30-12:30
Blocco 3: 16:30-19:30
La prima sessione plenaria inizierà alle h 9:30 del lunedì, la seconda alle h 16:30 del martedì, la terza alle h 6:30 del mercoledì e così via. Le registrazioni delle sessioni plenary saranno disponibili su YouTube il giorno seguente. Ogni blocco avrà 10 sessioni parallele che si svolgeranno in contemporanea, e in ciascuna saranno presentati 9 talks.
Il sito web del MG16 è http://www.icra.it/mg/mg16. Tutte le informazioni sui programmi delle sessioni plenarie e parallele, sulla registrazione e sulla sottomissione degli abstract sono disponibili sulla piattaforma Indico al seguente link: https://indico.icranet.org/event/1/. Chi volesse partecipare alla conferenza, deve registrarsi sia alla piattaforma Indico che alla conferenza MG16, usando i seguenti link:
Registrazione sulla piattaforma Indico: https://indico.icranet.org/register/
Registrazione alla conferenza MG16: https://indico.icranet.org/event/1/registrations/
Una volta registrati, sarete inseriti nel nostro database e riceverete tutte le comunicazioni necessarie inerenti al MG16 meeting.
Le date importanti sono:
* 15 Marzo 2021: apertura delle registrazioni
* 15 Aprile 2021: apertura della sottomissione degli abstract
* 15 Maggio 2021: chiusura delle registrazioni
* 15 Giugno 2021: chiusura della sottomissione degli abstract
Le registration fee per partecipare al meeting sono:
* Regular fee: 150 Euro (fino al 1 Aprile) - rinviata al 30 Aprile
* Late fee: 250 Euro (dopo il 30 Aprile)
* Reduced fee: 50 Euro (per studenti, pensionati e uditori fino al 30 Aprile) - rinviata al 30 Aprile
* Late Reduced fee: 80 Euro (a per studenti, pensionati e uditori dopo il 30 Aprile)
Per qualsiasi tipo di richiesta, contattare il seguente indirizzo mg16[AT]icranet.org
3. Inaugurazione del centro ICRANet Mazandaran (Iran), 28 Febbraio 2021
E' nostro grande piacere annunciare che sabato 28 Febbraio 2021, è stato inaugurato il centro ICRANet presso l'Università di Mazandaran - UMZ (Iran). Si tratta del secondo centro ICRANet in Iran. Alla cerimonia di inaugurazione hanno partecipato il Dr. Kourosh Nozari, Professore di fisica e Presidente dell'Università di Mazandaran e il Dr. Behzad Eslampanah, Professore di fisica presso l'Università di Mazandaran.
Durante un meeting tenutosi presso l'Ufficio per la Cooperazione internazionale e scientifica dell'Università (OISC), il Presidente Nozari, un eminente fisico Iraniano, ha sottolineato nuovamente l'importanza dell'ICRANet, descrivendolo come un importantissimo centro di ricerca capace di giocare un ruolo fondamentale nell'implementazione della ricerca in Fisica presso l'Università di Mazandaran e nell'intero paese. Il Presidente ha anche accolto con entusiasmo ogni tipo di collaborazione accademica tra l'ICRANet e l'UMZ, affermando che il centro è pronto per rafforzare ulteriormente la collaborazione bilaterale con l'ICRANet.
Fig. 3, 4 and 5: la cerimonia di inaugurazione del centro ICRANet presso l'Università di Mazandaran (Iran), 28 Febbraio 2021
For the press release (in English) please see the University of Mazandaran official website:
http://en.int.umz.ac.ir/index.aspx?siteid=122&fkeyid=&siteid=122&pageid=13816&newsview=26386.
Durante un meeting tenutosi presso l'Ufficio per la Cooperazione internazionale e scientifica dell'Università (OISC), il Presidente Nozari, un eminente fisico Iraniano, ha sottolineato nuovamente l'importanza dell'ICRANet, descrivendolo come un importantissimo centro di ricerca capace di giocare un ruolo fondamentale nell'implementazione della ricerca in Fisica presso l'Università di Mazandaran e nell'intero paese. Il Presidente ha anche accolto con entusiasmo ogni tipo di collaborazione accademica tra l'ICRANet e l'UMZ, affermando che il centro è pronto per rafforzare ulteriormente la collaborazione bilaterale con l'ICRANet.
Fig. 3, 4 and 5: la cerimonia di inaugurazione del centro ICRANet presso l'Università di Mazandaran (Iran), 28 Febbraio 2021
For the press release (in English) please see the University of Mazandaran official website:
http://en.int.umz.ac.ir/index.aspx?siteid=122&fkeyid=&siteid=122&pageid=13816&newsview=26386.
4. Nuovo Protocollo di cooperazione ICRA-ICRANet-Alzahra University, 9 Febbraio 2021
Il 9 Febbraio 2021 è stato firmato un nuovo protocollo di cooperazione tra l'ICRA, l'ICRANet e l'Alzahra University (Iran) dal Dr. Mahnaz Molanazari (Direttore dell'Alzahra University), dal Prof. Mohammad Taghi Mirtorabi (Professore associato presso il Dipartimento di Fisica e Chimica dell'Alzahra University), dal Prof. Remo Ruffini (Presidente ICRA e Direttore ICRANet) e dal Prof. Jorge A. Rueda (Professore della Faculty ICRANet). Le principali attività congiunte che saranno portate avanti nel quadro del progetto comprendono: la promozione di attività teoriche e pratiche nel campo dell'Astrofisica Relativistica; la collaborazione tra membri della Faculty, ricercatori, Dottorandi e studenti; l'organizzazione di corsi di insegnamento e ricerca, di seminari, conferenze, workshop, e il lavoro congiunto per le pubblicazioni scientifiche. L'accordo sarà valido per 5 anni.
Per il testo dell'accordo (sia in inglese che in persiano): http://www.icranet.org/index.php?option=com_content&task=view&id=1360
5. Rinnovo di 3 Accordi di collaborazione ICRANet in Iran
Rinnovo del Protocollo di Cooperazione ICRANet - Isfahan University of Technology (IUT), 26 Febbraio 2021
Il 26 Febbraio 2021, è stato rinnovato il Protocollo di Cooperazione tra l'ICRANet e l'Isfahan University of Technology - IUT (Iran). Il rinnovo è stato firmato dal Prof. Sayyed Mahdi Abtahi (Presidente dell'IUT) e dal Prof. Remo Ruffini (Direttore ICRANet). Questo accordo sarà valido per ulteriori 5 anni e principali attività congiunte che saranno portate avanti nel quadro del progetto comprendono: la promozione di attività teoriche e pratiche nel campo dell'Astrofisica Relativistica; la collaborazione tra membri della Faculty, ricercatori, Dottorandi e studenti; l'organizzazione di corsi di insegnamento e ricerca, di seminari, conferenze, workshop, e il lavoro congiunto per le pubblicazioni scientifiche.
Per il testo dell'accordo:
http://www.icranet.org/index.php?option=com_content&task=view&id=1059
Per la newsletter dell'IUT su questo evento (in inglese):
https://internationalnews.iut.ac.ir/book_treasure.php?mod=viewbook&book_id=31&slc_lang=en&sid=1
Rinnovo del Protocollo di Cooperazione tra l'ICRANet e l'Institute for Advanced Studies in Basic Sciences (IASBS), 1 Marzo 2021
Il giorno 1 Marzo 2021 è stato rinnovato il Protocollo di Cooperazione tra l'ICRANet e l'Institute for Advanced Studies in Basic Sciences - IASBS (Iran). Il rinnovo è stato firmato dal Prof. Babak Karimi (Presidente IASBS) e dal Prof. Remo Ruffini (Direttore ICRANet). Questo accordo sarà valido per ulteriori 5 anni e principali attività congiunte che saranno portate avanti nel quadro del progetto comprendono: la promozione di attività teoriche e pratiche nel campo dell'Astrofisica Relativistica; la collaborazione tra membri della Faculty, ricercatori, Dottorandi e studenti; l'organizzazione di corsi di insegnamento e ricerca, di seminari, conferenze, workshop, e il lavoro congiunto per le pubblicazioni scientifiche.
Per il testo dell'accordo:
http://www.icranet.org/index.php?option=com_content&task=view&id=1058
Rinnovo dell'Accordo ICRANet - Shiraz University, 5 Marzo 2021
Il 5 Marzo 2021, è stato rinnovato l'Accordo di Cooperazione tra l'ICRANet e la Shiraz University (Iran). Il rinnovo è stato firmato dal Prof. Dr. Hamid Nadgaran (Direttore della Shiraz University) e dal Prof. Remo Ruffini (Direttore ICRANet). Questo accordo sarà valido per ulteriori 5 anni e principali attività congiunte che saranno portate avanti nel quadro del progetto comprendono: la promozione di attività teoriche e pratiche nel campo dell'Astrofisica Relativistica; la collaborazione tra membri della Faculty, ricercatori, Dottorandi e studenti; l'organizzazione di corsi di insegnamento e ricerca, di seminari, conferenze, workshop, e il lavoro congiunto per le pubblicazioni scientifiche.
Per il testo dell'accordo:
http://www.icranet.org/index.php?option=com_content&task=view&id=1062
Il 26 Febbraio 2021, è stato rinnovato il Protocollo di Cooperazione tra l'ICRANet e l'Isfahan University of Technology - IUT (Iran). Il rinnovo è stato firmato dal Prof. Sayyed Mahdi Abtahi (Presidente dell'IUT) e dal Prof. Remo Ruffini (Direttore ICRANet). Questo accordo sarà valido per ulteriori 5 anni e principali attività congiunte che saranno portate avanti nel quadro del progetto comprendono: la promozione di attività teoriche e pratiche nel campo dell'Astrofisica Relativistica; la collaborazione tra membri della Faculty, ricercatori, Dottorandi e studenti; l'organizzazione di corsi di insegnamento e ricerca, di seminari, conferenze, workshop, e il lavoro congiunto per le pubblicazioni scientifiche.
Per il testo dell'accordo:
http://www.icranet.org/index.php?option=com_content&task=view&id=1059
Per la newsletter dell'IUT su questo evento (in inglese):
https://internationalnews.iut.ac.ir/book_treasure.php?mod=viewbook&book_id=31&slc_lang=en&sid=1
Rinnovo del Protocollo di Cooperazione tra l'ICRANet e l'Institute for Advanced Studies in Basic Sciences (IASBS), 1 Marzo 2021
Il giorno 1 Marzo 2021 è stato rinnovato il Protocollo di Cooperazione tra l'ICRANet e l'Institute for Advanced Studies in Basic Sciences - IASBS (Iran). Il rinnovo è stato firmato dal Prof. Babak Karimi (Presidente IASBS) e dal Prof. Remo Ruffini (Direttore ICRANet). Questo accordo sarà valido per ulteriori 5 anni e principali attività congiunte che saranno portate avanti nel quadro del progetto comprendono: la promozione di attività teoriche e pratiche nel campo dell'Astrofisica Relativistica; la collaborazione tra membri della Faculty, ricercatori, Dottorandi e studenti; l'organizzazione di corsi di insegnamento e ricerca, di seminari, conferenze, workshop, e il lavoro congiunto per le pubblicazioni scientifiche.
Per il testo dell'accordo:
http://www.icranet.org/index.php?option=com_content&task=view&id=1058
Rinnovo dell'Accordo ICRANet - Shiraz University, 5 Marzo 2021
Il 5 Marzo 2021, è stato rinnovato l'Accordo di Cooperazione tra l'ICRANet e la Shiraz University (Iran). Il rinnovo è stato firmato dal Prof. Dr. Hamid Nadgaran (Direttore della Shiraz University) e dal Prof. Remo Ruffini (Direttore ICRANet). Questo accordo sarà valido per ulteriori 5 anni e principali attività congiunte che saranno portate avanti nel quadro del progetto comprendono: la promozione di attività teoriche e pratiche nel campo dell'Astrofisica Relativistica; la collaborazione tra membri della Faculty, ricercatori, Dottorandi e studenti; l'organizzazione di corsi di insegnamento e ricerca, di seminari, conferenze, workshop, e il lavoro congiunto per le pubblicazioni scientifiche.
Per il testo dell'accordo:
http://www.icranet.org/index.php?option=com_content&task=view&id=1062
6. Nuovo Memorandum of Understanding e Accordo di cooperazione in Astrofisica Relativistica ICRA - University of Sciences and Technology of China (USTC), 16 Marzo 2021
Il 16 Marzo 2021, l'ICRA (International Center for Relativistic Astrophysics) ha firmato un Memorandum of Understanding e un Accordo di Cooperazione in Astrofisica Relativistica con l'Univerità di Scienze e Tecnologia della Cina (USTC). Entrambi i documenti sono stati firmati dal Prof. Yuao Chen (Rettore della Scuola di Scienze fisiche della USTC) e dal Prof. Remo Ruffini (Presidente ICRA e Direttore ICRANet).
L'obiettivo di entrambi i documenti è quello di collaborare nella ricerca e nell'istruzione nel campo dell'Astrofisica Relativistica. Le modalità attraverso le quali sarà attivata questa collaborazione comprendono lo scambio e la visita di Professori dello staff e della Faculty, così come l'implementazione di programmi congiunti per la ricerca e l'istruzione. Entrambe le parti collaboreranno nel campo dell'Astrofisica Relativistica e potranno nominare fino a 5 studenti all'anno come candidati: questi studenti otterranno le qualifiche e le competenze richieste inizialmente presso l'USTC, e poi saranno selezionati per recarsi presso l'ICRA al fine di lavorare su progetti congiunti R&D con la partecipazione a seminari pertinenti, se necessario. Entrambi i documenti saranno validi per 5 anni.
Per il testo dell'Accordo di Cooperazione in Astrofisica Relativistica: http://www.icranet.org/documents/agreementICRA-USTC.pdf
Per il testo del Memorandum of Understanding: http://www.icranet.org/documents/mouICRA-USTC.pdf
7. Nuovo Protocollo di cooperazione ICRANet - Ulugh Beg Astronomical Institute of Uzbekistan Academy of Sciences (UBAI), 26 Marzo 2021
Il 26 Marzo 2021, è stato firmato un nuovo Protocollo di Cooperazione tra l'ICRANet e l'Ulugh Beg Astronomical Institute of Uzbekistan Academy of Sciences (UBAI). Il documento è stato firmato dal Prof. Shuhrat Ehgamberdiev (Direttore dell'UBAI), dal Prof. Bobomurat Ahmedov (UBAI), dal Prof. Remo Ruffini (Direttore ICRANet) e dal Prof. Jorge A. Rueda (Professore della Faculty ICRANet). Le principali attività congiunte che saranno portate avanti nel quadro del progetto comprendono: la promozione di attività teoriche e pratiche nel campo dell'Astrofisica Relativistica; la collaborazione tra membri della Faculty, ricercatori, Dottorandi e studenti; l'organizzazione di corsi di insegnamento e ricerca, di seminari, conferenze, workshop, e il lavoro congiunto per le pubblicazioni scientifiche. L'accordo sarà valido per 5 anni.
Per il testo dell'accordo:
http://www.icranet.org/index.php?option=com_content&task=view&id=1362
8. 43° COSPAR Scientific Assembly meeting (online), 28 Gennaio - 4 Febbraio 2021
Il 43° COSPAR Scientific Assembly meeting si è tenuto virtualmente dal 28 Gennaio al 4 Febbraio 2021. Il giorno 3 Febbraio, il Prof. Ruffini, Direttore ICRANet, ha presentato una lecture dal titolo "On the energy extraction from a Kerr Black Hole by Blackholic quanta in GRBs and AGNs".
Di seguito l'abstract della lecture: 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 Niels-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. The corresponding analysis for Active Galactic Nuclei (AGN), scaling simply by the Black Hole mass, will be illustrated. 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.
Link YouTube alla lecture del Prof. Ruffini: https://youtu.be/vT-msfF4E7s
Di seguito l'abstract della lecture: 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 Niels-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. The corresponding analysis for Active Galactic Nuclei (AGN), scaling simply by the Black Hole mass, will be illustrated. 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.
Link YouTube alla lecture del Prof. Ruffini: https://youtu.be/vT-msfF4E7s
9. Seminario del Prof. Ruffini per Space Science at Drop tower, ZARM Brema (Germania), 8 Marzo 2021
Il giorno 8 Marzo 2021, il Prof. Ruffini, Direttore ICRANet, è stato invitato dal Prof. Claus Laemmerzahl per tenere un seminario online presso il Centro ZARM a Brema (Germania). Questo seminario è stato inserito nella serie dei "Space Science at the Drop Tower seminars", che si svolgono regolarmente nel mese di Marzo a Brema. Il titolo del seminario tenuto dal Prof. Ruffini è "Discovery of energy extraction from a Kerr Black Hole by discrete "Blackholic" quanta in GRBs and AGNs".
Di seguito l'abstract del seminario: 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 Niels-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. The corresponding analysis for Active Galactic Nuclei (AGN), scaling simply by the Black Hole mass, will be illustrated. 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.
Link YouTube al seminario del Prof. Ruffini: https://youtu.be/ekYHvNbhv_g
Di seguito l'abstract del seminario: 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 Niels-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. The corresponding analysis for Active Galactic Nuclei (AGN), scaling simply by the Black Hole mass, will be illustrated. 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.
Link YouTube al seminario del Prof. Ruffini: https://youtu.be/ekYHvNbhv_g
10. Rencontres de Moriond on Gravitation (poster session), 9-11 Marzo 2021
Il meeting "Rencontres de Moriond on Gravitation" si è svolto virtualmente dal 9 all'11 Marzo, attraverso la presentazione di poster da parte dei partecipanti. Mercoledì 10 Marzo, sono stati presentati sia il poster del Prof. Ruffini, Direttore ICRANet, intitolato "Morphology of the X-ray afterglows and of the jetted GeV emission in long GRBs", sia quello della Prof.ssa Simonetta Filippi, collaboratrice ICRANet, intitolato "Inferences of GRB 190114C for the Crab pulsar and the supernova remnant".
Di seguito l'abstract del poster del Prof. Ruffini: We recall evidence that all short and long gamma-ray bursts (GRBs) have binary progenitors and give new detailed examples. We focus on the binary progenitors of long GRBs, the binary-driven hypernovae (BdHNe), that consist of a carbon-oxygen core (CO core) and a binary neutron star (NS) companion. For binary periods of the order of 5 min, the energetic subclass BdHN I originates when the CO core collapses. They are characterized by: 1) an outstanding energetic supernova (the "SN-rise"); 2) a newborn black hole (BH) originating from the SN hypercritical accretion onto the NS companion. Only in some cases, the newborn BH via the "inner engine"' mechanism, is observed to lead to GeV emission characterized by an isotropic power-law luminosity LGeV = AGeV*t(-α). 3) The new NS (νNS), created at the SN center, accretes matter from the SN ejecta originating the X-ray afterglow with LX = AX*t(-&α;), always present in all BdHN I. We analyze 378 BdHN I and, among them, select four prototypes: GRB 130427A, GRB 160509A, GRB 180720B and GRB 190114C using a time-resolved spectral analysis and derive 1) the spectra, the luminosities and the duration of the SN-rise; 2) the amplitude A_X, the power-law index αX=1.48±0.32 of their X-ray afterglows, 3) the time-evolution of the νNS spin, and 4) AGeV and αGeV=1.19±0.04. From the latter, we infer for the first time the mass and spin of the BH powering long GRBs. We also deduce that there is a special morphology which explains why the GeV emission is present only in some BdHN I, and it is confirmded by dedicated three-dimensional smoothed-particle-hydrodynamics simulations of BdHN I. We conclude that the GeV radiation is observed only when emitted within a cone of half-opening angle of nealry 60 degrees from the normal to the orbital plane. The mass and spin of the Kerr BHs are obtained based upon the GRB "inner engine" originating the GeV emission by extracting the BH rotational energy. We obtain initial BH masses 2.3<M/MSun<8.9 and spins 0.27<a/M<0.87, and from their time evolution, we verify, for the first time, the validity of the BH mass-energy formula.
Di seguito l'abstract del poster della Prof.ssa Filippi: The understanding of binary-driven hypernovae of type I (BdHNe I) has identified the central role of the explosion of the supernova ("SN-rise") as well as of the role of the hypercritical accretion of the SN ejecta onto the binary companion neutron star (NS) and onto the newborn NS (νNS) in determining the GRB dynamics. We model the νNS through the equilibrium sequence of Maclaurin spheroids. By requiring that the νNS period extrapolated on 1000 yr coincides with the one of PSR B0531 + 21 (the Crab pulsar), we determine the initial spin of the νNS to be 0.9 ms, and follow the subsequent rotational and gravitational evolution of the eccentricity. The observed changes in the braking index are proposed to be correlated to pulsar glitches, whose intensities are predicted to be strongly correlated with the pulsar spin. We propose that the progenitor of the Crab nebula and of the Crab pulsar is a GRB very similar to GRB 190114C.
Di seguito l'abstract del poster del Prof. Ruffini: We recall evidence that all short and long gamma-ray bursts (GRBs) have binary progenitors and give new detailed examples. We focus on the binary progenitors of long GRBs, the binary-driven hypernovae (BdHNe), that consist of a carbon-oxygen core (CO core) and a binary neutron star (NS) companion. For binary periods of the order of 5 min, the energetic subclass BdHN I originates when the CO core collapses. They are characterized by: 1) an outstanding energetic supernova (the "SN-rise"); 2) a newborn black hole (BH) originating from the SN hypercritical accretion onto the NS companion. Only in some cases, the newborn BH via the "inner engine"' mechanism, is observed to lead to GeV emission characterized by an isotropic power-law luminosity LGeV = AGeV*t(-α). 3) The new NS (νNS), created at the SN center, accretes matter from the SN ejecta originating the X-ray afterglow with LX = AX*t(-&α;), always present in all BdHN I. We analyze 378 BdHN I and, among them, select four prototypes: GRB 130427A, GRB 160509A, GRB 180720B and GRB 190114C using a time-resolved spectral analysis and derive 1) the spectra, the luminosities and the duration of the SN-rise; 2) the amplitude A_X, the power-law index αX=1.48±0.32 of their X-ray afterglows, 3) the time-evolution of the νNS spin, and 4) AGeV and αGeV=1.19±0.04. From the latter, we infer for the first time the mass and spin of the BH powering long GRBs. We also deduce that there is a special morphology which explains why the GeV emission is present only in some BdHN I, and it is confirmded by dedicated three-dimensional smoothed-particle-hydrodynamics simulations of BdHN I. We conclude that the GeV radiation is observed only when emitted within a cone of half-opening angle of nealry 60 degrees from the normal to the orbital plane. The mass and spin of the Kerr BHs are obtained based upon the GRB "inner engine" originating the GeV emission by extracting the BH rotational energy. We obtain initial BH masses 2.3<M/MSun<8.9 and spins 0.27<a/M<0.87, and from their time evolution, we verify, for the first time, the validity of the BH mass-energy formula.
Di seguito l'abstract del poster della Prof.ssa Filippi: The understanding of binary-driven hypernovae of type I (BdHNe I) has identified the central role of the explosion of the supernova ("SN-rise") as well as of the role of the hypercritical accretion of the SN ejecta onto the binary companion neutron star (NS) and onto the newborn NS (νNS) in determining the GRB dynamics. We model the νNS through the equilibrium sequence of Maclaurin spheroids. By requiring that the νNS period extrapolated on 1000 yr coincides with the one of PSR B0531 + 21 (the Crab pulsar), we determine the initial spin of the νNS to be 0.9 ms, and follow the subsequent rotational and gravitational evolution of the eccentricity. The observed changes in the braking index are proposed to be correlated to pulsar glitches, whose intensities are predicted to be strongly correlated with the pulsar spin. We propose that the progenitor of the Crab nebula and of the Crab pulsar is a GRB very similar to GRB 190114C.
11. New results on the AXP 4U 01242+61 out of collaboration of ICRANet and ITA
Sarah Villanova Borges, una studentessa del Prof. Manuel Malheiro laureata nel 2017 all'ITA, che ha successivamente conseguito un master sotto la supervision della Dr. Claudia Rodrigues all'INPE nel 2018, lo scorso anno ha pubblicato un importante articolo su The Astrophysical Journal circa AXP 4U 01242+61, spiegando tutte le curve di luce (in particolare, lo spettro in raggi X) di questa sorgente, utilizzando un modello di Nana bianca calda e massiva. Questo lavoro, il modello, i calcoli e la scrittura dell'articolo sono stati fatti tutti da Sarah, che ha partecipato nel precedente MG15 meeting presentando un talk sui primi risultati su questo argomento.
Ora Sarah ha vinto una borsa di dottorato presso il Dipartimento di Fisica e Astronomia dell'Università del Wisconsin Milwaukee.
Questi risultati sono presentati sul canale YouTube dell'AAS: https://www.youtube.com/watch?v=JPqG7-ifE_k&t=1s
Link all'articolo su ApJ: https://iopscience.iop.org/article/10.3847/1538-4357/ab8add
Ora Sarah ha vinto una borsa di dottorato presso il Dipartimento di Fisica e Astronomia dell'Università del Wisconsin Milwaukee.
Questi risultati sono presentati sul canale YouTube dell'AAS: https://www.youtube.com/watch?v=JPqG7-ifE_k&t=1s
Link all'articolo su ApJ: https://iopscience.iop.org/article/10.3847/1538-4357/ab8add
12. Pubblicazioni recenti
Behzad Eslam Panah, Can the power Maxwell nonlinear electrodynamics theory remove the singularity of electric field of point-like charges at their locations?, accepted for publication in Europhysics Letters (EPL).
YES! We introduce a variable power Maxwell nonlinear electrodynamics theory which can remove the singularity of electric field of point-like charges at their locations. One of the main problems of Maxwell's electromagnetic field theory is related to the existence of singularity for electric field of point-like charges at their locations. In other words, the electric field of a point-like charge diverges at the charge location which leads to an infinite self-energy. In order to remove this singularity a few nonlinear electrodynamics (NED) theories have been introduced. Born-Infeld (BI) NED theory is one of the most famous of them. However the power Maxwell (PM) NED cannot remove this singularity. In this paper, we show that the PM NED theory can remove this singularity, when the power of PM NED is less than s<1/2.
Link ArXiv: https://arxiv.org/abs/2103.08343
Bing Zhang, Yu Wang and Liang Li, Dissecting the Energy Budget of a Gamma-Ray Burst Fireball, published in ApJL on March 1, 2021, Volume 909, number L3.
The jet composition and radiative efficiency of gamma-ray bursts (GRBs) are poorly constrained from the data. If the jet composition is matter-dominated (i.e., a fireball), the GRB prompt emission spectra would include a dominant thermal component originating from the fireball photosphere and a nonthermal component presumably originating from internal shocks whose radii are greater than the photosphere radius. We propose a method to directly dissect the GRB fireball energy budget into three components and measure their values by combining the prompt emission and early afterglow data. The measured parameters include the initial dimensionless specific enthalpy density (η), bulk Lorentz factors at the photosphere radius (Γph) and before fireball deceleration (Γ0), the amount of mass loading (M), and the GRB radiative efficiency (ηγ). All the parameters can be derived from the data for a GRB with a dominant thermal spectral component, a deceleration bump feature in the early afterglow lightcurve, and a measured redshift. The results only weakly depend on the density n of the interstellar medium when the composition γ parameter (typically unity) is specified.
DOI: https://doi.org/10.3847/2041-8213/abe6ab
Liang Li and Bing Zhang, Testing the High-latitude Curvature Effect of Gamma-Ray Bursts with Fermi Data: Evidence of Bulk Acceleration in Prompt Emission, published in ApJS on March 23, 2021, Volume 253, number 43.
When a gamma-ray burst (GRB) emitter stops emission abruptly, the observer receives rapidly fading emission from high latitudes with respect to the line of sight, known as the "curvature effect". Identifying such emission from GRB prompt-emission lightcurves would constrain the radius of prompt emission from the central engine and the composition of GRB jets. We perform a dedicated search of high-latitude emission (HLE) through spectral and temporal analyses of a sample of single-pulse bursts detected by the Gamma-ray Burst Monitor on board the Fermi satellite. We identify HLE from a subsample of bursts and constrain the emission radius to be RGRB ~ (1015–1016) cm from the central engine. Some bursts have the HLE decay faster than predicted by a constant Lorentz factor jet, suggesting that the emission region is undergoing acceleration during prompt emission. This supports the Poynting-flux-dominated jet composition for these bursts. The conclusion is consistent with previous results drawn from spectral-lag modeling of prompt emission and HLE analysis of X-ray flares. Scrivi un messaggio
DOI: https://doi.org/10.3847/1538-4365/abded1
Liang Li, Felix Ryde, Asaf Pe’er, Hoi-Fung Yu, and Zeynep Acuner, Bayesian Time-Resolved Spectroscopy of Multi-Pulsed GRBs: Variations of Emission Properties amongst Pulses, in press on ApJS 2021.
Gamma-ray bursts (GRBs) are highly variable and exhibit strong spectral evolution. In particular, the emission properties vary from pulse to pulse in multi-pulsed bursts. Here, we present a time-resolved Bayesian spectral analysis of a compilation of GRB pulses observed by the Fermi Gamma-ray Burst Monitor (GBM). The pulses are selected to have at least four time-bins with a high statistical significance, which ensures that the spectral fits are well determined and that spectral correlations can be established. The sample consists of 39 bursts, 117 pulses, and 1228 spectra. We confirm the general trend that pulses become softer over time, with mainly the low-energy power-law index α becoming smaller. A few exceptions from this trend exist with the hardest pulse occurring at late times. The first pulse in a burst is clearly different from the later pulses: 3/4 of them violate the synchrotron line-of-death (Preece 1998), while around half of them significantly prefer photospheric emission. These fractions decrease for subsequent pulses. We also find that in 2/3 of the pulses the spectral parameters (α and peak energy) track the light-curve variations. This is a larger fraction compared to what is found in previous samples. In conclusion, emission compatible with the GRB photosphere is typically found close to the trigger time, while the chance of detecting synchrotron emission is greatest at late times. This allows for coexistence of emission mechanisms at late times.
Link: https://arxiv.org/abs/2012.03038
MAGIC collaboration, MAGIC Observations of the Nearby Short Gamma-Ray Burst GRB 160821B, published on February 16, 2021 on ApJ, Volume 908, number 1.
The coincident detection of GW170817 in gravitational waves and electromagnetic radiation spanning the radio to MeV gamma-ray bands provided the first direct evidence that short gamma-ray bursts (GRBs) can originate from binary neutron star (BNS) mergers. On the other hand, the properties of short GRBs in high-energy gamma-rays are still poorly constrained, with only ∼20 events detected in the GeV band, and none in the TeV band. GRB 160821B is one of the nearest short GRBs known at z = 0.162. Recent analyses of the multiwavelength observational data of its afterglow emission revealed an optical-infrared kilonova component, characteristic of heavy-element nucleosynthesis in a BNS merger. Aiming to better clarify the nature of short GRBs, this burst was automatically followed up with the MAGIC telescopes, starting from 24 s after the burst trigger. Evidence of a gamma-ray signal is found above ∼0.5 TeV at a significance of ∼ 3σ during observations that lasted until 4 hr after the burst. Assuming that the observed excess events correspond to gamma-ray emission from GRB 160821B, in conjunction with data at other wavelengths, we investigate its origin in the framework of GRB afterglow models. The simplest interpretation with one-zone models of synchrotron-self-Compton emission from the external forward shock has difficulty accounting for the putative TeV flux. Alternative scenarios are discussed where the TeV emission can be relatively enhanced. The role of future GeV-TeV observations of short GRBs in advancing our understanding of BNS mergers and related topics is briefly addressed.
DOI: https://doi.org/10.3847/1538-4357/abd249
Alessandro Loppini, Alessandro Barone, Alessio Gizzi, Christian Cherubini, Flavio H. Fenton, and Simonetta Filippi, Thermal effects on cardiac alternans onset and development: A spatiotemporal correlation analysis, accepted for publication in Physical Review E on March 9, 2021.
Alternans of cardiac action potential duration represent critical precursors for the development of life-threatening arrhythmias and sudden cardiac death. The system’s thermal state affects these electrical disorders requiring additional theoretical and experimental effort to improve a patient-specific clinical understanding. In such a scenario, we generalize a recent work from {Loppini et al. 100 :020201 (2019)} by performing an extended spatiotemporal correlation study. We consider high-resolution optical mapping recordings of canine ventricular wedges’ electrical activity at different temperatures and pacing frequencies. We aim to recommend the extracted characteristic length as a potential predictive index of cardiac alternans onset and evolution within a wide range of system states. In particular, we show that a reduction of temperature results in a drop of the characteristic length, confirming the impact of thermal instabilities on cardiac dynamics. Moreover, we theoretically investigate the use of such an index to identify and predict different alternans regimes. Finally, we propose a novel constitutive phenomenological law linking conduction velocity, characteristic length, and temperature in view of future numerical investigations.
Link:
https://journals.aps.org/pre/accepted/db078R10MbeEb01f012d1f947e5adcb79433e8120
YES! We introduce a variable power Maxwell nonlinear electrodynamics theory which can remove the singularity of electric field of point-like charges at their locations. One of the main problems of Maxwell's electromagnetic field theory is related to the existence of singularity for electric field of point-like charges at their locations. In other words, the electric field of a point-like charge diverges at the charge location which leads to an infinite self-energy. In order to remove this singularity a few nonlinear electrodynamics (NED) theories have been introduced. Born-Infeld (BI) NED theory is one of the most famous of them. However the power Maxwell (PM) NED cannot remove this singularity. In this paper, we show that the PM NED theory can remove this singularity, when the power of PM NED is less than s<1/2.
Link ArXiv: https://arxiv.org/abs/2103.08343
Bing Zhang, Yu Wang and Liang Li, Dissecting the Energy Budget of a Gamma-Ray Burst Fireball, published in ApJL on March 1, 2021, Volume 909, number L3.
The jet composition and radiative efficiency of gamma-ray bursts (GRBs) are poorly constrained from the data. If the jet composition is matter-dominated (i.e., a fireball), the GRB prompt emission spectra would include a dominant thermal component originating from the fireball photosphere and a nonthermal component presumably originating from internal shocks whose radii are greater than the photosphere radius. We propose a method to directly dissect the GRB fireball energy budget into three components and measure their values by combining the prompt emission and early afterglow data. The measured parameters include the initial dimensionless specific enthalpy density (η), bulk Lorentz factors at the photosphere radius (Γph) and before fireball deceleration (Γ0), the amount of mass loading (M), and the GRB radiative efficiency (ηγ). All the parameters can be derived from the data for a GRB with a dominant thermal spectral component, a deceleration bump feature in the early afterglow lightcurve, and a measured redshift. The results only weakly depend on the density n of the interstellar medium when the composition γ parameter (typically unity) is specified.
DOI: https://doi.org/10.3847/2041-8213/abe6ab
Liang Li and Bing Zhang, Testing the High-latitude Curvature Effect of Gamma-Ray Bursts with Fermi Data: Evidence of Bulk Acceleration in Prompt Emission, published in ApJS on March 23, 2021, Volume 253, number 43.
When a gamma-ray burst (GRB) emitter stops emission abruptly, the observer receives rapidly fading emission from high latitudes with respect to the line of sight, known as the "curvature effect". Identifying such emission from GRB prompt-emission lightcurves would constrain the radius of prompt emission from the central engine and the composition of GRB jets. We perform a dedicated search of high-latitude emission (HLE) through spectral and temporal analyses of a sample of single-pulse bursts detected by the Gamma-ray Burst Monitor on board the Fermi satellite. We identify HLE from a subsample of bursts and constrain the emission radius to be RGRB ~ (1015–1016) cm from the central engine. Some bursts have the HLE decay faster than predicted by a constant Lorentz factor jet, suggesting that the emission region is undergoing acceleration during prompt emission. This supports the Poynting-flux-dominated jet composition for these bursts. The conclusion is consistent with previous results drawn from spectral-lag modeling of prompt emission and HLE analysis of X-ray flares. Scrivi un messaggio
DOI: https://doi.org/10.3847/1538-4365/abded1
Liang Li, Felix Ryde, Asaf Pe’er, Hoi-Fung Yu, and Zeynep Acuner, Bayesian Time-Resolved Spectroscopy of Multi-Pulsed GRBs: Variations of Emission Properties amongst Pulses, in press on ApJS 2021.
Gamma-ray bursts (GRBs) are highly variable and exhibit strong spectral evolution. In particular, the emission properties vary from pulse to pulse in multi-pulsed bursts. Here, we present a time-resolved Bayesian spectral analysis of a compilation of GRB pulses observed by the Fermi Gamma-ray Burst Monitor (GBM). The pulses are selected to have at least four time-bins with a high statistical significance, which ensures that the spectral fits are well determined and that spectral correlations can be established. The sample consists of 39 bursts, 117 pulses, and 1228 spectra. We confirm the general trend that pulses become softer over time, with mainly the low-energy power-law index α becoming smaller. A few exceptions from this trend exist with the hardest pulse occurring at late times. The first pulse in a burst is clearly different from the later pulses: 3/4 of them violate the synchrotron line-of-death (Preece 1998), while around half of them significantly prefer photospheric emission. These fractions decrease for subsequent pulses. We also find that in 2/3 of the pulses the spectral parameters (α and peak energy) track the light-curve variations. This is a larger fraction compared to what is found in previous samples. In conclusion, emission compatible with the GRB photosphere is typically found close to the trigger time, while the chance of detecting synchrotron emission is greatest at late times. This allows for coexistence of emission mechanisms at late times.
Link: https://arxiv.org/abs/2012.03038
MAGIC collaboration, MAGIC Observations of the Nearby Short Gamma-Ray Burst GRB 160821B, published on February 16, 2021 on ApJ, Volume 908, number 1.
The coincident detection of GW170817 in gravitational waves and electromagnetic radiation spanning the radio to MeV gamma-ray bands provided the first direct evidence that short gamma-ray bursts (GRBs) can originate from binary neutron star (BNS) mergers. On the other hand, the properties of short GRBs in high-energy gamma-rays are still poorly constrained, with only ∼20 events detected in the GeV band, and none in the TeV band. GRB 160821B is one of the nearest short GRBs known at z = 0.162. Recent analyses of the multiwavelength observational data of its afterglow emission revealed an optical-infrared kilonova component, characteristic of heavy-element nucleosynthesis in a BNS merger. Aiming to better clarify the nature of short GRBs, this burst was automatically followed up with the MAGIC telescopes, starting from 24 s after the burst trigger. Evidence of a gamma-ray signal is found above ∼0.5 TeV at a significance of ∼ 3σ during observations that lasted until 4 hr after the burst. Assuming that the observed excess events correspond to gamma-ray emission from GRB 160821B, in conjunction with data at other wavelengths, we investigate its origin in the framework of GRB afterglow models. The simplest interpretation with one-zone models of synchrotron-self-Compton emission from the external forward shock has difficulty accounting for the putative TeV flux. Alternative scenarios are discussed where the TeV emission can be relatively enhanced. The role of future GeV-TeV observations of short GRBs in advancing our understanding of BNS mergers and related topics is briefly addressed.
DOI: https://doi.org/10.3847/1538-4357/abd249
Alessandro Loppini, Alessandro Barone, Alessio Gizzi, Christian Cherubini, Flavio H. Fenton, and Simonetta Filippi, Thermal effects on cardiac alternans onset and development: A spatiotemporal correlation analysis, accepted for publication in Physical Review E on March 9, 2021.
Alternans of cardiac action potential duration represent critical precursors for the development of life-threatening arrhythmias and sudden cardiac death. The system’s thermal state affects these electrical disorders requiring additional theoretical and experimental effort to improve a patient-specific clinical understanding. In such a scenario, we generalize a recent work from {Loppini et al. 100 :020201 (2019)} by performing an extended spatiotemporal correlation study. We consider high-resolution optical mapping recordings of canine ventricular wedges’ electrical activity at different temperatures and pacing frequencies. We aim to recommend the extracted characteristic length as a potential predictive index of cardiac alternans onset and evolution within a wide range of system states. In particular, we show that a reduction of temperature results in a drop of the characteristic length, confirming the impact of thermal instabilities on cardiac dynamics. Moreover, we theoretically investigate the use of such an index to identify and predict different alternans regimes. Finally, we propose a novel constitutive phenomenological law linking conduction velocity, characteristic length, and temperature in view of future numerical investigations.
Link:
https://journals.aps.org/pre/accepted/db078R10MbeEb01f012d1f947e5adcb79433e8120