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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Evidence for a Multipolar Magnetic Field in SGR J1745-2900 from X-Ray Light-curve Analysis

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de Lima, Rafael C. R. [1, 2] ; Coelho, Jaziel G. [2, 3, 4] ; Pereira, Jonas P. [5, 6, 7] ; Rodrigues, V, Claudia ; Rueda, Jorge A. [8, 2, 9, 10, 11]
Total Authors: 5
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[1] Univ Estado Santa Catarina, Av Madre Benvenuta 2007, BR-88035901 Florianopolis, SC - Brazil
[2] ICRANet, Piazza Repubbl 10, I-65122 Pescara - Italy
[3] Univ Tecnol Fed Parana, Dept Fis, BR-85884000 Medianeira, Parana - Brazil
[4] V, Inst Nacl Pesquisas Espaciais, Div Astrofis, Ave Astronautas 1758, BR-12227010 Sao Jose Dos Campos, SP - Brazil
[5] Univ Fed ABC, Ctr Ciencias Nat & Humanas, Ave Estados, 5001 Bangu, BR-09210170 Santo Andre, SP - Brazil
[6] Univ Southampton, Math Sci & STAG Res Ctr, Southampton SO17 1BJ, Hants - England
[7] Polish Acad Sci, Nicolaus Copernicus Astron Ctr, Bartycka 18, PL-00716 Warsaw - Poland
[8] INAF, Ist Astrofis & Planetol Spaziali, Via Fosso Cavaliere 100, I-00133 Rome - Italy
[9] ICRANet Rio, Ctr Brasileiro Pesquisas Fis, Rua Dr Xavier Sigaud 150, BR-22290180 Rio De Janeiro - Brazil
[10] Univ Ferrara, Dipartimento Fis & Sci Terra, ICRANet Ferrara, Via Saragat 1, I-44122 Ferrara - Italy
[11] Univ Ferrara, Dipartimento Fis & Sci Terra, Via Saragat 1, I-44122 Ferrara - Italy
Total Affiliations: 11
Document type: Journal article
Source: ASTROPHYSICAL JOURNAL; v. 889, n. 2 FEB 1 2020.
Web of Science Citations: 0

SGR J1745-2900 was detected from its outburst activity in 2013 April and it was the first soft gamma repeater (SGR) detected near the center of the Galaxy (Sagittarius A{*}). We use 3.5 yr 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 semiapertures ranging from 16 degrees to 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 Neutron Star Interior Composition Explorer's (NICER) 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 yr evolution of SGR J1745-290 hot spots. (AU)

FAPESP's process: 17/21384-2 - Asteroseismology of quasi-periodic oscillations and constraints to hybrid neutron star models
Grantee:Jonas Pedro Pereira
Support type: Scholarships abroad - Research Internship - Post-doctor
FAPESP's process: 15/04174-9 - Some consequences of the microphysics of volumes and surfaces in compact systems
Grantee:Jonas Pedro Pereira
Support type: Scholarships in Brazil - Post-Doctorate
FAPESP's process: 13/26258-4 - Superdense matter in the universe
Grantee:Manuel Máximo Bastos Malheiro de Oliveira
Support type: Research Projects - Thematic Grants