@Article{LimaCoePerRodRue:2020:EvMuMa,
author = "Lima, Rafael Camargo Rodrigues de and Coelho, Jaziel Goulart and
Pereira, Jonas Pedro and Rodrigues, Cl{\'a}udia Vilega and Rueda,
Jorge A.",
affiliation = "{Universidade do Estado de Santa Catarina (UDESC)} and ICRANet and
{Universidade Federal do ABC (UFABC)} and {Instituto Nacional de
Pesquisas Espaciais (INPE)} and ICRANet",
title = "Evidence for a multipolar magnetic field in SGR J1745-2900 from
X-ray light-curve analysis",
journal = "Astrophysical Journal",
year = "2020",
volume = "889",
number = "2",
pages = "e165",
month = "fev.",
keywords = "dense matter – pulsars: general – stars: neutron – starspots –
X-rays: individual.",
abstract = "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° to 67°. 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 Explorers (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.",
doi = "10.3847/1538-4357/ab65f4",
url = "http://dx.doi.org/10.3847/1538-4357/ab65f4",
issn = "0004-637X and 1538-4357",
language = "en",
targetfile = "lima_evidence.pdf",
urlaccessdate = "27 abr. 2024"
}