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|Title:||The X-ray outburst of the Galactic Centre magnetar SGR J1745-2900 during the first 1.5 year||Authors:||Coti Zelati, F.
Pons, J. A.
Baganoff, F. K.
ISRAEL, Gian Luca
Torres, D. F.
|Issue Date:||2015||Journal:||MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY||Number:||449||Issue:||3||First Page:||2685||Abstract:||In 2013 April a new magnetar, SGR 1745-2900, was discovered as it entered an outburst, at only 2.4 arcsec angular distance from the supermassive black hole at the centre of the Milky Way, Sagittarius A*. SGR 1745-2900 has a surface dipolar magnetic field of ̃2 × 10<SUP>14</SUP> G, and it is the neutron star closest to a black hole ever observed. The new source was detected both in the radio and X-ray bands, with a peak X-ray luminosity L<SUB>X</SUB> ̃ 5 × 10<SUP>35</SUP> erg s<SUP>-1</SUP>. Here we report on the long-term Chandra (25 observations) and XMM-Newton (eight observations) X-ray monitoring campaign of SGR 1745-2900 from the onset of the outburst in 2013 April until 2014 September. This unprecedented data set allows us to refine the timing properties of the source, as well as to study the outburst spectral evolution as a function of time and rotational phase. Our timing analysis confirms the increase in the spin period derivative by a factor of ̃2 around 2013 June, and reveals that a further increase occurred between 2013 October 30 and 2014 February 21. We find that the period derivative changed from 6.6 × 10<SUP>-12</SUP> to 3.3 × 10<SUP>-11</SUP> s s<SUP>-1</SUP> in 1.5 yr. On the other hand, this magnetar shows a slow flux decay compared to other magnetars and a rather inefficient surface cooling. In particular, starquake-induced crustal cooling models alone have difficulty in explaining the high luminosity of the source for the first ̃200 d of its outburst, and additional heating of the star surface from currents flowing in a twisted magnetic bundle is probably playing an important role in the outburst evolution.||Acknowledgments:||FCZ and NR are supported by an NWO Vidi Grant (PI: Rea) and by the European COST Action MP1304 (NewCOMPSTAR). NR, AP, DV, and DFT acknowledge support by grants AYA2012-39303 and SGR2014-1073. AP is supported by a Juan de la Cierva fellowship. JAP acknowledges support by grant AYA 2013-42184-P. PE acknowledges a Fulbright Research Scholar grant administered by the US–Italy Fulbright Commission and is grateful to the Harvard–Smithsonian Center for Astrophysics for hosting him during his Fulbright exchange. DH acknowledges support from Chandra X-ray Observatory ( CXO ) Award Number GO3-14121X, operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060, and also by NASA Swift grant NNX14AC30G. GP acknowledges support via an EU Marie Curie Intra-European fellowship under contract no. FP-PEOPLE-2012-IEF- 331095 and the Bundesministerium für Wirtschaft und Technologie/Deutsches Zentrum für Luft-und Raumfahrt (BMWI/DLR, FKZ 50 OR 1408) and the Max Planck Society. RP acknowledges partial support by Chandra grants (awarded by SAO) G03-13068A and G04-15068X. RPM acknowledges funding from the European Commission Seventh Framework Programme (FP7/2007-2013) under grant agreement no. 267251. FCZ acknowledges CSIC-IEEC for very kind hospitality during part of the work and Geoffrey Bower for helpful discussions. The scientific results reported in this paper are based on observations obtained with the Chandra X-ray Observatory and XMM–Newton , an ESA science mission with instruments and contributions directly funded by ESA Member States and NASA. This research has made use of software provided by the Chandra X-ray Center ( CXC ) in the application package ciao , and of softwares and tools provided by the High Energy Astrophysics Science Archive Research Center (HEASARC), which is a service of the Astrophysics Science Division at NASA/GSFC and the High Energy Astrophysics Division of the Smithsonian Astrophysical Observatory.||URI:||http://hdl.handle.net/20.500.12386/23730||URL:||https://academic.oup.com/mnras/article/449/3/2685/1135550||ISSN:||0035-8711||DOI:||10.1093/mnras/stv480||Bibcode ADS:||2015MNRAS.449.2685C||Fulltext:||open|
|Appears in Collections:||1.01 Articoli in rivista|
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