Study of the progenitor of the magnetar 1E 2259+586 through Suzaku observations of the associated supernova remnant CTB 109

40-1 Publ. Astron. Soc. Japan (2017) 69 (3), 40 (1–10) doi: 10.1093/pasj/psx012 Advance Access Publication Date: 2017 April 12 Study of the progenitor of the magnetar 1E 2259+586 through Suzaku observations of the associated supernova remnant CTB 109 1 High Energy Astrophysics Laboratory, Nishina Center, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan 2 Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan 3 The Hakubi Center for Advanced Research, Kyoto University, Kitashirakawa-oiwake-cho, Sakyo-ku, Kyoto, Kyoto 606-8302, Japan 4 Research Center for the Early Universe, The University of Tokyo,7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033, Japan 5 MAXI Team, The Institute of Physics and Chemical Research, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan ∗ E-mail: Received 2016 September 26; Accepted 2017 February 6 Abstract We present a study of the progenitor of the magnetar 1E 2259+586, from Suzaku observations of the associated supernova remnant CTB 109. The Suzaku spectra, either spatially integrated or spatially resolved, were successfully described by a two-component plasma model, which reconfirms a previous Chandra result on the northwestern part of this remnant (Sasaki et al. 2013, A&A, 552, A45). The hotter component, with a temperature of ∼0.7 keV, can be identified as the stellar ejecta heated by reverse shock, because its contribution increases towards the remnant center. The cooler one, with a temperature of ∼0.25 keV, can be identified as the shocked interstellar matter. The abundances of Ne, Mg, Si, and S of the hotter component support these identifications. The total masses of the cooler and hotter components are estimated to be 220 ± 40 M and 42 ± 11 M , respectively. The remnant is considered to be adiabatically expanding as in the Sedov– Taylor phase. The explosion energy, estimated to be 1.0 × 1051 erg by a canonical Sedov model, is typical of a core-collapse supernova explosion. Assuming that the hotter component includes the ejecta as well as the matter lost by the progenitor star via stellar winds, 1E 2259+586 is inferred to have originated from a very massive star. Key words: ISM: supernova remnants — stars: magnetars — stars: magnetic fields — stars: neutron — X-rays: individual (CTB 109, 1E 2259+586) 1 Introduction Soft gamma repeaters (SGRs) and anomalous X-ray pulsars (AXPs), with rather long pulse periods of P = 2–11 s and very large period derivatives of Ṗ = 10−11 –10−14 s s−1 , are widely believed to be magnetars, which are young neutron stars (NSs) powered by their strong magnetic fields  C The Author 2017. Published by Oxford University Press on behalf of the Astronomical Society of Japan. All rights reserved. For Permissions, please email: Toshio NAKANO,1,∗ Hiroaki MURAKAMI,2 Yoshihiro FURUTA,2 Teruaki ENOTO,3 Miyu MASUYAMA,4 Toshikazu SHIGEYAMA,4 and Kazuo MAKISHIMA5 Publications of the Astronomical Society of Japan (2017), Vol. 69, No. 3 which make the nominally calculated characteristic ages of magnetars larger than their actual ages. The result reinforced the magnetar hypothesis, and also secured the physical association between CTB 109 and 1E 2259+586. In the present research, following Paper I, we perform further analysis of the Suzaku data of CTB 109 in order to gain insight into the progenitor of 1E 2259+586 and investigate the origin of magnetars. 2 Observations and data reduction As already described in table 1 of Paper I, the Suzaku observations of 1E 2259+586 and CTB 109 were performed in 2009 and 2011. Figure 1 shows a mosaic image obtained in these observations, where four squares indicate four pointings with the X-ray Imaging Spectrometer (XIS) in full-frame mode performed in 2011. The three cameras (XIS 0, 1, 3) of XIS were operated in 1/4 window mode (Koyama et al. 2007) in 2009 to study the central magnetar 1E 2259+586 (Enoto et al. 2010). The dotted crisscrossed region indicates the field of view (FOV) of the observation. The log of these observations is reproduced in table 1. In Paper I, only the data from the two eastern parts (506039010 and 506040010) were analyzed to obtain the age estimate of the remnant, because the western parts are disturbed by giant molecular clouds (GMCs) and not suitable for that purpose. In the present research, we analyze all the Suzaku data. Data reduction was performed with the HEADAS software version 6.16 and calibration data CALDB released in 2014 July. For the spectral analysis, XSPEC version 12.8.2 was employed, and ancillary response files (ARFs) and response files (RMFs) are produced by xisrmfgen and xsisimarfgen (Ishisaki et al. 2006), respectively. 3 Analysis and results 3.1 Background spectra We first extracted four spectra, one from each of the four pointings shown in figure 1. Figure 2 gives an example Table 1. Log of Suzaku observations of CTB 109 reprinted. α (J2000.0) δ (J2000.0) Start time 404076010 23h 01m 04.s 08 58◦ 58 15. 6 506037010 23h 01m 06.s 96 59◦ 00 50. 4 506038010 23h 00m 26.s 88 506039010 Observation ID Mode Exposure (ks) 2009-05-25 20:00:17 1/4 122.6 2011-12-13 06:48:41 Full 40.8 58◦ 44 13. 2 2011-12-14 04:47:02 Full 41.4 23h 03m 06.s 96 58◦ 58 51. 6 2011-12-15 01:57:25 Full 30.4 506040010 23h 03m 06.s 96 58◦ 40 51. 6 2011-12-15 18:03:52 Full 30.5 501100010 (Background) 23h 11m 44.s 86 61◦ 57 13. 7 2006-06-06 15:35:57 Full 72.2 that reach B = 1014−15 G (Duncan & Thompson 1992). The number of discovered magnetars is rapidly increasing (Olausen & Kaspi 2014), and the concept of “magnetar” has been reinforced by their observational properties, such as young characteristic ages, burst activities (e.g., Palmer et al. 2005), spectral features (Tiengo et al. 2013), and phase modulations in X-ray pulse (Makishima et al. 2014, 2016). However, the origin of magnetars still remains a mystery in the context of core-collapse supernovae (CC-SNe) and their products. The Galactic supernova remnant (SNR) CTB 109 is well known as a cradle of the magnetar 1E 2259+586, and is expected to yield information on the supernova (SN) explosion that left the central magnetar. The 1E 2259+586/CTB 109 system was discovered by the Einstein satellite in 1980 (Gregory & Fahlman 1980) as a diffuse X-ray source with a peculiar half moon shape and a central point source. The source, which was named as 1E 2259+586 later showed X-ray pulsations with P = 6.98 s (Fahlman & Gregory 1983). The dipole magnetic field of 1E 2259+586, B = 5.9 × 1013 G, estimated from the P value and its derivative, Ṗ = 4.84 × 10−13 s s−1 (Dib & Kaspi 2014), exceeds the quantum critical field Bqed ≡ 4.4 × 1013 G, and places this object in the magnetar category. In addition, 1E 2559+586 shows sporadic activities presumably due to its strong magnetic field, and spin irregularities, such as spin-up glitches in 2002 (Kaspi et al. 2002) and in 2007 and 2009 (İçdem et al. 2012), and an anti-glitch (...truncated)