2020ApJ...902...18K

Query : 2020ApJ...902...18K

2020ApJ...902...18K - Astrophys. J., 902, 18-18 (2020/October-2)

Two complete spectral transitions of Swift J0243.6+6124 observed by Insight-HXMT.

KONG L.D., ZHANG S., CHEN Y.P., ZHANG S.N., JI L., DOROSHENKO V., WANG P.J., TAO L., GE M.Y., LIU C.Z., SONG L.M., LU F.J., QU J.L., LI T.P., XU Y.P., CAO X.L., CHEN Y., BU Q.C., CAI C., CHANG Z., CHEN G., CHEN L., CHEN T.X., CHEN Y.B., CUI W., CUI W.W., DENG J.K., DONG Y.W., DU Y.Y., FU M.X., GAO G.H., GAO H., GAO M., GU Y.D., GUAN J., GUO C.C., HAN D.W., HUANG Y., HUO J., JIA S.M., JIANG L.H., JIANG W.C., JIN J., JIN Y.J., LI B., LI C.K., LI G., LI M.S., LI W., LI X., LI X.B., LI X.F., LI Y.G., LI Z.W., LIANG X.H., LIAO J.Y., LIU B.S., LIU G.Q., LIU H.W., LIU X.J., LIU Y.N., LU B., LU X.F., LUO Q., LUO T., MA X., MENG B., NANG Y., NIE J.Y., OU G., SAI N., SHANG R.C., SONG X.Y., SUN L., TAN Y., TUO Y.L., WANG C., WANG G.F., WANG J., WANG L.J., WANG W.S., WANG Y.S., WEN X.Y., WU B.B., WU B.Y., WU M., XIAO G.C., XIAO S., XIONG S.L., XU H., YANG J.W., YANG S., YANG Y.J., YANG Y.J., YI Q.B., YIN Q.Q., YOU Y., ZHANG A.M., ZHANG C.M., ZHANG F., ZHANG H.M., ZHANG J., ZHANG T., ZHANG W.C., ZHANG W., ZHANG W.Z., ZHANG Y., ZHANG Y.F., ZHANG Y.J., ZHANG Y., ZHANG Z., ZHANG Z., ZHANG Z.L., ZHAO H.S., ZHAO X.F., ZHENG S.J., ZHENG Y.G., ZHOU D.K., ZHOU J.F., ZHU Y.X. and ZHUANG R.L.

Abstract (from CDS):

We performed the broadband (1-100 keV) spectral analysis of the first Galactic Be ultraluminous X-ray pulsar (BeULX) Swift J0243.6+6124 observed by Insight-HXMT during the 2017-2018 outburst. The results show spectral transitions at two typical luminosities, roughly consistently with those reported previously via pure timing analysis. We find that the spectrum evolves and becomes softer and has higher cutoff energies until the luminosity reaches L1 (∼1.5 x 1038 erg s–1). Afterwards the spectrum becomes harder with lower cutoff energies until the luminosity increases to L2 (∼4.4 x 1038 erg s–1), around which the second spectral transition occurs. Beyond L2, the spectrum softens again and has larger cutoff energies. Similar behaviors were observed previously in other high-mass X-ray binary systems (HMXBs), especially for the second transition at higher luminosities, which is believed to have a correlation with the magnetic field of the harbored neutron star. Accordingly, we speculate that Swift J0243.6+6124 owns a neutron star with magnetic field strength >1013 G. The spectral transition at around L1 of Swift J0243.6+6124 is first observed thoroughly for any HMXB outburst characterized by strong evolution of the thermal component: the temperature of the blackbody drops sharply accompanied by a sudden increase of the blackbody radius. These spectral transitions can in principle be understood in a general scenario of balancing the emission patterns between the pencil and the fan beams at the magnetic pole, for which the extreme brightness of Swift J0243.6+6124 may provide an almost unique lab to probe the details.

Abstract Copyright: © 2020. The American Astronomical Society. All rights reserved.

Journal keyword(s): Accretion - Stellar accretion disks - Binary pulsars - Magnetic fields - Neutron stars - X-ray binary stars - X-ray astronomy

Simbad objects: 7

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Number of rows : 7
N Identifier Otype ICRS (J2000)
RA 		ICRS (J2000)
DEC 		Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2026 		#notes
1 SWIFT J0243.6+6124 HXB 02 43 40.4252869512 +61 26 03.757456824   13.71 12.84 12.57   O9.5Ve 208 0
2 NAME Magellanic Clouds GrG 03 00 -71.0           ~ 7988 0
3 V* V779 Cen HXB 11 21 15.0920532528 -60 37 25.630264596   14.4 12.27     O9III/Veq 1159 0
4 SWIFT J1626.5-5156 HXB 16 26 36.5197704024 -51 56 30.600051936       16.03 14.59 B0V 94 0
5 V* HZ Her LXB 16 57 49.8110126616 +35 20 32.486555472 11.90 14.89 13.63 13.88   B3/6ep 2172 0
6 KS 1947+300 HXB 19 49 35.4841147968 +30 12 31.775979852   15.16 14.22 13.53 12.88 B0Ve 194 0
7 V* V2246 Cyg HXB 20 32 15.2749858128 +37 38 14.843024844   22.16 19.41 17.32 15.18 B0Ve 480 0

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