New evidence of proton-cyclotron resonance in a magnetar strength field from SGR 1806-20

被引:80
作者
Ibrahim, AI
Swank, JH
Parke, W
机构
[1] NASA, Goddard Space Flight Ctr, High Energy Astrophys Lab, Greenbelt, MD 20771 USA
[2] George Washington Univ, Dept Phys, Washington, DC 20006 USA
基金
美国国家航空航天局;
关键词
stars : individual (SGR 1806-20); stars : magnetic fields; stars : neutron; X-rays : bursts;
D O I
10.1086/345774
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
A great deal of evidence has recently been gathered in favor of the picture that soft gamma repeaters and anomalous X-ray pulsars are powered by ultrastrong magnetic fields (B > 10(14) G; i.e., magnetars). Nevertheless, present determination of the magnetic field in such magnetar candidates has been indirect and model-dependent. A key prediction concerning magnetars is the detection of ion-cyclotron resonance features, which would offer a decisive diagnostic of the field strength. Here we present the detection of a 5 keV absorption feature in a variety of bursts from the soft gamma repeater SGR 1806-20, confirming our initial discovery (Ibrahim et al.) and establishing the presence of the feature in the source's burst spectra. The line feature is well explained as proton-cyclotron resonance in an ultrastrong magnetic field, offering a direct measurement of SGR 1806-20's magnetic field (B approximate to 10(15) G) and clear evidence of a magnetar. Together with the source's spin-down rate, the feature also provides the first measurement of the gravitational redshift, mass, and radius of a magnetar.
引用
收藏
页码:L17 / L21
页数:5
相关论文
共 30 条
[1]  
BEZCHASTNOV VG, 1996, AIP C P, V384, P907
[2]   Spectral effects of the vacuum resonance in soft gamma-ray repeaters [J].
Bulik, T ;
Miller, MC .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1997, 288 (03) :596-608
[3]  
CASH W, 1979, ASTROPHYS J, V228, P939, DOI 10.1086/156922
[4]  
DUNCAN R, 1999, AIP C P, V526, P380
[5]   FORMATION OF VERY STRONGLY MAGNETIZED NEUTRON-STARS - IMPLICATIONS FOR GAMMA-RAY BURSTS [J].
DUNCAN, RC ;
THOMPSON, C .
ASTROPHYSICAL JOURNAL, 1992, 392 (01) :L9-L13
[6]  
FOX DW, 2001, ASTROPH0107520
[7]   Anomalous X-ray pulsars and soft gamma-ray repeaters in supernova remnants [J].
Gaensler, BM ;
Slane, PO ;
Gotthelf, EV ;
Vasisht, G .
ASTROPHYSICAL JOURNAL, 2001, 559 (02) :963-972
[8]   Atmospheres and spectra of strongly magnetized neutron stars [J].
Ho, WCG ;
Lai, D .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 2001, 327 (04) :1081-1096
[9]   An optical counterpart to the anomalous X-ray pulsar 4U0142+61 [J].
Hulleman, F ;
van Kerkwijk, MH ;
Kulkarni, SR .
NATURE, 2000, 408 (6813) :689-692
[10]   An unusual burst from soft gamma repeater SGR 1900+14: Comparisons with giant flares and implications for the magnetar model [J].
Ibrahim, AI ;
Strohmayer, TE ;
Woods, PM ;
Kouveliotou, C ;
Thompson, C ;
Duncan, RC ;
Dieters, S ;
Swank, JH ;
van Paradijs, J ;
Finger, M .
ASTROPHYSICAL JOURNAL, 2001, 558 (01) :237-252