Recent X-ray measurements of the accretion-powered pulsar 4U 1907+09

被引:59
作者
in't Zand, JJM
Baykal, A
Strohmayer, TE
机构
[1] Space Res Org Netherlands, NL-3584 CA Utrecht, Netherlands
[2] Middle E Tech Univ, Dept Phys, TR-06531 Ankara, Turkey
[3] NASA, Goddard Space Flight Ctr, Lab High Energy Astron, Greenbelt, MD 20771 USA
关键词
accretion; accretion disks; binaries; general; pulsars; individual; (4U; 1907+09); stars; neutron; X-rays;
D O I
10.1086/305362
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
X-ray observations of the accreting X-ray pulsar 4U 1907 + 09 obtained during 1996 February with the Proportional Counter Array onboard the Rossi X-Ray Timing Explorer (RXTE) have made possible the first measurement of the intrinsic pulse period (P-pulse) since 1984: P-pulse = 440.341(-0.017)(+0.012) s. 4U pulse 1907 + 09 is in a binary system with a blue supergiant. The orbital parameters have been solved, which enables us to correct a measurement of P-pulse obtained in 1990 with Ginga for orbital delay effects. Thus, three spin-down rates can be extracted from four pulse periods obtained in 1983, 1984, 1990, and 1996. These are equal to within 8% to a value of (P) over dot(pulse) = +0.225 s yr(-1). This suggests that the pulsar has perhaps been in a monotonous spin-down mode since its discovery in 1983. Furthermore, the RXTE observations showed transient similar to 18 s oscillations during a flare that lasted about 1 hr. These oscillations could be interpreted as Keplerian motion of an accretion disk near the magnetospheric radius. This, and the notion that the corotation radius is much larger than any conceivable value for the magnetospheric radius (because of the long spin period), renders it unlikely that this pulsar spins near equilibrium, as is suspected for other slowing accreting X-ray pulsars. We suggest as an alternative that the frequent occurrence of a retrograde transient accretion disk may be consistently slowing the pulsar down. Further observations of flares could provide more evidence of this.
引用
收藏
页码:386 / 394
页数:9
相关论文
共 43 条
[1]   IS GX5-1 A MILLISECOND PULSAR [J].
ALPAR, MA ;
SHAHAM, J .
NATURE, 1985, 316 (6025) :239-241
[2]   THE DISCOVERY OF 0.2 HZ QUASI-PERIODIC OSCILLATIONS IN THE X-RAY FLUX OF THE TRANSIENT 42-SECOND PULSAR EXO 2030+375 [J].
ANGELINI, L ;
STELLA, L ;
PARMAR, AN .
ASTROPHYSICAL JOURNAL, 1989, 346 (02) :906-911
[3]  
ANGELINI L, 1989, 23RD P ESLAB S 2 TOP, V1, P81
[4]  
ANZER U, 1980, ASTRON ASTROPHYS, V83, P133
[5]   Observations of accreting pulsars [J].
Bildsten, L ;
Chakrabarty, D ;
Chiu, J ;
Finger, MH ;
Koh, DT ;
Nelson, RW ;
Prince, TA ;
Rubin, BC ;
Scott, DM ;
Stollberg, M ;
Vaughan, BA ;
Wilson, CA ;
Wilson, RB .
ASTROPHYSICAL JOURNAL SUPPLEMENT SERIES, 1997, 113 (02) :367-408
[6]   VELA X-1 PULSE TIMING .1. DETERMINATION OF THE NEUTRON-STAR ORBIT [J].
BOYNTON, PE ;
DEETER, JE ;
LAMB, FK ;
ZYLSTRA, G .
ASTROPHYSICAL JOURNAL, 1986, 307 (02) :545-563
[7]   GEOMETRY AND PULSE PROFILES OF X-RAY PULSARS - ASYMMETRIC RELATIVISTIC FITS TO 4U-1538-52 AND VELA-X-1 [J].
BULIK, T ;
RIFFERT, H ;
MESZAROS, P ;
MAKISHIMA, K ;
MIHARA, T ;
THOMAS, B .
ASTROPHYSICAL JOURNAL, 1995, 444 (01) :405-414
[8]   On the correlation of torque and luminosity in GX 1+4 [J].
Chakrabarty, D ;
Bildsten, L ;
Finger, MH ;
Grunsfeld, JM ;
Koh, DT ;
Nelson, RW ;
Prince, TA ;
Vaughan, BA ;
Wilson, RB .
ASTROPHYSICAL JOURNAL, 1997, 481 (02) :L101-L105
[9]  
CHICHKOV MA, 1995, PISMA ASTRON ZH, V21, P491
[10]   THE X-RAY-PROPERTIES OF 3A1907+09 [J].
COOK, MC ;
PAGE, CG .
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 1987, 225 (02) :381-392