A deep Chandra survey of the globular cluster 47 tucanae:: Catalog of point sources

被引:188
作者
Heinke, CO
Grindlay, JE
Edmonds, PD
Cohn, HN
Lugger, PM
Camilo, F
Bogdanov, S
Freire, PC
机构
[1] Harvard Smithsonian Ctr Astrophys, Cambridge, MA 02138 USA
[2] Northwestern Univ, Dept Phys & Astron, Evanston, IL 60208 USA
[3] Indiana Univ, Dept Astron, Bloomington, IN 47405 USA
[4] Columbia Univ, Astrophys Lab, New York, NY 10027 USA
[5] Arecibo Observ, Natl Astron & Ionosphere Ctr, Arecibo, PR 00612 USA
关键词
globular clusters : individual (NGC 104); novae; cataclysmic variables; pulsars : general; stars : neutron; X-rays : binaries;
D O I
10.1086/429899
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We have detected 300 X-ray sources within the half-mass radius (2.'79) of the globular cluster 47 Tucanae in a deep (281 ks) Chandra exposure. We perform photometry and simple spectral fitting for our detected sources and construct luminosity functions, X-ray color-magnitude, and color-color diagrams. Eighty-seven X-ray sources show variability on timescales from hours to years. Thirty-one of the new X-ray sources are identified with chromospherically active binaries from the catalogs of Albrow and coworkers. The radial distributions of detected sources imply that roughly 70 are background sources of some kind. The radial distribution of the known millisecond pulsar ( MSP) systems is consistent with that expected from mass segregation, if the average neutron star mass is 1: 39 +/- 0: 19 M-circle dot. Most source spectra are well fitted by thermal plasma models, except for quiescent low-mass X-ray binaries (qLMXBs; containing accreting neutron stars) and MSPs. We identify three new candidate qLMXBs with relatively low X-ray luminosities. One of the brightest cataclysmic variables (CVs; X10) shows evidence (a 4.7 hr period pulsation and strong soft X-ray emission) for a magnetically dominated accretion flow as in AM Her systems. Most of the bright CVs require intrinsic N-H columns of order 10(21) cm(-2), suggesting a possible DQ Her nature. A group of X-ray sources associated with bright ( sub) giant stars also requires intrinsic absorption. By comparing the X-ray colors, luminosities, variability, and quality of spectral fits of the detected MSPs to those of unidentified sources, we estimate that a total of similar to 25 MSPs exist in 47 Tuc (< 60 at 95% confidence), regardless of their radio beaming fraction. We estimate that the total number of neutron stars in 47 Tuc is of order 300, reducing the discrepancy between theoretical neutron star retention rates and observed neutron star populations in globular clusters. Comprehensive tables of source properties and simple spectral fits are provided electronically.
引用
收藏
页码:796 / 824
页数:29
相关论文
共 127 条
  • [1] The frequency of binary stars in the core of 47 Tucanae
    Albrow, MD
    Gilliland, RL
    Brown, TM
    Edmonds, PD
    Guhathakurta, P
    Sarajedini, A
    [J]. ASTROPHYSICAL JOURNAL, 2001, 559 (02) : 1060 - 1081
  • [2] Anderson A. J., 1997, PhD thesis
  • [3] Arnaud KA, 1996, ASTR SOC P, V101, P17
  • [4] The velocity distribution of isolated radio pulsars
    Arzoumanian, Z
    Chernoff, DF
    Cordes, JM
    [J]. ASTROPHYSICAL JOURNAL, 2002, 568 (01) : 289 - 301
  • [5] AURIERE M, 1989, ASTRON ASTROPHYS, V214, P113
  • [6] The neutron star helium white dwarf population in the Galactic disk
    Backer, DC
    [J]. ASTROPHYSICAL JOURNAL, 1998, 493 (02) : 873 - 878
  • [7] ON THE LUMINOSITY FUNCTION, LIFETIMES, AND ORIGIN OF BLUE STRAGGLERS IN GLOBULAR-CLUSTERS
    BAILYN, CD
    PINSONNEAULT, MH
    [J]. ASTROPHYSICAL JOURNAL, 1995, 439 (02) : 705 - 714
  • [8] DOES TIDAL CAPTURE PRODUCE CATACLYSMIC VARIABLES
    BAILYN, CD
    GRINDLAY, JE
    GARCIA, MR
    [J]. ASTROPHYSICAL JOURNAL, 1990, 357 (02) : L35 - L37
  • [9] X-ray sources and their optical counterparts in the globular cluster M4
    Bassa, C
    Pooley, D
    Homer, L
    Verbunt, F
    Gaensler, BM
    Lewin, WHG
    Anderson, SF
    Margon, B
    Kaspi, VM
    van der Klis, M
    [J]. ASTROPHYSICAL JOURNAL, 2004, 609 (02) : 755 - 765
  • [10] Gravitational bending of light near compact objects
    Beloborodov, AM
    [J]. ASTROPHYSICAL JOURNAL, 2002, 566 (02) : L85 - L88