本篇論文將描述兩個低核密度球狀星團：NGC6144、以及E3的X光與可見光觀測及分析，並藉此討論其中X光源數量與球狀星團內，恆星經由遭遇生成雙星系統、以及原生雙星系統的關係。我們使用錢卓拉X光望遠鏡的觀測資料，經由CIAO軟體分析；以及使用哈伯太空望遠鏡尋找其可見光之對應物，並經由DOLPHOT軟體分析。在NGC614以及E3各自的半質量半徑內，我們分別偵測到NGC6144有六個X光源；而E3有三個X光源。然而在我們的觀測中，NGC6144估計將有4-5個X光源來自背景；E3則會有2個X光源來自背景，從統計上的結果，我們無法排除所有偵測到的光源皆不是來自背景。因為觀測時間與儀器敏感度，我們只會偵測到光度(在光子能量介於0.3-10千電子伏範圍內) 大於每秒 1.7×10^30 爾格的光源。經由分析，我們確定在NGC6144中有1-2組激變變星(CVs)及一組活躍雙星(ABs)；在E3中則有一組疑似激變變星。這些結果為原生雙星的重要證據。

We report on the Chandra X-ray Observatory and Hubble Space Telescope observation of two low core density globular clusters, NGC6144 and E3. Within the half-mass radius and at a detection limit of L_X = 1.7 × 10^30 ergs/s , we found 6 X-ray sources in NGC6144, of which 4-5 are expected to be background sources; and 3 X-ray sources within the half-mass radius of E3, of which 2 are expected to be background sources. Therefore, we cannot exclude that all our sources are background sources. However, combining the results from X-ray and optical observations, we found that 1-2 sources in NGC6144 and 1 source in E3 are likely to be cataclysmic variables and that 1 source in NGC6144 is an active binary, based on the X-ray and optical properties. The number of faint X-ray sources in NGC6144 and E3 found with Chandra and HST is higher than a prediction based on collision frequency, but is closer to that based on mass. Our observations strongly suggest that the compact binary systems in NGC6144 and E3 are primordial in origin.

[1]Alcaino, G., 1980, The globular cluster NGC 6144 and its neighbouring region, Astronomy and Astrophysics Supplement Series, vol. 39, Mar. 1980, p. 315-323.

[2]Andersen, J.; Clausen, J. V.; Nordstrom, B.; Tomkin, J.; Mayor, M., 1991, Absolute dimensions of eclipsing binaries., XVII - TZ Fornacis: Stellar and tidal evolution in a binary with a fully-fledged red giant. Astronomy and Astrophysics (ISSN 0004-6361), vol. 246, no. 1, June 1991, p. 99-117.

[3]Anderson, J. & King, I. 2006, ACS/ISR 2006-01

[4]Bassa, Cees; Pooley, David; Homer, Lee; Verbunt, Frank; Gaensler, Bryan M.; Lewin, Walter H. G.; Anderson, Scott F.; Margon, Bruce; Kaspi, Victoria M.; van der Klis, Michiel, 2004, X-Ray Sources and Their Optical Counterparts in the Globular Cluster M4., The Astrophysical Journal, Volume 609, Issue 2, pp. 755-765.

[5]Bassa, Cees., 2006, Optical Studies of Compact Binaries in Globular Cluster and the Galactic Disk., PhD thesis.

[6]Bassa, C. G.; Pooley, D.; Verbunt, F.; Homer, L.; Anderson, S. F.; Lewin, W. H. G., 2008, X-ray and optical observations of M55 and NGC 6366: evidence for primordial binaries., Astronomy and Astrophysics, Volume 488, Issue 3, 2008, pp.921-933.

[7]Bailyn, Charles D.; Grindlay, Jonathan E.; Garcia, Michael R., 1990, Does tidal capture produce cataclysmic variables?, Astrophysical Journal, Part 2 - Letters (ISSN 0004-637X), vol. 357, July 10, 1990, p. L35-L37.

[8]Bedin, Luigi R.; Cassisi, Santi; Castelli, Fiorella; Piotto, Giampaolo; Anderson, Jay; Salaris, Maurizio; Momany, Yazan; Pietrinferni, Adriano., 2005, Transforming observational data and theoretical isochrones into the ACS/WFC Vega-mag system. Monthly Notices of the Royal Astronomical Society, Volume 357, Issue 3, pp. 1038-1048.

[9]Bildsten, Lars; Rutledge, Robert E., 2000, Coronal X-Ray Emission from the Stellar Companions to Transiently Accreting Black Holes., The Astrophysical Journal, Volume 541, Issue 2, pp. 908-917.

[10]Bogdanov, Slavko; Grindlay, Jonathan E.; Heinke, Craig O.; Camilo, Fernando; Freire, Paulo C. C.; Becker, Werner., 2006, Chandra X-Ray Observations of 19 Millisecond Pulsars in the Globular Cluster 47 Tucanae., The Astrophysical Journal, Volume 646, Issue 2, pp. 1104-1115.
Clark, G. W., 1975, X-ray binaries in globular clusters., Astrophysical Journal, vol. 199, Aug. 1, 1975, pt. 2, p. L143-L145.

[11]Clark, G. W.; Markert, T. H.; Li, F. K., 1975, Observations of variable X-ray sources in globular clusters., Astrophysical Journal, vol. 199, July 15, 1975, pt. 2, p. L93-L96

[12]Cool, Adrienne M.; Grindlay, Johnathan E.; Cohn, Haldan N.; Lugger, Phyllis M.; Slavin, Shawn D., 1995, Discovery of candidate cataclysmic variables in the post-core-collapse globular cluster NGC 6397, The Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 439, no. 2, p. 695-704.

[13]Cool, A. M., Haggard, D., & Carlin, J. 2002, in Omega Centauri, A Unique Window into Astrophysics, eds. F. van Leeuwen, J. Hughes, & G. Piotto, 265, 277

[14]Cropper, Mark, 1990, The Polars., Space Science Reviews (ISSN 0038-6308), vol. 54, Dec. 1990, p. 195-295

[15]Davies, Melvyn B. 1997, Cataclysmic variable production in globular clusters., Monthly Notices of the Royal Astronomical Society, Volume 288, Issue 1, pp. 117-128.

[16]Dempsey, Robert C.; Linsky, Jeffrey L.; Fleming, Thomas A.; Schmitt, J. H. M. M., 1993, The ROSAT All-Sky Survey of active binary coronae. I - Quiescent fluxes for the RS Canum Venaticorum systems., Astrophysical Journal Supplement Series (ISSN 0067-0049), vol. 86, no. 2, p. 599-609.

[17]Dolphin, Andrew E., 2000, WFPC2 Stellar Photometry with HSTPHOT, The Publications of the Astronomical Society of the Pacific, Volume 112, Issue 776, pp. 1383-1396.

[18]Edmonds, Peter D.; Heinke, Craig O.; Grindlay, Jonathan E.; Gilliland, Ronald L., 2002, Hubble Space Telescope Detection of a Quiescent Low-Mass X-Ray Binary Companion in 47 Tucanae., The Astrophysical Journal, Volume 564, Issue 1, pp. L17-L20.

[19]Fabian, A. C.; Pringle, J. E.; Rees, M. J., 1975, Tidal capture formation of binary systems and X-ray sources in globular clusters., Royal Astronomical Society, Monthly Notices, vol. 172, Aug. 1975, p. 15p-18p.

[20]Freeman, P. E.; Kashyap, V.; Rosner, R.; Lamb, D. Q., 2002, A Wavelet-Based Algorithm for the Spatial Analysis of Poisson Data, The Astrophysical Journal Supplement Series, Volume 138, Issue 1, pp. 185-218.

[21]Giacconi, R.; Murray, S.; Gursky, H.; Kellogg, E.; Schreier, E.; Tananbaum, H.,1972, The Uhuru catalog of X-ray sources., Astrophys. J., Vol. 178, p. 281 – 308
Giacconi, R.; Rosati, P.; Tozzi, P.; Nonino, M.; Hasinger, G.; Norman, C.; Bergeron, J.; Borgani, S.; Gilli, R.; Gilmozzi, R.; Zheng, W., 2001, First Results from the X-Ray and Optical Survey of the Chandra Deep Field South, The Astrophysical Journal, Volume 551, Issue 2, pp. 624-634.

[22]Gratton, R. G.; Ortolani, S.,1987, Deep photometry of globular clusters. VI - E2 and E3., Astronomy and Astrophysics Supplement Series (ISSN 0365-0138), vol. 67, no. 3, Feb. 1987, p. 373-393.

[23]Green, P. J.; Silverman, J. D.; Cameron, R. A.; Kim, D.-W.; Wilkes, B. J.; Barkhouse, W. A.; LaCluyzé, A.; Morris, D.; Mossman, A.; Ghosh, H.; Grimes, J. P.; Jannuzi, B. T.; Tananbaum, H.; Aldcroft, T. L.; Baldwin, J. A.; Chaffee, F. H.; Dey, A.; Dosaj, A.; Evans, N. R.; Fan, X.; Foltz, C.; Gaetz, T.; Hooper, E. J.; Kashyap, V. L.; Mathur, S.; McGarry, M. B.; Romero-Colmenero, E.; Smith, M. G.; Smith, P. S.; Smith, R. C.; Torres, G.; Vikhlinin, A.; Wik, D. R., 2004, The Chandra Multiwavelength Project: Optical Follow-up of Serendipitous Chandra Sources., The Astrophysical Journal Supplement Series, Volume 150, Issue 1, pp. 43-71.

[24]Grindlay, J. E.; Heinke, C. O.; Edmonds, P. D.; Murray, S. S.; Cool, A. M., 2001, Chandra Exposes the Core-collapsed Globular Cluster NGC 6397., The Astrophysical Journal, Volume 563, Issue 1, pp. L53-L56.

[25]Grindlay, J. E.; Camilo, F.; Heinke, C. O.; Edmonds, P. D.; Cohn, H.; Lugger, P., 2002, Chandra Study of a Complete Sample of Millisecond Pulsars in 47 Tucanae and NGC 6397., The Astrophysical Journal, Volume 581, Issue 1, pp. 470-484.
Harris, William E., 1996, A Catalog of Parameters for Globular Clusters in the Milky Way., Astronomical Journal v.112, p.1487.

[26]Herschel, William. 1786, Catalogue of One Thousand New Nebulae and Clusters of Stars. By William Herschel, LL.D. F. R. S., Philosophical Transactions of the Royal Society of London, Vol. 76, pp. 457-499.

[27]Hendry, Paul D.; Mochnacki, Stefan W., 2000, Doppler Imaging of VW Cephei: Distribution and Evolution of Starspots on a Contact Binary., The Astrophysical Journal, Volume 531, Issue 1, pp. 467-493.

[28]Heinke, C. O.; Grindlay, J. E.; Edmonds, P. D.; Cohn, H. N.; Lugger, P. M.; Camilo, F.; Bogdanov, S.; Freire, P. C., 2005, A Deep Chandra Survey of the Globular Cluster 47 Tucanae: Catalog of Point Sources., The Astrophysical Journal, Volume 625, Issue 2, pp. 796-824.

[29]Hertz, P.; Grindlay, J. E., 1983, An X-ray survey of globular clusters and their X-ray luminosity function., Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 275, Dec. 1, 1983, p. 105-119.
Hills,J.G.,1975, Encounters between binary and single stars and their effect on the dynamical evolution of stellar systems., Astronomical Journal, vol. 80, Oct. 1975, p. 809-825.

[30]Hills, J. G., 1976, The formation of binaries containing black holes by the exchange of companions and the X-ray sources in globular clusters., Royal Astronomical Society, Monthly Notices, vol. 175, Apr. 1976, p. 1P-4P.

[31]Hut, P.; Verbunt, F., 1983, White dwarfs and neutron stars in globular cluster X-ray sources., Nature, vol. 301, Feb. 17, 1983, p. 587-589.

[32]Jonker, Peter G.; Steeghs, Daniel; Chakrabarty, Deepto; Juett, Adrienne M., 2007, The Cold Neutron Star in the Soft X-Ray Transient 1H 1905+000, The Astrophysical Journal, Volume 665, Issue 2, pp. L147-L150.

[33]Kalberla, P. M. W.; Burton, W. B.; Hartmann, Dap; Arnal, E. M.; Bajaja, E.; Morras, R.; Pöppel, W. G. L., 2005, The Leiden/Argentine/Bonn (LAB) Survey of Galactic HI. Final data release of the combined LDS and IAR surveys with improved stray-radiation corrections, Astronomy and Astrophysics, Volume 440, Issue 2, September III 2005, pp.775-782.

[34]King, Ivan R., 1966, The structure of star clusters. III. Some simple dynamical models., Astronomical Journal, Vol. 71, p. 64.

[35]Kong, Albert K. H.; McClintock, Jeffrey E.; Garcia, Michael R.; Murray, Stephen S.; Barret, Didier, 2002, The X-Ray Spectra of Black Hole X-Ray Novae in Quiescence as Measured by Chandra, The Astrophysical Journal, Volume 570, Issue 1, pp. 277-286

[36]Kong, Albert K. H.; Bassa, Cees; Pooley, David; Lewin, Walter H. G.; Homer, Lee; Verbunt, Frank; Anderson, Scott F.; Margon, Bruce, 2006, Chandra and Hubble Space Telescope Study of the Globular Cluster NGC 288., The Astrophysical Journal, Volume 647, Issue 2, pp. 1065-1074.

[37]Lu, Ting Ni; Kong, Albert K. H.; Bassa, Cees; Verbunt, Frank; Lewin, Walter H. G.; Anderson, Scott F.; Pooley, David., 2009, X-ray Sources and Their Optical Counterparts in the Galactic Globular Cluster M12 (NGC 6218). , arXiv:0904.2772v1

[38]Majer, P.; Schmitt, J. H. M. M.; Golub, L.; Harnden, F. R., Jr.; Rosner, R., 1986, X-ray spectra and the rotation-activity connection of RS Canum Venaticorum binaries., Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 300, Jan. 1, 1986, p. 360-373.

[39]Narayan, Ramesh; Garcia, Michael R.; McClintock, Jeffrey E., 1997, Advection-dominated Accretion and Black Hole Event Horizons., Astrophysical Journal Letters v.478, p.L79.

[40]Neely, Ray Kreswell; Sarajedini, Ata; Martins, Donald H., 2000, CCD Photometry of the Galactic Globular Cluster NGC 6144., The Astronomical Journal, Volume 119, Issue 4, pp. 1793-1802.

[41]Nousek, John A.; Shue, David R., 1989, Chi-squared and C statistic minimization for low count per bin data., Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 342, July 15, 1989, p. 1207-1211.

[42]Patterson, J., 1984, The evolution of cataclysmic and low-mass X-ray binaries., Astrophysical Journal Supplement Series (ISSN 0067-0049), vol. 54, April 1984, p. 443-493.

[43]Pooley, David; Hut, Piet, 2006, Dynamical Formation of Close Binaries in Globular Clusters: Cataclysmic Variables., The Astrophysical Journal, Volume 646, Issue 2, pp. L143-L146.

[44]Pooley, David; Lewin, Walter H. G.; Anderson, Scott F.; Baumgardt, Holger; Filippenko, Alexei V.; Gaensler, Bryan M.; Homer, Lee; Hut, Piet; Kaspi, Victoria M.; Makino, Junichiro; Margon, Bruce; McMillan, Steve; Portegies Zwart, Simon; van der Klis, Michiel; Verbunt, Frank, 2003, Dynamical Formation of Close Binary Systems in Globular Clusters., The Astrophysical Journal, Volume 591, Issue 2, pp. L131-L134.

[45]Pooley, David; Hut, Piet
Pryor, Carlton; Schommer, Robert A.; Olszewski, Edward W., 1991, Primordial binary stars in the low density globular clusters NGC 5053 and NGC 5466., The formation and evolution of star clusters (A93-48676 20-90), p. 439-442.

[46]Pryor, C.; Meylan, G., 1993, Velocity Dispersions for Galactic Globular Clusters, Structure and Dynamics of Globular Clusters., Proceedings of a Workshop held in Berkeley, California, July 15-17, 1992, to Honor the 65th Birthday of Ivan King. Editors, S.G. Djorgovski and G. Meylan; Publisher, Astronomical Society of the Pacific, Vol. 50, San Francisco, California, 1993. P.357.

[47]Saito, Y.; Kawai, N.; Kamae, T.; Shibata, S.; Dotani, T.; Kulkarni, S. R., 1997, Detection of Magnetospheric X-Ray Pulsation from Millisecond Pulsar PSR B1821-24., Astrophysical Journal Letters v.477, p.L37.

[48]Sarajedini, Ata; Bedin, Luigi R.; Chaboyer, Brian; Dotter, Aaron; Siegel, Michael; Anderson, Jay; Aparicio, Antonio; King, Ivan; Majewski, Steven; Marín-Franch, A.; Piotto, Giampaolo; Reid, I. Neill; Rosenberg, Alfred., 2007, The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters without Previous Hubble Space Telescope Photometry., The Astronomical Journal, Volume 133, Issue 4, pp. 1658-1672.

[49]Sirianni, M.; Jee, M. J.; Benítez, N.; Blakeslee, J. P.; Martel, A. R.; Meurer, G.; Clampin, M.; De Marchi, G.; Ford, H. C.; Gilliland, R.; Hartig, G. F.; Illingworth, G. D.; Mack, J.; McCann, W. J., 2005, The Photometric Performance and Calibration of the Hubble Space Telescope Advanced Camera for Surveys., The Publications of the Astronomical Society of the Pacific, Volume 117, Issue 836, pp. 1049-1112

[50]Skumanich, A., 1972, Time Scales for CA II Emission Decay, Rotational Braking, and Lithium Depletion., Astrophysical Journal, vol. 171, p.565.

[51]Smak, Jozef, 2001, Cataclysmic Variables., In: Binary stars: selected topics on observations and physical processes. Lectures held at the Astrophysics School XII organized by the European Astrophysics Doctoral Network (EADN) in La Laguna, Tenerife, Spain, 6 - 17 September 1999, Eds.: F. C. Lázaro, M. J. Arévalo, Lecture notes in physics, Vol. 563. Physics and astronomy online library. Berlin: Springer, 2001, p. 110 – 150.

[52]Strassmeier, Klaus G., 2001, Magnetic Activity in Binary Stars., In: Binary stars: selected topics on observations and physical processes. Lectures held at the Astrophysics School XII organized by the European Astrophysics Doctoral Network (EADN) in La Laguna, Tenerife, Spain, 6 - 17 September 1999, Eds.: F. C. Lázaro, M. J. Arévalo, Lecture notes in physics, Vol. 563. Physics and astronomy online library. Berlin: Springer, 2001, p. 48 – 109.

[53]Tom R. Marsh, 2001, Observations of Cataclysmic Variable and Double Degenerate Stars., In: Binary stars: selected topics on observations and physical processes. Lectures held at the Astrophysics School XII organized by the European Astrophysics Doctoral Network (EADN) in La Laguna, Tenerife, Spain, 6 - 17 September 1999, Eds.: F. C. Lázaro, M. J. Arévalo, Lecture notes in physics, Vol. 563. Physics and astronomy online library. Berlin: Springer, 2001, p. 151-202

[54]Uchida, Y.; Sakurai, T., 1985, Magnetodynamical processes in interacting magnetospheres of RS CVn binaries., IN: Unstable current systems and plasma instabilities in astrophysics; Proceedings of the 107th Symposium, College Park, MD, August 8-11, 1983 (A85-48801 24-90). Dordrecht, D. Reidel Publishing Co., 1985, p. 281-285; Discussion, p. 286.

[55]van den Bergh, S.; Demers, S.; Kunkel, W. E, 1980, The dying globular cluster E3., Astrophysical Journal, Part 1, vol. 239, July 1, 1980, p. 112-120.

[56]Veronesi, C.; Zaggia, S.; Piotto, G.; Ferraro, F. R.; Bellazzini, M., 1996, Binaries in Globular Clusters. A Useful Window: E3., Formation of the Galactic Halo...Inside and Out, ASP Conference Series, Vol. 92, 1996, Heather Morrison and Ata Sarajedini, eds., p. 301.

[57]Verbunt, F.; Hut, P., 1987, The Globular Cluster Population of X-Ray Binaries, IAU Symposium., No. 125, p.187.

[58]Verbunt, F.; 2003, Binary Evolution and Neutron Stars in Globular Clusters., New Horizons in Globular Cluster Astronomy, ASP Conference Proceedings, Vol. 296, held 24-28 June 2002 at Dipartimento di Astronomia, Universita' di Padova, Padova, Italy. Edited by Giampaolo Piotto, Georges Meylan, S. George Djorgovski and Marco Riello, p.245

[59]Verbunt, F. ; Lewin W. H. G., 2006, Globular Cluster X-ray Sources., In: Compact Stellar X-ray Sources. P341-379, Walter Lewin & Michiel van der Klis, Cambridge University Press.

[60]Verbunt, Frank; Pooley, Dave; Bassa, Cees., 2007, Observational Evidence for the Origin of X-ray Sources in Globular Clusters., Dynamical Evolution of Dense Stellar Systems, Proceedings of the International Astronomical Union, IAU Symposium, Volume 246, p. 301-310

[61]Wijnands, Rudy; Heinke, Craig O.; Pooley, David; Edmonds, Peter D.; Lewin, Walter H. G.; Grindlay, Jonathan E.; Jonker, Peter G.; Miller, Jon M. 2005, The Hard Quiescent Spectrum of the Neutron Star X-Ray Transient EXO 1745-248 in the Globular Cluster Terzan 5., The Astrophysical Journal, Volume 618, Issue 2, pp. 883-890.

[62]Wilson, O. C., 1976, Absolute magnitudes of stars from widths of chromospheric Ca II emission lines., Astrophys. J., Vol. 205, p. 823 – 840.