A census of variability in globular cluster M 68 (NGC 4590)

Globular clusters: individual: M 68; Stars: variables: general; Stars: variables: RR Lyrae; Astrophysics; Image analysis; Surveys; Telescopes; Time series analysis; Electron multiplying ccds; Empirical relations; Fourier decomposition; Globular clusters; Globular clusters: individual; Spatial resolution; Stars

Abstract :

[en] Aims. We analyse 20 nights of CCD observations in the V and I bands of the globular cluster M 68 (NGC 4590) and use them to detect variable objects. We also obtained electron-multiplying CCD (EMCCD) observations for this cluster in order to explore its core with unprecedented spatial resolution from the ground. Methods. We reduced our data using difference image analysis to achieve the best possible photometry in the crowded field of the cluster. In doing so, we show that when dealing with identical networked telescopes, a reference image from any telescope may be used to reduce data from any other telescope, which facilitates the analysis significantly. We then used our light curves to estimate the properties of the RR Lyrae (RRL) stars in M 68 through Fourier decomposition and empirical relations. The variable star properties then allowed us to derive the cluster's metallicity and distance. Results. M 68 had 45 previously confirmed variables, including 42 RRL and 2 SX Phoenicis (SX Phe) stars. In this paper we determine new periods and search for new variables, especially in the core of the cluster where our method performs particularly well. We detect 4 additional SX Phe stars and confirm the variability of another star, bringing the total number of confirmed variable stars in this cluster to 50. We also used archival data stretching back to 1951 to derive period changes for some of the single-mode RRL stars, and analyse the significant number of double-mode RRL stars in M 68. Furthermore, we find evidence for double-mode pulsation in one of the SX Phe stars in this cluster. Using the different classes of variables, we derived values for the metallicity of the cluster of [Fe/H] = -2.07 ± 0.06 on the ZW scale, or -2.20 ± 0.10 on the UVES scale, and found true distance moduli μ<inf>0</inf> = 15.00 ± 0.11 mag (using RR0 stars), 15.00 ± 0.05 mag (using RR1 stars), 14.97 ± 0.11 mag (using SX Phe stars), and 15.00 ± 0.07 mag (using the M<inf>V</inf> -[Fe/H] relation for RRL stars), corresponding to physical distances of 10.00 ± 0.49, 9.99 ± 0.21, 9.84 ± 0.50, and 10.00 ± 0.30 kpc, respectively. Thanks to the first use of difference image analysis on time-series observations of M 68, we are now confident that we have a complete census of the RRL stars in this cluster. © ESO, 2015.

Disciplines :

Space science, astronomy & astrophysics

Author, co-author :

Kains, N.; Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, United States, European Southern Observatory, Karl-Schwarzschild Straße 2, Garching bei München, Germany

Arellano Ferro, A.; Instituto de Astronomía, Universidad Nacional Autónoma de Mexico, Coyoácan, Mexico

Figuera Jaimes, R.; European Southern Observatory, Karl-Schwarzschild Straße 2, Garching bei München, Germany, SUPA School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, United Kingdom

Bramich, D. M.; Qatar Environment and Energy Research Institute, Qatar Foundation, PO Box 5825, Doha, Qatar

Skottfelt, J.; Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, Copenhagen, Denmark, Centre for Star and Planet Formation, Geological Museum, Øster Voldgade 5, Copenhagen, Denmark

Jørgensen, U. G.; Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, Copenhagen, Denmark, Centre for Star and Planet Formation, Geological Museum, Øster Voldgade 5, Copenhagen, Denmark

Tsapras, Y.; Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Goleta, CA, United States, School of Mathematical Sciences, Queen Mary, University of London, Mile End Road, London, United Kingdom

Street, R. A.; Las Cumbres Observatory Global Telescope Network, 6740 Cortona Drive, Goleta, CA, United States

Browne, P.; SUPA School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, United Kingdom

Dominik, M.; SUPA School of Physics and Astronomy, University of St. Andrews, North Haugh, St. Andrews, United Kingdom

More authors (25 more)

Language :

English

Title :

A census of variability in globular cluster M 68 (NGC 4590)

Publication date :

2015

Journal title :

Astronomy and Astrophysics

ISSN :

0004-6361

eISSN :

1432-0746

Publisher :

EDP Sciences

Volume :

578

Peer reviewed :

Peer Reviewed verified by ORBi

Available on ORBi :

since 15 January 2018

Statistics

Number of views

47 (0 by ULiège)

Number of downloads

103 (0 by ULiège)

More statistics

Scopus citations^®

Scopus citations^®
without self-citations

OpenCitations

Bibliography

Alard, C. 1999, A&A, 343, 10
Alard, C. 2000, A&ASS, 144, 363
Albrow, M. D., Horne, K., Bramich, D. M., et al. 2009, MNRAS, 397, 2099
Alcaino, G. 1977, A&ASS, 29, 9
Alcaino, G., Liller, W., Alvarado, F., & Wenderoth, E. 1990, AJ, 99, 1831
Arellano Ferro, A., Rojas López, V., Giridhar, S., & Bramich, D. M. 2008, MNRAS, 384, 1444
Arellano Ferro, A., Giridhar, S., & Bramich, D. M. 2010, MNRAS, 402, 226
Arellano Ferro, A., Figuera Jaimes, R., Giridhar, S., et al. 2011, MNRAS, 416, 2265
Arellano Ferro, A., Bramich, D. M., Figuera Jaimes, R., et al. 2013a, MNRAS, 434, 1220
Arellano Ferro, A., Bramich, D. M., Giridhar, S., et al. 2013b, Acta Astron., 63, 429
Arellano Ferro, A., Ahumada, J. A., Calderón, J. H., & Kains, N. 2014, Rev. Mex. Astron. Astrofis., 50, 307
Bellini, A., Anderson, J., & Bedin, L. R. 2011, PASP, 123, 622
Belserene, E. P. 1964, AJ, 69, 475
Benedict, G. F., McArthur, B. E., Fredrick, L. W., et al. 2002, AJ, 123, 473
Bessell, M. S. 2005, Ara& A, 43, 293
Bica, E. L. D., & Pastoriza, M. G. 1983, A&SS, 91, 99
Blažko, S. 1907, Astron. Nachr., 175, 325
Bono, G., Caputo, F., Castellani, V., et al. 2003, MNRAS, 344, 1097
Bragaglia, A., Gratton, R. G., Carretta, E., et al. 2001, AJ, 122, 207
Bramich, D. M. 2008, MNRAS, 386, L77
Bramich, D. M., & Freudling, W. 2012, MNRAS, 424, 1584
Bramich, D. M., Figuera Jaimes, R., Giridhar, S., & Arellano Ferro, A. 2011, MNRAS, 413, 1275
Bramich, D. M., Horne, K., Albrow, M. D., et al. 2013, MNRAS, 428, 2275
Brocato, E., Castellani, V., & Ripepi, V. 1994, AJ, 107, 622
Brocato, E., Castellani, V., & Piersimoni, A. 1997, ApJ, 491, 789
Cacciari, C., Corwin, T. M., & Carney, B. W. 2005, AJ, 129, 267
Caloi, V., D'Antona, F., & Mazzitelli, I. 1997, AS&S, 320, 823
Carney, B. W. 1996, PASP, 108, 900
Carretta, E., Bragaglia, A., Gratton, R., D'Orazi, V., & Lucatello, S. 2009a, A&A, 508, 695
Carretta, E., Bragaglia, A., Gratton, R., & Lucatello, S. 2009b, A&A, 505, 139
Carretta, E., Bragaglia, A., Gratton, R. G., et al. 2009c, A&A, 505, 117
Castelli, F. 1999, A&A, 346, 564
Catelan, M. 2009, A&SS, 320, 261
Chaboyer, B., Demarque, P., Kernan, P. J., Krauss, L. M., & Sarajedini, A. 1996, MNRAS, 283, 683
Chieffi, A., & Straniero, O. 1989, ApJS, 71, 47
Clement, C. M. 1990, AJ, 99, 240
Clement, C. M., Ferance, S., & Simon, N. R. 1993, ApJ, 412, 183
Clement, C. M., Muzzin, A., Dufton, Q., et al. 2001, AJ, 122, 2587
Cohen, R. E., & Sarajedini, A. 2012, MNRAS, 419, 342
Cox, A. N. 1991, ApJ, 381, L71
Di Fabrizio, L., Clementini, G., Maio, M., et al. 2005, A&A, 430, 603
Dotter, A., Chaboyer, B., Jevremovíc, D., et al. 2007, AJ, 134, 376
Dotter, A., Chaboyer, B., Jevremovíc, D., et al. 2008, ApJS, 178, 89
Dworetsky, M. M. 1983, MNRAS, 203, 917
Feuchtinger, M. U. 1998, A&A, 337, L29
Figuera Jaimes, R., Arellano Ferro, A., Bramich, D. M., Giridhar, S., & Kuppuswamy, K. 2013, A&A, 556, A20
Freedman, W. L., Madore, B. F., Gibson, B. K., et al. 2001, ApJ, 553, 47
Gilliland, R. L., Bono, G., Edmonds, P. D., et al. 1998, ApJ, 507, 818
Gratton, R. G., & Ortolani, S. 1989, A&A, 211, 41
Gratton, R. G., Fusi Pecci, F., Carretta, E., et al. 1997, ApJ, 491, 749
Gratton, R. G., Bragaglia, A., Clementini, G., et al. 2004, A&A, 421, 937
Greenstein, J. L., Bidelman, W. P., & Popper, D. M. 1947, PASP, 59, 143
Guldenschuh, K. A., Layden, A. C., Wan, Y., et al. 2005, PASP, 117, 721
Harpsøe, K. B. W., Jørgensen, U. G., Andersen, M. I., & Grundahl, F. 2012, A&A, 542, A23
Harris, W. E. 1975, ApJS, 29, 397
Harris, W. E. 1996, AJ, 112, 1487
Jeon, Y.-B., Lee, M. G., Kim, S.-L., & Lee, H. 2003, AJ, 125, 3165
Jeon, Y.-B., Lee, M. G., Kim, S.-L., & Lee, H. 2004, AJ, 128, 287
Jimenez, R., Thejll, P., Jorgensen, U. G., MacDonald, J., & Pagel, B. 1996, MNRAS, 282, 926
Jurcsik, J. 1995, Acta Astron., 45, 653
Jurcsik, J. 1998, A&A, 333, 571
Jurcsik, J., & Kovács, G. 1996, A&A, 312, 111
Jurcsik, J., Hajdu, G., Szeidl, B., et al. 2012, MNRAS, 419, 2173
Kains, N., Bramich, D. M., Figuera Jaimes, R., et al. 2012, A&A, 548, A92
Kains, N., Bramich, D. M., Arellano Ferro, A., et al. 2013, A&A, 555, A36
Kinman, T. D. 2002, IBVS, 5354, 1
Kovács, G. 1998, Mem. Soc. Astron. Ital., 69, 49
Kovács, G. 2002, in Omega Centauri, A Unique Window into Astrophysics, eds. F. van Leeuwen, J. D. Hughes, & G. Piotto, ASP Conf. Ser., 265, 163
Kovács, G., & Walker, A. R. 2001, A&A, 371, 579
Kovacs, G., Buchler, J. R., & Marom, A. 1991, A&A, 252, L27
Kunder, A., Chaboyer, B., & Layden, A. 2010, AJ, 139, 415
Kunder, A., Stetson, P. B., Cassisi, S., et al. 2013a, AJ, 146, 119
Kunder, A., Stetson, P. B., Catelan, M., Walker, A. R., & Amigo, P. 2013b, AJ, 145, 33
Lane, R. R., Kiss, L. L., Lewis, G. F., et al. 2009, MNRAS, 400, 917
Lee, Y.-W. 1991, ApJ, 367, 524
Lee, J.-W., & Carney, B. W. 1999, AJ, 118, 1373
Lee, Y.-W., Demarque, P., & Zinn, R. 1990, ApJ, 350, 155
Lenz, P., & Breger, M. 2005, Commun. Asteroseismol., 146, 53
Marconi, M., Coppola, G., Bono, G., et al. 2015, ApJ, submitted [arXiv: 1505.02531
McClure, R. D., Hesser, J. E., Stetson, P. B., Vandenberg, D. A., & Bell, R. A. 1987, AJ, 93, 1144
Minniti, D., Geisler, D., Peterson, R. C., & Claria, J. J. 1993, ApJ, 413, 548
Montegriffo, P., Ferraro, F. R., Origlia, L., & Fusi Pecci, F. 1998, MNRAS, 297, 872
Morgan, S. M., Wahl, J. N., & Wieckhorst, R. M. 2007, MNRAS, 374, 1421
Nemec, J. M., Hazen-Liller, M. L., & Hesser, J. E. 1985, ApJS, 57, 329
Nemec, J. M., Cohen, J. G., Ripepi, V., et al. 2013, ApJ, 773, 181
Oosterhoff, P. T. 1939, The Observatory, 62, 104
Petersen, J. O. 1973, A&A, 27, 89
Peterson, C. J. 1987, PASP, 99, 1153
Piersimoni, A. M., Bono, G., & Ripepi, V. 2002, AJ, 124, 1528
Pojmanski, G. 2002, Acta Astron., 52, 397
Poretti, E., Paparó, M., Deleuil, M., et al. 2010, A&A, 520, A108
Pritzl, B. J., Smith, H. A., Catelan, M., & Sweigart, A. V. 2001, AJ, 122, 2600
Pritzl, B. J., Smith, H. A., Catelan, M., & Sweigart, A. V. 2002, AJ, 124, 949
Racine, R. 1973, AJ, 78, 180
Rakos, K., & Schombert, J. 2005, PASP, 117, 245
Rathbun, P., & Smith, H. 1997, PASP, 109, 1128
Rosenberg, A., Saviane, I., Piotto, G., & Aparicio, A. 1999, AJ, 118, 2306
Rosino, L., & Pietra, S. 1953, Mem. Soc. Astron. Ital., 24, 331
Rosino, L., & Pietra, S. 1954, Mem. Soc. Astron. Ital., 25, 227
Rutledge, G. A., Hesser, J. E., Stetson, P. B., et al. 1997, PASP, 109, 883
Salaris, M., & Weiss, A. 2002, A&A, 388, 492
Salaris, M., Chieffi, A., & Straniero, O. 1993, ApJ, 414, 580
Sandage, A. 1993, AJ, 106, 687
Santolamazza, P., Marconi, M., Bono, G., et al. 2001, ApJ, 554, 1124
Sariya, D. P., Lata, S., & Yadav, R. K. S. 2014, New Astron., 27, 56
Sekiguchi, M., & Fukugita, M. 2000, AJ, 120, 1072
Shapley, H. 1919, PASP, 31, 226
Shapley, H. 1920, ApJ, 51, 49
Simon, N. R., & Clement, C. M. 1993, ApJ, 410, 526
Skottfelt, J., Bramich, D. M., Figuera Jaimes, R., et al. 2013, A&A, 553, A111
Smith, H. A., & Manduca, A. 1983, AJ, 88, 982
Smith, H. A., & Wesselink, A. J. 1977, A&A, 56, 135
Sollima, A., Cassisi, S., Fiorentino, G., & Gratton, R. G. 2014, MNRAS, 444, 1862
Soszýnski, I., Udalski, A., Szymánski, M. K., et al. 2009, Acta Astron., 59, 1
Stagg, C., & Wehlau, A. 1980, AJ, 85, 1182
Stetson, P. B. 2000, PASP, 112, 925
Straniero, O., & Chieffi, A. 1991, ApJS, 76, 525
Sturch, C. 1966, ApJ, 143, 774
Suntzeff, N. B., Kinman, T. D., & Kraft, R. P. 1991, ApJ, 367, 528
Terzan, A., Rutily, B., & Ounnas, C. 1973, in Variable Stars in Globular Clusters and in Related Systems, ed. J. D. Fernie, IAU Colloq., 21, 76
van Agt, S. L. T. J., & Oosterhoff, P. T. 1959, Annalen van de Sterrewacht te Leiden, 21, 253
van Albada, T. S., & Baker, N. 1971, ApJ, 169, 311
Vandenberg, D. A. 1986, Mem. Soc. Astron. Ital., 57, 373
VandenBerg, D. A., Brogaard, K., Leaman, R., & Casagrande, L. 2013, ApJ, 775, 134
Walker, A. R. 1994, AJ, 108, 555
Yoon, S.-J., & Lee, Y.-W. 2002, Science, 297, 578
Zacharias, N., Finch, C., Girard, T., et al. 2010, AJ, 139, 2184
Zinn, R. 1980, ApJS, 42, 19
Zinn, R. 1993a, in The Globular Cluster-Galaxy Connection, eds. G. H. Smith & J. P. Brodie, ASP Conf. Ser., 48, 302
Zinn, R. 1993b, in The Globular Cluster-Galaxy Connection, eds. G. H. Smith, & J. P. Brodie, ASP Conf. Ser., 48, 38
Zinn, R., & West, M. J. 1984, ApJS, 55, 45