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René Timcenko Tronsgaard Rasmussen

Many new variable stars discovered in the core of the globular cluster NGC 6715 (M54) with EMCCD observations

Research output: Contribution to journal/Conference contribution in journal/Contribution to newspaperJournal articleResearchpeer-review

  • R. Figuera Jaimes, European Southern Observ Astron Res Southern Hemi
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  • D. M. Bramich, HBKU, Qatar Foundation, Qatar Fdn, QEERI
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  • N. Kains, Space Telescope Sci Inst
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  • J. Skottfelt, Univ Copenhagen, University of Copenhagen, Nat Hist Museum Denmark, Ctr Star & Planet Format
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  • U. G. Jorgensen, Univ Copenhagen, Niels Bohr Institute, University of Copenhagen, Niels Bohr Inst, Dark Cosmol Ctr, Univ Copenhagen, University of Copenhagen, Nat Hist Museum Denmark, Ctr Star & Planet Format
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  • K. Horne, Univ St Andrews, University of St Andrews, SUPA, Sch Phys & Astron
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  • M. Dominik, Univ St Andrews, University of St Andrews, SUPA, Sch Phys & Astron
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  • K. A. Alsubai, HBKU, Qatar Foundation, Qatar Fdn, QEERI
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  • V. Bozza, Ist Nazl Fis Nucl, Istituto Nazionale Geofisica e Vulcanologia (INGV), Istituto Nazionale di Fisica Nucleare, Sez Napoli
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  • M. J. Burgdorf, Univ Hamburg, University of Hamburg, Inst Meteorol
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  • S. Calchi Novati, IIASS
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  • S. Ciceri, Stockholm Univ, Stockholm University, Dept Astron, Oskar Klein Ctr, AlbaNova
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  • G. D'Ago
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  • D. F. Evans
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  • P. Galianni, Univ St Andrews, University of St Andrews, SUPA, Sch Phys & Astron
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  • S. -H. Gu, Chinese Acad Sci, Chinese Academy of Sciences, Key Lab Struct & Evolut Celestial Objects, Natl Astron Observat Yunnan Observ
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  • K. B. W. Harpsoe, Univ Copenhagen, Niels Bohr Institute, University of Copenhagen, Niels Bohr Inst, Dark Cosmol Ctr
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  • T. Haugbolle, Univ Copenhagen, Niels Bohr Institute, University of Copenhagen, Niels Bohr Inst, Dark Cosmol Ctr, Univ Copenhagen, University of Copenhagen, Nat Hist Museum Denmark, Ctr Star & Planet Format
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  • T. C. Hinse, Korea Astron & Space Sci Inst
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  • M. Hundertmark, Univ Copenhagen, University of Copenhagen, Nat Hist Museum Denmark, Ctr Star & Planet Format
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  • D. Juncher, Univ Copenhagen, University of Copenhagen, Nat Hist Museum Denmark, Ctr Star & Planet Format
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  • E. Kerins, Univ Manchester, Jodrell Bank Centre for Astrophysics, University of Manchester, Sch Phys & Astron, Ctr Astrophys, Jodrell Bank
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  • H. Korhonen, Univ Copenhagen, Niels Bohr Institute, University of Copenhagen, Niels Bohr Inst, Dark Cosmol Ctr
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  • M. Kuffmeier, Univ Copenhagen, University of Copenhagen, Nat Hist Museum Denmark, Ctr Star & Planet Format
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  • L. Mancini, Max Planck Inst Astron, Max Planck Society
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  • N. Peixinho, Univ Coimbra, Universidade de Coimbra, Astron Observ, Ctr Earth & Space Sci Res, CITEUC 20
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  • A. Popovas, Univ Copenhagen, University of Copenhagen, Nat Hist Museum Denmark, Ctr Star & Planet Format
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  • M. Rabus, Pontificia Univ Catolica Chile, Pontificia Universidad Catolica de Chile, Fac Fis, Inst Astrofis
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  • S. Rahvar, Sharif Univ Technol, Sharif University of Technology, Dept Phys
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  • G. Scarpetta, IIASS
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  • R. W. Schmidt, Heidelberg Univ, Ruprecht Karl University Heidelberg, Astron Rechen Inst, Zentrum Astron
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  • C. Snodgrass, Max Planck Inst Solar Syst Res, Max Planck Society
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  • J. Southworth, Keele Univ, Keele University, Lennard Jones Labs, Astrophys Grp
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  • D. Starkey, Univ St Andrews, University of St Andrews, SUPA, Sch Phys & Astron
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  • R. A. Street, Las Cumbres Observ Global Telescope Network
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  • J. Surdej, Univ Liege, University of Liege, Inst Astrophys & Geophys
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  • René Tronsgaard Rasmussen
  • E. Unda-Sanzana, Univ Antofagasta, Universidad de Antofagasta, Fac Cs Bas, Unidad Astron
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  • C. von Essen
  • X. -B. Wang, Chinese Acad Sci, Chinese Academy of Sciences, Yunnan Astron Observ, Chinese Acad Sci, Chinese Academy of Sciences, Key Lab Struct & Evolut Celestial Objects, Natl Astron Observat Yunnan Observ
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  • O. Wertz, Univ Liege, University of Liege, Inst Astrophys & Geophys
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  • MiNDSTEp Consortium

Context. We show the benefits of using electron-multiplying CCDs and the shift-and-add technique as a tool to minimise the effects of atmospheric turbulence, such as blending between stars in crowded fields, and to avoid saturated stars in the fields observed. We intend to complete, or improve on, the census of the variable star population in globular cluster NGC 6715.

Aims. Our aim is to obtain high-precision time-series photometry of the very crowded central region of this stellar system via the collection of better angular resolution images than has been previously achieved with conventional CCDs on ground-based telescopes.

Methods. Observations were carried out using the Danish 1.54-m telescope at the ESO La Silla observatory in Chile. The telescope is equipped with an electron-multiplying CCD that enables short-exposure-time images to be obtained (ten images per second) that were stacked using the shift-and-add technique to produce the normal-exposure-time images (minutes). The high precision photometry was performed via difference image analysis employing the DanDIA pipeline. We attempted automatic detection of variable stars in the field.

Results. We statistically analysed the light curves of 1405 stars in the crowded central region of NGC 6715 to automatically identify the variable stars present in this cluster. We found light curves for 17 previously known variable stars near the edges of our reference image (16 RR Lyrae and 1 semi-regular) and we discovered 67 new variables (30 RR Lyrae, 21 irregular (long-period type), 3 semi-regular, 1 W Virginis, 1 eclipsing binary, and 11 unclassified). Photometric measurements for these stars are available in electronic form through the Strasbourg Astronomical Data Centre.

Original languageEnglish
Article number120
JournalAstronomy & Astrophysics
Volume592
Number of pages17
ISSN1432-0746
DOIs
Publication statusPublished - Aug 2016

    Research areas

  • atmospheric effects, instrumentation: high angular resolution, globular clusters: individual: NGC 6715 (M54), methods: observational, stars: variables: general, stars: variables: RR Lyrae, SAGITTARIUS DWARF GALAXY, RR-LYRAE VARIABLES, DIFFERENCE IMAGE-ANALYSIS, CROWDED CENTRAL REGION, SPHEROIDAL GALAXY, ACS SURVEY, OOSTERHOFF DICHOTOMY, DYNAMICAL MODELS, GALACTIC BULGE, BLACK-HOLE

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