Journal Article

High-resolution optical imaging of the core of the globular cluster M15 with FastCam

Anastasio Díaz-Sánchez, Antonio Pérez-Garrido, Isidro Villó, Rafael Rebolo, Jorge A. Pérez-Prieto, Alejandro Oscoz, Sergi R. Hildebrandt, Roberto López and Luis F. Rodríguez

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 423, issue 3, pages 2260-2269
Published in print July 2012 | ISSN: 0035-8711
Published online June 2012 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2012.21034.x
High-resolution optical imaging of the core of the globular cluster M15 with FastCam

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We present high-resolution I-band imaging of the core of the globular cluster M15 obtained at the 2.5-m Nordic Optical Telescope with FastCam, a low readout noise L3CCD-based instrument. Short exposure times (30 ms) were used to record 200 000 images (512 × 512 pixels each) over a period of 2 h and 43 min. The lucky imaging technique was then applied to generate a final image of the cluster centre with full width at half-maximum ∼0.1 arcsec and 13 × 13 arcsec2 field of view. We obtained a catalogue of objects in this region with a limiting magnitude of I= 19.5. I-band photometry and astrometry are reported for 1181 stars. This is the deepest I-band observation of the M15 core at this spatial resolution. Simulations show that crowding is limiting the completeness of the catalogue. At shorter wavelengths, a similar number of objects have been reported using Hubble Space Telescope (HST)/Wide Field Planetary Camera observations of the same field. The cross-match with the available HST catalogues allowed us to produce colour–magnitude diagrams where we identify new blue straggler star candidates and previously known stars of this class.

Keywords: instrumentation: high angular resolution; techniques: photometric; binaries: close; blue stragglers; Hertzsprung–Russell and colour–magnitude diagrams; globular clusters: individual: M15

Journal Article.  6686 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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