Many new variable stars discovered in the core of the globular cluster NGC 6715 (M 54) with EMCCD observations

R. Figuera Jaimes, D. M. Bramich, N. Kains, J. Skottfelt, U. G. Jørgensen, K. Horne, M. Dominik, Khalid Al-Subai, V. Bozza, M. J. Burgdorf, S. Calchi Novati, S. Ciceri, G. D'Ago, D. F. Evans, P. Galianni, S. H. Gu, K. B. W Harpsøe, T. Haugbølle, T. C. Hinse, M. Hundertmark & 21 others D. Juncher, E. Kerins, H. Korhonen, M. Kuffmeier, L. Mancini, N. Peixinho, A. Popovas, M. Rabus, S. Rahvar, G. Scarpetta, R. W. Schmidt, C. Snodgrass, J. Southworth, D. Starkey, R. A. Street, J. Surdej, R. Tronsgaard, E. Unda-Sanzana, C. Von Essen, X. B. Wang, O. Wertz

Research output: Contribution to journalReview article

1 Citation (Scopus)

Abstract

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 numberA120
JournalAstronomy and Astrophysics
Volume592
DOIs
Publication statusPublished - 1 Aug 2016

Fingerprint

variable stars
globular clusters
stars
charge coupled devices
telescopes
light curve
photometry
electron
image resolution
census
stellar systems
image analysis
Chile
shift
atmospheric turbulence
European Southern Observatory
angular resolution
observatory
turbulence
time series

Keywords

  • Atmospheric effects
  • Globular clusters: individual: NGC 6715 (M 54)
  • Instrumentation: high angular resolution
  • Methods: observational
  • Stars: variables: general
  • Stars: variables: RR Lyrae

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

Many new variable stars discovered in the core of the globular cluster NGC 6715 (M 54) with EMCCD observations. / Figuera Jaimes, R.; Bramich, D. M.; Kains, N.; Skottfelt, J.; Jørgensen, U. G.; Horne, K.; Dominik, M.; Al-Subai, Khalid; Bozza, V.; Burgdorf, M. J.; Calchi Novati, S.; Ciceri, S.; D'Ago, G.; Evans, D. F.; Galianni, P.; Gu, S. H.; W Harpsøe, K. B.; Haugbølle, T.; Hinse, T. C.; Hundertmark, M.; Juncher, D.; Kerins, E.; Korhonen, H.; Kuffmeier, M.; Mancini, L.; Peixinho, N.; Popovas, A.; Rabus, M.; Rahvar, S.; Scarpetta, G.; Schmidt, R. W.; Snodgrass, C.; Southworth, J.; Starkey, D.; Street, R. A.; Surdej, J.; Tronsgaard, R.; Unda-Sanzana, E.; Von Essen, C.; Wang, X. B.; Wertz, O.

In: Astronomy and Astrophysics, Vol. 592, A120, 01.08.2016.

Research output: Contribution to journalReview article

Figuera Jaimes, R, Bramich, DM, Kains, N, Skottfelt, J, Jørgensen, UG, Horne, K, Dominik, M, Al-Subai, K, Bozza, V, Burgdorf, MJ, Calchi Novati, S, Ciceri, S, D'Ago, G, Evans, DF, Galianni, P, Gu, SH, W Harpsøe, KB, Haugbølle, T, Hinse, TC, Hundertmark, M, Juncher, D, Kerins, E, Korhonen, H, Kuffmeier, M, Mancini, L, Peixinho, N, Popovas, A, Rabus, M, Rahvar, S, Scarpetta, G, Schmidt, RW, Snodgrass, C, Southworth, J, Starkey, D, Street, RA, Surdej, J, Tronsgaard, R, Unda-Sanzana, E, Von Essen, C, Wang, XB & Wertz, O 2016, 'Many new variable stars discovered in the core of the globular cluster NGC 6715 (M 54) with EMCCD observations', Astronomy and Astrophysics, vol. 592, A120. https://doi.org/10.1051/0004-6361/201628864
Figuera Jaimes, R. ; Bramich, D. M. ; Kains, N. ; Skottfelt, J. ; Jørgensen, U. G. ; Horne, K. ; Dominik, M. ; Al-Subai, Khalid ; Bozza, V. ; Burgdorf, M. J. ; Calchi Novati, S. ; Ciceri, S. ; D'Ago, G. ; Evans, D. F. ; Galianni, P. ; Gu, S. H. ; W Harpsøe, K. B. ; Haugbølle, T. ; Hinse, T. C. ; Hundertmark, M. ; Juncher, D. ; Kerins, E. ; Korhonen, H. ; Kuffmeier, M. ; Mancini, L. ; Peixinho, N. ; Popovas, A. ; Rabus, M. ; Rahvar, S. ; Scarpetta, G. ; Schmidt, R. W. ; Snodgrass, C. ; Southworth, J. ; Starkey, D. ; Street, R. A. ; Surdej, J. ; Tronsgaard, R. ; Unda-Sanzana, E. ; Von Essen, C. ; Wang, X. B. ; Wertz, O. / Many new variable stars discovered in the core of the globular cluster NGC 6715 (M 54) with EMCCD observations. In: Astronomy and Astrophysics. 2016 ; Vol. 592.
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title = "Many new variable stars discovered in the core of the globular cluster NGC 6715 (M 54) with EMCCD observations",
abstract = "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.",
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author = "{Figuera Jaimes}, R. and Bramich, {D. M.} and N. Kains and J. Skottfelt and J{\o}rgensen, {U. G.} and K. Horne and M. Dominik and Khalid Al-Subai and V. Bozza and Burgdorf, {M. J.} and {Calchi Novati}, S. and S. Ciceri and G. D'Ago and Evans, {D. F.} and P. Galianni and Gu, {S. H.} and {W Harps{\o}e}, {K. B.} and T. Haugb{\o}lle and Hinse, {T. C.} and M. Hundertmark and D. Juncher and E. Kerins and H. Korhonen and M. Kuffmeier and L. Mancini and N. Peixinho and A. Popovas and M. Rabus and S. Rahvar and G. Scarpetta and Schmidt, {R. W.} and C. Snodgrass and J. Southworth and D. Starkey and Street, {R. A.} and J. Surdej and R. Tronsgaard and E. Unda-Sanzana and {Von Essen}, C. and Wang, {X. B.} and O. Wertz",
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TY - JOUR

T1 - Many new variable stars discovered in the core of the globular cluster NGC 6715 (M 54) with EMCCD observations

AU - Figuera Jaimes, R.

AU - Bramich, D. M.

AU - Kains, N.

AU - Skottfelt, J.

AU - Jørgensen, U. G.

AU - Horne, K.

AU - Dominik, M.

AU - Al-Subai, Khalid

AU - Bozza, V.

AU - Burgdorf, M. J.

AU - Calchi Novati, S.

AU - Ciceri, S.

AU - D'Ago, G.

AU - Evans, D. F.

AU - Galianni, P.

AU - Gu, S. H.

AU - W Harpsøe, K. B.

AU - Haugbølle, T.

AU - Hinse, T. C.

AU - Hundertmark, M.

AU - Juncher, D.

AU - Kerins, E.

AU - Korhonen, H.

AU - Kuffmeier, M.

AU - Mancini, L.

AU - Peixinho, N.

AU - Popovas, A.

AU - Rabus, M.

AU - Rahvar, S.

AU - Scarpetta, G.

AU - Schmidt, R. W.

AU - Snodgrass, C.

AU - Southworth, J.

AU - Starkey, D.

AU - Street, R. A.

AU - Surdej, J.

AU - Tronsgaard, R.

AU - Unda-Sanzana, E.

AU - Von Essen, C.

AU - Wang, X. B.

AU - Wertz, O.

PY - 2016/8/1

Y1 - 2016/8/1

N2 - 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.

AB - 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.

KW - Atmospheric effects

KW - Globular clusters: individual: NGC 6715 (M 54)

KW - Instrumentation: high angular resolution

KW - Methods: observational

KW - Stars: variables: general

KW - Stars: variables: RR Lyrae

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U2 - 10.1051/0004-6361/201628864

DO - 10.1051/0004-6361/201628864

M3 - Review article

VL - 592

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

SN - 0004-6361

M1 - A120

ER -