J/A+A/553/A111 Light curves of two NGC6981 variables (Skottfelt+, 2013)
EMCCD photometry reveals two new variable stars in the crowded central region
of the globular cluster NGC 6981.
Skottfelt J., Bramich D.M., Figuera Jaimes R., Jorgensen U.G., Kains N.,
Harpsoe K.B.W., Liebig C., Penny M.T., Alsubai K.A., Andersen J.M.,
Bozza V., Browne P., Calchi Novati S., Damerdji Y., Diehl C., Dominik M.,
Elyiv A., Giannini E., Hessman F., Hinse T.C., Hundertmark M., Juncher D.,
Kerins E., Korhonen H., Mancini L., Martin R., Rabus M., Rahvar S.,
Scarpetta G., Southworth J., Snodgrass C., Street R.A., Surdej J.,
Tregloan-Reed J., Vilela C., Williams A.
<Astron. Astrophys., 553, A111 (2013)>
=2013A&A...553A.111S 2013A&A...553A.111S
ADC_Keywords: Clusters, globular ; Stars, variable ; Photometry, CCD
Keywords: globular clusters: individual: NGC 6981 - stars: variables: RR Lyrae -
instrumentation: high angular resolution - stars: variables: general
Abstract:
Two previously unknown variable stars in the crowded central region of
the globular cluster NGC 6981 are presented. The observations were
made using the electron multiplying CCD (EMCCD) camera at the Danish
1.54m Telescope at La Silla, Chile. The two variables were not
previously detected by conventional CCD imaging because of their
proximity to a bright star. This discovery demonstrates that EMCCDs
are a powerful tool for performing high-precision time-series
photometry in crowded fields and near bright stars, especially when
combined with difference image analysis.
Description:
EMCCD time-series i+z photometry for the new variables V57 and V58 in
NGC 6981.
Objects:
-----------------------------------------------------------------
RA (2000) DE Designation(s) (Per)
-----------------------------------------------------------------
20 53 27.38 -12 32 13.3 V57 = Cl* NGC 6981 SAW V57 (P=0.334)
20 53 27.12 -12 32 13.9 V58 = Cl* NGC 6981 SAW V58 (P=0.285)
-----------------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
photom.dat 39 250 EMCCD time-series i+z photometry for the new
variables V57 and V58 in NGC 6981
--------------------------------------------------------------------------------
See also:
J/MNRAS/413/1275 : VrI light curves of NGC6981 variables (Bramich+, 2011)
Byte-by-byte Description of file: photom.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- VName [V57 V58] Variable star ID
5- 7 A3 --- Filter [i+z] Observation filter (1)
9- 21 F13.5 d HJD Heliocentric Julian date at mid-exposure
23- 31 F9.3 s-1 DFlux Difference flux (in ADU/s unit)
33- 39 F7.3 s-1 e_DFlux Difference flux uncertainty (in ADU/s unit)
--------------------------------------------------------------------------------
Note (1): The filter i+z represents the EMCCD imager passband which roughly
corresponds to the combination of the SDSS i and z filters.
--------------------------------------------------------------------------------
Acknowledgements:
Jesper Skottfelt, skottfelt(at)astro.ku.dk
Daniel Bramich, dan.bramich(at)hotmail.co.uk
(End) Daniel Bramich [ESO, Germany], Patricia Vannier [CDS] 10-Oct-2013