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J/A+A/588/A128     Variable stars in globular clusters   (Figuera Jaimes+, 2016)

Exploring the crowded central region of ten Galactic globular clusters using EMCCDs. Variable star searches and new discoveries. Figuera Jaimes R., Bramich D.M., Skottfelt J., Kains N., Jorgensen U.G., Horne K., Dominik M., Alsubai K.A., Bozza V., Calchi Novati S., Ciceri S., D'Ago G., Galianni P., Gu S.-H., W Harpsoe K.B., Haugbolle T., Hinse T.C., Hundertmark M., Juncher D., Korhonen H., Mancini L., Popovas A., Rabus M., Rahvar S., Scarpetta G., Schmidt R.W., Snodgrass C., Southworth J., Starkey D., Street R.A., Surdej J., Wang X.-B., Wertz O. (The MiNDSTEp Consortium) <Astron. Astrophys. 588, A128 (2016)> =2016A&A...588A.128F (SIMBAD/NED BibCode)
ADC_Keywords: Clusters, globular ; Stars, variable ; Photometry Keywords: blue stragglers - galaxies: star clusters: general - globular clusters: general - stars: variables: RR Lyrae - novae, cataclysmic variables - instrumentation: high angular resolution Abstract: To obtain time-series photometry of the very crowded central regions of Galactic globular clusters. To obtain better angular resolution than has been previously achieved with conventional CCDs on ground-based telescopes. To complete, or improve, the census of the variable star population in those stellar systems. Images were taken using the Danish 1.54-m Telescope at the ESO observatory at La Silla in Chile. The telescope was equipped with an electron-multiplying CCD, and the short-exposure-time images obtained (ten images per second) were stacked using the shift-and-add technique to produce the normal-exposure-time images (minutes). Photometry was performed via difference image analysis. Automatic detection of variable stars in the field was attempted. The light curves of 12541 stars in the cores of ten globular clusters were statistically analysed to automatically extract the variable stars. We obtained light curves for 31 previously known variable stars (3 long-period irregular, 2 semi-regular, 20 RR Lyrae, 1 SX Phoenicis, 3 cataclysmic variables, 1 W Ursae Majoris-type and 1 unclassified) and we discovered 30 new variables (16 long-period irregular, 7 semi-regular, 4 RR Lyrae, 1 SX Phoenicis and 2 unclassified). Description: Observations were taken during 2013 and 2014 as part of an ongoing program at the 1.54m Danish telescope at the ESO observatory at La Silla in Chile that was implemented from April to September each year. table1.dat file contains the time-series I photometry for all the variables in the globular clusters studied in this work. We list standard and instrumental magnitudes and their uncertainties corresponding to the variable star identification, filter, and epoch of mid-exposure. For completeness, we also list the reference flux, difference flux, and photometric scale factor, along with the uncertainties on the reference and difference fluxes. File Summary:
FileName Lrecl Records Explanations
ReadMe 80 . This file stars.dat 98 61 Ephemerides and main characteristics of the variable stars in the field of globular clusters (tables 4-12) table1.dat 103 4697 Time series I photometry for all the variables studied in this work
Byte-by-byte Description of file: stars.dat
Bytes Format Units Label Explanations
1- 7 A7 --- Cluster Globular cluster name 9- 15 A7 --- Star Variable star ID 18- 19 I2 h RAh Right ascension (J2000) 21- 22 I2 min RAm Right ascension (J2000) 24- 29 F6.3 s RAs Right ascension (J2000) 31 A1 --- DE- Declination sign (J2000) 32- 33 I2 deg DEd Declination (J2000) 35- 36 I2 arcmin DEm Declination (J2000) 38- 42 F5.2 arcsec DEs Declination (J2000) 44- 55 F12.4 d Epoch ? Epoch used (HJD) 57- 66 F10.6 d Per ? Period 68- 75 F8.6 d e_Per ? rms uncertainty on Per 77- 81 F5.2 mag Imed ? Median I magnitude 83- 86 F4.2 mag Amp ? Peak-to-peak amplitude in the light curve, A(i'+z') 88- 90 I3 --- Nep Number of epoch 92- 98 A7 --- Type Classification of the variable
Byte-by-byte Description of file: table1.dat
Bytes Format Units Label Explanations
1- 7 A7 --- Cluster Globular cluster name 9- 15 A7 --- Star Variable star ID 17 A1 --- Filt [I] Observation filter 19- 31 F13.5 d HJD Heliocentric Julian date at mid-exposure 33- 38 F6.3 mag magst Standard magnitude 40- 44 F5.3 mag maginst Instrumental magnitude 46- 50 F5.3 mag e_maginst Magnitude uncertainty (standard or instrumental) 52- 62 F11.3 s-1 Fref Reference flux (in ADU/s unit) (1) 64- 74 F11.3 s-1 e_Fref Reference flux uncertainty (in ADU/s unit) 76- 87 F12.3 s-1 DFlux Difference flux (in ADU/s unit) (1) 89- 96 F8.3 s-1 e_DFlux Difference flux uncertainty (in ADU/s unit) 98-103 F6.4 --- p Photometric scale factor (1)
Note (1): Light curves for each star were constructed by calculating the total flux ftot(t) in adu/s at each epoch t from ftot(t)=fref+fdiff(t)/p(t) where fref is the reference flux (adu/s), fdiff(t) is the differential flux (adu/s) and p(t) is the photometric scalefactor (the integral of the kernel solution) Conversion to instrumental magnitudes was achieved using mins(t)=17.5-2.5log(ftot(t)) where mins(t) is the instrumental magnitude of the star at time t. Uncertainties were propagated in the correct analytical fashion.
Acknowledgements: Roberto Figuera, robertofiguera(at) History: * 30-Mar-2016: First on-line version * 13-Apr-2016: Error of period of NGC5286 V63 corrected
(End) Patricia Vannier [CDS] 01-Feb-2016
The document above follows the rules of the Standard Description for Astronomical Catalogues.From this documentation it is possible to generate f77 program to load files into arrays or line by line

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