J/MNRAS/443/2492 {Delta}a observations of 3 globular clusters (Paunzen+, 2014) ================================================================================ The first {Delta}a observations of three globular clusters. Paunzen E., Iliev I.KH., Pintado O.I., Baum H., Maitzen H.M., Netopil M., Onehag A., Zejda M., Fraga L. =2014MNRAS.443.2492P ================================================================================ ADC_Keywords: Clusters, globular ; Photometry Keywords: techniques: photometric - stars: chemically peculiar - stars: horizontal branch - globular clusters: individual: NGC 104 - globular clusters: individual: NGC 6205 - globular clusters: individual: NGC 7099 Abstract: Globular clusters are main astrophysical laboratories to test and modify evolutionary models. Thought to be rather homogeneous in their local elemental distribution of members, results suggest a wide variety of chemical peculiarities. Besides different main sequences, believed to be caused by different helium abundances, peculiarities of blue horizontal-branch stars and on the red giant branch were found. This whole zoo of peculiar objects has to be explained in the context of stellar formation and evolution. The tool of {Delta}a photometry is employed in order to detect peculiar stars in the whole spectral range. This three filter narrow-band system measures the flux distribution in the region from 4900 to 5600{AA} in order to find any peculiarities around 5200{AA}. It is highly efficient to detect classical chemically peculiar stars of the upper main sequence, Be/Ae, shell and metal-weak objects in the Milky Way and Magellanic Clouds. We present {Delta}a photometry of 2266 stars from 109 individual frames for three globular clusters (NGC 104, NGC 6205, and NGC 7099). A comparison with published abundances, for three horizontal-branch stars, only, yields an excellent agreement. According to the 3{sigma} detection limit of each globular cluster, about 3 percent of the stars lie in abnormal regions in the diagnostic diagrams. The first observations of three widely different aggregates give very promising results, which will serve as a solid basis for follow-up observations including photometric as well as spectroscopic studies. Description: The observations of the three globular clusters were performed at two different sites: * 2m Ritchey-Chretien-Coude telescope [Bulgarian National Astronomical Observatory (BNAO, Rozhen)], direct imaging, SITe SI003AB 1024x1024-pixel CCD, 5' field of view, 1pixel=0.32arcsec, and * 2.15m telescope [El Complejo Astronomico El Leoncito (CASLEO)], direct imaging with focal reducer, TEK-1024 CCD, 9.5-arcmin field of view, 1pixel=0.813arcsec. Objects: ---------------------------------------------------------- RA (ICRS) DE Designation(s) ---------------------------------------------------------- 00 24 05.36 -72 04 53.2 NGC 104 = 47 Tuc 16 41 41.63 +36 27 40.7 NGC 6205 = M 13 21 40 22.12 -23 10 47.5 NGC 7099 = M 30 ---------------------------------------------------------- File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file ngc104.dat 73 1107 NGC 104 complete photometric data of the programme stars ngc6205.dat 73 365 NGC 6205 complete photometric data of the programme stars ngc7099.dat 73 794 NGC 7099 complete photometric data of the programme stars -------------------------------------------------------------------------------- See also: II/248 : UBV photometry and proper motions in M13 (Kadla, 1966) J/AJ/112/1061 : BV photometry of NGC 7099 (Bergbusch 1996) J/AJ/113/669 : Stars in M13 core (Cohen+ 1997) J/AJ/116/1757 : M30 UBV photometry (Guhathakurta+, 1998) J/ApJ/518/262 : CCD VIc Photometry of M30 Stars (Sandquist+, 1999) J/A+A/398/541 : VI light-curves of the variable stars in M13 (Kopacki+, 2003) J/AJ/129/303 : Abundances of stars in M3 and M13 (Cohen+, 2005) J/A+A/462/L9 : Radial velocities in NGC 7099 (Scarpa+, 2007) J/ApJ/657/286 : Chandra X-ray sources in M30 (NGC 7099) (Lugger+, 2007) J/AJ/143/50 : White dwarfs in 47 Tuc (NGC 104) with HST (Woodley+, 2012) J/ApJ/754/L38 : Abundances and radial velocities of M13 giants (Johnson+, 2012) J/A+A/555/A36 : VrI light curves of NGC7099 variables (Kains+, 2013) J/ApJ/772/148 : Blue straggler and red giant stars in M30 (Lovisi+, 2013) J/A+A/566/A58 : Radial velocities in M3, M13, and M92 (Kamann+, 2014) J/ApJ/780/94 : Abundances of red giants in 47 Tuc (Cordero+, 2014) Byte-by-byte Description of file: ngc104.dat ngc6205.dat ngc7099.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- Seq Star sequential number within the cluster 6- 7 I2 h RAh Right ascension (J2000) 9- 10 I2 min RAm Right ascension (J2000) 12- 16 F5.2 s RAs Right ascension (J2000) 18 A1 --- DE- Declination sign (J2000) 19- 20 I2 deg DEd Declination (J2000) 22- 23 I2 arcmin DEm Declination (J2000) 25- 28 F4.1 arcsec DEs Declination (J2000) 30- 35 F6.3 mag g1-y [-1.3/0.3] g1-y colour index (1) 37- 41 F5.3 mag e_g1-y [0/0.05] rms uncertainty on g1-y 43- 47 F5.3 mag amag [0.2/1.0] a index (1) 49- 53 F5.3 mag e_amag [0/0.05] rms uncertainty on amag 55- 60 F6.3 mag Da [-0.09/0.11] Intrinsic peculiarity index {Delta}a (2) 62- 67 F6.3 mag Vmag V magnitude 69- 73 F5.3 mag e_Vmag rms uncertainty on Vmag -------------------------------------------------------------------------------- Note (1): a index defined as (Maitzen 1976A&A....51..223M) a = g2-(g1+y)/2, from g1 = {lambda}_c_=5007{AA}, FWHM=126{AA}), g2 = {lambda}_c_=5199{AA}, FWHM=95{AA}) and y = {lambda}_c_=5466{AA}, FWHM=108{AA}). Note (2): defined as the difference between the a-value of the studied star and a_0_, a-value for non-peculiar star of the same colour. -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Patricia Vannier [CDS] 16-Apr-2015