J/A+A/369/862 VI light curves of the variable stars in M92 (Kopacki, 2001)
Variable stars in the globular cluster M 92.
Kopacki G.
<Astron. Astrophys. 369, 862 (2001)>
=2001A&A...369..862K 2001A&A...369..862K
ADC_Keywords: Clusters, globular ; Stars, variable ; Photometry, CCD
Keywords: stars: population II - stars: variables: RR Lyr -
stars: variables: Cepheids - globular clusters: individual: M 92
Abstract:
Results of a search for variable stars in the central region of the
Oosterhoff II type globular cluster M 92 are presented. Out of the 28
variable and suspected variable stars listed in the Catalogue of
Variable Stars in Globular Clusters (Clement, 1997, Cat. V/97) only
two were not observed. Surprisingly, almost half of the observed
suspected variables did not show any evidence of variability. Only one
out of the 11 candidate RR Lyrae variables of Kadla et al.
(1983PZ.....21..827K 1983PZ.....21..827K) appeared to be variable. Moreover, variable V7,
until now classified as an RR Lyrae star with a period of about
0.515d, turned out to be of the BL Herculis type, with the period
approximately twice that long. In addition, six new variables were
found in the very core of the cluster: four of the RR Lyrae and the
remaining two of the SX Phoenicis type. RRc variable V11 shows changes
in the light curve shape. Due to the aliasing problems, however, we
can state only that this star is biperiodic. There is a possibility
that V11 belongs to the new group of recently discovered double-period
RRc variables pulsating in non-radial mode. Altogether, light curves
were obtained for 20 variable stars. The total number of known RR
Lyrae stars in M92 equals now 17, 11 of type RRab and the remaining 6,
RRc.
The CCD observations presented here were carried out at the Bialkow
station of the Wroclaw University Observatory with the same equipment
as that described by Kopacki & Pigulski (1995AcA....45..753K 1995AcA....45..753K). Two
6x4arcmin2 fields of view, one centred approximately on the core of
M92 and the other shifted about 2.5arcmin north and 2.6arcmin east,
were observed through V and Ic filters of the Johnson-Kron-Cousins
UBV(RI)c system.
The observations were carried out in two seasons: on 9 nights between
1998 July 20 and September 1, and on 17 nights between 2000 May 4 and
June 20. During the 1998 season only a few frames of the second field
were taken. The main field, centred on the core of the cluster, was
observed during both seasons.
Objects:
----------------------------------------------------------
RA (2000) DE Designation(s)
----------------------------------------------------------
17 17 07.3 +43 08 11 M 92 = NGC 6341
----------------------------------------------------------
File Summary:
--------------------------------------------------------------------------------
FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 40 20 Variable positions and periods
dao-i.dat 39 3004 DAOPHOT I-filter photometry for 13 variables
located well outside the cluster core
dao-v.dat 39 2910 DAOPHOT V-filter photometry for 13 variables
located well outside the cluster core
ism-i.dat 47 3642 Image Subtraction Method (ISM) I-filter
photometry of 14 variables
ism-v.dat 47 5003 Image Subtraction Method (ISM) V-filter
photometry of all observed variables
--------------------------------------------------------------------------------
See also:
V/97 : Updated 3rd Cat Variable Stars in Globular Clusters (Clement+ 1997)
Byte-by-byte Description of file: table1.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Var Variable designation (VNN, Cat. V/97) (G1)
6- 11 A6 --- Type Type of variability
15- 20 F6.2 arcsec Xpos Relative x position from cluster center (1)
24- 29 F6.2 arcsec Ypos Relative y position from cluster center (1)
32- 40 F9.7 d Per Period
--------------------------------------------------------------------------------
Note (1): Field center, 17 15.6 +43 12 (1950)
--------------------------------------------------------------------------------
Byte-by-byte Description of file: dao-i.dat dao-v.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Var Variable designation (VNN, Cat. V/97) (G1)
5- 17 F13.5 d HJD Heliocentric Julian Date
19- 25 F7.4 mag mag Magnitude (I for dao-i.dat, V for dao-v.dat)
27- 32 F6.4 mag e_mag Error of I magnitude
34- 39 F6.4 --- X Airmass
--------------------------------------------------------------------------------
Byte-by-byte Description of file: ism-i.dat ism-v.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- Var Variable designation (VNN, Cat. V/97) (G1)
6- 19 F14.6 d HJD Heliocentric Julian Date
23- 33 F11.4 --- Flux Flux (in arbitrary flux units, ADU/s)
(I for ism-i.dat, V for ism-v.dat)
39- 47 F9.4 --- e_Flux Error of flux (in arbitrary flux units, ADU/s)
--------------------------------------------------------------------------------
Global notes:
Note (G1): Cl* NGC 6341 SAW VNN in Simbad
--------------------------------------------------------------------------------
Acknowledgements: Grzegorz Kopacki
(End) Patricia Bauer [CDS] 05-Apr-2001