CDROM/APJ/V412/P183 RR Lyrae Variables in M68 (Clement+ 1993) ================================================================================ The RR Lyrae Variables in the Globular Cluster M68 Christine M. Clement, Stephen Ferance, & Norman R. Simon <1993, ApJ, 412, 183> =1993ApJ...412..183C ================================================================================ Abstract: New observations, made with the Helen Sawyer Hogg telescope at Las Campanas, have been analyzed in a search for double-mode pulsators (RRd stars) in the metal-poor globular cluster, Messier 68. Of the 30 stars studied, nine have been identified as RRd stars; V33, which exhibited the characteristics of an RRd star in 1950, now appears to be an RRc star. Reliable periods and period ratios have been determined for six of the RRd stars. Masses for these RRd stars, calculated from fitting formulas given by Kovacs, Buchler, & Marom, range from 0.75 to 0.90 solar masses, depending on the assumed luminosity and metal abundance. These masses are in the same range as those for the RRd stars in M15, whose RRd sample resembles that of M68 very closely. Fourier parameters determined for the light curves of the M68 variables show that the RRc stars in the two clusters are also very similar. In particular, on the plot of phase parameter Phi_{31} with period, the M15 and M68 RRc samples are virtually indistinguishable. A comparison of the new M68 observations with observations made 40 yr ago shows that the periods of some of the stars have changed, but the 40 yr interval is too short for detecting period changes caused by evolutionary effects. Keywords: globular clusters: individual (M68) -- stars: variables: other (RR Lyrae) -- stars: oscillations File Summary: -------------------------------------------------------------------------------- File Name Lrecl Records Explanations -------------------------------------------------------------------------------- table3.dat 189 157 B Magnitudes for 30 RR Lyrae Variables in M68 table4.dat 36 30 Elements of the RR Lyrae Variables in M68 (based on the Las Campanas observations) -------------------------------------------------------------------------------- Byte-by-byte Description of file: table3.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 9 F9.3 day HJD Heliocentric Julian Date - 2400000 10- 15 F6.2 mag V1 V1 magnitude 16- 21 F6.2 mag V2 V2 magnitude 22- 27 F6.2 mag V3 V3 magnitude 28- 33 F6.2 mag V4 V4 magnitude 34- 39 F6.2 mag V5 V5 magnitude 40- 45 F6.2 mag V6 V6 magnitude 46- 51 F6.2 mag V7 V7 magnitude 52- 57 F6.2 mag V8 V8 magnitude 58- 63 F6.2 mag V9 V9 magnitude 64- 69 F6.2 mag V11 V11 magnitude 70- 75 F6.2 mag V13 V13 magnitude 76- 81 F6.2 mag V14 V14 magnitude 82- 87 F6.2 mag V15 V15 magnitude 88- 93 F6.2 mag V16 V16 magnitude 94- 99 F6.2 mag V18 V18 magnitude 100-105 F6.2 mag V19 V19 magnitude 106-111 F6.2 mag V20 V20 magnitude 112-117 F6.2 mag V21 V21 magnitude 118-123 F6.2 mag V22 V22 magnitude 124-129 F6.2 mag V23 V23 magnitude 130-135 F6.2 mag V24 V24 magnitude 136-141 F6.2 mag V25 V25 magnitude 142-147 F6.2 mag V26 V26 magnitude 148-153 F6.2 mag V28 V28 magnitude 154-159 F6.2 mag V29 V29 magnitude 160-165 F6.2 mag V30 V30 magnitude 166-171 F6.2 mag V31 V31 magnitude 172-177 F6.2 mag V32 V32 magnitude 178-183 F6.2 mag V33 V33 magnitude 184-189 F6.2 mag V34 V34 magnitude -------------------------------------------------------------------------------- Byte-by-byte Description of file: table4.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 A4 --- Star Star 5- 6 A2 --- Bailey Bailey type 7-11 I5 arcsec X *X position relative to the cluster center 12-16 I5 arcsec Y *Y position relative to the cluster center 17-25 F9.6 day P Primary period 26-31 F6.2 mag B Mean B magnitude 32-36 F5.2 mag A_B B amplitude -------------------------------------------------------------------------------- Notes for file: table4.dat -------------------------------------------------------------------------------- X, Y: Position relative to the cluster center according to Sawyer Hogg (1973, Publ. David Dunlap Obs., 3, No. 6) -------------------------------------------------------------------------------- ================================================================================ (End) Lee Brotzman [ADS] 23-Mar-1995