The Clusters AgeS Experiment (CASE): Variable Stars in the Globular Cluster M55
Kaluzny, J.; Thompson, I. B.; Krzeminski, W.; Zloczewski, K.
Abstract:
We report time-series photometry for 55 variable stars located in the central part of the globular cluster M55. The sample includes 28 newly identified objects of which 13 are eclipsing binaries. Three of these are detached systems located in the turn-off region on the cluster color–magnitude diagram. Two of them are proper motion (PM) members of M55 and are excellent candidates for a detailed follow-up study aimed at a determination of the cluster age and distance. Other detached binaries are located along the unevolved part of the cluster main sequence. Most of the variable stars are cluster blue straggler stars. This group includes 35 SX Phe stars, two contact binaries, and one semi-detached binary. V60 is a low mass, short period Algol with the less massive and cooler component filling its Roche lobe. The more massive component is an SX Phe variable star. The orbital period of V60 increases at a rate of dP/P = 3.0×10−9. In addition to numerous variable blue stragglers we also report the detection of two red stragglers showing periodic variability. Both of these are PM members of M55. We note and discuss the observed paucity of contact binaries among unevolved main sequence stars in M55 and NGC 6752. This apparent paucity supports an evolution model in which the formation of contact binaries is triggered by stellar evolution at the main-sequence turn off.

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The paper (PDF) "The Clusters AgeS Experiment (CASE): Variable Stars in the Globular Cluster M55"
Kaluzny, J.; Thompson, I. B.; Krzeminski, W., Zloczewski, K.
2010, Acta Astronomica, vol 60, p. 245-260
Template image
in V-band (FITS)
From 1-m Swope telescope.
Template image
in V-band (FITS)
From 2.5-m duPont telescope.
refbv.cm2 Color-magnitude V/B-V data for the observed field.
XY coordinates correspond to the image 'refv.fits'.
Some objects have multiple entries.
refv.radec Rectangular and equatorial coordinates for stars identified in the field defined by 'refv.fits'.
IDs for stars are the same as in 'refbv.cm2'.


Table 1:Basic properties of variable stars in M55
Star Xa Ya Period [days] Vmax Δ V B-V PMb Typec V light-curved B light-curved Remarks
V16 746.66 1421.89 0.05341898(1) 16.974 0.006 0.357 Y SX V16.dat B16.dat
V17 678.81 1795.95 0.04126184(1) 17.191 0.018 0.332 Y SX V17.dat B17.dat
V18 815.77 1400.00 0.04655539(1) 16.999 0.011 0.318 Y SX V18.dat B18.dat
V19 1086.89 1470.69 0.03823603(2) 17.326 0.012 0.309 Y SX V19.dat B19.dat
V20 1164.91 1655.64 0.03321202(5) 17.018 0.033 0.342 Y SX V20.dat B20.dat
V21 1065.60 1757.35 0.13559137(1) 15.775 0.010 0.425 Y SX V21.dat B21.dat
V22 781.91 1906.65 0.04563898(1) 16.806 0.123 0.296 Y SX V22.dat B22.dat
V23 1262.01 1315.61 0.04140053(1) 17.231 0.018 0.32 Y SX V23.dat B23.dat
V24 1448.94 1340.87 0.04181954(4) 17.062 0.002 0.318 Y SX V24.dat B24.dat
V25 1269.19 1381.14 0.09853144(1) 15.882 0.285 0.328 Y SX V25.dat B25.dat
V26 1399.78 1550.10 0.0820104(2) 16.110 0.047 0.385 Y SX V26.dat B26.dat
V27 1191.26 1618.82 0.0410321(1) 17.131 0.010 0.34 Y SX V27.dat B27.dat
V29 1534.99 1332.07 0.0343117(2) 20.681 0.090 0.161 - SX V29.dat B29.dat
V31 987.28 1596.34 0.03884781(5) 17.278 0.016 0.35 Y SX V31.dat B31.dat
V32 1070.50 1680.59 0.0414872(1) 16.953 0.037 0.322 Y SX V32.dat B32.dat
V33 1173.71 1877.97 0.0573482(6) 16.400 0.055 0.325 Y SX V33.dat B33.dat
V34 981.59 1967.51 0.03701723(6) 17.238 0.011 0.304 Y SX V34.dat B34.dat
V35 1306.23 1223.26 0.0486828(2) 16.586 0.015 0.308 Y SX V35.dat B35.dat
V36 1356.80 1436.94 0.03939643(2) 16.741 0.024 0.295 Y SX V36.dat B36.dat
V37 1316.49 1568.61 0.04379779(6) 16.949 0.017 0.29 Y SX V37.dat B37.dat
V38 1049.56 1639.16 0.03817392(7) 16.709 0.018 0.399 Y SX V38.dat B38.dat
V39 654.75 2162.31 0.0358108(1) 17.209 0.012 0.286 SX V39.dat B39.dat
V40 964.48 1277.94 0.03697678(3) 17.217 0.010 0.317 Y SX V40.dat B40.dat
V41 928.32 1668.76 0.09033409(1) 16.536 0.040 0.29 Y SX V41.dat B41.dat
V42 1058.40 1522.33 0.0366654(2) 17.180 0.018 0.243 Y SX V42.dat B42.dat
V43 759.65 1720.59 19.1 0.68 Y CV V43.dat B43.dat
V44 706.90 1614.45 2.166123(5) 17.843 0.25 0.538 Y EA V44.dat B44.dat
V45 756.80 1499.02 0.03083606(5) 16.330 0.004 0.242 Y SX V45.dat B45.dat
V46 835.01 1650.99 0.31941843(1) 16.462 0.35 0.260 U EW V46.dat B46.dat
V47 877.85 1594.23 0.0249482(3) 16.786 0.003 0.267 Y SX V47.dat B47.dat
V48 930.48 1531.12 0.0330509(3) 16.113 0.024 0.265 Y SX V48.dat B48.dat
V49 657.98 1633.98 1.95902(4) 19.15 0.47 1.06 N EA V49.dat B49.dat
V50 615.78 1839.75 17.08 0.30 0.90 N ? V50.dat B50.dat
V51 688.40 1173.48 0.4522456(4) 18.445 0.07 0.269 N EW V51.dat B51.dat
V52 822.60 1802.37 0.0276799(3) 16.153 0.003 0.206 SX V52.dat B52.dat
V53 859.45 1789.74 0.32524682(1) 16.545 0.05 0.251 Y EW V53.dat B53.dat
V54 1685.23 1483.13 9.26917(1) 18.300 0.36 0.56 Y EA V54.dat B54.dat
V55 784.02 1439.74 0.0323921(1) 17.228 0.002 0.387 Y SX V55.dat B55.dat
V56 985.24 1512.91 0.29186192(1) 17.74 0.36 0.51 U EW V56.dat B56.dat
V57 1030.62 1451.01 0.02185877(8) 16.644 0.003 0.25 Y SX V57.dat B57.dat
V58 1048.73 1475.98 8.6205 18.01 0.20 0.55 U EA V58.dat B58.dat
V59 897.19 1632.57 0.02624428(7) 16.650 0.007 0.247 SX V59.dat B59.dat
V60 1084.56 1572.21 1.1830214(7) 16.83 1.78 0.41 Y EA V60.dat B60.dat
V61 993.85 1805.68 0.03490324(9) 17.305 0.008 0.315 Y SX V61.dat B61.dat
V62 1325.04 1063.96 1.2358474(5) 20.26 0.49 0.82 Y EA V62.dat B62.dat
V63 1335.59 1404.18 0.05308522(9) 16.399 0.002 0.308 Y SX V63.dat B63.dat
V64 1396.29 1498.07 12.945 17.02 0.18 0.77 Y ? V64.dat B64.dat
V65 1275.18 1746.66 5.587538 17.22 0.19 0.88 Y ? V65.dat B65.dat
V66 1423.61 1828.07 0.5496634(7) 20.22 0.41 0.92 U EA V66.dat B66.dat
V67 1444.33 1960.05 0.121062 18.31 0.12 0.53 Y ? V67.dat B67.dat
V68 981.81 1974.48 0.53857748(3) 20.65 0.52 0.24 U EA V68.dat B68.dat
V69 1195.61 1990.05 0.0450622(2) 17.027 0.007 0.323 Y SX V69.dat B69.dat
V70 1807.49 1077.97 0.22287334(4) 19.40 0.72 0.76 U EW V70.dat B70.dat
V71 916.84 1751.85 8.0399 16.87 0.69 0.13 Y ? V71.dat B71.dat
a Pixel coordinate in the template image from the Swope telescope
b Proper motion membership status — Y - member, N - field star, U - uncertain.
c Variable type

EW - contact binary; EB - close ecppsing binary; EA - detached ecppsing binary;

SX - SX-Phenicis type pulsator; CV - cataclismic variable

d Data columns:
  1. HJD - 2 450 000.0
  2. magnitude
  3. error of magnitude (dummy points are maked with the error=9.999)
  4. phase
e X - likely counterpart of an X-ray source Ch-nnnnnnn.n-nnnnnn cataloged by Heinke et al. (2005)
f OGLE-SMC-RRLYR-nnnn = stars cataloged by Soszynski et al. (2010)
g OGLE-SMC-LPV-nnnnn = stars cataloged by Soszynski et al. (2011)
h independently discovered by Poleski (2012)