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T he Im pact ofLarge Scale Surveys on Pulsating Stars Research A SP C onference Series,Vol.X X X ,1999 L.Szabados, and D .K urtz,eds. W arsaw V ariab...
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T he Im pact ofLarge Scale Surveys on Pulsating Stars Research A SP C onference Series,Vol.X X X ,1999 L.Szabados, and D .K urtz,eds.

W arsaw V ariability Surveys

arXiv:astro-ph/9909362v2 22 Sep 1999

Janusz K aluzny C opernicus A stronom icalC enter,ul. B artycka 18,00-716 W arsaw & W arsaw U niversity O bservatory,A l. U jazdowskie 4,00-478 W arsaw, Poland A bstract. Four large/m edium size photom etric surveys are being conducted by W arsaw astronom ers: W arsaw -LC O survey of globular clusters,O G LE,D IR EC T and A SA S.In this contribution we provide short description of these projects and discuses brie y som e results obtained for pulsating variables.

1. W arsaw -LC O survey of globular clusters T he m ain goal of the survey is identi cation of detached eclipsing binaries in globularclusters.Such binariescan be used asexcellentdistance and age indicators(Paczynski1997). T hirteen globularclusterweresurveyed since1993. Starting w ith 1997 m ostofthe data are collected w ith the LasC am panas1.0m Swope telescope equipped w ith SITe 2048 3150 C C D giving eld ofview 14:4 22:8 arcm in2. Som e additionalfollow -up observations are conducted on the 2.5m du Pont telescope. For a given cluster the totallength ofm onitoring ranges from 30 to 150 hours w ith the m edian value around 70 hours. Precise and well sam pled light curves of R R Lyr and SX Phe stars are collected asa side resultofthe survey. T hese data becom e available through Internet (http://sirius.astrouw .edu.pl/~jka/) im m ediately after results for a given object are published. A list of m onitored clusters and num bers of variables identi ed in them are given in Table 1. W hile m onitoring M 55 we identi ed ve variables being likely m em bers ofthe Sagittarius dwarfgalaxy: two R R ab stars and three SX Phe variables.

1.1. N on radial pulsators in M 55 O ur sam ple of pulsating variables from the globular cluster M 55 includes ve new ly identi ed R R c stars. T he light curves of three of these stars exhibit changes in am plitude of over 0:1 m ag on the tim e scale shorter than a week. D etailed analysis indicates that observed changes are m ostprobably due to non radialpulsations (O lech et al.1999). A t least 12 out of24 SX Phe variables identi ed in M 55 show a presence of two or m ore periodicities in their light curves. Table 2 lists principalperiods,ratio P 1=P 2 and am plitudes for rst term s ofFourier series calculated for both periods after appropriate pre-w hitening was applied. T he derived values of P 1=P 2 indicate that we are dealing w ith non radial pulsations. In Fig. 1 1

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Janusz K aluzny Table 1.

Pulsating variables detected in the m onitored G C s

C luster ! C en N G C 288 N G C 4372 N G C 6397 N G C 6362 N G C 6752 M3 M4 M5 M 10 M 55 R u 106 Total

R R Lyr SX Phe R eference 132 34 K aluzny et al.(1997,1997a) 3 5 K aluzny et al.(1997b) 0 8 K aluzny et al.(1993) 1 2 K aluzny (1997) 18 4 M azur et al.(1999) 35 4 K aluzny et al.in prep 0 3 T hom pson et al.(1999) 42 1 K aluzny et al.(1998) 31 0 K aluzny et al.,in prep. 99 5 K aluzny et al.(1999a,1999b) O lech et al.(1999a) 1 3 K aluzny et al.,in prep. 13 O lech et al.(1999) 24 K aluzny et al.in prep. 12 3 K aluzny et al.(1995) 387 96

we present light curves obtained on two consecutive night for one ofthe m ultiperiodic SX Phe stars from M 55. W e note that also light curve ofan SX Phe variableidenti ed in M 3 by K aluzny etal.(1998)exhibitsevidence fornon radial pulsations ofthat star.

Table 2.

M ulti-m odalSX Phe stars in M 55 ID P1[d] P1/P2 A 11 19336 0.0388 1.017 0.020 19407 0.0415 1.023 0.048 25078 0.0593 1.034 0.027 25204 0.0370 1.026 0.014 31780 0.0487 1.075 0.035 34347 0.0394 1.054 0.033 34461 0.0438 1.023 0.025 19084 0.0382 0.974 0.029 12618 0.0358 1.049 0.017 15539 0.0370 1.067 0.014 19176 0.0452 1.239 0.053 19480 0.0367 1.029 0.026

A 21 0.009 0.019 0.018 0.006 0.010 0.012 0.011 0.012 0.008 0.007 0.024 0.017

1.2. M 3/M 55 dichotom y O ur sam ple of m onitored clusters includes M 3 and M 55. T hese objects have sim ilar m etallicities and exhibit sim ilar m orphology of their color-m agnitude

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16.65 16.7 16.75 16.8 5.7

5.8

5.9

6.7

6.8

6.9

16.65 16.7 16.75 16.8

Figure 1.

HJD - CONST Light curve for one ofm ulti-periodic SX Phe stars from M 55.

diagram s (in particular horizontal branches are sim ilar to each other). B oth cluster are rich in blue stragglers yet show very di erent relative frequencies of SX Phe stars. T his can be illustrated by com paring num bers ofblue stragglers for w hich we obtained good quality light curves w ith num bers ofidenti ed SX Phe stars: M 55: N B S = 40,N S X = 24,[Fe=H ]= 1:81 M 3: N B S = 25,N S X = 1, [Fe=H ]= 1:57 O urdata forM 3 show severalblue stragglerslocated inside instability strip w hich do not show any variability exceeding about 0.02 m ag in the V band. 1.3. H ow com plete is a sam ple of SX P he stars identi ed in G C s? Figure 2 show sfullam plitude versusperiod diagram for96 SX Phe starsidentied by our group in globular clusters. 53 out ofthese stars exhibit light curves w ith full range not exceeding 0:10 m ag in the V band. M any variables show am plitudes approaching detection lim it of our survey w hich,for m ost clusters reaches 0:02 0:03 m ag. T hat indicates that a signi cant fraction of SX Phe stars residing in surveyed cluster was m ost likely m issed. 2. O G LE -1 survey T heO G LE project(U dalskietal.1993;http://sirius.astrouw .edu.pl/~ftp/ogle/) is aim ed prim arily at detection and photom etry of m icrolensing events in the

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Figure 2. Full am plitude versus period for SX Phe stars identi ed during our survey ofglobular clusters. G alactic bulge and LM C /SM C .T he rst phase ofthe survey,refereed here as O G LE-1,wasconducted atLasC am panasO bservatory on the 1.0m Swope telescope during 4 seasons covering the period 1992-1995. A bout 2 106 stars in 20 15 15 arcm in2 elds toward the G alactic bulge were m onitored. 20 m icrolensing events were detected (W ozniak & Szym anski1998). Five partsofthe Variable Star C atalog were published,containing 2861 stars from the G alactic bulge (U dalskietal.1997a). T hatcatalog includes269 pulsating objects,m ostly R R Lyr stars. Severalside projects were attem pted by the O G LE-1 team . W e list here these of them w hich yield som e possibly interesting results for pulsating variables. M ateo et al. (1995) searched w ith success for R R Lyr stars belonging to the Sagittarius dwarfgalaxy. T hey reported V I photom etry for 7 variables from that galaxy. V band data for 226 R R Lyr stars from the Sculptor dSph galaxy were obtained by K aluzny et al.(1995a). T hat galaxy m ay prove to be an idealtarget for calibration ofthe lum inosity-m etallicity relation for R R Lyr stars. Population ofstars hosted by Sculptor show s signi cant range ofm etallicities and the interstellar reddening toward the galaxy is very low . K aluzny et al.(1996,1997) identi ed 34 SX Phe stars in the globular cluster ! C en. V band data for 141 R R Lyr stars (33 new ly identi ed) and Pop II C epheids in the sam e cluster were published by K aluzny et al.(1997a). In 1996 the O G LE project entered its second phase know n as O G LE-2 (U dalski, Szym anski & K ubiak 1997). O G LE-2 results are described in this volum e by Paczynski(1999).

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3. D IR E C T T heD IR EC T project(http://cfa-harvard.edu/~kstanek/D IR EC T /)aim satdeterm ination of distance to M 31 and M 33 galaxies by using detached eclipsing binaries and C epheids. T he projectis currently conducted by a group including astronom ers from C fA and W arsaw . A bout 200 nights on the 1.2m FLW O and 1.3 M D M telescopes were used between Septem ber 1996 and N ovem ber 1999 to search both galaxiesforvariablessuitable form ore detailed follow -up. So far ve catalogs ofvariables in M 31 were released (K aluzny et al.1998a,1999;Stanek et al. 1998, 1999; M ochejska et al. 1999). 410 variables (m ost of them new ) were identi ed,including 206 C epheids and 48 eclipsing binaries. Photom etry ofm any RV Tau and LPV starswasalso reported. T he rem aining catalogs shall be released overthe com ing year. Som e resultsofD IR EC T concerning C epheids are presented in this volum e by Sasselov (1999)

4. A SA S A SA S (the A llSky A utom ated Survey;Pojm anski1997; http://w w w .astrouw .edu.pl/~gp/asas) is a project w hich ultim ate goal is low costm onitoring ofthe w hole sky on a nightly basisdow n to about15 m agnitude. A prototype robotic telescope consisting ofthe 135m m telephoto lens,o -theshelf C C D cam era (512 x 768 pixels) and sm allautom ated m ount was set up at the Las C am panas O bservatory in A pril 1997. It has been m onitoring 24 selected elds covering about 150 deg2 ofthe sky. U sefullphotom etry in the I band was obtained for over 45000 stars brighter than 13 m agnitude. T he rst two m onth ofobservation revealed 126 shortperiod variables (Pojm anski1998), ofw hich 70 % were previously unknow n. T he catalogue includes severalnew ly identi ed R R Lyrstarsand C epheids.In 1998 the survey wasextended to cover additional150 deg2 and the updated version ofthe catalogue w illinclude data for a large num ber ofpulsating stars w ith periods up to 300 days (Pojm anski 1999, private com m unication). A t the end of1999 two new robotic telescopes w ith 2K 2 C C D ’s w illbe installed at Las C am panas. A cknow ledgm ents. JK was supported by the Polish C om m ittee ofScienti c R esearch through grant2P03D 000.00 and by N SF grantsA ST -9528096 and A ST -9819787 to B ohdan Paczynski.

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