Peremennye Zvezdy (Variable Stars) 28, No. 9, 2008 Received 28 October; accepted 15 December.
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Sternberg Astronomical Institute, Moscow State University, Russia; e-mail: berdnik@sai.msu.ru
Institute of Astronomy, Russian Academy of Sciences, Russia; e-mail: pastukhova@sai.msu.ru
We present a list of 109 probable RS CVn variables among stars in the ASAS-3 catalog with Population II Cepheid classification as the main one or an alternative one. These stars are identified with X-ray sources and have light curves (from ASAS-3 data) in no contradiction with the suggested RS CVn classification. |
Classical Cepheids are very important as distance indicators as well as for studies of stellar evolution, structure and kinematics of our Galaxy. An extensive program of Cepheid studies is under way in the Sternberg Astronomical Institute and Institute of Astronomy (Russian Academy of Sciences) (Samus et al. 2007). Population II Cepheids are also of astrophysical interest, and some of them enter our programs of observations. We are interested in the largest possible volume of our Cepheid sample and in clear separation of Population I and Population II Cepheids from objects of other nature resembling them by periods and light-curve shapes.
Recently, thousands of new variable stars were discovered in the ASAS-3 automatic survey (Pojmanski 2002). Many of them have ASAS-3 classification as Cepheids or possible Cepheids. However, our trial observations of objects from the ASAS-3 variable star catalog revealed that some stars had photometric behavior incompatible with their Cepheid classification. Most of them can be identified with Galactic X-ray sources and thus, most probably, are RS CVn variables.
In this study, we analyzed the complete list of stars in the ASAS-3 variable-star catalog with Population II (CW) classification as the main one or as an alternative possibility. Among stars we were able to identify with known X-ray sources of the following catalogs: 1RXS (Voges et al. 1999, 2000), 1RXH (ROSAT Consortium 2000), 1WGA (White et al. 2000), and 2E (Harris 1994), 109 objects have light curves (from ASAS-3 data) permitting us to consider them RS CVn variables.
The list of our RS CVn candidates is presented in the Table. The lines of the Table contain: coordinates (right ascension and declination) from the 2MASS catalog; the X-ray catalog identification; the ASAS-3 catalog identification; the star's variability period from the ASAS-3 catalog; our revised period value (if available); the GCVS/NSV designation and GCVS type (if available). The revised periods are often twice shorter than those suggested in the ASAS-3 catalog.
Note that the star ASAS-3 032406+0729.5 is probably an eclipsing RS CVn star, the only case in our sample. Alternatively, it could even be an EW variable with the period 067645. The ASAS-3 data give no possibility to rule out any of these options.
The star ASAS-3 082250+0151.6 (NSV 17868) was correctly identified as an RS CVn variable in Henry et al. (1995). The period given for this star in the Table is from the cited paper, we retained the star in the Table for the sake of completeness.
Acknowledgements: The authors gratefully acknowledge support for this work by research funding awarded through the Russian Foundation of Basic Research (RFBR, grants 07-02-00380 and 08-02-00375), through the Program of Support for Leading Scientific Schools of Russia, and through the program "Origin and Evolution of Stars and Galaxies" of the Presidium of Russian Academy of Sciences. Thanks are due to the Editor, N.N. Samus, for valuable suggestion towards improvement of the manuscript.
References:
Harris, D.E., Forman, W., Gioa, I.M., et al., 1994, VizieR On-line Data Catalog: IX/13
Henry, G.W., Fekel, F.C., Hall, D.S., 1995, Astron. J., 110, 2926
Pojmanski, G., 2002, Acta Astron., 52, 397
ROSAT Consortium, 2000, VizieR On-line Data Catalog: IX/28A
Samus, N.N., Antipin, S.V., Berdnikov, L.N., et al., 2007, Odessa Astron. Publ., 20, 197
Voges, W., Aschenbach, B., Boller, Th., et al., 1999, VizieR On-line Data Catalog: IX/10A
Voges, W., Aschenbach, B., Boller, Th., et al., 2000, VizieR On-line Data Catalog: IX/29
White, N.T., Giommi, P., Angelini, L., 2000, VizieR On-line Data Catalog: IX/31
2MASS coordinates | X-ray Identification | ASAS-3 | , | GCVS, | |
(2000.0) | ASAS-3 | NSV | |||
00220344 +130335 2 | 1RXS J002204.0+130351 | 002203+1303.6 | 3462 | ||
00 41 34.48 +21 18 02.6 | 1RXS J004133.3+211817 | 004135+2118.1 | 5.882 | 2941 | |
01 05 06.40 +09 35 08.3 | 1RXS J010506.8+093505 | 010507+0935.1 | 9.98 | ||
01 05 15.94 +01 59 14.2 | 1RXH J010516.0+015915 | 010516+0159.2 | 6.9058 | ||
01 21 39.26 +25 17 47.4 | 1RXS J012140.1+251743 | 012139+2517.8 | 12.994 | ||
01 22 15.44 +20 21 30.2 | 1RXS J012215.4+202139 | 012216+2021.5 | 10.21 | ||
01 36 27.81 +25 08 35.6 | 1RXS J013628.0+250835 | 013628+2508.5 | 1.335951 | ||
02 20 32.40 +20 07 28.7 | 1RXS J022033.7+200759 | 022032+2007.5 | 18.36 | 9.18 | |
02 42 36.22 +07 17 26.1 | 2E 647 | 024236+0717.4 | 52.84 | ||
03 12 34.29 +09 44 57.0 | 1RXS J031232.3+094426 | 031234+0944.9 | 12.419 | 6.209 | |
03 24 05.62 +07 29 27.0 | 1RXS J032405.3+072926 | 032406+0729.5 | 40.89 | 20.43 | |
04 18 10.78 +23 17 04.9 | 1RXS J041811.1+231700 | 041811+2317.1 | 1.8969 | 1.8787 | NSV 15941 |
04 30 49.18 +21 14 10.6 | 1RXS J043049.5+211356 | 043049+2114.2 | 2.835 | ||
04 42 18.61 +01 17 39.9 | 1RXS J044219.2+011741 | 044219+0117.7 | 8.771 | ||
04 48 57.99 +19 14 56.1 | 1RXS J044858.4+191500 | 044858+1915.0 | 16.055 | ||
05 00 49.28 +15 27 00.6 | 1RXS J050049.1+152658 | 050049+1527.0 | 2.763 | ||
05 13 05.82 +08 51 31.4 | 1RXS J051305.8+085122 | 051306+0851.5 | 4.0182 | ||
05 13 19.01 +01 34 47.0 | 1RXS J051319.1+013525 | 051319+0134.8 | 7.431 | 3.656 | |
05 22 54.79 +08 58 04.7 | 1RXS J052254.9+085803 | 052255+0858.1 | 5.941 | ||
05 36 30.99 +11 19 40.2 | 1RXS J053632.0+111935 | 053631+1119.7 | 12.285 | ||
05 39 14.80 +00 31 13.4 | 1RXS J053914.8+003110 | 053915+0031.2 | 8.105 | 4.0525 | |
05 39 27.10 -03 47 04.4 | 1RXS J053927.0-034655 | 053927-0347.1 | 1.92952 | ||
05 39 58.77 +07 08 30.5 | 1RXS J053959.1+070832 | 053959+0708.5 | 2.1133 | ||
05 43 52.80 -02 50 43.5 | 1RXS J054353.4-025038 | 054353-0250.7 | 1.73393 | 6.64 | |
07 16 50.45 +21 45 00.1 | 1RXS J071650.8+214509 | 071650+2145.0 | 80.7 | 40.35 | |
08 22 49.96 +01 51 33.6 | 1RXS J082250.2+015152 | 082250+0151.6 | 6.6 | 3.296 | NSV 17868 |
08 35 26.86 +24 15 39.6 | 1RXS J083526.4+241538 | 083527+2415.7 | 20.74 | ||
08 49 19.81 +05 52 29.8 | 1RXS J084919.7+055234 | 084920+0552.5 | 14.593 | 7.2965 | |
10 12 17.64 -03 44 40.4 | 1RXS J101217.2-034442 | 101218-0344.8 | 21.535 | ||
10 13 23.88 +12 08 45.8 | 1RXS J101324.2+120849 | 101324+1208.7 | 34.23 | 34.00 | EQ Leo (LB:) |
10 30 02.68 -00 47 32.0 | 1RXS J103002.8-004726 | 103003-0047.5 | 30.74 | 15.37 | |
10 39 59.00 +13 27 22.1 | 1RXS J103958.4+132733 | 103959+1327.4 | 6.198 | 6.217 | |
10 59 20.11 +04 53 17.4 | 1RXS J105920.5+045308 | 105920+0453.3 | 2.1155 | 17.50 | |
11 56 51.66 +08 27 21.9 | 1RXS J115651.8+082726 | 115652+0827.3 | 4.4821 | 4.402 | |
12 03 15.65 +16 06 37.7 | 1RXS J120316.6+160634 | 120316+1606.6 | 3.5274 | 3.530 | |
12 15 30.72 -39 48 42.6 | 1RXS J121527.9-394843 | 121531-3948.7 | 5.067861 | ||
12 16 52.98 +05 41 26.2 | 1WGA J1216.8+0541 | 121653+0541.4 | 13.94847 | 14.26 | |
12 19 06.45 +18 21 21.2 | 1RXS J121906.1+132119 | 121906+1821.4 | 5.653 | 5.658 | FN Com (LB) |
12 25 49.91 +09 45 46.6 | 1RXS J1225.8 +0945 | 122550+0945.8 | 7.736 | 7.718 | |
12 48 48.20 +14 45 32.3 | 1RXS J124848.7+144531 | 124848+1445.5 | 2.45647 | 2.455 | |
12 50 51.67 -51 56 36.1 | 1RXS J125051.3-515655 | 125051-5156.6 | 2.76116 | ||
13 05 29.53 +12 49 45.1 | 1RXS J130528.5+124925 | 130529+1249.6 | 3.6885 | ||
13 12 53.57 +08 23 35.4 | 1RXS J131253.3+082341 | 131254+0823.6 | 9.886 | 9.870 | NSV 19563 |
13 56 49.20 +24 29 27.4 | 1RXS J135649.4+242941 | 135649+2429.4 | 1.08555 | 12.23 | |
14 07 01.16 -42 33 00.7 | 1RXS J140657.7-423325 | 140701-4233.0 | 1.693846 | ||
15 02 07.25 -12 01 51.7 | 1RXS J150206.0-120206 | 150207-1201.9 | 2.684136 | 2.6831 | |
15 02 47.37 +22 18 20.7 | 1RXS J150246.8+221821 | 150248+2218.4 | 7.395547 | ||
15 17 21.23 -19 00 59.0 | 1RXS J151720.9-190103 | 151721-1901.0 | 11.33163 | 11.38 | |
15 22 16.27 -26 52 25.2 | 1RXS J152216.6-265215 | 152216-2652.4 | 6.835125 | ||
15 23 46.11 -00 44 24.7 | 1RXS J152346.8-004434 | 152346-0044.4 | 11.561 | 11.685 | |
15 35 07.61 -08 49 49.5 | 1RXS J153506.2-085002 | 153508-0849.8 | 39.44995 | 19.725 | |
15 36 34.46 +12 19 31.5 | 1RXS J153633.6+121919 | 153634+1219.5 | 5.4026 | 5.407 | |
15 48 40.95 -03 10 44.2 | 1RXS J154840.5-031106 | 154841-0310.7 | 3.8587 | 1.9236 | |
15 51 07.58 +11 16 18.8 | 1RXS J155108.0+111559 | 155108+1116.3 | 6.606 | 6.603 | |
15 54 44.94 -07 52 04.5 | 1RXS J155442.6-075142 | 155445-0752.0 | 5.617744 | 5.624 | |
15 55 06.71 -19 46 31.3 | 1RXS J155506.8-194638 | 155507-1946.5 | 4.877127 | 4.880 | |
15 57 06.80 -87 29 49.0 | 1RXS J155706.8-872949 | 155703-8730.1 | 3.115622 | 3.114 | |
16 02 53.96 -20 22 48.1 | 1RXS J160254.9-202242 | 160254-2022.8 | 1.95349 | ||
16 07 04.28 +02 38 24.4 | 1RXS J160704.4+023823 | 160704+0238.4 | 3.7836 |
2MASS coordinates | X-ray Identification | ASAS-3 | , | GCVS, | |
(2000.0) | ASAS-3 | NSV | |||
16093805 +055237 2 | 1RXS J160938.4+055238 | 160938+0552.6 | 1085670 | PX Ser (LB:) | |
16 19 59.93 +04 36 46.8 | 1RXS J161959.5+043636 | 162000+0436.8 | 1.438 | 1437 | |
16 23 07.83 -23 00 59.7 | 1RXS J162308.8-230046 | 162308-2301.0 | 8.107618 | 4.0538 | |
16 24 02.03 -29 10 44.9 | 1RXS J162402.5-291042 | 162402-2910.8 | 4.018315 | ||
16 24 23.39 +04 45 22.1 | 1RXS J162423.5+044507 | 162423+0445.4 | 9.929 | 4.963 | |
16 25 10.00 +05 14 54.0 | 1RXS J162509.9+051446 | 162510+0514.9 | 3.4482 | ||
16 49 42.93 +22 20 03.8 | 1RXS J164943.4+222009 | 164943+2220.1 | 11.586 | ||
16 53 57.72 +07 34 50.4 | 1RXS J165357.6+073450 | 165358+0734.8 | 11.58509 | 11.510 | |
17 03 13.52 +24 53 21.0 | 1RXS J170313.2+245332 | 170313+2453.3 | 11.565 | ||
18 46 52.56 -62 10 36.7 | 1RXS J184657.3-621037 | 184653-6210.3 | 5.373217 | NSV 24575 | |
19 05 25.05 -78 26 44.3 | 1RXS J190524.3-782658 | 190525-7826.8 | 2.8037 | ||
19 11 34.70 -34 35 08.8 | 1RXS J191134.7-343500 | 191135-3435.2 | 3.378621 | ||
19 17 43.75 -44 00 16.4 | 1RXS J191744.3-440021 | 191743-4400.3 | 9.424 | ||
19 39 06.45 -25 44 05.7 | 1RXS J193906.7-254358 | 193906-2544.1 | 12.745 | 12.76 | |
20 01 51.98 -17 52 00.9 | 1RXS J200152.7-175211 | 200152-1752.0 | 6.579693 | ||
20 05 56.41 -32 16 59.2 | 1RXS J200556.1-321651 | 200556-3217.0 | 8.307 | ||
20 09 55.06 -45 59 45.2 | 1RXS J200955.9-460002 | 200955-4559.8 | 10.705 | ||
20 19 02.95 -14 02 04.5 | 1RXS J201903.1-140205 | 201903-1402.1 | 11.722 | 11.794 | |
20 28 42.27 -09 43 17.0 | 1RXS J202843.1-094217 | 202842-0943.3 | 2.40015 | 2.402 | |
20 36 08.30 -36 07 11.5 | 1RXS J203608.6-360713 | 203609-3607.2 | 2.1256 | ||
20 41 42.25 -22 19 20.5 | 1RXS J204142.6-221910 | 204142-2219.4 | 5.2987 | 5.3080 | NSV 25239 |
20 44 30.10 -00 28 45.5 | 1RXS J204430.1-002845 | 204430-0028.6 | 5.874621 | ||
20 48 59.59 -06 44 54.4 | 1RXS J204859.5-064453 | 204900-0644.9 | 1.93626 | ||
20 49 22.86 +06 47 39.3 | 1RXS J204924.0+064737 | 204923+0647.6 | 8.958 | ||
21 01 21.54 -49 33 04.6 | 1RXS J210121.2-493322 | 210121-4933.1 | 6.235 | 6.238 | |
21 10 44.82 +16 23 23.7 | 1RXS J211044.8+162312 | 211045+1623.4 | 10.576 | 10.590 | |
21 10 54.19 +08 58 16.4 | 1RXS J211053.1+085810 | 211055+0858.2 | 13.988 | ||
21 13 05.27 -17 29 12.6 | 1RXS J211305.8-172912 | 211305-1729.2 | 4.9274 | 4.820 | |
21 16 32.71 +19 42 13.0 | 1RXS J211633.6+194214 | 211633+1942.2 | 15.246 | ||
21 20 44.09 -54 37 59.3 | 1RXS J212043.3-543801 | 212044-5438.0 | 2.39861 | 2.3988 | |
21 41 05.79 +02 22 15.4 | 1RXS J214108.2+022239 | 214106+0222.2 | 10.956 | ||
21 56 16.94 -40 08 27.2 | 1RXS J215616.4-400829 | 215617-4008.4 | 2.7398 | 2.7388 | |
21 57 51.47 -68 12 50.1 | 1RXS J215753.2-681237 | 215752-6812.8 | 3.3765 | NSV 25792 | |
22 00 18.93 -10 02 47.8 | 1RXS J220019.8-100300 | 220019-1002.8 | 7.114 | ||
22 18 46.62 -84 38 29.6 | 1RXS J221851.8-843847 | 221846-8438.5 | 15.231 | 15.28 | |
22 20 07.49 -48 37 38.4 | 1RXS J222008.8-483734 | 222008-4837.6 | 2.9028 | 2.901 | |
22 23 00.44 -03 22 56.4 | 1RXS J222259.9-032303 | 222300-0322.9 | 7.593 | 7.589 | NSV 25885 |
22 38 35.71 -63 34 21.4 | 1RXS J223836.2-633439 | 223836-6334.3 | 1.10603 | 1.1138 | NSV 14251 |
22 42 26.53 -34 04 29.4 | 1RXS J224227.1-340434 | 224226-3404.5 | 11.53804 | 11.56 | |
22 46 46 13 -20 58 37.9 | 1RXS J224647.8-205837 | 224646-2058.6 | 5.0237 | ||
22 47 05.53 +26 52 54.7 | 1RXS J224705.3+265257 | 224705+2652.9 | 2.2207 | ||
22 47 22.72 +23 13 16.7 | 1RXS J224721.8+231256 | 224723+2313.4 | 5.543 | 5.541 | |
22 56 58.59 -45 13 20.4 | 1RXS J225659.0-451319 | 225659-4513.3 | 9.609 | 9.590 | |
22 57 26.02 -56 45 41.1 | 1RXS J225725.9-564544 | 225726-5645.7 | 6.0245 | ||
23 08 40.17 -16 22 59.9 | 1RXS J230841.0-162313 | 230840-1623.0 | 0.83783 | 5.160 | |
23 10 34.25 +09 29 51.2 | 1RXS J231034.3+093000 | 231034+0929.9 | 3.7693 | 3.772 | |
23 12 29.01 +17 09 21.8 | 1RXS J231229.1+170935 | 231229+1709.4 | 3.0896 | ||
23 14 55.88 +27 39 59.3 | 1RXS J231456.5+273957 | 231456+2740.0 | 11.75 | ||
23 17 32.21 -52 48 07.5 | 1RXS J231732.2-524807 | 231733-5248.2 | 11.084 | 11.223 | |
23 50 51.08 -01 09 22.6 | 1RXS J235051.1-010916 | 235051-0109.4 | 5.6184 |