Peremennye Zvezdy

Article in PDF
"Peremennye Zvezdy",
Prilozhenie
,
vol. 8, N 32 (2008)

Mira Variables from the OGLE II Galactic Disc Photometric Database in Centaurus and Norma

J. Greaves
Northants, England, UK

ISSN 2221–0474

Draft in Preparation;   accepted:   6.11.2008
(E-mail for contact: bydra@safe-mail.net)


#NameOtherCoord (J2000)TypeMaxMinSystemPeriodEpoch (JD)typeSpCommentL.CurveFind.ChartData
1 Cen_SC1 2472013 56 45.55, -62 36 02.2M14.4>17.2I600::2451319Max  Cen_SC1_24720.gif Cen_SC1_24720.dat
2 Cen_SC1 3993113 57 09.84, -62 56 53.6M14.016.7:I520: other  Cen_SC1_39931.gif Cen_SC1_39931.dat
3 Cen_SC1 7977513 58 09.60, -63 13 14.7M<16.2>18.7I400:2451626Max  Cen_SC1_79775.gif Cen_SC1_79775.dat
4 Cen_SC1 7588613 58 11.10, -63 25 12.9M13.0>15.4I400:2451672Max  Cen_SC1_75886.gif Cen_SC1_75886.dat
5 Cen_SC2 179813 58 35.53, -63 24 55.5M13.314.1I3952451314Max  Cen_SC2_1798.gif Cen_SC2_1798.dat
6 Cen_SC2 2859413 59 15.88, -63 09 44.1M<14.8>17.6I380 other  Cen_SC2_28594.gif Cen_SC2_28594.dat
7 Cen_SC2 3439413 59 25.70, -62 54 22.8M13.015.5I2002451618Max  Cen_SC2_34394.gif Cen_SC2_34394.dat
8 Cen_SC2 8363314 00 09.71, -62 37 12.8M<16.5>17.9I3952450919Min  Cen_SC2_83633.gif Cen_SC2_83633.dat
9 Nor_SC1 805716 12 22.06, -54 28 02.7M<10.913.3I4302450925Min  Nor_SC1_8057.gif Nor_SC1_8057.dat
10 Nor_SC1 7249416 12 33.48, -54 23 16.7M11.114.3I3462451686Max  Nor_SC1_72494.gif Nor_SC1_72494.dat
11 Nor_SC1 21440616 13 38.92, -54 08 19.0M11.7>14.3I3502451230Max  Nor_SC1_214406.gif Nor_SC1_214406.dat
12 Nor_SC2 3263116 13 52.33, -54 01 55.0M<12.514.0I3922451328Min  Nor_SC2_32631.gif Nor_SC2_32631.dat
13 Nor_SC2 9792716 14 00.84, -54 06 03.0M12.014.7I3232451730Max  Nor_SC2_97927.gif Nor_SC2_97927.dat
14 Nor_SC2 11622216 14 03.59, -53 54 04.8M15.718.3:I4742451340Max  Nor_SC2_116222.gif Nor_SC2_116222.dat
15 Nor_SC2 20141816 14 31.10, -53 36 59.8M11.613.7:I3192451635Max  Nor_SC2_201418.gif Nor_SC2_201418.dat
16 Nor_SC3 13245116 15 42.90, -53 34 49.5M12.114.9I3032451291Max  Nor_SC3_132451.gif Nor_SC3_132451.dat
17 Nor_SC3 13243516 15 48.65, -53 33 05.8M11.514.5I600:2450921Max  Nor_SC3_132435.gif Nor_SC3_132435.dat
18 Nor_SC3 17452416 16 06.35, -53 54 43.5M<12.313.9I3822451312Min  Nor_SC3_174524.gif Nor_SC3_174524.dat
19 Nor_SC3 21729216 16 41.81, -54 15 30.6M12.114.9I560:2450974Max  Nor_SC3_217292.gif Nor_SC3_217292.dat
20 Nor_SC4 6805116 16 49.02, -53 26 13.8M11.1:12.8I3852451259Min  Nor_SC4_68051.gif Nor_SC4_68051.dat
21 Nor_SC4 2998116 16 50.93, -53 56 53.2M12.215.1:I4252451328Max  Nor_SC4_29981.gif Nor_SC4_29981.dat
22 Nor_SC4 12532916 17 13.41, -53 33 55.6M11.814.6I  other  Nor_SC4_125329.gif Nor_SC4_125329.dat
23 Nor_SC4 18188616 17 28.99, -53 41 33.0M12.715.9I  other  Nor_SC4_181886.gif Nor_SC4_181886.dat
24 Nor_SC4 20857216 17 48.10, -54 12 25.6M11.513.7I2512450947Max Comm. 24Nor_SC4_208572.gif Nor_SC4_208572.dat
25 Nor_SC6 10391116 24 18.04, -52 20 13.0M<12.0>13.2I365 other  Nor_SC6_103911.gif Nor_SC6_103911.dat
26 Nor_SC6 22615116 25 01.15, -52 27 27.6M<13.014.9I3772451238Min  Nor_SC6_226151.gif Nor_SC6_226151.dat
27 Nor_SC7 5985016 25 41.54, -51 53 06.5M12.515.3I4022450958Max Comm. 27Nor_SC7_59850.gif Nor_SC7_59850.dat
28 Nor_SC7 10000916 25 55.08, -52 15 19.2M<11.914.5I410 other  Nor_SC7_100009.gif Nor_SC7_100009.dat
29 Nor_SC7 12806916 26 08.63, -51 51 42.0M12.5:15.9I500: other Comm. 29Nor_SC7_128069.gif Nor_SC7_128069.dat
30 Nor_SC8 4675816 27 10.07, -52 02 39.3M12.8>15.0I3852451270Max Comm. 30Nor_SC8_46758.gif Nor_SC8_46758.dat
31 Nor_SC8 15643116 27 54.67, -52 06 35.8M12.213.9I2552450950Max Comm. 31Nor_SC8_156431.gif Nor_SC8_156431.dat
32 Nor_SC8 20820016 28 14.44, -52 04 14.3M<11.813.5I3352451681Min  Nor_SC8_208200.gif Nor_SC8_208200.dat

Comments:


24. First noted as a variable star in Derut et al. (2002).

27. First noted as a variable star in Derut et al. (2002).

29. First noted as a variable star in Derut et al. (2002).

30. First noted as a variable star in Derut et al. (2002).

31. First noted as a variable star in Derut et al. (2002).

Remarks:
The OGLE On-line Photometric Databases (Szymanski 2005) carry epoch photometry from the OGLE II surveys (Udalski et al. 1997) released to the public domain, and including a survey pointed at some fields in the Galactic Disc for which apparently no variability study has been published despite being available for several years.

Of lesser duration than the Bulge and Magellanic Cloud surveys, this dataset nevertheless can be seen to contain nearly one million stars fulfilling the criterion of having about one hundred plus observations each and is spread over an approximately one thousand day interval. This is sufficient for the assessment of period and variability type for many types of variable star, especially periodic ones, and even long period variables such as Mira stars.

An examination of the database returned 78 certain Mira variables, 32 from the Centaurus and Norma fields are presented here. A further 46 can be found in the Scorpius fields. The Carina fields appeared to have no readily apparent certain Mira variables that could be readily distinguished from semiregular variables. This compares well with a survey for Miras (Groenewegen and Blommaert 2005) conducted upon the admittedly slightly denser OGLE II Bulge fields of roughly thirty million stars, which reported nearly three thousand Mira variables. That is, the fraction of Miras is an order of four less in these two cases.

This list of 32 Mira variables gives details of the stars. As the OGLE II experiments use a passband that is very near to Cousins I, the amplitude of variability for these Miras is somewhat suppressed relative to situation with Johnson V, which is normally the case (see for example Lockwood and Wing (1971) for I band lightcurves of well known classical Miras), but the morphology of the lightcurves make the class evident enough. Another similarity to the Lockwood and Wing paper is the fact that despite a passband being used that is away from the opaque Titanium Oxide absorption lines, the lightcurves do not necessarily repeat cleanly from one cycle to the next, whether in peak magnitude or in ascending branch hump location or in cycle to cycle interval.

The seasonal nature of the survey, the short duration relative to the periods involved, and the magnitude limits, all combine to not allow coverage of more than three to four cycles at most for these objects, with maxima and minima being missing in some instances. Nevertheless period analysis of the data allows some good and very good periods to be determined, as well as approximate ones, and if minima are used in addition to the traditional maxima, epoch information can also be gleaned.

None of the stars are noted in the GCVS, NSV (http://www.sai.msu.su/groups/cluster/gcvs/gcvs/iii/html/ ) nor ASAS variable star listings (http://www.astrouw.edu.pl/asas/?page=download ), the resources most likely to cover these regions, which is to be somewhat expected as Mira variables will on the whole have V-Ic colours of 2, 3 or higher, thus often being much fainter in the more traditionally used Johnson V and visual ranges used in traditional variability surveys. Five stars (Nor_SC4 208572, Nor_SC7 59850, Nor_SC7 128069, Nor_SC8 46758, and Nor_SC8 156431) were found variable in the EROS II project (Derut et al. 2002) but not studied in any detail.

References:
Derue, F., Marquette, J.-B., Lupone, S., et al., 2002, Astron. Astrophys., 389, 149
Groenewegen, M.A.T., Blommaert, J.A.D.L., 2005, Astron. Astrophys., 443, 143
Lockwood, G.W., Wing, R.F., 1971, Astrophys. J., 169, 63
Szymanski, M., 2005, Acta Astronomica, 55, 43
Udalski, A., Kubiak, M., Szymanski, M., 1997, Acta Astronomica, 47, 319



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