Peremennye Zvezdy

Peremennye Zvezdy (Variable Stars) 32, No. 4, 2012

Received 1 July; accepted 15 August.

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New Variables in Pegasus: How Can We Use WASP0 Data

E. V. Kazarovets1, E. N. Pastukhova1, N. N. Samus1,2, E. M. Bogdanova2

  1. Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya Str. 48, 119017 Moscow, Russia; e-mail: helene@inasan.ru, pastukhova@sai.msu.ru, samus@sai.msu.ru

  2. Sternberg Astronomical Institute, Lomonosov Moscow University, University Ave. 13, 119992 Moscow, Russia


In the course of our work on the 80th Name-List of Variable Stars, we encountered a field in Pegasus with about 70 variable stars announced as new discoveries from the WASP0 survey. Our analysis shows that the amount of wrong information published for these stars is unacceptably large. We present correct information on WASP0 variables, both those that still remain unstudied by other authors and those with reliable studies in the literature. Our new information is based on publicly available sky surveys. We also discuss requirements to presentation of data on new variable stars that permit to include information into variable-star catalogs without a too large amount of extra work for catalog compilers.

1. Introduction

In the era of data-intensive astronomy, new Name-Lists of the General Catalogue of Variable Stars (GCVS) become very large. A large amount of information on new variable stars comes from sky surveys, partially or completely automatic. Such surveys use different (often small) wide-angle telescopes, they differ in limiting magnitude, photometric system, pixel size, time coverage. Extracting information from them, also often semi-automatic, results in rather heterogeneous and sometimes not very reliable results. Understandably, large amounts of data make it impossible for GCVS compilers to always address raw data and thus derive reliable variability information for catalog purposes.

By now, two of the three parts of the 80th Name-List of Variable Stars (NL80) have been published (Kazarovets et al. 2011ab). The third part, now in preparation, will present new variable stars in the right ascension range between 16 and 24. Working on the third part, we encountered a number of new variable stars reported by Kane et al. (2005) in a field of Pegasus as a result of observations with the Wide Angle Search for Planet Prototype (WASP0) instrument. Preparing information on these stars for the NL80, we spent considerable effort and obtained a number of new results worth publishing. Besides, we think that this study teaches us important lessons on how to present results of variable-star research in a form permitting catalog compilers to easily incorporate new variable stars into the GCVS.

For complete understanding of the following discussion, it is necessary to know some details of the WASP0 survey. The aperture of the telescope is 6.3 cm. The field of view is 9, with a -pixel unfiltered, rather red-sensitive CCD. The size of a pixel on the sky is . In the field in Pegasus, Kane et al. (2005) announced 75 variable stars between magnitudes 7.69 and 13.76, 73 of them believed to be new. For all 75 stars, periods were presented (to one thousandth of a day). 14 stars were announced  Scuti variables; 2 stars, possible  Scuti variables; 18 stars, EW-type eclipsing variables; 9 stars, possible EW variables; 4 stars, RR Lyrae variables; 3 stars, BY Draconis variables (two of them uncertain); 2 stars, EB-type eclipsing variables; 2 stars, EA eclipsing variables; 3 stars, possible eclipsing variables (no subtype specified); and 18 stars have unknown types. The stars in the cited paper are identified with their numbers in the Tycho or USNO B1.0 catalog.

Periods were determined by Kane et al. (2005) using the Lomb-Scargle statistics. It should be noted that the observations were too time-limited and rather unfavorably distributed in time (about 6 hours per night for a total of four nights; "each of these nights was spaced seven nights apart"). Thus, there exists a possibility of not only one-day aliases of the true periods but also of one-week aliases.

2. Data Analysis and Results

Kane et al. (2005) indicate two of the 75 variable stars, Nos. 54 and 69, as known variable stars; they are AV Peg and NSV 25772. Actually, their list also contains the GCVS stars CY Peg, known since 1934 (No. 40), and VV Peg, known since 1910 (No. 53). Though improved coordinates for all GCVS stars in Pegasus were published slightly later (Samus et al. 2006), the GCVS coordinates for VV Peg used before that time are quite accurate; those used, at that time, for CY Peg differ by less than (about 3 WASP0 pixels) from the accurate coordinates.

For 47 stars listed in the Table, we were able to check catalog identifications suggested in Kane et al. (2005) using the publicly available ROTSE-I/NSVS (Wozniak et al. 2004), ASAS-3 (Pojmanski 2002), SuperWASP (Butters et al. 2010), Catalina (http://www.lpl.arizona.edu/css/) sky surveys. Identifications suggested by Kane et al. for variables No. 17 and No. 43 are wrong, they are respectively in and of the correct positions; our finding charts are presented in Figs. 1 and 2. The correct identification of No. 17 (ASAS 220149+1759.7, GSC 1684.00522) was first suggested by Otero et al. (2006). Our light curve of the variable No. 43 is reproduced in Fig. 3. A special case is No. 30 (Fig. 4). This close pair ( separation) has a single entry in the USNO-B1.0 catalog, with coordinates between the two components. The good angular resolution of the Catalina survey permitted us to establish the variable component of the pair. The identification currently (August 2012) adopted in the International Variable Star Index (VSX) corresponds to the other component.

Besides the coordinates, the Table contains types and periods from Kane et al. (2005) as well as those we adopted for the NL80; variation ranges (magnitudes marked and are close to standard and bands of the Johnson system; are ROTSE-I/NSVS red magnitudes; means -calibrated instrumental Catalina magnitudes); magnitudes in the secondary minimum, if appropriate; remarks and references. Our information on types and periods was either derived by us using the publicly available surveys or resulted from research of other authors (see the column "Ref.").

Figure 5 is another example of a light curve based on Catalina data (star No. 46, type EA). The Catalina survey provides good light curves for stars fainter than 13. This light curve presents the variable's eclipses much better than it would be possible with ROTSE-I/NSVS data.

Table. WASP0 variable stars

No. RA Dec WASP0 WASP0 GCVS , d Range MinII Rem. Ref.
  (J2000.0) (J2000.0) type , d type          
  h, m, s                
3 21 58 32.7 +21 49 25 DSCT 0.081 DSCT 0.080784 12.33-12.54   1 1
4 22 17 34.8 +15 31 33 DSCT 0.087 DSCTC 0.096321 11.24-11.33     2
5 21 48 27.4 +22 37 02 DSCT 0.094 DSCT 0.090257 12.5-12.7   1 2
7 21 51 52.3 +17 44 43 DSCT 0.113 DSCT 0.10772127 13.4-13.9     3
8 21 47 44.3 +19 29 08 DSCT 0.120 DSCTC 0.13683: 10.36-10.40     4
12 21 52 47.7 +18 17 34 DSCT 0.153 EW 0.312817 9.43-9.52 9.51 2 2
13 22 20 54.4 +16 18 35 DSCT 0.168 EW 0.58566 12.9-13.4 13.3   1
14 22 12 17.2 +15 11 46 DSCT 0.200 EB 0.436739 11.85-12.12 12.03   5
17 22 01 49.3 +17 59 42 ? 0.207 EW 0.41521 11.77-12.08 12.00   6
18 22 08 27.1 +18 35 25 ? 0.217 EW: 0.38510 11.12-11.17 11.16:   4
19 22 00 36.1 +16 15 01 ? 0.230 EW 0.459624 13.1-13.5 13.4   2
22 21 49 56.1 +20 58 43 EW 0.271 EW 0.295664 13.65-14.32 14.18 1 7
23 22 12 47.5 +18 24 10 EW 0.276 EW 0.265106 13.08-13.36 13.34   7
27 22 00 14.2 +23 05 01 EW 0.292 EW 0.298323 12.85-13.45 13.30 1 7
28 22 13 46.9 +18 21 03 EW 0.297 EW 0.303093 13.16-13.86 13.71   7
30 22 05 42.0 +19 55 08 EW 0.310 EW 0.303620 11.76-12.00 11.95   5
32 21 55 01.2 +20 20 26 EW 0.342 EW 0.274751 11.65-11.75 11.75 1 1
33 22 16 52.2 +22 29 34 EW 0.346 EB 0.346453 13.0-14.2 13.7 1 8
34 21 50 25.6 +17 43 43 EW 0.347 EW 0.3305685 11.60-12.15 12.05   5
35 21 50 23.7 +17 46 22 EW? 0.349 EA: 1.14228: 13.1-13.6 13.5   4
36 22 08 25.9 +18 34 57 EW? 0.349 EW 0.385135 13.16-13.50 13.48   7
37 22 15 38.7 +22 19 34 EW? 0.370 EW 0.343122 13.39-13.88 13.86 1 7
39 21 59 29.0 +14 58 17 EW 0.389 EW 0.412371 11.37-11.52 11.51   2
40 21 49 47.2 +21 08 38 RR 0.399 RRAB 0.64793 12.0-13.2   3 2
41 21 56 42.1 +22 03 12 EW? 0.406 EW 0.3735416 12.9-13.3 13.3 1 2
42 21 59 05.4 +17 44 32 EW 0.407 EW 0.395357 13.00-13.26