Peremennye Zvezdy (Variable Stars) 32, No. 4, 2012
Received 1 July; accepted 15 August.
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|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.|
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.
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
|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||13.22||7|
|43||22 01 42.5||+17 28 45||?||0.407||EB||1.794670||12.72-13.38||12.90||7|
|44||21 50 25.4||+14 51 06||?||0.414||EB||0.878990||12.05-12.50||12.35||2|
|46||22 03 30.2||+19 39 13||EW?||0.433||EA||1.136793||13.11-13.83||13.60:||4||7|
|47||21 57 11.2||+22 40 11||EW||0.435||EW||0.422024||9.55-9.95||9.90||1||9|
|48||22 07 53.8||+22 43 59||EW||0.440||EW||0.469433||12.50-13.00||12.95||1|
|51||22 01 49.3||+17 59 42||EW||0.456||EW||0.415211||11.77-12.08||12.0||6|
|52||21 55 25.4||+19 37 17||EB||0.487||EA||1.285180||9.81-10.5||9.9||5||10|
|53||22 13 03.9||+18 27 04||RR||0.488||RRAB||0.4883871||11.13-12.31||6||11|
|54||21 52 02.8||+22 34 29||RR||0.502||RRAB||0.3903814||9.93-10.99||7||12|
|56||22 06 00.1||+19 35 50||EB||0.515||EB||0.57983||11.45-12.6||11.65||1|
|57||21 53 21.2||+22 37 11||EA||0.524||SR||43.5||11.5-11.8||1||2|
|58||22 12 51.8||+17 20 16||RR||0.556||EW||0.960564||12.27-12.64||12.64||13|
|60||21 54 29.8||+19 03 52||EW||0.566||EW||0.59057||12.7-13.3||13.2||2|
|61||21 53 45.3||+18 31 59||EW||0.587||EA||0.9382||11.18-11.33||11.31||4|
|62||22 03 28.0||+18 19 23||EW||0.596||EB||0.475533||11.24-11.41||11.33||2|
|63||22 04 51.5||+14 46 19||EW||0.603||EB||0.659481||12.68-13.25||13.0||5|
|64||22 17 40.0||+17 10 17||EW||0.647||EB||0.677572||12.77-13.15||13.04||4|
|69||21 50 08.2||+19 25 26||DSCT?||1.041||ELL+||1.4708||7.40-7.49||8||14|
|71||21 53 12.0||+22 23 38||EA||1.187||EA||1.62394||12.50-13.0||12.60||1||4|
|72||22 03 11.0||+22 32 07||E?||1.212||EB:||0.714821||11.96-12.45||12.10||1|
|73||21 52 43.7||+21 44 53||E?||1.741||EA:||3.05174:||8.54-8.62||8.57||2||2|
Remarks. 1. SuperWASP data are available and agree with the tabulated results. 2. Sp F2. 3. CY Peg. 4. . 5. Sp A2. 6. VV Peg. Sp A9-F4. 7. AV Peg. Sp A7-F6. 8. NSV 25772. The orbital period is tabulated; Scuti periods: 006479 and 006337. Sp A8+F7V:.
References. 1. ASAS catalog (Pojmanski et al. 2005). 2. This paper, ASAS-3 data. 3. Wils et al. (2011). 4. This paper, ROTSE-I/NSVS data. 5. S. Otero (VSX), ASAS-3 data. 6. Otero et al. (2006). 7. This paper, Catalina data. 8. Diethelm (2010). 9. Diethelm (2011). 10. Szczygie et al. (2008). 11. Samus et al. (2012). 12. Szczygie et al. (2009). 13. Otero (2008). 14. Henry et al. (2004).
It appears from the Table that we suggested types for all stars given in Kane et al. (2005) without a type. Types were found different, often absolutely different (for example, pulsating variables instead of eclipsing stars or vice versa), for a large fraction of the stars. More than half of all stars in the Table have unacceptably wrong periods in Kane et al. (2005). The data now tabulated permits us to include the stars into the NL80 with sufficiently reliable information.
In the era of data-intensive astronomy, it is important that researchers present data on their new variable-star discoveries satisfying, as completely as possible, needs of future variable-star catalogs. In particular, it is important to present sufficiently accurate coordinates. Surely, star numbers from known positional catalogs permit to find the coordinates but, if not accompanied with coordinates, make the task of catalog compilers more difficult. Researchers working with small telescopes and large pixel sizes should remember that, with the exception of cases of still undetected serious mistakes, the GCVS electronic catalog currently presents coordinates accurate to approximately one second of arc. We do not want to deteriorate this level of positional accuracy, achieved by large effort of GCVS compilers. Thus, stars with poorly determined coordinates will remain outside the GCVS for a long time period.
It is preferable to arrange photometric observations of new variable stars so that the time distribution of the observations would permit to avoid spurious period determinations. We are currently preparing a complete GCVS-format version of the NL80, like that we prepared for the 79th Name-List (Kazarovets et al. 2009). Knowledge of correct periods greatly contributes to such work.
Finally, it is important to provide access to raw data, in order to make it possible to verify the results (or re-reduce them) using the same information that was used by the authors.
Meeting these requirements will strongly facilitate the transition to more automatic methods of variable-star-catalog compilation.
Acknowledgments: We have used data from the WASP public archive in this research. This study made use of the ASAS and ROTSE-I/NSVS data bases, USNO Image and Catalog Archive, and Aladin Sky Atlas. Thanks are due to Dr. S.V. Antipin for his assistance. We gratefully acknowledge financial support from the program "Origin and Evolution of Stars and Galaxies" of the Presidium of Russian Academy of Sciences.
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