N.N. Samus 1,2,3 S.V. Antipin 2,1 1 Institute of Astronomy, Russian Acad. Sci. 2 Sternberg Astronomical Institute, Moscow University 3 Euro-Asian Astronomical Society Variable Stars and Data-Intensive Astronomy XXVIII General Assembly of the IAU, SPS15 Beijing, August 31, 2012

Principal problem: No amplitude limit defining a variable star. General Catalogue of Variable Stars: peak-to-peak amplitudes from >19 m (V1500 Cyg) down to m (α Aql). The combined light curve of V1500 Cyg (Nova Cyg 1975) 18 hours of space-borne infrared photometry of Altair (D. Buzasi et al., 2005, ApJ, 619, 1072) Beijing, 2012

CCD Discoveries of Galactic Variable Stars USNO-B1.0 catalog (2003): 1,042,618,261 objects (stars and galaxies), ~ 1 billion stars to 20–21 m One star of 80–100 is variable at the 0 m.03–0 m.05 level, and thus ~10 million variable stars are potentially detectible with a ground-based 1-m telescope, ordinary CCD detector, and standard software for automatic search for variable stars. Currently (August 2012) known are ~ variable stars of our Galaxy (International Star Register of the AASVO – VSX, the web facility working quite independently of the GCVS but keeping close everyday contact), i.e. ~2% of those potentially detectable using CCD techniques. Beijing, 2012

Prospects of Variable-Star Discoveries known variables Variables not yet known And what is this? Beijing, 2012

V376 Peg (HD ): the first star of our Galaxy with photometrically detected transits of a big exoplanet across the stellar disk (S. Jha et al., 2000, 540, L45). New possibilities for surface mapping! Such eclipses are observable even for amateur astronomers. Beijing, 2012

A transit observed for the same star by the Hubble Space Telescope (T. Brown et al., 2001, ApJ, 552, 699) Beijing, 2012

The ASAS-3 survey (G. Pojmanski). Two 20-cm telescopes. Southern sky. Some new variable stars. Observations of some stars online. Beijing, 2012

The ROTSE-I/NSVS survey. Northern sky. A small fraction of possible variable-star discoveries made by the authors, photometry of about stars online. The light curve shown is for T And Beijing, 2012

By New Year 2012, open access was provided to photometry of the Catalina Sky Survey (50 – 70-cm Schmidt telescopes, all the northern sky except the Milky Way strip, very-high-quality photometry, working magnitudes from 13 to 19) Beijing, 2012

New Types Accretion-Disk Precession (A.V. Khruslov, 2011, PZP, 11, 17) Beijing, 2012

RR Lyrae Stars with Two Closely Spaced Frequencies P 1 /P 2 = 0.90 ÷ 0.99 (S. Antipin & J. Jurcsik, 2005, IBVS, No. 5632) Beijing, 2012

Considerable Number Increase of Several Variability Types During Recent Years BY Dra / RS CVn High-Amplitude Delta Scuti Stars (HADSs) Double-Mode Cepheids Eclipsing Variables Beijing, 2012

Number increase of known double-mode Cepheids (mainly due to data mining in ASAS-3 data) (A.V. Khruslov, 2010, PZP, 10, 16) 18 in in 2010 (23 of them, F+1O, and 15, 1O+2O) Khruslov’s discoveries (as of 2012): 12 double-mode Cepheids, 11 of them 1O+2O + 3 similar RR near galactic plane Beijing, 2012

One of the scanners used to digitize the Moscow plate stacks Beijing, 2012

D.M. Kolesnikova et al. (2008, AcA, 58, 279; 2010, ARep, 54, 1000) discovered, in a field of 100 square degrees reasonably well studied using traditional methods, almost 500 new variable stars. Beijing, 2012

Number Increase of Known HADS Variables Search for variables using scans of plates from Moscow stacks. In the field centered at 66 Oph, 10°x10° (less than 0.25% of the total area of the sky), 13 HADSs were detected, leading to an estimate >5000 for the whole sky. The GCVS number of Delta Scuti stars with amplitudes of at least 0 m.2 is 121. (D.M. Kolesnikova et al., 2010) Beijing, 2012

Different Period Distribution of Eclipsing Stars from the Same Scans The period distribution of newly discovered eclipsing stars is considerably shifted towards shorter periods (the GCVS frequencies are in brackets): PEAEBEW 0.2–0.4 d13% (1.7%)50% (47.8%) 0.4–0.6 d47% (15.4%)42% (30.9%) 0.6–0.8 d22% (3.7%)22% (17.8%)6% (14.0%) 0.8–1.0 d17% (5.0%)9% (13.4%)2% (5.5%) >1 d61% (89.2%)9% (51.7%) (D.M. Kolesnikova et al., 2010) Beijing, 2012

Problems of Variable-Star Classification in Sky Surveys The existing classification systems (GCVS etc.) are far from being perfect; good software for automatic classification is not available; it is very tiresome to manually classify thousands of new discoveries; in many cases, classification solely from the light curve is impossible; additional information on the spectral type, X- rays, radial velocity variations is needed. Beijing, 2012

Problems of Variable-Star Classification (V. Solovyov, A. Samokhvalov, B. Satovskiy, 2011, PZP, 11, 14) Eclipses? Pulsations? Rotational variability of a spotted star? Beijing, 2012

SPACE MISSIONS The first space mission that discovered many variable stars: HIPPARCOS (ESA, 29-cm telescope, in operation in 1989–1993) About 5000 new variables discovered About 3000 new variables added to the GCVS (others remained insufficiently well studied)

Corot mission launched with a Russian rocket (December 2006) Just a 27-cm telescope! Corot main goals: – Asteroseismology – Search for exoplanets Phase effects and an eclipse of an exoplanet (I.A.G. Snellen et al., 2009, Nature, 459, 543) Beijing, 2012

Kepler mission (NASA): a 95-cm telescope. Monitors a field at the boundary of Cygnus and Lyra. Launched on March 7, As of August 8, 2012 (no changes for several recent months…), discovery of 2321 exoplanet candidates was announced; 74 of them confirmed. Also announced are 2165 discoveries of eclipsing variable stars. Stars with amplitudes of several thousandths of a magnitude show reliable details on their light curves! New types of eclipsing (+ pulsating) stars Beijing, 2012

KEPLER Mission 42 CCDs, 2200х1024 ~ stars Expected active time: 3.5 years Able to detect a transit of an earth-type planet of a solar- type star at a 4σ level Beijing, 2012

Ampl = 0 m.06 Ampl = 0 m.006 A Couple of New Kepler Var’s (J. Greaves, 2010, PZP, 10, 7) Beijing, 2012

Preliminary results: Of ~ program stars, ~ are periodic variables, ~ stars vary with poorly detectable periodicity or aperiodically (G. Basri et al., 2011, AJ, 141, 20) Two thirds of all stars are variable for KEPLER precision of photometry! KEPLER Observatory Beijing, 2012

GAIA mission (ESA). Expected launch: 2013 (as of August 2012, the particular month, March, has recently disappeared from the GAIA web site), with a Russian Soyuz-Fregat rocket to the L 2 point. Astrometry, photometry. Is expected to discover several million new variables down to the 20 th magnitude (no better prediction on the GAIA web site!). Two 1.45×0.5-m telescopes Beijing, 2012

The planned Russian space experiment “Lyra” on board the International Space Station A 50-cm telescope. Multicolor photometry (catalog) of 100 to 400 million stars; the whole sky observed some 20 times per year. The project is being worked on at the Sternberg Institute (Moscow) Beijing, 2012

P.P. Parenago (1906 – 1960) B.V. Kukarkin (1909 – 1977) THE GENERAL CATALOGUE OF VARIABLE STARS (GCVS) – SINCE 1946 ON BEHALF OF THE INTERNATIONAL ASTRONOMCAL UNION P.N. Kholopov (1922 – 1988) Beijing, 2012

The GCVS team Beijing, 2012

Current contents of the GCVS: about “named” variable stars (about 2150 will be added before the end of 2012); about “suspected” variable stars. Compare to about variable stars in the AAVSO VSX. So far, evaluation of information for the GCVS is still made on the star-by-star basis by staff members of the GCVS. No software able to provide classification of variable stars with uncertainties within reasonable limits. WE ARE BEHIND THE FLOW OF DISCOVERIES! New classification system badly needed. However, it seems that new discoveries change the general picture too strongly to introduce it now! Beijing, 2012

Final Remarks With full-scale results from Kepler (and then from similar missions) approaching, everything we know about variability statistics will have to be revised; The era of traditional variable-star catalogs is probably near its end, despite traditional Argelander-style variable-star names being still popular; A possible solution could be universal star catalogs, with variability information as a minor part of them; The commission established by the IAU C27 six years ago to study the future of variable-star catalogs apparently finds no brilliant ideas how to proceed in order to solve this problem, really important for the astronomical community. New ideas from the virtual-observatory community are welcome. Beijing, 2012

Thank you!!! Beijing, 2012