N.N. Samus 1,2,3 S.V. Antipin 2,1

N.N. Samus1,2,3

S.V. Antipin2,1 1Institute of Astronomy, Russian Acad. Sci.

2Sternberg Astronomical Institute, Moscow University 3Euro-Asian Astronomical Society

Variable Starsand 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 >19m (V1500 Cyg) down to 0.004m (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 20–21m

One star of 80–100 is variable at the 0m.03–0m.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 ~ 212000 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 200 000

Variables not yet known 10 000 000

And what is this?

Beijing, 2012

V376 Peg (HD 209458): 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 30000 new variable stars. Observations of some 15000000

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 14000000 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 TypesAccretion-Disk Precession

(A.V. Khruslov, 2011, PZP, 11, 17)

Beijing, 2012

RR Lyrae Stars with Two Closely Spaced Frequencies

P1/P2 = 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 2000

38 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 0m.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):

P EA EB EW0.2–0.4 d 13% (1.7%) 50% (47.8%)0.4–0.6 d 47% (15.4%) 42% (30.9%)0.6–0.8 d 22% (3.7%) 22% (17.8%) 6% (14.0%)0.8–1.0 d 17% (5.0%) 9% (13.4%) 2% (5.5%)>1 d 61% (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 discoveredAbout 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, 2009.

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~ 150 000 starsExpected 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 = 0m.06

Ampl = 0m.006

A Couple of New Kepler Var’s

(J. Greaves, 2010, PZP, 10, 7)Beijing, 2012

Preliminary results:Of ~ 150 000 program stars,~ 60 000 are periodic variables,~ 34 000 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 L2

point. Astrometry, photometry. Is expected to discover several million new variables down to the 20th 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 45700 “named” variable stars (about 2150 will be added before the end of 2012);about 20000 “suspected” variable stars.

Compare to about 212000 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