The Gaia mission and the variable objects Laurent Eyer, N.Mowlavi, M.Varadi, M.Spano, Observatoire de Genève, Suisse G.Clementini, Université de Bologne, Italie Lundi, 29 Juin 2009 Kursaal Besançon, France
An attempt to organise the variable celestial objects Variability Tree Asteroids Extrinsic Intrinsic AGN Rotation Eclipse Stars Stars Microlensing Eclipse Rotation Eclipse Eruptive Cataclysmic Pulsation Secular Asteroid occultation EA Eclipsing binary EB Credit : L. Eyer & N. Mowlavi (03/2009) EW Planetary transits ELL FKCOM Single red giants β Per, α Vir SXA SX Arietis MS (B0-A7) with strong B fields ACV RCB Binary red giants α 2 Canes Venaticorum MS (B8-A7) with strong B fields BY Dra RS CVn DY Per UV Ceti Red dwarfs (K-M stars) FU PMS Be stars WR GCAS ZAND Symbiotic SN Supernovae LBV S Dor SPBe λ Eri N Novae ACYG α Cygni Hot OB Supergiants β Cephei UG Dwarf novae BCEP Slowly pulsating B stars PG 1159 (DO,V GW Vir) He/C/O-WDs SPB V361 Hya (EC14026) short period sdb V1093 Her (PG1716+426, Betsy) long period sdb V777 Her (DBV) He-WDs SXPHE SX Phoenicis PV Tel He star ZZ Ceti (DAV) H-WDs PMS δ Scuti DST δ Scuti Solar-like roap Photom. RR RR Lyrae GDOR FG Sge Sakurai, V605 Aql γ Doradus L SARV Small ampl. red var. CEP δ Cepheids SR Irregulars RV Period R Hya (Miras) δ Cep (Cepheid) M CW Miras Semiregulars RV Tau (W Vir) Type II Ceph. Gaia will detect most variable types on this tree
HR diagram for variable stars Gaia: Imagine 10-20 million variable stars in this HR-diagram Precise statistical description of variable types Precise position of instability strips A.Gautschy 2008
Variable stars in 12 Colour-Magnitude Diagram Variable stars Eclipsing Be Cepheids:[Fund][1st Ov][2nd Ov] RRLyr:[rrab][rrc][rrd] [rre] Ellipsoidal Lpv (Long Period Variables) LMC OGLE data 14 Gaia: 1) Full description of HR 16 diagram (parallax) 2) better precision (detection of many additional types) Ecl. Bin. EW RV Tau 18 3) simultaneous data in G, BP, RP 4) Radial Velocities R CrB 20 V4334 Sgr FG Sge Added secular evolution 22 0 2 v-i 4 Spano et al 2009
Fraction of variables from some surveys Hipparcos satellite: 3.3 years, 118,204 stars ASAS 1-2: 3 years, 140,000 stars 9.7 % variable stars Gaia: 10%? =100 million variables! 2.9 % variable stars OGLE-II: ~3-4 years, 40 million stars 0.7 % variable stars MOST satellite (J.Matthews, private communication) 20 % variable stars CoRoT satellite, 2.5 years, 120,000 stars (Debosscher s PhD Thesis) 40 % variable stars Kepler satellite, 3.5 years, 100,000 stars? % variable stars (a majority of variable stars?)
The Gaia mission: Observed Objets 1 billion stars (~100 million variable objets) 1 million galaxies -astrometry, photometry -spectro-photometry ~80 (40-250) measurements over 5 years 0.5 million QSO 0.3 million asteroids of our solar system mostly main belt asteroids -Radial Velocity Spectrometer ~40 (20-120) measurements over 5 years for objects brighter than G=14-15
The DPAConsortium: the global view Two main concepts: 1. Coordination Units 2. Data Processing Centres CU2 Simulation CU1 Architecture ESAC/BPC/OAOT CU3 Astrometry BPC/CNES CU4 Objects CU5 Photometry CU6 Spectroscopy CU7 Variability CU8 A.P. CNES Cambridge CNES ObsGE/ISDC CNES 385 people
CU7 Variability Analysis functional analysis
Study of Period search algorithm (J.Cuypers) Hipparcos data
CU7 Variability Analysis functional analysis
Specific Object Studies N.Mowlavi (ObsGe/ISDC)
Gaia Focal Plane 0.7 deg x0.7 deg
The Gaia photometric precision G-band In the G band transit photometry 20 mmag at G=20 Limiting magnitude of Gaia ~1 mmag at 10<G<14 per ccd observation per transit (9 CCDs) end-of-mission (80 observ.) C. Jordi modified by M.Varadi
The Gaia mission sampling properties Rotation of the satellite 6 hours, precession in 63 days Preceding-Following Field of View: 1h46 Following to Preceding FoV: 4h14 Gaps of about 30 days
A Number comparison of field oftransits over 5 years time differences and spectral windows
A comparison of time differences and spectral windows
Period recovery rate for strictly period signals 1. Signal(t)= A sin(2 π ν t + φ) + noise 2. Two parameters: a) S/N ratio = 0.75 b) Period = 1/ν = 0.2 day 3. Gaia sampling 4. Period search algorithm determine the success rate Aitoff projection in Ecliptic coordinates 90 (very defavorable case) 180-180 -90 0 20 40 60 80 100 Percentage Eyer & Mignard 2005
Period recovery rate: exploring the parameter space Frequency cycle/day 1 millimag error 1.3 millimag signal recovered 97-100 % Normalised S/N = sqrt(nmes/80) S/N Eyer & Mignard 2005
More complex light curves: Simulated ZZ Ceti stars (pulsating white dwarfs) Simulation of a typical ZZ Ceti star (properties derived from the star GD29-38) Work done with Stefan Jordan (Heidelberg), code re-written by M.Varadi
Caveat: Pulsation assumed stable Analysis of simulated time series of GD29-38 - multiperiodic signal + noise - 5 year long data set - Gaia sampling (AGISLab) 82*9=738 per-ccd data 2 frequencies with highest amplitude can be recovered correct period recovered Gaia Goal: Correct detection of such objects with possibilty main period & determination of luminosity
Transient variable: Microlensing and Supernovae 1) Microlensing: L. Wyrzykowski 1324 out of 1988 microlensing events from OGLE with at least one measurement within lensing event event duration > 30 days: rate is 93% OGLE Bulge Microlensing events D.Evans, I.Lecoeur, L.Eyer Algorithm of microlensing detection, high recovery rate on OGLE-II data 2) Supernovae (Gilmore & Belokurov): 6,000 to G=19 about 1/3 before maximum light
Ground based Observations Within Gaia Data Processing and Analysis Consortium (DPAC): Help to prepare the data reduction GBOG (Ground-Based Observations for Gaia, Coordinated by Caroline Soubiran) CU7: Use of HAT, SDSS, Hipparcos, OGLE, CU2; Super- Verify-Validate the data analysis Macho, CoRoT,... - CU5 for the Alert system - CU7 Scientific Community: Scientific exploitation (for example GREAT, Gaia Research for European Astronomy Training), following - Scientific follow-up of alerts, announcements - Catalogue releases Telescopes of 1m-2m, 2m-4m are valuable for the Gaia validation & science
Telescopes that could be used for CU7 Validation Onderjov Obs. Koubsky/Houdec 0.6-2m L.Figl Obs. Lebzelter 1-1.5m Castelgrande Obs. Ripepi 1.5m La Silla Chile Eyer Euler 1.2m La Silla Chile Koubsky Danish 1.5m CTIO, Chile Lebzelter SMARTS 0.9-1.5m La Palma Eyer Mercator 1.2m LaionaObs. Clementini 0.6-1m Pic du midi Shultheis 1-2m Pisykesteto Obs. Szabados 1m Maidanak Obs. Ibrahimov 2*0.6-1-1.5m
Ground based observations Establish: List of (planned) instruments attached to the telescope the relevance for Gaia validation and science Importance for the future of telescopes
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