PradaMoroni pisa2013 web - Benvenuto · PDF file• Dario%Grasso% ... Tognelli ,%Prada...

From binary stars to the expanding Universe

Pier Giorgio Prada Moroni Dipar&mento di Fisica “E. Fermi”

INFN – Sezione di Pisa

Permanent staff

•  Scilla Degl’Innocen? •  Anna Nobili •  Paolo Paolicchi •  Pier Giorgio Prada Moroni •  Steve N. Shore

INFN •  Dario Grasso

Non-‐permanent staff

•  MaDeo Dell’Omodarme •  Emanuele Tognelli

•  Giada Valle

Research

•  Stellar physics •  Galac?c structure and evolu?on

•  Interstellar medium

•  Planetary / Extrasolar

•  High energy astrophysics

Distance measurements

•  Structure, dimension and expansion history of the Universe

•  Structure, dimension and luminosity of astronomical objects

•  Ages

•  Test of theore?cal models

Distance measurements •  Very difficult, indirect, and not very precise

•  Only informa?on on posi?on and brightness

•  Geometric techniques limited to nearby objects

•  Distance ladder: from geometrically measured distances for nearby stars to the far universe via mul?ple overlapping steps

•  Standard candles

Classical Cepheids

•  1908-‐1912: HenrieDa LeaviD

•  25 Cepheids in SMC

•  Period-‐Luminosity rela?on

LeaviD & Pickering 1912 (Harvard Coll. Obs. Cir., 173, 1)

Extragalac?c distances

•  6/10/1923: Edwin Hubble discovered the first Cepheid in M31

•  The Great Debate was defini?vely seDled: Andromeda lies beyond our galaxy

•  The Universe became much bigger V1 in Andromeda


•  Hubble’s Law (1929-‐1931)

v = H0 d

•  Distancy of nearby galaxies

Hubble 1929 (Proc. Nat. Acad. Sci. USA, 15, 168)


•  The Universe’s expansion is accelera3ng (Riess et al. 1998, PerlmuOer et al. 1999)

•  Nobel Prize 2011: S. PerlmuDer, B. Schmidt, A. Riess

Classical Cepheids

•  The main primary distance indicator

•  Visible up to 30 Mpc

•  Used to calibrate cosmological standard candles

•  Hubble constant H0

Large Magellanic Cloud

•  the first rung of the extragalac?c distance ladder

•  Many different stellar distance indicators

•  Several thousands of Cepheids

•  The slope of the PL rela?on is both sta?s?cally and systema?cally well determined

Classical Cepheids


•  The zero point of the PL rela?onship would be determined once the LMC distance is known

•  Many different measurement techniques


Schaefer 2008 (AJ, 135, 112) μ= -‐5 + 5 log d (pc)

Double-‐lined eclipsing binaries

Provide a class of distance indicators:

•  direct and simple

•  very accurate

Paczynski 1997


The analysis of:

•  the light curve •  the radial velocity

•  Purely geometrical determina?on of R Credit: ESO/L. Calçada


•  For late-‐type stars an accurate (2%) empirical surface brightness color rela?onship

•  From (V-‐K)

•  Surface brightness Sv

•  angular diameters

Credit: ESO/L. Calçada


From:

•  linear radii R1 and R2 •  angular diameters

•  distance

Credit: ESO/L. Calçada


Difficul?es:

•  The common late-‐type dwarfs are too faint in LMC •  The late-‐type giants are very rare •  The very long period binaries are difficult to iden?fy

•  Very large stellar database •  Observa?ons over very long ?me scale

Eclipsing binaries in LMC

OGLE Collabora3on

•  Database 3.5 107 stars in the LMC field

•  16 yr of observa?ons

ARAUCARIA Project •  8 long period (60-‐772 d),

late-‐type, double lined EBs

Pietrzynski, et al. 2013 (Nature 495, 76)



OGLE-‐LMC-‐ECL06575


•  LMC distance accurate at 2.2%

•  H0 accurate at 3% Pietrzynski, et al. 2013 (Nature 495, 76)

49.97 ± 0.19 (stat) ± 1.11 (sys) Kpc

Magellan Clay Telescope (6.5 m), Las Campanas

18.493 ± 0.008 (stat) ± 0.047 (sys) mag


•  Accurate determina?on of stellar parameters: M, R, L, Te

•  Severe test for theore?cal models

Theory/Observa?ons

OGLE Collabora3on

•  First detec?on of a Cepheid in a well detached, double-‐lined eclipsing binary system

•  Mass determina?on with the unprecedented precision of 1%

LMC OGLE CEP 0227


Prada Moroni, et al. 2012 (Astrophysical Journal 749, 108)

Theory/Observa?ons: OGLE CEP0227

•  the most probable solu?ons were obtained by using the models with βov=0.2 and η=0.4

•  Primary (Cepheid) M = 4.14+0.04-‐0.05 Mo

•  Secondary M = 4.15+0.04-‐0.05 Mo

•  agreement at the 1% level with dynamical mass measurements. Prada Moroni, et al. 2012

(Astrophysical Journal 749, 108)

RR Lyrae

•  Variable stars in the He-‐burning phase •  Accurate distance indicators •  Much fainter than classical Cepheids

•  Not visible beyond the Local Group •  Crucial tests for consistency of zero points

OGLE RRLYR02792 •  First RR Lyrae observed in an

eclipsing binary •  M= 0.261 ± 0.015 Mo

•  Can not be an He-‐burning star, as classical RR Lyrae

(Prada Moroni & Straniero 2009, Astronomy & Astrophysics 507, 1575)

•  Discovered a new class of stellar variable


Interpreta?on of observa?ons: OGLE RRLYR02792

Credit: Janusz Bogucki

Interpreta?on of observa?ons: OGLE RRLYR02792

•  Ini?al binary system M1= 1.4 Mo and M2= 0.8 Mo

orbi?ng with P= 2.9 d •  Aqer 5.4 Gyr, P= 15.9 d and

M1=0.268 Mo, M2= 1.665


Stellar models

They are indispensable tools in many astrophysical research areas, since they allow to:

•  understand the structure and evolu?on of stars •  assign ages and masses to the observed stars

•  infer vital informa?on (SFR and IMF) about complex stellar systems, as clusters and galaxies

•  derive cosmological parameters

Pisa Stellar Models Database Pre-‐MS Database: •  11653 evolu?onary tracks (M=0.2-‐7 Mo)

•  9756 isochrones (1-‐100 Myr)

•  20 metallicity values (Z=0.0001 – 0.03)

•  3 helium abundance values

•  2 deuterium abundance values

•  3 mixing-‐length values (1.2, 1.64, 1.9)

Tognelli, Prada Moroni, Degl’Innocen? 2011 (Astronomy & Astrophysics 533, 109)

Theory/Observa?ons

Gennaro, Prada Moroni, Tognelli 2012 (MNRAS 420, 986)

Pisa Stellar Models Database Low-‐mass Database: •  32646 evolu?onary tracks (M=0.3-‐1.1 Mo)

•  9720 isochrones (8-‐15 Gyr) •  216 chemical composi?ons

•  20 metallicity values (Z=0.0001 – 0.01)

•  5 helium abundance values

•  2 heavy-‐element mixtures

•  3 mixing-‐length values (1.7, 1.8, 1.9) Dell’Omodarme, Valle, Degl’Innocen?, Prada Moroni 2012 (Astronomy & Astrophysics 540, 26)

Pisa Stellar Models Database

Physical uncertain?es in stellar models

By simultaneously varying the main input physics, we obtained the first es3mate of the cumula?ve theore?cal uncertainty affec?ng:

•  M=0.9 Mo track: 2187 perturbed models

•  12 Gyr isochrone: 567 perturbed isochrones


Valle, Dell’Omodarme, Prada Moroni, Degl’Innocen? 2013 (Astronomy & Astrophysics, 549, 50)

First error stripe associated to a theore?cal stellar track


Valle, Dell’Omodarme, Prada Moroni, Degl’Innocen? 2013 (Astronomy & Astrophysics, 549, 50)

For a given turn-‐off luminosity, the inferred age varies in a range of ≈ ±0.375 Gyr

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