Cepheid multiplicity and masses fundamental parameters
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Cepheid Multiplicity and Masses: Fundamental Parameters. Nancy Remage Evans. Outline. Multiplicity: Motivation What we know Implications Masses: Motivation What we know Implications. Cepheids. 4-7 M  Formerly B stars Young ~50 Myr Post-RGB, core He burning

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Cepheid Multiplicity and Masses: Fundamental Parameters

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Cepheid multiplicity and masses fundamental parameters

Cepheid Multiplicity and Masses: Fundamental Parameters

Nancy Remage Evans

Thanks to Henrietta Leavitt


Outline

Outline

  • Multiplicity:

    • Motivation

    • What we know

    • Implications

  • Masses:

    • Motivation

    • What we know

    • Implications

Thanks to Henrietta Leavitt


Cepheids

Cepheids

  • 4-7 M

  • Formerly B stars

  • Young ~50 Myr

  • Post-RGB, core He burning

  • Evolve without strong mass loss of O stars

Thanks to Henrietta Leavitt


Multiplicity

Multiplicity

  • Star formation

    Binary, triple,….

    Distribution of mass ratios

    Maximum separation

    High vs low mass

  • Basis: ground-based orbits

Thanks to Henrietta Leavitt


High mass companions iue survey

High Mass Companions: IUE Survey

  • Particularly complete binary information

  • Evolved cool stars: sharp lines

  • Hot companions dominate in UV

  • Observed the 75 brightest Cepheids with IUE

  • All companions through early A detected

  • 21% companions

  • Using RV: 34%

Thanks to Henrietta Leavitt


Energy distributions

Energy Distributions

  • Hot companions

  • Normalized at 1600 A

  • Generally very low reddening

  • Well determined spectral types, mass

Thanks to Henrietta Leavitt


Mass ratios

Mass Ratios

  • M2/M1

  • Strong preference for low mass companions

  • Selection: orbital periods longer than 1 year

  • Contrast: binaries with P<40d: equal mass preference (Tokovinin, 2000)

Thanks to Henrietta Leavitt


Multiplicity completeness

Multiplicity: Completeness

  • Cepheids with orbits

  • 18 observed with IUE => hot companions known

  • Multiplicity?

M2unknown

Thanks to Henrietta Leavitt


Multiplicity completeness1

Multiplicity: Completeness

UV high res

  • High resolution UV spectra (HST, IUE): velocity of companion

  • 8 of 18

  • 5 of 8 are triples

Thanks to Henrietta Leavitt


Multiplicity s sge

Multiplicity:S Sge

  • Orbit => mass function: M1, M2, sin i

  • Mass from IUE spectrum

  • Secondary double

S Sge B IUE

Thanks to Henrietta Leavitt


Multiplicity completeness2

Multiplicity: Completeness

Triples

  • Cepheids with orbits + companion spectrum

  • 8 (possibly 9) are triple: 44% (50%)

Thanks to Henrietta Leavitt


Low mass companions

Low Mass Companions?

  • Cepheid companions young

  • Alpha Per Cluster: age of a typical Cepheid

  • Rosat observations: filled symbols are X-ray detections

  • Essentially all stars cooler than F5 V

  • Field stars would not be detected in X-rays

Thanks to Henrietta Leavitt


Expectations

Expectations

Duquennoy and Mayor

Solar type

  • Low mass companions?

  • Wide companions

  • Expectations

(days)

Cepheid Orbits

Thanks to Henrietta Leavitt


Chandra observation of polaris

Chandra Observation of Polaris

  • Center 3’ of ACIS-I field

  • Putative components marked

  • A = Aa + Ab

  • B F3 V

  • C, D

  • X-ray but no 2MASS: background AGN

Thanks to Henrietta Leavitt


System summary

System Summary

  • A = Aa +Ab

  • B (no low mass companion)

  • 2 possible distant stars (0.16 and 0.29 pc)

  • Searched:

    Magnitude difference of 15 mag

    Mass ratio range of 10

    Separation of 0.1 pc

Thanks to Henrietta Leavitt


Polaris a

Polaris A

  • Originally: no full amplitude Cepheid had been detected in X-rays

  • Probability favored Ab dwarf companion

  • BAAS 2009: Engle, Guinan, Evans, and DePasquale X-rays with XMM from 2 other Cepheids

  • X-rays not so good for unresolved low mass companions

  • Cepheid + K companion

  • Very interesting for atmospheric heating

Thanks to Henrietta Leavitt


Multiplicity results

Multiplicity: Results

  • High binary fraction

  • High triple fraction

  • Many small M2/M1for P > 1 yr

  • Needed: low mass companions?

  • Needed: Cepheid X-rays?

Thanks to Henrietta Leavitt


Masses

Masses

  • Why?

  • Benchmark for evolutionary tracks

  • Pulsation calculations

  • Problem: mass mismatch

  • Problem: blue loops

Thanks to Henrietta Leavitt


Masses evolutionary tracks

Masses: Evolutionary Tracks

  • Luminosity: mass of He burning core

    Core convective overshoot

    Rotation

    Radiative opacity

    Mass loss

Thanks to Henrietta Leavitt


Masses1

Masses

  • How?

  • Ground-based spectroscopic orbit

  • Double-lined spectroscopic binaries:high resolution UV spectroscopy: orbital velocity amplitude ratio + mass of secondary

  • Astrometric orbit of Cepheid (Benedict, et al.) + mass of secondary

  • Astrometric orbit of both (Polaris)

Thanks to Henrietta Leavitt


Masses2

Masses

  • Evolutionary framework

  • Padua, Geneva tracks: decreasing overshoot from left to right

  • S Mus,V350 Sgr:HST velocities

  • W Sgr, FF Aql: Benedict orbits

No overshoot

Thanks to Henrietta Leavitt


S mus

S Mus

  • Hottest companion

  • GHRS high resolution velocities

  • Temperature

Thanks to Henrietta Leavitt


S mus1

S Mus

H2

  • FUSE spectra

  • Standards reddened to match S Mus

  • H2 absorption

Thanks to Henrietta Leavitt


S mus2

S Mus

  • Example

S Mus, B3 V

B5 V

Thanks to Henrietta Leavitt


W sgr

W Sgr

  • Spectroscopic orbit: 4.3 yr

  • IUE: hot companion: A0 V

  • Small orbital velocity amplitude: face-on?

  • Inconsistent with reasonable Cepheid mass

  • Resolved?

Thanks to Henrietta Leavitt


W sgr b

W Sgr B

2625 A

  • STIS spectrum

  • Component B: resolved, hot

  • Spectroscopic binary: Cepheid Aa + Ab, cool

2800 A

Ceph +Comp Ab

0.16”

Comp B

Thanks to Henrietta Leavitt


W sgr1

W Sgr

  • Solid: extracted Cepheid Aa+ Ab spectrum

  • Dashed: Alp Aqr: slightly cooler than Cepheid

  • Ab not detected

  • MAb < 1.4 M

  • Mcep< 5.4 M

Thanks to Henrietta Leavitt


Eta aql

Eta Aql

  • B9.8 V companion

  • Orbit?

  • Eaton: 1 year

Thanks to Henrietta Leavitt


Summary pointers to the future

Summary: Pointers to the Future

  • List of orbits: future possibilities

  • Multiplicity: X-rays, (UV)

  • Masses: roadmap

Thanks to Henrietta Leavitt


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