Asteroseismology and the Time Domain Revolution in

Astronomy

Marc Pinsonneault

Ohio State UniversityCollaborators:The APOKASC teamMelissa NessMarie Martig

The Need for Precision Stellar Astrophysics

Stars are important across a wide range of astrophysics

Origins Questions– Planet Formation– Structure Formation

Complex Observational Patterns: Things Move!Þ Precise Data NeededÞ Need Better Stellar Physics

Kepler mission:160,000 stars

monitored

Waves are Generated by Turbulence in Stars

Two Major Impacts of AsteroseismologyWe can measure fundamental properties (mass, radius, age, rotation) in bulk stellar populations

Extremely precise surface gravities are a natural product

We have entirely new categories of stellar observables– Surface CZ depth– He ionization– Core rotation– Core mass and density

Spectroscopy + Asteroseismology 2Gether 4Ever

Solar-like Oscillations in Kepler16 Cyg AMetcalfe et al. 2012

Pure p-mode pattern

nmaxRotational Splittings

The observed oscillation

pattern is a strong

function of log g

From Chaplin & Miglio 2013

Giants and Kepler

Giants are high-amplitude pulsators– Periods of days to months

Long period is a huge advantageÞ Accessible with 30 minute cadenceÞ 16,000 stars monitored, essentially all detected

(Mosser et al. 2009; Hekker et al. 2010)

Observed frequency pattern is complex!

Giant and Dwarf Frequency Patterns Compared

CM13

The Complex Giant Pattern is Explained by Mixed Modes

Mixed modes propagate as p-modes in the convective envelope and g-modes in the deep core; especially strong impact on l=1

l=0 modes are pure p-modes

Seen in red giants (Bedding et al. 2010) because the p and g mode frequencies become commensurate

Comparing the two yields distinct diagnostics of core and envelope properties

Distinct Patterns in Different Evolutionary States

Dwarf Subgiant

RGB RCCM13

Scaling Relations for Bulk Populations

Two most basic observables: – Frequency of maximum

power– Mean frequency spacing

Hekker et al. 2010data for Kepler giants

Radius and Mass Scaling in ClustersDiscrepancy for clump giant radii relative to RGB radii (~0.05) tied to structural properties

Small but real mass difference 0.06-0.08 Msun, RGB vs. that expected from EB constraints on the MS (Brogaard et al. 2012)

Miglio et al. (2012)

Epstein et al. (2014)

Trouble In Halo-Land

Halo Star Masses From SR Are WellAbove Expected Values….

Beyond Scaling Relations:Towards Reliable Masses

Boutique Modeling:Reasonable Mass!

Parallax+ Dn:Reasonable Mass!

Gaia will have a huge impact

Calibrate…Correct…OR

Two Paths ForwardBoutique Modeling

Use the full information in the frequency spectrum

Use absolute frequencies for evolutionary state

Replace nu(max) with g-mode spacings

Add in proper modeling of mean density

Parallax Über Alles

P + Fluxes+ Teff = R

Add in proper modeling of mean density

Profit!

APOGEE at a GlanceThe Apache Point Observatory Galactic Evolution ExperimentOperates in the near-infrared (H band): 1.51-1.68 mmTargeted ~105 RG stars sampling the bulge, disk(s), and halo(es)DR10 (Ahn et al. 2014): [M/H], [a/Fe] DR11-12 (Alam et al. 2015) 15 Element Mix (C, N, O, Na, Mg, Al, Si, S, K, Ca, Ti, V, Mn, Fe, Ni)

More numbers!• S/N = 100+/pixel• R ~ 22,500• ~230 science fibers, 7 deg2

FOV• RV precision: ~ 100 m/s• Abundance precision: <0.1

dexS. R. Majewski

APOKASC SummarizedORIGINAL KEPLER FIELD

Dwarfs: Kepler Field Control– ~2,000 (AU 2015)– ~7,000 (SU 2016)

Giants: Population Asteroseismology– DR10: 1,916 (Pinsonneault et al. 2014)– DR11+12: ~8,000 (AU 2015)– DR13: ~16,000 (SU 2016)

Targeting Criterion:H<11 (1 hour exposure)Teff < 5500 K

Automated Pipeline Analysis

Boutique analysis of 100,000 targets…NO.

Automated fitting algorithm (FERRE) for the entire H band spectrum

Ex post facto calibration of results against independent measurements– Star cluster members– Asteroseismic log g

Calibrating the Pipeline: Temperatures

Meszaros et al. (2013)Star Cluster Data

Holtzman et al. (2015)Low Reddening Photometric Temperatures

Calibrating the Pipeline:Surface Gravity

Meszaros et al. (2013):Cluster Star + asteroseismic log g

Holtzman et al. (2015)Pure asteroseismic log g

Calibrating the Pipeline:Metallicities

Meszaros et al. (2013)

Holtzman et al. (2015)

New: 15 Element Mixture

Individual Elements fit with a limited line list calibrated vs. cluster stars

APOGEE: 100,000 Red Giant Spectra

The APOKASC ApproachAPOGEE sample: 1916 stars that pass quality control checks

Extract mean asteroseismic properties (Dn, nmax)

Scaling relations + grid-based modeling

Pinsonneault et al. 2014

Results: Snapping Into Focus

Photometry Spectroscopy Asteroseismology +SpectroscopyPinsonneault et al. 2014

Mass Trends, Fixed [Fe/H]

Metallicity Trends, Fixed Mass

A Test of Atmospheres

The difference between asteroseismic and spectroscopic log g is different for RC, RGB

Is this an atmospheres or asteroseismic systematic?

One Size Does Not Fit All

Macroturbulence is very different in the clump and RGB

Þ Different line broadening

Þ Impacts gravities

Massarotti et al. 2008

Testing the Assumptions of Chemical Tagging

Martig et al. 2015 4% of high [a/Fe] stars are young (or mergers)

…Invisible to Traditional Surveys

On the Way:Much larger a-rich, metal-poor samples

New in 2015: Richer Phase Space Coverage

Much Larger Sample Size

The Future of Large Spectroscopic Surveys?

Ness et al. 2015a

“Cannon”

Compare Spectra toEmpirical Calibrators,Not Directly to Models

From Spectra to Mass and Age

Surface C/N, C12/C13 are strongly related to mass through 1st dredge-up

=> Spectroscopic Mass labelling of red giants!

Martig et al. 2015b

An Age Map of the Red Clump…

Asteroseismic Masses Inferred From Spectra (Ness et al. 2015b)

…Across the Galaxy

Ness et al. 2015b

Kepler Rebooted: K2

The New Kepler Mission: Step and Stare in the Ecliptic PlaneStrong overlap with APOGEE fields; opportunity for samplinga wide range of stellar populations-TESS; PLATO;…..

Future: SDSS-4 + K2

SDSS-4: Two spectrographs (north and south)

K2 – numerous APOGEE targets already in fields, used for targeting.

10,000+ fibers reserved for K2 targets