FIELD BLUE STRAGGLERS AND RELATED MASS TRANSFER ISSUES George Preston, ESO, Santiago, 2012

FIELD BLUE STRAGGLERS AND

RELATED MASS TRANSFER ISSUES

George Preston, ESO, Santiago, 2012

TO BEGIN: A LITTLE HOMAGE

We stand on the shoulders of giants who pioneered stellar structure and evolution in interacting binaries

G. P. Kuiper

O. StruveZ. Kopal

R. Kippenhahn

B. Paczynski

F. Hoyle

H. Bondi

W. H. McCrea

L. Lucy

A. Sandage

mass transfer giants

of the 20th century

G. P. Kuiper

O. StruveZ. Kopal

R. Kippenhahn

B. Paczynski

F. Hoyle

H. Bondi

W. H. McCrea

L. Lucy

A. Sandage

mentor

mentor

friend friend

friend


of the 20th century

G. P. Kuiper

O. StruveZ. Kopal

R. Kippenhahn

B. Paczynski

F. Hoyle

H. Bondi

W. H. McCrea

DetachedSemi-detached

Contact

gas streamsBeta Lyrae

Bondi-Hoyle accretion

Hoyle-Bondi accretion

The BS mass-transfer

model

CasesAB&C

Roche lobe overflow

Mass transfer

The Algol paradox

& more L. Lucy

The mostcamera-shy

giant known

A. SandageHe discoveredBlue stragglers


of the 20th century

While reading papers on the subject of my talk, I was surprised to discover

…

how often first-class astronomers ignore each other’s work!

Thus,Sandage (AJ 1953) first identified blue stragglers unambiguosly in M3

McCrea invented an explanation for Sandage’s blue stragglers 11 years later (MNRAS 1964) with no reference to Sandage.

Böhm-Vitense (ApJ 1980) confirmed operation of McCrea’s process 16 years later in the ζ Capricorni system with no reference to eitherSandage or McCrea.

McClure (ApJ 1984) brilliantly generalized Böhm-Vitense’s result 4 years later with no reference to Sandage or McCrea or Böhm-Vitense.

how often first-class astronomers ignore each other’s work!

Thus,Sandage (AJ 1953) first identified blue stragglers unambiguosly in M3

McCrea invented an explanation for Sandage’s blue stragglers 11 years later (MNRAS 1964) with no reference to Sandage.

Böhm-Vitense (ApJ 1980) confirmed operation of McCrea’s process 16 years later in the ζ Capricorni system with no reference to Sandage or McCrea.

McClure (ApJ 1984) brilliantly generalized Böhm-Vitense’s result 4 years later with no reference to Sandage or McCrea or Böhm-Vitense.

Three decades of ignoring!

WTF!

Finally, in 1989 Peter Leonard set the stage for this conferenceAJ 98, 217

CHRONOLOGICAL LISTOF HYPOTHESES

HOW TO IDENTIFY FBS

Of necessity, in the field we first identified metal-poor FBS by colorimetry.

Preston et al. 1994

BM

P st

ars

HK Survey: Beers et al. 1985, 1992

MS [Fe/H] = 0

MS [Fe/H = 1

Metal poor stars near GC turnoff

BHB

W. W. Morgan would have calledthe BMP stars a“natural group”.


Any photometricsystem with a

uv filter will work.

RHB

BM

P st

ars

MS [Fe/H] = 0

MS [Fe/H = 1

Metal poor stars near GC turnoff

BHB

W. W. Morgan would have calledthe BMP stars a“natural group”.


Any photometricsystem with a

uv filter will work.

RHB

FBS area subset of BMP

Preston et al. 1994

In BMP domain isochrones with a wide range

of ages and metallicities overlap in a tangled mess.

Preston & Sneden 2000

Isochrones of various [Fe/H] values and ages overlap in a 2-color diagram of the BS domain.

RYI IsochronesGreen et al. (1987)

main sequence isochrones

subgiant isochrones

Turnoffs for: [Fe/H] = 2.2 ages 3 7,10 Gy

Hence, “straggle”

In BMP domain isochrones with a wide range

of ages and metallicities overlap in a tangled mess.

Isochrones of various [Fe/H] values and ages overlap in a 2-color diagram of the BS domain.

main sequence isochrones

subgiant isochrones

Turnoffs for: [Fe/H] = 2.2 ages 3 7,10 Gy

Hence, “straggle”

Location in this trapezoid doesn’t tell us much about

age and composition


RYI IsochronesGreen et al. (1987)

The cool (red) edge of the BS domain in any stellar system is defined by stars

that are not members of the domain

Mandushev, Fahlman, Richer 1997, AJ

MEMBERSHIP CRITERION

STRANGE DEFINITION

The cool (red) edge of the BS domain in any stellar system is defined by stars

that are not members of the domain

STRANGE DEFINITION


MEMBERSHIP CRITERION

what I see

what they did

mass transfer sequence

MOST FBS COMPRISE A SUBSET OF A LARGER FAMILY OF MAIN SEQUENCE MASS-TRANSFER BINARIES


Use of MSTO coloras a boundary

obscures this reality

STRANGE DEFINITION


Use of MSTO coloras a boundary

obscures this reality


What happened here?

We all do it!


Struve - dodging

12 Gy isochrone

surely FBS

CS 22949-008pri. & sec.

CASE IN POINTMetal-poor CEMP binaries below MSTO in hierarchical triples

Masseron et al. 2012, ApJ, 751:14


CS 22964-161

= CEMP, literature

~ 3

mag

.


3 m

ag

CS 22949-008secondary



Various tools have been devised to isolate field blue stragglers.Pier (1983) pioneered the identification of FBSs.

FBS

BHBD(0.2)

0.2

Ca II K line versus color Abundance calibration of Ca II K line

any Balmer line what it accomplishes

FBS

BHB

Manduca & Bell 1978

Clewley et al. borrowed this one from extragalactic astronomy.The Sersic function

Y =

Galaxies are merely Balmer lines turned upside down

Clewley et al. borrowed this one from extragalactic astronomy.Sersic (b,c) Balmer parameters isolate FBS particularly well.

Their use does not require knowledge of photometric colors.

FBS

BHB

Clewley et al. 2002

Clewley et al. borrowed this one from extragalactic astronomy.Sersic (b,c) Balmer parameters isolate FBS particularly well.

Their use does not require knowledge of photometric colors.

FBS

BHB

Clewley et al. 2002

An application of Sersic parameters to Sloan data in the distant halo

(n = 4985)

(n = many)

Xue et al. 2011

A nuisance for Xue et al.

“One man's trash is another man's treasure.”

- old English aphorism

Sarajedini 1993, ASP Conf. Ser.

Globular clusters provide luminosity calibrationfor Galactic structure applications, e.g. halo (R)

Z = 0.0001 Z = 0.004

MV) 0.5 mag/star(distance) 3 %/100 stars

Sarajedini 1993, ASP Conf. Ser.

Globular clusters provide luminosity calibrationfor Galactic structure applications, e.g. halo (R)

Z = 0.0001 Z = 0.004

68% within 1

GROUP PROPERTIES OF FBS

It is easy to find binaries among FBS candidates

RV-constant stars Binary stars

A child can do it

JD - 2400000

10 years

A high % of FBS are members of spectroscopic binaries


4 km/s

20 km/s

vertical scales are not uniform

Very high (70% vs 15%)

Preston & Sneden 2000, AJ

A high % of FBS are members of spectroscopic binaries

But a low % of FBS are in double-lined spectroscopic binaries

Very low (essentially zero)

≤

The one DLSB, CS 22873-139, included here is contested by Spite et al. 2000, A&A, 360, 1077


FBS & CEMP binaries have distinctive orbital characteristics

Normal MS binaries disk = xhalo = o

BMPblue metal-poor

C, s-process rich


FBS & CEMP binaries have a high % of small orbital eccentricities, deficits of short periods, and no P > 4000 d

deficit of short periods

excess of low eccentricities

Normal MS binaries disk = xhalo = o

BMPblue metal-poor

C, s-process rich


COROTATIONcircularization

Vrot 50R/Porb

Porb Vrot

25 2 10 5 5 10 1 50

no BMP, CEMPbinaries

with P > 4000 d

and their small mass functions suggest companions with white dwarf masses (~ 0.6M).

f1 = K13 P / (2 π G) = M2

3 (sin3 i) / (M1 + M2)2

FBS Ba, CH cousins

Preston & Sneden 2000, AJ McClure & Woodsworth 1990, ApJ

FBS BaII

All of the preceding:High binary fractionDeficit of short (and very long) periodsLow orbital eccentricitiesSmall mass functionsNo visible secondaries *And Thank You, Erika, for Capricorni

tell us that FBS are a species sui generis

* Hierarchical triples excepted

white dwarfflux red wing of L

in white dwarf

All of the preceding:High binary fractionDeficit of short periodsLow orbital eccentricitiesSmall mass functionsFew (no) visible secondariesAnd Thank You, Erika, for Capricorni

tell us that FBS are a species sui generis

My perspective:Wide binary disruption is main reason

for the specific frequency deficitin GCs relative to the Galactic field

4.0

FBS

FBS

Specific frequency of FBS appears to be the upper bound of a sequence defined by OCs (DeMarchi et al 2006) and GCs (Piotto et al 2004)

This is a lo

garithm

This isn’t

Something like “concentration” must be what matters


visualbinaries

c.p.m.binaries{

radial velocitybinaries P<4000 d

This 13% of radial velocity binaries with P 5 d merge in less than a Hubble time (Vilhu, 1982, A&A, 109, 17). Hence, the deficit of short period binaries in the field.

These more frequent wide binaries are largely disrupted in GCs. Hence, the relatively low specific frequency of blue stragglers in globular clusters.

This interpretation follows fromthe presumption that the

Duquennoy-Mayor (1991, A&A)period distribution is universal.

Ockham’s Razor, etc

William of Ockham1248-1307

DUSTING

DUSTING

Wind accretion

How do you hide it?

DUST: The thin layer that you notice on tables

just before your guests arrive

In the house use this



In stars redistribute by thermohaline mixing.



Reconciliation of theory and observation

Observational facts & procedures:

Census of orbital parameters for MS and post-MS C and Ba starsDetection criteriaDetection threshholds bias incompletenessObserver persistence (w/r RV)

Theory:

Mass transfer by winds Including details like solving the Davies-Pringle (1980) puzzle.

AGB theory and practice of Busso & Gallino andConvective envelopesGravitational settling and stabilizing molecular gradientsDilution with and without thermohaline mixing

those

those

all

otherItalian

s

those

all

How many MS CEMP survive the RGB ascent?

INNOCENT QUESTION:

Is the observed density ratio (RGB)/(MS) OK?

MS

CEMP(RGB)

CEMP(MS)

(kpc-3) = space densityn = nuclear time scale

relative volumes searched (in apparent magnitude limited surveys)

RGB

IF (crude example) LRGB /LMS ~ 40

i. e.,Volume ratio = VR ~ 250

and withn(RGB)/n(MS) ~ 102

OBTAIN(RGB)/(MS) ~ VR*n~ 2.5

Is this OK?

M

V ~ 4 m

ag

those

all

How many MS CEMP survive the RGB ascent?

INNOCENT QUESTION: Is the observed density ratio (RGB)/(MS) OK?

MS

CEMP(RGB)

CEMP(MS)

relative volumes searched (in apparent magnitude limited surveys)

RGB

In other words,Do

Thesemapinto

Those?

THE QUESTION:Does

This populationmapinto

That population

?

those

those

all

Stars with “no-dilution” solutions

dilution dil = log MCE/MAGBacc

x

dilutions from Bisterzo et al. 2012, MNRAS, 422, 849

All the CEMP stars with “no-dilution” solutionslie near or above MSTO; ~ half are FBS)

MSTO

n(RGB)/n(MS) ~ 2.5 in Bisterzo et al. sample. Agreement not so bad. I was a bit surprised.

dilu

tio

n

pure AGB

Vertical lines indicate ranges of solutions

No dilution

2012

FBS 7000ºK no dilution RGB 5280ºK dil = 0.7, 1.7

adjust model parameters to minimize residuals 0.2 dex

We have very little information about wind accretion at large distances from an AGB donor.

[s]

Regression below is anchored by two long-period SLSBswith primaries originally classified as ordinary GK giants!

Griffin 1985

G8 III

K0 III

[s]

Regression below is anchored by two long-period SLSBswith primaries originally classified as ordinary GK giants!

Griffin 1985

G8 III

K0 III

Want more candidates? See McWilliam 1990, ApJS, 74

23/671= 4% of GK giantsV(mag) 6.0, [s] > 0.2

Expect 20,000 more in HD (V<11)

[s]

0.2

A bunch of calculations for MS stars with various

ages and [Fe/H]

Pinsonneault, DePoy, & Coffee 2001, ApJ

FBS convection zone rapidly disappears at Teff > 6500 K

He, Sr, Ba, sink in M2 prior to AGB evolution of M1.

Negative –gradient inhibits thermohaline mixingWhat happens when a Ba-rich long-P FBS ascends RGB?

Will we recognize it, or will it disappear?

7000

-3.5

-4.0

Humoris still alive in

the USA!

FBS live here

loga

rith

ms!

!

VB

CPM

The period distribution of Ba stars declines at P > 2000 d and dies at P ~ 5000 d, but the period distribution of MS binaries peaks at P > 10000 d.

(Jorissen & Van Eck 2001)

Extant data provide a clue.

F-G binaries ofDuquennoy & Mayor 1991

(Jorissen & Van Eck 2001)

F-G binaries ofDuquennoy & Mayor 1991

VB

CPM

The period distribution of Ba stars declines at P > 2000 d and dies at P ~ 5000 d, but the period distribution of MS binaries peaks at P > 10000 d.

Extant data provide a clue.

observer persistence problem?

or what?

Orbital speeds at P = 10000 days are easily measured by modern spectrographs.

An unavoidable conclusion: winds “run out of gas” at some long P. Which?

2 3 4 5 6

log P(days)

0

5

10

15

20

K1 (k

m/s

)

m1 = 0.8, m2=0.5

K13P = constant

Newton’s laws are very tolerant of long orbital periods.

VB CPMRV source of data

THOSE YOUNG A-TYPE STARS FAR FROM THE GALACTIC PLANE

ANOTHER INCONVENIENT TRUTH

This began long ago with Charles Perry and Alex Rodgers

Perry*1969 Rodgers*1971; Rodgers*, Harding*& Sadler 1981

I circled and boxeddata for

metal-rich A starsthat stray far from

Galactic plane

AVG = 5250 AVG = -0.23

* People I have known forever

This all began with Perry and Rogers, Harding & Sadler

Perry 1969 Rogers, Harding & Sadler 1981

I circled and boxeddata for

metal-rich A starsthat stray far from

Galactic plane

AVG = 5250 AVG = -0.23

Santos et al. 2009, A&AThe average [Fe/H] for these A-Stars 5 kpc from the Galactic plane is slightly lower

than the average value near the sun.

* People I have known forever

Perry 1969 Lance 1988

north south

log

g

= 5040/T

W(A stars) = 62 km/sW(thick disk) = 42 km/s

Lance (1987): Early A-type stars far from the Galactic plane

two-slope density signature, larger W, hotter than BMP

700

0

800

0

900

0

100

00

Teff

Perry 1969 Lance 1988

They are apparently quite youngIf they are blue stragglers, what do they straggle behind?

north south

log

g

= 5040/T


isochrone fort = 5.0E+8 y

isochrone fort = 5.0E+8 y

Rodgers/Lance hypothesis: star formation during recent interaction

of a metal-poor, gas-rich satellite with the disk of the Milky Way.

They are apparently quite youngIf they are blue stragglers, what do they straggle behind?

log

g

= 5040/T


Rodgers/Lance hypothesis: widely ignored in discussions of Milky Way halo

widely accepted in discussions of distant mergers

Young GCs in NGC 7252

(Schweizer & Seitzer 1998)

Lots of young stars In these globular clusters!

Rodgers/Lance hypothesis: widely ignored in discussions of Milky Way halo

widely accepted in discussions of distant mergers

H imageTrue Color

youn

g fie

ld s

tars

1st p

ass

over

lap

regi

ondu

st o

bscu

red

2nd

pass

even

you

nger

sta

rs2n

d pa

ss

(Whitmore et al. 1999)

CHEMICAL ABUNDANCES ABOVE AND BELOW

THE MSTO

Deep mixing accompanying merger, collision, mass transferburns 7Li to 4He ash low Li is a straggler signature.

BUT confirmation requires a big telescope for most FBS.

data from Thorburn 1994, ApJ, 421

M

ST

O

TERRITORY

BLUE STRAGGLER

Deep mixing accompanying merger, collision, mass transferburns 7Li to 4He ash low Li is a straggler signature.

BUT confirmation requires a big telescope for most FBS.

data from Thorburn 1994, ApJ, 421

M

ST

O

NB: Li deficiencies also occur below MSTO

Mass transfer sequence again

?

!!!

BLUE STRAGGLER

TERRITORY

?

data from Preston & Sneden 2000, AJ

Galactic FBS

dSph red giants

halo stars

Compare dSph red giants to Galactic stars – Venn et al. 2004, AJ

thick disk

thin disk

What we might learn from the -elements.

What we might learn from the -elements.

data from P&S 2000, AJ

Galactic FBS

dSph red giants

halo stars

Compare dSph red giants to Galactic stars – Venn et al. 2004, AJthick disk

thin disk

RV-constant BMP stars: Intermediate-Age captures

from a dSph satellite like Carina?

Stetson et al. 2011, ESO Messenger

13 Gy

8 Gy

CH

The “non-variable” spectrum is the

mean of three stars

The FBS binary CS 29497-030 illustrates how the carbon signature responds to an increase in Teff

C I

Enter the AGB: Carbon and n-capture elements

G-band becomes inconspicuous

Atomic C becomesbetter signature

Sneden, Preston, & Cowan 2003, ApJ

Note similarities of Fe-peak lines

versus disparities of the Ba and Pb lines

The “non-variable” spectrum is the mean

of three stars

CS 29497-030 = FBS (B-V)0 = 0.30

CS 29497-030 = FBS (B-V)0 = 0.30

OTHER DIAGNOSTICS

Sneden, Preston, & Cowan 2003, ApJ

Lead-rich binary CS 29497-030

The “non-variable” spectrum is the mean of

three stars

Question:Is this a FBS?(B-V)0 = +0.30(U-B)0 = - 0.14[Fe/H] = - 2.6

CS 29497-030 = FBS (B-V)0 = 0.30

CS 29497-030 = FBS (B-V)0 = 0.30

MSTO color vs [Fe/H]

Every FBS has its own red color boundary

Answer: Yes

Lead-rich binary CS 29497-030

So, use [Fe/H], (B-V)0 to identify FBS, star-by-star

Question:Is this a FBS?(B-V)0 = +0.40(U-B)0 = - 0.14[Fe/H] = - 2.2

MSTO color vs [Fe/H]

Answer: No

hypothetical FBS candidate x

Hypothetical FBS candidate

DÉJÀ VU ALL OVER AGAIN!

neutron/seed ratio decreases

X = IA pop = BS pop

x

Orbit dimensions, RGB, AGB mass transfer FBS binaries ( ): n-capture normal abundances (low [C/N], high 13C/12C )

mass transfer only during RGB evolution

FBS binaries ( ): n-capture over-abundances (low [C/N], high 13C/12C ) mass transfer during RGB & AGB evolution

FBS single stars (X): n-capture normal abundances (high [C/N], low 13C/12C ) no mass transfer

FBS PULSATORSFBS PULSATORS

Pulsation like this would produce chaos in FBS binary RV curves,so we know that such pulsators are rare among FBS binaries.

30 km

/s

ORBIT

PULSATION

ΔV ~ 0.1 mag.

Shift due toorbital motion

Preston & Landolt 1999 AJ

54 minutes

317 days

30 km

/s

54 minutes

Conclusion: Such pulsation is rare among metal-poor FBS(like 1/42 2 or 3 %) although most FBS lie in instability strip

ORBIT

PULSATION

Preston & Landolt 1999 AJ

HADS confined to narrow band in the instability strip.McNamara (1997), Petersen & Dalsgaard (1999)Kepler data confirm (Balona & Dziembowski 2011)Pulsator fraction: ~ 0.5 only in HADS band < 0.5 everywhere else

Sct instability strip

McN

amar

a’s

field

sta

rs

Poretti et al. 2008, ApJ

RR Lyraes fill their instability strip, but SX Phe stars in Fornax II probably are confined to McNamara’s HADS strip.

RR Lyraes fill their instability strip, but SX Phe stars in Fornax II probably are confined to McNamara’s HADS strip.

Poretti et al. 2008, ApJ

RR Lyr

SX Phe

STARS THAT DON’T FIT

2500 3000 3500 4000 4500 5000 5500

Julian Date

-60

-50

-40

-30

-20

-10

0

10

20

30

RV

(km

/s)

TY Gru 2003 - 2010

C & s-process rich stars that don’t fitC & s-process rich stars that don’t fit

1 km/s

20 years

2500 3000 3500 4000 4500 5000 5500

Julian Date

-60

-50

-40

-30

-20

-10

0

10

20

30

RV

(km

/s)

TY Gru 2003 - 2010


After so many years of this– NADA!

1 km/s

2500 3000 3500 4000 4500 5000 5500

Julian Date

-60

-50

-40

-30

-20

-10

0

10

20

30

RV

(km

/s)

TY Gru 2003 - 2010


After so many years of this– NADA!

1 km/s

Tengo 82 anos – no mas para mi. I quit!

Typical FBS

CS 22949-008

Not yet

Lyrae

Evans, D. 19XX (GWP can’t find reference)

Documents

FIELD BLUE STRAGGLERS AND RELATED MASS TRANSFER ISSUES George Preston, ESO, Santiago, 2012