GLOBULAR PROTEINS. TYPES OF PROTEINS GLOBULAR PROTEINS FIBROUS PROTEINS.
Observations of Binaries in Globular Clusters Adrienne Cool San Francisco State University.
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Transcript of Observations of Binaries in Globular Clusters Adrienne Cool San Francisco State University.
Observations of ^ Binaries in Globular Clusters
Adrienne Cool San Francisco State University
Primordial
OUTLINE
• Why bother?
• What do we want to know?
• How can we find out?
• What’s new?
• What’s next?
Why bother?
• Binary fraction is a fundamental parameter
• Primordial binaries play a key role in cluster dynamics
• Primordial binaries are implicated in the formation of many more exotic populations
What do we want to know?
• What fraction of globular cluster stars are binaries? • Do clusters have different binary fractions (fb)? Any correlation with particular cluster parameters?
• Are there signs of dynamical evolution of binaries?
• How are the binaries distributed in…• period (Porb)• eccentricity (e)• mass ratio (q m2/m1)• primary mass
How can we find out?
radial velocity variables
photometric variables
outliers incolor-magnitude diagrams
3 methods used so far…
Pryor / Hut et al. 1992 Kaluzny et al. 1999 Rubenstein & Bailyn 1997
Method 1: Radial velocity variables
• ground-based spectroscopy• samples of ~30-300 giants• ~2-4 velocities per star• accuracies ~0.6–3 km/s• baselines ~ 1-20 years
Cote et al. 1996 – M22
sensitive to binaries withPorb ~ days – years
fb estimates depend oneccentricity distribution
cluster MV c bin/total fb Porb reference47 Tuc, M2, M3
M12, M13, M71–9.4 –
–5.6
2.03 –
1.15
6 / 393 ~ 5 % (circ)
~ 12 % (therm)
0.2 – 20 yr Pryor et al.
1989
NGC 3201 –7.5 1.30 2 / 276 6 – 10 % (circ)
15 – 18 % (therm)
0.1 – 10 yr Cote et al.
1994
NGC 5053 –6.7 0.84 6 / 66 ~ 20 – 30% 3 day – 10 yr Yan & Cohen
1996
M71 –5.6 1.15 12 / 121 10 – 30 % (circ)
15 – 40 % (therm)
3 day – 10 yr Barden et al.
1996
M22 –8.5 1.31 0–1 / 109 1+10–1 % (circ)
3+16–3 % (therm)
0.2 – 40 yr Cote et al.
1996
M4 –7.2 1.59 0 – 2 / 33 15 15% @ > 4 rc 2 day – 3 yr Cote & Fischer 1996
Cen –10.3 1.61 ? / 310 3 – 4% 0.5 – 10 yr Mayor et al.
1996
Pal 5 –5.2 0.70 -- / 17 40 20%
(68% conf)
a < 50 A.U. Odenkirchen et al. 2002
searches for radial velocity variables
Method 2: photometric variables
Albrow et al. 2001 – 47 Tuc
• HST & ground-based imaging• ~ 2000 – 40,000 stars sampled• 250 – 1300 images• baselines ~ 1 week – 1 month
sensitive to binaries withPorb ~ 0.1 day – few days
fb estimates depend on assumedPorb, e, q distributions
cluster MV c bin/total fb Porb reference
M71 –5.6 1.15 5 / 5300
~ 0.09 %
4 contact
10 – 72 %
Porb < 800 yr
0 – 5 rc
hours - days Yan & Mateo 1994
M5 –8.8 1.83 6 / 3600
~ 0.17 %
5 contact
22 – 39 %
2.5 day – 550 yr
4 – 8 rc
hours - days Yan & Reid 1996
47 Tuc –9.4 2.03 26 / 46,422
~ 0.06 %
11 detached
16 contact
13 6 %
(5 w/Porb> 4 day)
0 – 4 rc
0.3 hr – 15 day Albrow et al. 2001
47 Tuc –9.4 2.03 28 / 43,067
~ 0.07 %
7 detached
21 contact
--
15 rc – 0.6 rt
2 hr – 60 day Weldrake et al. 2004
M4 –7.2 1.59 0 – 1 / 2102
0.05 %
--
@ 6 rc
4 hr – 6 day Ferdman et al. 2004
searches for eclipsing binaries – selected results
Method 3: Outliers in color-magnitude diagrams
Cool & Bolton 2002 – NGC 6397
• HST & gnd-based imaging• 100s – 1000s of stars• 2 filters is enough• no repeat measure required• high photometric accuracy
sensitive to binaries with… any Porb, e, inclination!
fb estimates depend on assumed q distribution, F(q)
cluster MV c fb note ref.
M92 –8.2 1.81 < 9 % @ 10 – 30 rc all q Romani & Weinberg 1991
M30 –7.3 2.50
pcc
< 4 % @ 25 – 65 rc all q Romani & Weinberg 1991
NGC 288 –6.7 0.96 ~ 10 % @ 0 – 6 rc lower limit
q 0.7
Bolte
1992
E 3 –2.8 0.75 29 9 % @ 0 – 2 rc
lower limit?
q 0.7 ?
Veronesi et al.
1996
NGC 2808 –9.4 1.77 24 4 % @ 24 rc lower limit
q 0.8 ?
Ferraro et al.
1998
M30 –7.3 2.50
pcc
5 2 % @ 100 rc lower limit
q 0.7-0.8 ?
Alcaino et al.
1998
searches in color-magnitude diagrams – selected early results
cluster MV c fb note ref.
NGC 6752 –7.7 2.50
pcc
15 – 38 % [99.7% conf.] @ < 1 rc
< 16 % [99.7 % conf.] @ > 1 rc
Monte-Carlo
various F(q)
Rubenstein & Bailyn 1997
NGC 6397 –6.6 2.50
pcc
3 % (q 0.45) @ 0 – 18 rc
5 – 7 % (all q) @ 0 – 18 rc
flat F(q)
extrapolated
Cool & Bolton
2002
NGC 288 –6.7 0.96 10–20 % [8–38% @ 99.9%] @ < 1 rh
0 – 10 % [<10% @ 99.9%] @ 1-2 rh
Monte-Carlo
various F(q)
Bellazzini et al. 2002
Pal 5 –5.2 0.70 9 1 % @ < 1 rc (Poisson errors)
9 8 % @ 2 – 3 rc
lower limit
(high q only)
Koch et al.
2004
Pal 13 –3.7 1.31 30 4 % (Poisson errors) @ 0-18 rc
lower limit
(high q only)
Clark et al. 2004
M4 –7.2 1.59 ~ 2 % @ < 1 rc
~ 1 % @ > 1 rc
lower limit
(high q only)
Richer et al.
2004
M3 –8.9 1.84 6 – 22 % [3–35% @95%] @ < 1 rc
1 – 3 % [0–22% @ 95%] @ 1-2 rc
Monte-Carlo
various F(q)
Zhao & Bailyn
2005
searches in color-magnitude diagrams -- more recent results
What fraction fb of globular cluster stars are binaries?
Does fb differ among clusters? Range?
Do any clusters have fb = 0% ? 100% ??
cluster MV c bin/total fb Porb fb (3 decades)
Cen –10.3 1.61 ? / 310 3 – 4% 0.5 – 10 yr 7 – 9 %
M22 –8.5 1.31 0–1 / 109 1+10–1 % (circ)
3+16–3 % (therm)
0.2 – 40 yr 1.3+13–1.3 % (circ)
4+21–4 % (therm)
NGC 3201 –7.5 1.30 2 / 276 6 – 10 % (circ)
15 – 18 % (therm)
0.1 – 10 yr 9 – 15 % (circ)
23 –27 % (therm)
M4 –7.2 1.59 0 – 2 / 33 15 15% @ > 4 rc 2 day – 3 yr 16 16% @ > 4 rc
NGC 5053 –6.7 0.84 6 / 66 ~ 20 – 30% 3 day – 10 yr ~ 20 – 30%
M71 –5.6 1.15 12 / 121 10 – 30 % (circ)
15 – 40 % (therm)
3 day – 10 yr 10 – 30 % (circ)
15 – 40 % (therm)
radial velocity variables – global binary fractions
• typical fb ~ 15% (~5% per decade)
• trend toward lower fb for massive clusters (high , low Pcrit)
disruption of soft binaries? Cote et al. 1996
Odenkirchen et al. 2002 – Pal 5
• MV = –5.2
• c = 0.70
• single epoch, VLT
• 17 cluster stars
• accuracy ~ 0.15 km/s
broad pedestal under narrow peak = binaries?
fb = 40 20 %
Pal 5
photometric variables – global binary fractions
cluster MV c bin/total Porb fb Porb assumed ref
47 Tuc –9.4 2.03 26 / 46,422
~ 0.06 %
11 detached
16 contact
0.1 hr –
15 day
13 6 %
(5 w/Porb> 4 day)
0 – 4 rc
2.5 d – 50 yr A01
M5 –8.8 1.83 6 / 3600
~ 0.17 %
5 contact
hours –
days
22 – 39 %
4 – 8 rc
2.5 day – 550 yr YR96
M71 –5.6 1.15 5 / 5300
~ 0.09 %
4 contact
hours –
days
10 – 72 %
0 – 5 rc
< 800 yr YM94
47 Tuc: fb ~ 2 – 5 % per decade for hard binaries
consistent with vrad results
CMD outliers – binary fractions – “all q” subset
cluster MV c fb note ref.
M3 –8.9 1.84 6 – 22 % [3–35% @ 95%] @ < 1 rc
1 – 3 % [0–22% @ 95%] @ 1-2 rc
Monte-Carlo
various F(q)
Zhao & Bailyn
2005
M92 –8.2 1.81 < 9 % @ 10 – 30 rc max likelihood
Romani & Weinberg 1991
NGC 288 –6.7 0.96 10–20 % [8–38% @ 99.9%] @ < 1 rh
0 – 10 % [<10% @ 99.9%] @ 1-2 rh
Monte-Carlo
various F(q)
Bellazzini et al. 2002
NGC 6752 –7.7 2.50
pcc
15 – 38 % [99.7% conf.] @ < 1 rc
< 16 % [99.7 % conf.] @ > 1 rc
Monte-Carlo
various F(q)
Rubenstein & Bailyn 1997
M30 –7.3 2.50
pcc
< 4 % @ 25 – 65 rc max likelihood
Romani & Weinberg 1991
NGC 6397 –6.6 2.50
pcc
3 % (q 0.45) @ 0 – 18 rc
5 – 7 % (all q) @ 0 – 18 rc
flat F(q)
extrapolated
Cool & Bolton
2002
Zhao & Bailyn 2005 – M3
q = 1
more high q
~ flat
more low q
mass ratiodistribution F(q)
core 1 – 2 rc
CMD outliers – binary fractions – “all q” subset
cluster MV c fb note ref.
M3 –8.9 1.84 6 – 22 % [3–35% @ 95%] @ < 1 rc
1 – 3 % [0–22% @ 95%] @ 1-2 rc
Monte-Carlo
various F(q)
Zhao & Bailyn 2005
NGC 288 –6.7 0.96 10–20 % [8–38% @ 99.9%] @ < 1 rh
0 – 10 % [<10% @ 99.9%] @ 1-2 rh
Monte-Carlo
various F(q)
Bellazzini et al. 2002
NGC 6397 –6.6 2.50
pcc
3 % (q 0.45) @ 0 – 18 rc
5 – 7 % (all q) @ 0 – 18 rc
flat F(q)
extrapolated
Cool & Bolton 2002
NGC 6752 –7.7 2.50
pcc
15 – 38 % [99.7% conf.] @ < 1 rc
< 16 % [99.7 % conf.] @ > 1 rc
Monte-Carlo
various F(q)
Rubenstein & Bailyn 1997
• all Porb, all e, any inclination… 4 - 5 decades in Porb
why not higher fb ?
• maybe M3 is okay, but NGC 288?
• how come a post-collapse cluster has such a high fb??
CMD outliers – binary fractions – high q subset
cluster MV c fb note ref.
NGC 2808 –9.4 1.77 24 4 % @ 24 rc q 0.8 ? Ferraro et al. 1998
M30 –7.3 2.50 5 2 % @ 100 rc q 0.7-0.8 ? Alcaino et al. 1998
M4 –7.2 1.59 ~ 1 – 2 % 0 – 4 rc high q Richer et al. 2004
NGC 288 –6.7 0.96 ~ 10 % @ 0 – 6 rc q 0.7 Bolte 1992
Pal 5 –5.2 0.70 ~ 9 % @ 0 – 3 rc high q Koch et al. 2004
Pal 13 –3.7 1.31 30 4 % @ 0 – 18 rc high q Clark et al. 2004
E 3 –2.8 0.75 29 9 % @ 0 – 2 rc q 0.7 ? Veronesi et al. 1996
• 3 cases with fb ~ 25 – 30 % … extrapolate to all q (×3??) 75 – 90 % ?!
• NGC 2808 so high even far outside core ?
• Pal 5 with tidal stripping… why not higher?
• M4… why so low?
Koch et al. 2004
Odenkirchen et al. 2002
Pal 5 – compare 2 methods
CMDs: fb ~ 9 1% vrad: fb ~ 40 20 %
Richer et al. 2004
M4 – compare 3 methods
CMDs: fb ~ 1–2 % (high q)
vrad: fb ~ 15 15 % Cote et al. 1996
variables: fb (observed) < 0.05%
(similar to 47 Tuc w/fb ~ 13%)
Ferdman et al. 2004
Primordial binary fraction in globular clusters
• all GCs studied have at least some binaries
• not all GCs have same binary fraction… at present low end: < 5 – 7 % ? (NGC 6397) high end: ~ 30% ~ 90% for all q ?? (E3, Pal 13)
• fb = 100% is not ruled out for some poor clusters
• fb = 0% is possible in outskirts of some clusters
• trend toward higher fb for poorer clusters, with exceptions
Are there signs of dynamical evolution of binaries?
• trends toward lower fb for higher mass clusters consistent with destruction of binaries beyond hard/soft boundary
… or are fb values in loose clusters justenhanced by tidal stripping?
• low fb in NGC 6397 and M30 destruction in collapsed cores?
… but what about NGC 6752??
Albrow et al. 2001 – 47 Tuc
mass segregation of binaries in 47 Tuc
71 BY Dra stars in 47 Tuc! an untapped resource
Weldrake et al. 2004 – 47 Tuc
period segregation of eclipsing binaries in 47 Tuc
contact all stars detached
• segregation of binaries by mass is observed
• 47 Tuc: shorter period binaries are more centrally concentrated than long period binaries
mass effect?? binary hardening?
More signs of dynamical evolution…
What about binary parameters?
• Radial velocities can give Porb, e and more… long-term tracking of candidates required
• Eclipsing binaries beginning to give information on Porb
• CMDs in principle can give information on q = m1/m2
What’s next?
• better constraints on binary fraction and distribution
* vrad – need larger samples! Fabry-Perot underway
* eclipsing – large samples are proven to work
* CMDs – exploit highest possible photometric accuracy
– look for MS-WD pairs too?
• contraints on binary parameters? track candidates!
* vrad – already done for some
* CMDs – spectroscopy on MS-MS binaries? – BY Dra stars: more complete sample?? • HST very valuable, especially in crowded cluster cores• ground-based work equally powerful in sparse clusters (e.g. Pal 13) or outskirts (e.g. 47 Tuc)