1. Ages of Our Stellar Neighbors
Tom Ayres (CASA)

2. Z/Z~ 1 Prot~ 23 d Age~ 2 Gyr Z/Z~ 1.8 Prot~ 30 d Age~ 6 Gyr PROCYONL P
CEN
Prot~ 30 d
Age~ 6 Gyr

3. ALPHA
CEN
PROCYON A B A B
PORB~ 41 yr
PORB~ 80 yr
α CMi B [WD: DQZ]

4. Breakthrough Starshot
“To boldly go where no nanobot has gone before...”

5. Flannery & Ayres 1978
t~ 6 ± 1 Gyr A A B B

6. π (marcs) MA MB Age (Gyr)
Flannery & Ayres 1978
1.11
0.92
746
Kamper+‘78
6±1
Pourbaix+‘99
(0.97)
737
self-determined
Guenther & Demarque ‘00
1.10
747
Söderhjelm ‘99
Morel+2000
Pourbaix+‘02
& Several**
0.93
assumed
Porto de Mello+‘08;
Pourbaix+‘16
1.13
(0.89)-0.97
743
(Hipp: 742)
bottom line
2017
6±1 ??
**Thoul+2003; Eggenberger+2004; Miglio+2005; Seismic; Vis orbit + RVs

7. Alpha Cen AB: Two Decades of X-rays
−20
A ??
ROSAT
XMM-Newton
Chandra
Year
Note: brighter source (B) located at 0” on y-axis (Δdec), and at date of observation (x-axis); relative AB orientation and separation maintained

8. Iconic view of solar X-ray cycle (Yohkoh: 1990’s)

9. Ups & Downs of Alpha Centauri
 X-ray Index is LX/Lbol in units of 10-7

10. Ups & Downs of Alpha Centauri
8.4 yr 
Sun: 14 yr ?!
PROCYON ??
19.5 yr ?
 X-ray Index is LX/Lbol in units of 10-7

11. Stellar Ca II HK cycles (Mt Wilson) seem to split into two
Ricky Egeland (HAO/MSU)+2016 (CS19)
Sun unique?
maybe not… A A A
20 y
Cycle Period
(some are double-period) B B B
30 d
young
old
Rotation Period
Stellar Ca II HK cycles (Mt Wilson) seem to split into two
branches, Active (A) and Inactive (I), with Sun in middle

12.  faster Rotation Period (days) 10 20 30 40  4 6 8 10 Age (Gyr)
Spin-Down Law
Age (Gyr)
Metcalfe & van Saders (2017): older solar analogs not slowing down as fast as Skumanich law; shift in character of Dynamo?

13.  faster Rotation Period (days) 10 20 30 40  4 6 8 10 Age (Gyr)
Spin-Down Law
Age (Gyr)
Metcalfe & van Saders (2017): older solar analogs not slowing down as fast as Skumanich law; shift in character of Dynamo?

14. Conclusions
Nearby, visual binary systems offer prospect for accurately determining ages: benchmarks for stellar population studies, rotation-activity connection, Dynamos, etc. However, best case scenario α Centauri -- shows that slight uncertainties in mass of more evolved star, mainly from disputed distance, can affect age estimates significantly. Nevertheless, α Cen appears to be perhaps 1 Gyr older than Sun, consistent with magnetic activity signatures.
Caveat for rotation-activity is that middle-aged stars might be in a somewhat unstable transition between long and short cycling states. Coronal wind braking then possibly affected by changes in the global field.

15. Alpha Centauri at a Crossroads
Chandra Spring
2017 Newsletter