Ages of Our Stellar Neighbors Tom Ayres CASA

Ages of Our Stellar Neighbors Tom Ayres (CASA)

P R O C Y O N A L P C E N Z/Z ~ 1 Prot~ 23 d Age~ 2 Gyr Z/Z ~ 1. 8 Prot~ 30 d Age~ 6 Gyr

P R O C Y O N B A PORB~ 41 yr α CMi B [WD: DQZ] A L P H A C E N A PORB~ 80 yr B

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

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

MA MB 1. 11 0. 92 1. 17 -1. 09 (0. 97) 1. 10 0. 92 Morel+2000 1. 16 -1. 10 Pourbaix+‘ 02 & Several** Porto de Mello+‘ 08; Pourbaix+‘ 16 Flannery & Ayres 1978 Pourbaix+‘ 99 Guenther & Demarque ‘ 00 bottom line 2017 π (marcs) Age (Gyr) 746 6± 1 737 2. 7 -6. 2 747 6. 8 -7. 6 0. 97 -0. 92 737 2. 7 -5. 6 1. 11 0. 93 747 6. 4 -6. 8 1. 13 (0. 89)-0. 97 743 4. 5 -5. 3 Kamper+‘ 78 self-determined Söderhjelm ‘ 99 assumed self-determined (Hipp: 742) 6± 1 ? ? **Thoul+2003; Eggenberger+2004; Miglio+2005; Seismic; Vis orbit + RVs

Alpha Cen AB: Two Decades of X-rays +20 0 − 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

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

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

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

Ricky Egeland (HAO/MSU)+2016 (CS 19) young maybe not… Cycle Period (some are double-period) Sun unique? A B 20 y A A B B 30 d 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

20 30 40 Sp in - faster Rotation Period (days) 10 Do 2 4 6 w n La w Age (Gyr) 8 10 Metcalfe & van Saders (2017): older solar analogs not slowing down as fast as Skumanich law; shift in character of Dynamo?

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.

Alpha Centauri at a Crossroads Chandra Spring 2017 Newsletter