How Did I End Up in the Galactic Center? Frederick Baganoff MIT Kavli Institute for Astrophysics and Space Research Nedfest 2017 --- UCLA Ned @ 40 • My first research advisor – Quasar reddening – IRC +10 216 • I learned a lot about programming • Ned’s & Mark’s 40th birthday party – Ned: “brevity is the soul of wit” ‒ Hamlet – Francoise hiding Ned’s rock ‘n roll albums • Playing tennis with Ned – Ned: “You don’t have to hit the ball when you toss it.” Good Advice! Ned @ 40 • Thesis project? – COBE launch 2+ years away – Ned: “All I have are programming projects. You don’t want to do that.” • Off to work with Matt on AGN variability • Which lead to Sgr A* and the Galactic Center Ned @ 70 Chandra, Hubble & Spitzer Views of the Galactic Center Chandra Image of the Galactic Center N E Red: 2-3.7 keV Green: 3.7-4.5 keV Blue: 4.5-8 keV 5 pc Central Parsec G359.945-0.044 2-3.5, 3.5-5, 5-8 keV GC Magnetar Outburst SGR J1745-2900 GC Magnetar SGR J1745-2900 • Swift/BAT discovered outburst 2013 Apr 24 (Kennea et al. 2013) • NuSTAR follow-up revealed 3.76 s period (Mori et al. 2013) • Chandra imaging places it 2.4” SE of Sgr A* (Baganoff et al. 2013) • One of a handful of radio magnetars • Eatough et al. (2013) infer super- equipartition B ~ 8 mG near Bondi radius GC Magnetar SGR J1745-2900 • VLBA proper motion yields transverse velocity 236 +/- 11 km/s wrt Sgr A* (Bower et al. 2015) • Radial velocity unknown but chance alignment unlikely • Velocity & position consistent with bound orbit originating within CW disk of massive stars orbiting Sgr A* • Orbital period 700+ yr Chandra monitoring of initial 3.5 yr of outburst decay analyzed by Coti Zelati et al. (2015, 2017) Temporal Evolution of Spin Frequency 0 −50 Hz) µ −100 −150 0.2657 Hz ( − ν −200 05 − 10 1.9147E − Hz) 5 µ 0 (t) ( B ν −5 − ν −10 5.68×104 5.7×104 5.72×104 5.74×104 5.76×104 5.1434E+04, LI= 1.992 , QU= Time (MJD) − Approximately linear spin down CO= Pulsed Fraction Slightly Rising 1.4 ~55% 1.2 1 60 0.8 2013 May 12 ~37% 1.5 (%) 40 1 8 keV pulsed fraction 8 keV normalized intensity − − 20 0.3 0.3 10 100 1000 0.5 2016 Oct 8−14 Time (days since outburst onset) 0.3-8 keV normalized intensity normalized 0.3-8 keV 0 0.5 1 1.5 2 PhasePhase (cycle) Time Evolution of Blackbody T & R 1 0.9 BB 0.8 kT (keV) 0.7 3 2 BB R (km) τR~356 d 1 ) 1 − 10 s 2 − 1 erg cm 12 − Absorbed flux (10 ) 600 1 − 100 500 erg s 400 33 (10 Luminosity 300 10 10 20 30 40 50 20 50100 200 500 1000 Time (days since outburst onset) L has double exponential decay: τ1 ~ 96 d, τ2 ~ 326 d Correcting for Dust Scattering Halo —- without correction for the halo - - - with correction for the halo 30 20 + BB Norm ID: 14702 10 + + ID: 16963 ID: 18058 + + + 0.6 0.8 kTBB (keV) Spectral Fits & Beloborodov Model 2013 May 12 0.1 2016 Oct 14 1 keV 0.01 1 100 3 ) 10 1 10 4 erg s 33 (1o Normalized counts s 10 keV luminosity 4 ) 0.3 σ 2 10 0 2 Residuals ( 4 12 5 0.51 2 5 Energy (keV) 11 2 ABB (10 cm ) Summary • Crustal cooling model predicts hotspot should remain fairly constant in size while it cools as internal heat conducted up to outer crust; inconsistent with our observations • Alternative model of untwisting bundle of current- carrying closed field lines in magnetosphere works better (Beloborodov 2009) • Other models being tested Summary • Magnetar was still visible to Chandra in 2017 July • Day-long exposures measured spin • Two more long Chandra observations approved for 2018 July => follow spin evolution for 5 yr Lots more to do in the GC Thanks, Ned! Happy Birthday! Ned @ 100? .