1. Collaborators: Michael Muno (UCLA) Frederick Baganoff (MIT) Yoshitomo Maeda (ISAS) Mark Morris (UCLA) George Chartas (Penn State) Divas Sanwal (Penn State) David Burrows (Penn State) Gordon Garmire (Penn State) A Candidate Neutron Star & Its Association with Sgr A East High Energy Phenomena in the Galactic Center, High Energy Phenomena in the Galactic Center, Paris, France, June 15, 2005 Sangwook Park Department of Astronomy & Astrophysics The Pennsylvania State University

2. Introduction Sgr A East: Sgr A East: -Nonthermal radio shell -Nonthermal radio shell -X-ray detected by ROSAT, ASCA, Beppo-SAX -Chandra: Maeda et al. (2002) -Chandra: Maeda et al. (2002) MM SNR, kT=2 keV, CIE MM SNR, kT=2 keV, CIE E ~ 2 x 10 49 ergs, M ~ 2 M sun E ~ 2 x 10 49 ergs, M ~ 2 M sun Fe-rich center: He-like Fe line Fe-rich center: He-like Fe line Abund ratios => Type II SN Abund ratios => Type II SN -XMM: Sakano et al. (2004) -XMM: Sakano et al. (2004) SNR, central He- & H-like Fe SNR, central He- & H-like Fe => kT=1 keV & 4 keV, CIE => kT=1 keV & 4 keV, CIE Abund pattern =>Type Ia or II? Abund pattern =>Type Ia or II? “Neutral” Fe (6.4 keV) “Neutral” Fe (6.4 keV) ACIS-I: Sgr A* ACIS-I: Sgr A* 1999-9 ~ 2002-6: 1999-9 ~ 2002-6: 7 GTO & 5 GO obs 7 GTO & 5 GO obs => ~590 ks => ~590 ks Spatially-resolved spectroscopy Spatially-resolved spectroscopy with high photon statistics with high photon statistics - to test “Chandra vs XMM” - to test “Chandra vs XMM” - to test SN type - to test SN type Core-collapse SN: potential NS Core-collapse SN: potential NS => CXOGC J174545.5-285829 => CXOGC J174545.5-285829 (Muno et al. 2003) (Muno et al. 2003) Is CXOGC J174545.5-285829 Is CXOGC J174545.5-285829 a NS associated with SNR Sgr A East? a NS associated with SNR Sgr A East?

3. 3-Color & Fe EW images Red: 1.5-4.5 keV Green: 4.5-6.0 keV Blue: 6.0-8.0 keV He-like Fe XXV (E ~ 6.6 keV) Ar He  (3.1 keV) Ca He  (3.9 keV) Park et al. 2005, ApJ, in press

4. Sgr A East: Spectra & Fe Mass 1.5-8 keV Plume Center kT=1.1 keV + 5.3 keV Fe=5.8 solar kT=1.3 keV Fe=1 solar Fe ejecta mass: EM => n Fe ~ 0.12 f -0.5 cm -3 M Fe < 0.15 - 0.27 M sun Type Ia: M Fe ~ 0.5 – 0.8 M sun (Nomoto et al. 1997a) Type II: M Fe ~ 0.15 M sun for M star = 13 – 15 M sun M Fe ~ 0.05 – 0.08 M sun for M star = 18 – 70 M sun (Nomoto et al. 1997b) => Sgr A East is likely from a core-collapse SN.

5. Neutron Star Candidate: “the Cannonball” N E NS  =1.6 L x =3x10 33 ergs s -1 No varibility detected High velocity NS? - Tail: ~0.1 pc physical size - ~2’ from “center”: v ~ (455-912)/sin  km s -1 for SNR age ~ 5000 – 10000 yr - Mach number ~ 2.2: v ~ 880 km s -1 for ISM kT ~ 1 keV - Pressure balance: P PWN (E dot /   ) = P therm (2n e kT) = P ram (  v 2 ) where  = 2.36-0.021 E dot -0.5 (Gotthelf 2003), v ~ 550 km s -1 =>Three velocities from independent estimates are consistent. =>Also consistent with typical Galactic high-velocity pulsars (e.g. Cordes & Chernoff 1998). The cannonball

6. Summary CXOGC J174545.5-285829 (the Cannonball): A High-V NS? CXOGC J174545.5-285829 (the Cannonball): A High-V NS? - Cometary morphology - Cometary morphology - X-ray spectrum: Hard, nonthermal continuum,  = 1.6 - X-ray spectrum: Hard, nonthermal continuum,  = 1.6 - X-ray luminosity L x = 3 x 10 33 ergs s -1 - X-ray luminosity L x = 3 x 10 33 ergs s -1 - No variability - No variability Associated with Sgr A East? Associated with Sgr A East? - Proximity to Sgr A East: estimated velocities are reasonable - Proximity to Sgr A East: estimated velocities are reasonable - Positional coincidence at the “tip” of Sgr A East Plume - Positional coincidence at the “tip” of Sgr A East Plume - Cometary tail extending toward Sgr A East - Cometary tail extending toward Sgr A East - Sgr A East is likely a core-collapse SNR: M Fe < 0.27 M sun - Sgr A East is likely a core-collapse SNR: M Fe < 0.27 M sun However, no evidence for a “pulsar”: - XMM/PN places an upper limit of ~40% on the pulsed fraction - XMM/PN places an upper limit of ~40% on the pulsed fraction at P > 147 ms. at P > 147 ms. => High time-resolution, high-sensitivity X-ray/radio => High time-resolution, high-sensitivity X-ray/radio observations are necessary. observations are necessary.