Collaborators:

1
A Candidate Neutron Star Its Association with
Sgr A East
High Energy Phenomena in the Galactic Center,
Paris, France, June 15, 2005
Sangwook Park
Department of Astronomy Astrophysics
The Pennsylvania State University

• 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)

2
Introduction

• Sgr A East
• -Nonthermal radio shell
• -X-ray detected by
• ROSAT, ASCA, Beppo-SAX
• -Chandra Maeda et al. (2002)
• MM SNR, kT2 keV, CIE
• E 2 x 1049 ergs, M 2 Msun
• Fe-rich center He-like Fe line
• Abund ratios gt Type II SN
• -XMM Sakano et al. (2004)
• SNR, central He- H-like Fe
• gt kT1 keV 4 keV, CIE
• Abund pattern gtType Ia or II?
• Neutral Fe (6.4 keV)

• ACIS-I Sgr A
• 1999-9 2002-6
• 7 GTO 5 GO obs
• gt 590 ks
• Spatially-resolved spectroscopy
• with high photon statistics
• - to test Chandra vs XMM
• - to test SN type
• Core-collapse SN potential NS
• gt CXOGC J174545.5-285829
• (Muno et al. 2003)
• Is CXOGC J174545.5-285829
• a NS associated with SNR Sgr A East?

3
3-Color Fe EW images
Park et al. 2005, ApJ, in press
He-like Fe XXV (E 6.6 keV)
Ar Hea (3.1 keV)
Ca Hea (3.9 keV)
Red 1.5-4.5 keV Green 4.5-6.0 keV Blue 6.0-8.0
keV
4
Sgr A East Spectra Fe Mass
1.5-8 keV
Fe ejecta mass EM gt nFe 0.12 f-0.5 cm-3
MFe lt 0.15 - 0.27 Msun Type Ia MFe 0.5 0.8
Msun (Nomoto et al. 1997a) Type II MFe 0.15
Msun for Mstar 13 15 Msun MFe
0.05 0.08 Msun for Mstar 18 70 Msun
(Nomoto et al. 1997b) gt Sgr A East is
likely from a core-collapse SN.
Plume
kT1.3 keV Fe1 solar
Center
kT1.1 keV 5.3 keV Fe5.8 solar
5
Neutron Star Candidate the Cannonball
N
The cannonball
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 PPWN
(Edot/4?cR2) Ptherm (2nekT) Pram (?v2)
where ? 2.36-0.021
Edot-0.5 (Gotthelf 2003),
v 550 km s-1 gtThree velocities from
independent estimates are consistent. gtAlso
consistent with typical Galactic high-velocity
pulsars (e.g. Cordes Chernoff 1998).
E
??1.6 Lx3x1033 ergs s-1
No varibility detected
N
S
6
Summary

• CXOGC J174545.5-285829 (the Cannonball) A High-V
  NS?
• - Cometary morphology
• - X-ray spectrum Hard, nonthermal
  continuum, ? 1.6
• - X-ray luminosity Lx 3 x 1033 ergs s-1
• - No variability
• Associated with Sgr A East?
• - Proximity to Sgr A East estimated
  velocities are reasonable
• - Positional coincidence at the tip of Sgr
  A East Plume
• - Cometary tail extending toward Sgr A East
• - Sgr A East is likely a core-collapse SNR
  MFe lt 0.27 Msun
• However, no evidence for a pulsar
• - XMM/PN places an upper limit of 40 on the
  pulsed fraction
• at P gt 147 ms.
• gt High time-resolution, high-sensitivity
  X-ray/radio
• observations are necessary.