Transcript Vela Jr. SNR

The Slow X-Ray Expansion of
the Northwestern Rim of Vela Jr.
Satoru Katsuda (1, 2), Hiroshi Tsunemi (1), & Koji Mori (3)
(1. Osaka U.; 2. NASA/GSFC; 3. Miyazaki U.)
Vela Jr. NW rim
(XMM)
Vela Jr.
(ROSAT)
This talk is based on ApJ, 678, L35 (2008)
Vela Jr. SNR
H.E.S.S. 0.5-20 TeV
ROSAT all-sky survey
Radio (4850MHz)
0.1-2.4 keV
1.3-2.4
Aharonian+ (2007)

Stupar+ (2005)
Discovered by ROSAT (Aschenbach 1998).


Aschenbach (1998)
High energy X-rays ⇒ Young(<1500yr)
Large (R~1deg)⇒Near(<1kpc)
SN Type ：Core-collapse (?)

A possible candidate of a neutron star around the
center of the SNR (Slane+2001; Kargaltsev+2002).
But, the age (a few 1000 yr) and the distance
(>~1kpc) are not consistent with those of Vela Jr.
⇒ need confirmation of the relation
ASCA GIS image
Slane+2001
X-ray wideband
(Aschenbach 1998)
X-ray hard band
(Aschenbach 1998)
44Ti
Decay Line
COMPTEL detected 44Ti
decay g-ray line (Iyudin+
1998), making Vela Jr.
the 2nd object from which
44Ti line was detected
(1st was Cas A).
44Ti → 44Sc+2g → 44Ca+g
t~90 yr
g-ray line image @1.157 MeV
Iyudin+ (1998)
44Ti
t~8 hr
Very young (~700 yr)
Very near (~200 pc)
Detection of K Lines from Ca (Sc)
Line feature
ROSAT image of
Vela Jr.
XMM-Newton
(Iyudin+2005)
He-like 44Ca Ka
ASCA SIS0
(Tsunemi+2000)
Chandra
(Bamba+2005)
Line feature
The age estimated from the amount of 44Ca and 44Ti is ~1000 yr
(Tsunemi+2000).
Doubt for the Distance (and Age)
~Radio Observations~
S-D plot
(Duncan & Green 2000)
Duncan & Green (2000)
If d = 200 pc
⇒ Very unusual
If d = 1 kpc
⇒ Normal
Radio surface brightness
4.85 GHz Radio Image
Vela Jr.
SNR radius
Doubts for Age and Distance
~g- and X-ray Observations~
44Ti
g-ray line images
Result in 2000
Result in 1998
RX J0852
(Schonfelder+2000)
(Iyudin+1998)
ASCA GIS spectra
Slane+ (2001)
1
2
5 (keV)
Doubts for Age：
- Re-analysis of COMPTEL data
showed only 2 s significance of
the 44Ti decay line (Schonfelder+
2000).
- ASCA SIS1 did not detect the
line feature around 4 keV (Slane+
2001).
⇒Is the detection of 44Ti true?
⇒Is Vela Jr. so young?
Doubts for Distance：
The interstellar absorption for Vela
Jr. is 10 times larger than that for
the Vela SNR (Slane+2001)
⇒Is Vela Jr. so close?
Our Approach
Measure the expansion rate of Vela Jr.
The first expansion measurement for this
SNR.
 Estimate the age and the distance based
on the expansion rate.
 Discuss

the relation between Vela Jr. and the possible
candidate of the neutron star.
 the detection of emission lines related 44Ti.

XMM-Newton Observations of Vela Jr.
Obs. Date
Exp. Time
1. 04/25/2001
6.5 yr 2. 06/22/2003
3. 11/01/2005
4. 10/24/2007
31 ks
26 ks
64 ks
63 ks
XMM-Newton image
ROSAT image
~60’
- Radius:
- Age:
~60’
~700 yr
Mean velocity ~ 35”/6.5 yrs
Red:
0.4-1keV
Green: 1-1.5 keV
Blue:
1.5-8 keV
Astrometric Accuracy
XMM hard band (1.5-8 keV) image
Absolute position accuracy
of XMM-Newton is ~2”
(Kirsch 2007).
We investigated the
positions of 4 point sources
in each observation.
⇒We confirmed that all
sources are detected within
2” circles.
5 arcmin
⇒We take 2” as a systematic
error.
Difference Image
Hard band image (2001)
Difference Image (2001-2007)
5 arcmin
The motion of the shock can be seen as a black filament.
X-ray image
Radial Profile
Proper motion
~5”/6.5 yr
Quantitative shift estimation
n
 l   
2
k 1
x1 (k  l )  x2 (k )
2
s 12 (k  l )  s 22 (k )
l : shift parameter, k: bin
Shift the 2001 profile, and
compare it with 2003, 2005, or
2007 profiles.
⇒Search for the best-shift
position which minimizes the 2
–value.
2

Distribution
2001-2003
2001-2005
2001-2007
6arcseconds
Proper motion
Expansion rate
⇒ 0.84”±0.23” yr-1.
⇒ 0.023±0.006% (=0.84”/60’) yr-1.
Expansion Index
~Comparison with other SNRs~
Free expansion
1
R
m
t
2
4
Vela Jr.
3
Sedov
Snowplow
Vela Jr. : ~1000–3000 年
5
1☆: Cas A (e.g., Vink+ 1998)
2☆: Kepler (This work; Vink 2008)
3☆: Tycho (Reynoso+ 1997; This work)
4☆: SN 1006 (Moffett+ 1993; This work)
5☆: Cygnus Loop (Blair+ 2005)
Estimation of the Distance
Slane+ (2001)
Dominated by
nonthermal emission
(Tsunemi+2000;
Slane+2001;
Bamba+ 2005)
In general, nonthermally-dominated shocks have high
shock velocities of >3000 km/sec (e.g., Uchiyama+ 2003).
SNR
Shock velocity
SN1006 (NE rim)
5000 km/sec
Kepler
4200 km/sec
Tycho
3300 km/sec
Cas A
3200 km/sec
D >~750 (v/3000 km sec-1)(μ/0”.84 yr-1) pc.
Relation between Vela Jr. and NS
－ AX J0851.9-4617.4 －
- Age: ~ A few 103 yr (Kargaltsev+
2002)
⇒Consistent with the age of Vela
Jr. estimated here (1000–3000 yr)
AX J0851.9-4617.4
ASCA GIS 0.7-10keV
Slane+ (2001)
- Distance: Farther than the Vela
SNR (Slane+ 2001; Kargaltsev+
2002) .
⇒ Consistent with the distance of
Vela Jr. estimated here.
The NS candidate is strongly suggested to
be the stellar remnant of Vela Jr. SNR.
On the Detection of 44Ti Decay Line
g-ray line image
Iyudin+ (1998)
44Ti
Based on the newly estimated age
and distance, the initial amount of
44Ti is calculated to be ~solar mass
(if we believe the detection by
Iyudin+1998)
⇒Probably, the g-ray emission
detected by COMPTEL has no
relation to Vela Jr.
Age effect: The new age (1000–3000 yr) is about twice that of
680 yr. Since the 44Ti decays exponentially with time, the
initial amount of 44Ti increases by 4000 times of that estimated
in Iyudin+1998.
Distance effect: The new distance is at least 4 larger than that
estimated previously.⇒The amount of 44Ti increases 16 times.
Summary




We, for the first time, measured the expansion of Vela Jr.
with XMM-Newton. We found that the expansion rate is
0.84”±0.23” yr-1, which is only1/7of the free expansion.
The relation between expansion index and the age of
SNRs indicates that the age and the distance of Vela Jr.
are ~1000–3000 yr and >~750 pc, respectively.
Neutron star: The newly estimated age and distance are
consistent with those of the NS candidate.
⇒The NS candidate is likely the very NS left behind the
SN explosion which produced Vela Jr.
44Ti: The newly estimated age and distance indicates no
detection of 44Ti from Vela Jr.
⇒Probably, the emission line from 44Ti detected by
Iyudin+1998 is not related to Vela Jr.