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.(ROSAT)

Vela Jr. NW rim(XMM)

This talk is based on ApJ, 678, L35 (2008)

Vela Jr. SNRROSAT all-sky survey

Aschenbach (1998)

Discovered by ROSAT (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⇒

Aharonian+ (2007)

H.E.S.S. 0.5-20 TeV Radio (4850MHz)

Stupar+ (2005)

ASCA GIS image

Slane+2001

0.1-2.4 keV1.3-2.4 keV

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

ÞVery young (~700 yr) ÞVery near (~200 pc)

t~90 yr t~8 hr

44Ti g-ray line image @1.157 MeV Iyudin+ (1998)

X-ray hard band(Aschenbach 1998)X-ray wideband

(Aschenbach 1998)

Detection of K Lines from Ca (Sc)

The age estimated from the amount of 44Ca and 44Ti is ~1000 yr (Tsunemi+2000).

ROSAT image of Vela Jr.

ASCA SIS0 (Tsunemi+2000)

He-like 44Ca Ka Chandra (Bamba+2005)

Line feature

XMM-Newton(Iyudin+2005)

Line feature

Doubt for the Distance (and Age)~Radio Observations~

Duncan & Green (2000)

S-D plot(Duncan & Green 2000)

4.85 GHz Radio Image

Vela Jr.

SNR radius

Rad

io s

urfa

ce b

right

ness

If d = 200 pc Very unusual ⇒

If d = 1 kpc Normal⇒

Doubts for Age and Distance~g- and X-ray Observations~

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?

ASCA GIS spectra

Slane+ (2001)

RX J0852

44Ti g-ray line images

(Schonfelder+2000)

1 2 5 (keV)

Result in 1998 Result in 2000

(Iyudin+1998)

Our ApproachMeasure 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 31 ks2. 06/22/2003 26 ks3. 11/01/2005 64 ks4. 10/24/2007 63 ks

- Radius: ~60’ - Age: ~700 yr

Red: 0.4-1keVGreen: 1-1.5 keVBlue: 1.5-8 keV

Mean velocity ~ 35”/6.5 yrs

6.5 yr

~60’

XMM-Newton image

ROSAT image

Astrometric Accuracy

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.

⇒We take 2” as a systematic error.

XMM hard band (1.5-8 keV) image

5 arcmin

Difference Image

5 arcmin

The motion of the shock can be seen as a black filament.

Hard band image (2001) Difference Image (2001-2007)

Radial Profile

n

k klkkxlkxl

122

21

2212

)()()()(

ss

Quantitative shift estimation

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.

Proper motion ~5”/6.5 yr

X-ray image

2 Distribution

2001-20032001-20052001-2007

6arcseconds

Proper motion ⇒ 0.84”±0.23” yr-1.Expansion rate ⇒ 0.023±0.006% (=0.84”/60’) yr-1.

Expansion Index ~Comparison with other SNRs~

5 : Cygnus Loop (Blair+ 2005)☆4 : SN 1006 (Moffett+ 1993; This work)☆

1 : Cas A (e.g., Vink+ 1998)☆2 : Kepler (This work; Vink 2008) ☆3 : Tycho (Reynoso+ 1997; This work)☆

1

23

4

5

tRm

Free expansion

Sedov

Snowplow

Vela Jr.

Vela Jr. : ~1000–3000 年

Estimation of the Distance

In general, nonthermally-dominated shocks have high shock velocities of >3000 km/sec (e.g., Uchiyama+ 2003).

SNR Shock velocitySN1006 (NE rim) 5000 km/sec

Kepler 4200 km/sec

Tycho 3300 km/sec

Cas A 3200 km/sec

Dominated by nonthermal emission (Tsunemi+2000; Slane+2001; Bamba+ 2005)

D >~750 (v/3000 km sec-1)(μ/0”.84 yr-1) pc.

Slane+ (2001)

Relation between Vela Jr. and NS

Slane+ (2001)

ASCA GIS 0.7-10keV

AX J0851.9-4617.4

－ AX J0851.9-4617.4 － Age: ~ A few 103 yr (Kargaltsev+

2002)

Distance: Farther than the Vela SNR (Slane+ 2001; Kargaltsev+ 2002) . ⇒ Consistent with the distance of

Vela Jr. estimated here.

⇒Consistent with the age of Vela Jr. estimated here (1000–3000 yr)

The NS candidate is strongly suggested to be the stellar remnant of Vela Jr. SNR.

On the Detection of 44Ti Decay Line

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.

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.

44Ti g-ray line image Iyudin+ (1998)

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.