1. Satoru Katsuda (Chuo University, Japan)
Detection of Thermal X-Ray Emission & Proper Motions in RX J
Satoru Katsuda (Chuo University, Japan)
in collaboration with F. Acero (AIM/CEA-Saclay), N. Tominaga (Konan U.), Y. Fukui (Nagoya U.), J. S. Hiraga (Kwansei Gakuin U.), K. Koyama (Kyoto U.), S-H. Lee (Kyoto U.), K. Mori (Miyazaki U.), S. Nagataki (RIKEN), Y. Ohira (Aoyama Gakuin U.), R. Petre (NASA GSFC), H. Sano (Nagoya U.), Y. Takeuchi (RIKEN), T. Tamagawa (RIKEN), N. Tsuji (Rikkyo U.), H. Tsunemi (Osaka U.), Y. Uchiyama (Rikkyo U.), & J. Ballet (CEA)
Thermal X-rays: SK, Acero, Tominaga, et al., ApJ, 814, 29 (2015)
Proper motions: Acero, SK, Ballet, Petre, A&A, 597, 106 (2017)

2. RX J1713.7-3946: A Prototypical Cosmic-Ray AcceleratorN N W W
R ~
CCO (1WGA )
CO emission contours overlaid on X-ray image
X-ray by ROSAT PSPC
TeV image by HESS
Discovered by ROSAT (Pfeffermann & Aschenbach 1996)
Host a CCO  Core-collapse SN
Remnant of SN 393? (Wang et al. 1997)
D ~ 1 kpc from interactions with CO clouds (e.g., Fukui et al. 2003; Sano et al. 2010)
Synchrotron X-ray dominated (e.g., Koyama et al. 1997; Slane et al. 1999)
Very strong TeV source, being the hardest gamma-ray emitter
Acero et al. (2015)
See also talks by Ballet, Zhang, Fukui on Friday

3. Peculiarity of RX J1713.7-3946: No Thermal X-Rays Despite Two Decades of Searches
N132D for comparison
RX J
Si Hea
Fe L
S Hea
No lines!
Ne Hea
O VIII
Mg Hea
Ne Lya
O VII
Suzaku XIS
(Takahashi+2007; Tanaka+2008)
Fe Hea
Suzaku XIS taken on
Other objects of this family are only Vela Jr. and HESS J1731.

4. Archival X-Ray Data with XMM-Newton & Suzaku

5. Background from Suzaku
ROSAT all-sky survey image
We construct model BG spectra, based on two off-source observations with Suzaku.

6. Adjacent Background from XMM-Newton
BG-A
BG-A
MOS1, MOS2
Model = Suzaku’s OFF2
BG-B
BG-B
MOS1, MOS2
OFF2
XMM BGs from two adjacent regions are similar to those of Suzaku BGs.
Model = Suzaku’s OFF2

7. We select the softest area.
X-Ray Softness Map
Soft region:
High thermal/synchrotron ratio
Low absorption
keV / keV
Ideal site to detect thermal X-rays.
We select the softest area.

8. Modeling by Power-law + Local BG

9. Introducing a Thermal Component
Emission measure = x 1014 cm-5 for 84 arcmin2  Roughly 1/10 of Hiraga et al. (2005)

10. Abundances Mg/Ne: 2.0―2.6 solar Si/Ne: 1.5―2.0 solar
Fe/Ne < 0.05 solar
Relatively high metallicity  SN ejecta
Small amount of Fe  CC-SN ejecta
NB: No information about swept-up matter.  We leave discussions on CR acceleration to a future work.

11. Proper Motion Studies NW SE SE limb by Acero, SK, Ballet, Petre (2017)
NW limb by Tsuji & Uchiyama (2016) NW SE
XMM-Newton observations:
(12 ks)
(64 ks)

12. Defining Shock Fronts
We defined shock frons, by using canny edge detection algorithm.
Results
We focus on well-defined edges to measure proper motions.

15. Measurements of Proper Motions
Not extremely fast (m ~ 0.6 for an age ~ 1615 yr), consistent with a presence of an HI cloud (Fukui et al. 2012; Sano et al. 2013), which in turn supports the association with SN 393.

16. Summary
We have detected thermal X-ray line emission (i.e., Ne Lya, Mg Hea, Si Hea) from RX J for the first time, by using archival XMM-Newton + Suzaku data.
The relative abundances were measured to be Mg/Ne ~ , Si/Ne ~ , Fe/Ne < 0.05 solar values, suggesting that the emission originates from core-collapse SN ejecta.
Proper motions in the NW and SE limbs were recently measured to be about 0.75 ”/yr, corresponding to ~3500 km/s at a distance of 1 kpc.
The age of the remnant inferred from the proper motions agrees with SN 393.

18. Previous Searches for Thermal X-Rays
Pannuti et al. (2003) argued for the presence of thermal X-rays, based on the ROSAT PSPC & ASCA GIS data.
Hiraga et al. (2005) also pointed out the possibility of thermal X-rays, based on XMM-Newton’s EPIC data.
Xspec normalization
EM = nenHV/4pd2 = x 1014 cm-5 for the central ~140 arcmin2 area.
Both of these claims are not yet established, especially because they did not detect clear “line” emission.

19. Comparison with Nucleosynthetic ModelsMg Fe Ni Si Ne
13 solar mass
Z = 0.02
(Umeda+2002)
Integrate from the outermost envelope up to where the best-match composition can be found.

20. Comparison with Nucleosynthetic Models
Mg/Ne Si/Ne Fe/Ne
indicating the progenitor mass of < 20 M◉
Why does the Mg/Ne ratio become larger for low-mass stars? For relatively low-mass stars, high-T is achieved at a He core.
Explosive burning synthesizes more Mg
Static burning synthesizes more O (20Ne  4He + 16O)

21. Progenitor Mass Inferred from a Cavity Size
Fukui et al. (2003)
RX J1713 probably occurred in a cavity whose radius is 6--9 pc based on the location of the molecular cloud.
Chevalier (1999)
Wind bubble size

22. The Blastwave Speed Suggests a Stripped-Envelope SN?
Vmean (R=9.6 pc / age=1600 yr) = 6000 km/s
Given that the current forward shock speed is up to ~4000 km/s, the initial speed must have been faster than 6000 km/s (perhaps ~10,000 km/s).
Early photospheric velocity (km/s)
Type IIP
~ (Spiro et al. 2014)
Stripped-envelope
~10, (Wheeler et al. 2015)
 RX J likely originated from a stripped-envelope SN.

23. Nucleosynthetic Models after Removing H&He Envelopes
Mg/Ne Si/Ne Fe/Ne
Consistent with the progenitor mass of < 20 M◉

24. A Binary System for the Progenitor of RX J1713.7-3946
[Relatively low mass (M<20M◉)] + [Stripped-envelope (Ib/c)]
 suggests a binary progenitor system in which binary interactions remove the H/He envelope.
No obvious optical/IR candidate for a companion star.
Optical IR
The IR spectrum suggests that it is a very nearby (d=28 pc) low-mass (0.15 M◉) star.
CCO
Unlikely to be a companion

25. PSR J1713-3945 PSR J1713-3945 is located ~5 arcmin away from the CCO.
Lazendic et al. (2003)
PSR J is located ~5 arcmin away from the CCO.
However, its distance has been estimated to be 4-5 kpc, ruling out the association with RX J (and the CCO).
Crawford et al. (2002)

26. Thermal Emission from RX J1713.7-3946
keV Softness map ( /1--8 keV)

27. MOS Spectrum with BG1 Exposure = 380 ks (for one MOS) Powerlaw
Local BG1 from Suzaku
Ne/Fe ~ 6 solar
Mg/Fe ~ 9 solar
Ejecta
Thermal

28. MOS Spectrum with BG2 Powerlaw Ne/Fe ~ 5 solar Local BG2 from Suzaku
Mg/Fe ~ 10 solar
Ejecta
Thermal