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On the minimum mass of neutron stars Yudai Suwa Kyoto Sangyo - - PowerPoint PPT Presentation

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On the minimum mass of neutron stars Yudai Suwa Kyoto Sangyo University collaboration with T. Yoshida (Tokyo), M. Shibata (Kyoto/AEI), H. Umeda (Tokyo), K. Takahashi (Bonn) Yudai Suwa @ Stellar deaths and their diversity, NAOJ Kyoto

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Yudai Suwa

（Kyoto Sangyo University）

collaboration with

  • T. Yoshida (Tokyo), M. Shibata (Kyoto/AEI), H. Umeda (Tokyo), K. Takahashi (Bonn)

On the minimum mass of neutron stars

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Yudai Suwa @ Stellar deaths and their diversity, NAOJ

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Kyoto Sangyo University（京都産業大学）

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Kyoto Station Kyoto University Kyoto Sangyo University ~10km (~40min w/ metro & bus) Long-term workshop “Multi-messenger astrophysics in the GW era” (24 Sep.-25 Oct. 2019)

  • incl. YKIS conference

(7 Oct.-11 Oct. 2019)

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Yudai Suwa @ Stellar deaths and their diversity, NAOJ

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Pulsar number is increasing

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pulsar millisecond pulsar pulsar w/ precise mass

compiled data from ATNF pulsar catalog and P. Freire’s table

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Mass measurements of NSs

>2600 pulsars have been found in the Galaxy 10% in the binary system
 →mass measurement possible 15 double NSs so far [Tauris+ 2017]

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J0453+1559 J0453+1559c J0737-3039A J0737-3039B B1534+12 B1534+12c J1756-2251 J1756-2251c J1906+0746 J1906+0746c B1913+16 B1913+16c B2127+11C B2127+11Cc J1518+4904 J1518+4904c J1811-1736 J1811-1736c J1829+2456 J1829+2456c J1930-1852 J1930-1852c J0337+1715 J0348+0432 J0437-4715 J0621+1002 J0751+1807 J1012+5307 J1614-2230 J1713+0747 J1738+0333 J1802-2124 J1807-2500B B1855+09 J1903+0327 J1909-3744 J1910-5958A J1946+3417 J2222-0137 J2234+0611 J0024-7204H J0514-4002A B1516+02B J1748-2021B J1748-2446I J1748-2446J J1750-37A B1802-07 J1824-2452C EXO 1745-248 4U 1608-52 4U 1820-30 KS 1731-260 SAX J1748.9-2021 4U 1724-207 Cyg X-2 Vela X-1 SMC X-1 LMC X-4 Cen X-3 SAX J1802.7-2017 XTE J1855-026 EXO 1722-363 OAO 1657-415 Her X-1 4U1538-52 B2303+46 J1141-6545

Double neutron stars Recycled pulsars Bursters Slow pulsars

Mass (M☉)

0.0 1.0 2.0 3.0

6 5 4 3

Likelihood

2 1 0.8 1.0 1.2 Double neutron stars Recycled pulsars Slow pulsars 1.4 1.6 1.8 2.0

Mass (M☉)

Özel & Freie 2016

http://www3.mpifr-bonn.mpg.de/stafg/pfreire/NS_masses.html

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Massive NSs tell us nuclear physics

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0.0 7 8 9 10 11 Radius (km) 12 13 14 15 0.5 1.0 1.5 2.0

AP4

J1903+0327 J1909-3744 systems Double neutron s Double neutron star sy sy

J1614-2230 AP3 ENG MPA1 GM3 GS1 PAL6 FSU SQM3 SQM1 PAL1 MS0 MS2 MS1

2.5 GR Causality Rotation P < ∞ Mass (M()

Demorest+ 2010

←1.97±0.04M⊙

NB) mass estimation was updated by Arzoumanian+ 2018 as 1.908±0.016M⊙ Another massive NS was reported by Antoniadis+ (2013), J0348+0432, 2.01±0.04M⊙

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So, what does a small NS tell?

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Yudai Suwa @ Stellar deaths and their diversity, NAOJ

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Double NSs

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J0453+1559 J0453+1559c J0737-3039A J0737-3039B B1534+12 B1534+12c J1756-2251 J1756-2251c J1906+0746 J1906+0746c B1913+16 B1913+16c B2127+11C B2127+11Cc J1518+4904 J1518+4904c J1811-1736 J1811-1736c J1829+2456 J1829+2456c J1930-1852 J1930-1852c J1750-37A

Double neutron stars

Vela X-1 Mass (M☉)

0.0 1.0 2.0 3.0

concentrating within a small range

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First asymmetric DNS system

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  • w

w >

  • w

= = D = =

Martinez+ 2015

Mp=1.559±0.005M⊙

Mc=1.174±0.004M⊙

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Yudai Suwa @ Stellar deaths and their diversity, NAOJ

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A low-mass NS

MNS=1.174M⊙! (NB, it ‘s gravitational mass, baryonic mass is ~1.28M⊙) Is it a white dwarf? Maybe no

a large eccentricity (e=0.112) is diffjcult to explain by slow evolution into a WD

How to make it?

a small iron core of massive star?
 (typically MFe~1.4–1.8M⊙) getting rid of mass from a NS?

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15 20 25 30 35 40 MZAMS [M] 1.3 1.4 1.5 1.6 1.7 1.8 1.9 Iron Core Mass [M] ˙ MN ˙ MN/2

Sukhbold+ 2018

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Yudai Suwa @ Stellar deaths and their diversity, NAOJ

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A path toward a low mass NS?: Ultra-stripped SN

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[Suwa+, MNRAS, 454, 3073 (2015); Yoshida+, MNRAS, 471, 4275 (2017)]

´

  • ´

´

  • ´
  • t

¥

  • R

=

  • ~
  • Tauris+ 2017
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5 10 15 20 25 30 35 40 1040 1041 1042 Absolute Magnitude Luminosity [erg s-1] Days since explosion CO145 CO15 CO145: Ye-B SN2005ek

MC/O=1.45M⊙ MC/O=2.0M⊙ lower MC/O

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Yudai Suwa @ Stellar deaths and their diversity, NAOJ

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When does a core collapse?

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Time till collapse Mass

MChandra Mcore collapse!

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Modified Chandrasekhar mass

Chandrasekhar mass without temperature correction Chandrasekhar mass with temperature correction To make a small core, low Ye and low entropy are necessary

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Baron+ 1990; Timmes+ 1996

MCh0(Ye) = 1.46M⊙ ( Ye 0.5)

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MCh(T) = MCh0(Ye)[1 + ( se πY2 )

2

] se = 0.5ρ−1/3

10 (Ye/0.42)2/3TMeV

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Mch vs. Mcore

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0.6 0.8 1 1.2 1.4 1.6 1.8 2 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 Mass [M⊙] Time until ρc=1010g cm-3 [year] CO138 CO145 15M⊙ 0.6 0.8 1 1.2 1.4 1.6 1.8 2 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 Mass [M⊙] Time until ρc=1010g cm-3 [year] CO138 CO145 15M⊙ 0.6 0.8 1 1.2 1.4 1.6 1.8 2 10-7 10-6 10-5 10-4 10-3 10-2 10-1 100 101 102 Mass [M⊙] Time until ρc=1010g cm-3 [year] CO138 CO145 15M⊙

MCh0 MCh MFe

[Suwa, Yoshida, Shibata, Umeda, Takahashi, MNRAS, 481, 3305 (2018)]

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Explosion simulations and NS masses

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Model MCO (M⊙) MZAMS (M⊙) MFe (M⊙) MNS,b (M⊙) MNS,g (M⊙) CO137 1.37 9.35 1.280 1.289 1.174 CO138 1.38 9.4 1.274 1.296 1.179 CO139 1.39 9.45 1.258 1.302 1.184 CO140 1.4 9.5 1.296 1.298 1.181 CO142 1.42 9.6 1.265 1.287 1.172 CO144 1.44 9.7 1.234 1.319 1.198 CO145 1.45 9.75 1.277 1.376 1.245

MNS,b-MNS,g=0.084M⊙(MNS,g/M⊙)2 (Lattimer & Prakash 2001)

[Suwa, Yoshida, Shibata, Umeda, Takahashi, MNRAS, 481, 3305 (2018)]

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Yudai Suwa @ Stellar deaths and their diversity, NAOJ

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Discussion

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MNS,g

(M⊙)

MCO (M⊙)

~1.37 ~1.42 ~1.20 ~1.17 ONeMg core -> electron-capture SN Fe core -> core-collapse SN

MNS,b

(M⊙)

~1.28 ~1.32

[Suwa, Yoshida, Shibata, Umeda, Takahashi, MNRAS, 481, 3305 (2018)]

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Yudai Suwa @ Stellar deaths and their diversity, NAOJ

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Summary

A low-mass NS of MNS,g=1.174M⊙ was found Q: Is it possible to make such a low-mass NS with standard modeling of SN? A: Yes, it is.

The minimum mass is ~1.17M⊙. If a new observation fjnds even lower mass NS, we cannot make

  • it. Something wrong.

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