Close-by young isolated neutron stars (and black holes)

Sergey Popov

(Sternberg Astronomical Institute)

Plan of the talk

NS: introduction Close-by NSs Population synthesis Test of cooling curves Close-by BHs Final conclusions

http://xray.sai.msu.ru/~polar/html/kniga.html

Neutron stars: introduction

Progenitors – massive stars Born in SN explosions R=10 km =1014 g/cm3 (nuclear density) Appear in many flavours

Radio pulsars X-ray binaries AXPs SGRs CCOs RINSs

Evolution of NS: spin + magnetic field

Ejector → Propeller → Accretor → Georotator

(Lipunov 1992) (astro-ph/0101031)

1 – spin-down2 – passage through a molecular cloud3 – magnetic field decay

Evolution of NSs:temperature

Yakovlev et al. (1999)Physics Uspekhi

Close-by radioquiet NSs

Discovery: Walter et al. (1996)

Proper motion and distance: Kaplan et al.

No pulsations Thermal spectrum Later on: six brothers

RX J1856.5-3754

Magnificent Seven

Name Period, s

RX 1856 -

RX 0720 8.39

RBS 1223 10.31

RBS 1556 -

RX 0806 11.37

RX 0420 3.45

RBS 1774 9.44

RadioquietClose-byThermal emissionLong periods

Population of close-by young NSs

Magnificent seven Geminga and 3EG J1853+5918 Four radio pulsars with thermal emission

(B0833-45; B0656+14; B1055-52; B1929+10) Seven older radio pulsars, without detected

thermal emission.

We need population synthesis studies of this population

Population synthesis: ingredients

Birth rate Initial spatial distribution Spatial velocity (kick) Mass spectrum Thermal evolution Interstellar absorption Detector properties

A brief review on populationsynthesis in astrophysics canbe found in astro-ph/04011792

Solar vicinity

Solar neighborhood is not a typical region of our Galaxy

Gould Belt R=300-500 pc Age: 30-50 Myrs 20-30 SN per Myr (Grenier 2000) The Local Bubble Up to six SN in a few Myrs

The Gould Belt

Poppel (1997) R=300 – 500 pc Age 30-50 Myrs Center at 150 pc from

the Sun Inclined respect to the

galactic plane at 20 degrees

2/3 massive stars in 600 pc belong to the Belt

Mass spectrum of NSs

Mass spectrum of local young NSs can be different from the general one (in the Galaxy)

Hipparcos data on near-by massive stars

Progenitor vs NS mass: Timmes et al. (1996); Woosley et al. (2002)

astro-ph/0305599

Cooling of NSs

Direct URCA Modified URCA Neutrino bremstrahlung Superfluidity Exotic matter (pions,

quarks, hyperons, etc.)

Kaminker et al. (2001)

Log N – Log S

Task: to understand the Gould Belt contribution

Calculate separately disc (without the belt) and both together

Cooling curves from Kaminker et al. (2001)

Flat mass spectrum Single maxwellian kick Rbelt=500 pc

astro-ph/0304141

Log N – Log S as an additional test

Standard test: Age – Temperature Sensitive to ages <105 years Uncertain age and temperature Non-uniform sample

Log N – Log S Sensitive to ages >105 years Definite N (number) and S (flux) Uniform sample

Two test are perfect together!!!

astro-ph/0411618

List of models (Blaschke et al. 2004)

Model I. Pions. Model II. No pions. Model III. Pions. Model IV. No pions. Model V. Pions. Model VI. No pions. Model VII. Pions. Model VIII.Pions. Model IX. Pions.

Blaschke et al. used 16 sets of cooling curves.

They were different in three main respects:

1. Absence or presence of pion condensate

2. Different gaps for superfluid protons and neutrons

3. Different Ts-Tin

Model I

Pions. Gaps from Takatsuka & Tamagaki

(2004) Ts-Tin from Blaschke, Grigorian,

Voskresenky (2004)

Can reproduce observed Log N – Log S

Model II

No Pions Gaps from Yakovlev et al.

(2004), 3P2 neutron gap suppressed by 0.1

Ts-Tin from Tsuruta (1979)

Cannot reproduce observed Log N – Log S

Model III

Pions Gaps from Yakovlev et al.

(2004), 3P2 neutron gap suppressed by 0.1

Ts-Tin from Blaschke, Grigorian, Voskresenky (2004)

Cannot reproduce observed Log N – Log S

Model IV

No Pions Gaps from Yakovlev et al.

(2004), 3P2 neutron gap suppressed by 0.1

Ts-Tin from Blaschke, Grigorian, Voskresenky (2004)

Cannot reproduce observed Log N – Log S

Model V

Pions Gaps from Yakovlev et al.

(2004), 3P2 neutron gap suppressed by 0.1

Ts-Tin from Tsuruta (1979)

Cannot reproduce observed Log N – Log S

Model VI

No Pions Gaps from Yakovlev et al.

(2004), 3P2 neutron gap suppressed by 0.1

Ts-Tin from Yakovlev et al. (2004)

Cannot reproduce observed Log N – Log S

Model VII

Pions Gaps from Yakovlev et

al. (2004), 3P2 neutron gap suppressed by 0.1.

1P0 proton gap suppressed by 0.5

Ts-Tin from Blaschke, Grigorian, Voskresenky (2004)

Cannot reproduce observed Log N – Log S

Model VIII

Pions Gaps from Yakovlev et al.

(2004), 3P2 neutron gap suppressed by 0.1. 1P0

proton gap suppressed by 0.2 and 1P0 neutron gap suppressed by 0.5.

Ts-Tin from Blaschke, Grigorian, Voskresenky (2004)

Can reproduce observed Log N – Log S

Model IX

No Pions Gaps from Takatsuka &

Tamagaki (2004) Ts-Tin from Blaschke,

Grigorian, Voskresenky (2004)

Can reproduce observed Log N – Log S

Resume

Magnificent Seven and other close-by NSs are genetically connected with the Gould Belt

Log N – Log S for close-by NSs can serve as a test for cooling curves

Two tests (LogN–LogS and Age-Temperature) are perfect together.

Black holes

Black holes are born from very massive progenitors

It is very difficult to observe as isolated BH: Microlensing Weak accretion …….?

It is important to try to estimate at least approximate positions

Close-by BHs and runaway stars

56 runaway stars inside 750 pc (Hoogerwerf et al. 2001)

Four of them have M > 30 Msolar

Prokhorov, Popov (2002)

Star Mass Velocity km/s

Age, Myr

ξ Per 33 65 1

HD 64760

25-35 31 6

ς Pup 67 62 2

λ Cep 40-65 74 4.5

Supernova explosion in a binary

ς Pup

Distance: 404-519 pc Velocity: 33-58 km/s Error box: 12o x 12o

NEGRET: 1

ξ Per

Distance: 537-611 pc Velocity: 19-70 km/s Error box: 7o x 7o

NEGRET: 1

Resume

Approximate positions of young close-by BHs can be estimated basing on data on massive runaway stars

For two cases we obtained relatively small error boxes

For HD 64760 and for λ Cep we obtained very large error boxes (40-50o)

Several EGRET sources inside

Final conclusions

We live in the region of the Galaxy enriched with young NSs and BHs

NSs appear as radio pulsars, gamma and X-ray sources

Local population teaches us that radio pulsars do not represent all young NSs

Log N – Log S can be a good additional test for cooling curves of NSs

Position of close-by isolated BHs can be roughly estimated for those originated from binary systems