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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
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