Population synthesis of isolated NSs and tests of cooling curves Sergei Popov (Sternberg...
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Transcript of Population synthesis of isolated NSs and tests of cooling curves Sergei Popov (Sternberg...
Population synthesis of isolated NSs and tests of cooling curves
Sergei Popov
(Sternberg Astronomical Institute)Co-authors: D. Blaschke, H.Grigorian, B. Posselt, R. Turolla
JINR, Dubna, September 01, 2006
2
Plan of the talk
Intro. Close-by NSs Population synthesis Solar vicinity. Stars Spatial distribution Mass spectrum Two tests of cooling Brightness constraint Sensitivity of two tests Mass constraint Application to hybrid stars Future plans Age-Distance diagram Final conclusions
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Isolated neutron stars population: in the Galaxy and at the backyard
INSs appear in many flavours Radio pulsars AXPs SGRs CCOs RINSs RRATs
Local population of young NSs is different (selection)
Radio pulsarsGeminga+RINSs
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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
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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
Radioquiet (?)Close-byThermal emissionLong periods
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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.
It is useful to study these stars using the population synthesis technique
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Population synthesis: ingredients
Birth rate of NSs 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/0411792
To build an artificial model
of a population of some astrophysical sources and
to compare the results ofcalculations with observations.
Task:
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Gould Belt : 20 NS Myr-1
Gal. Disk (3kpc) : 250 NS Myr-1
Arzoumanian et al. 2002
ROSAT
• Cooling curves by• Blaschke et al. • Mass spectrum
18°Gould BeltGould Belt
Population synthesis – I.
© Bettina Posselt
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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
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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
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Distribution of open clusters
(Piskunov et al. astro-ph/0508575)
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Surface density of open clusters
(Piskunov et al.)
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Spatial distribution of close-by open clusters in 3D
(Piskunov et al.)
Grey contours show projected densitydistribution of young(log T<7.9) clusters.
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Clusters and absorption
(Piskunov et al.)
Triangles – Gould Belt clusters.
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Initial spatial distribution
A very simple model for PS-I: The Gould Belt as a flat inclined disc pluscontribution from the galactic disc up to 3 kpc.
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Some results of PS-I.:Spatial distribution
(Popov et al. 2005 Ap&SS 299, 117)
More than ½ are in+/- 12 degrees from the galactic plane.
19% outside +/- 30o
12% outside +/- 40o
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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(masses of secondary objects in NS+NS)
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Woosley et al. 2002
Progenitor mass vs. NS mass
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Woosley et al. 2002
Core mass vs. initial mass
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Two tests
Age – Temperature
&
Log N – Log S
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Standard test: temperature vs. age
Kaminker et al. (2001)
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Uncertainties in temperature
(Pons et al. astro-ph/0107404)
• Atmospheres (composition)• Magnetic field• Non-thermal contributions to the spectrum• Distance• Interstellar absorption• Temperature distribution
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Luminosity and age uncertainties
Page, Geppertastro-ph/0508056
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Log N – Log S
Log of flux (or number counts)
Lo
g o
f th
e n
um
ber
of
sou
rces
bri
gh
ter
than
th
e g
iven
flu
x
-3/2 sphere: number ~ r3
flux ~ r-2
-1 disc: number ~ r2
flux ~ r-2
calculations
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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 (when applied to close-by NSs) Definite N (number) and S (flux) Uniform sample
Two test are perfect together!!!astro-ph/0411618
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List of models (Blaschke et al. 2004)
Model I. Yes C A Model II. No D B Model III. Yes C B Model IV. No C B Model V. Yes D B Model VI. No E B Model VII. Yes C B’ Model VIII.Yes C B’’ Model IX. No C A
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
Pions Crust Gaps
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Model I
Pions. Gaps from Takatsuka & Tamagaki
(2004) Ts-Tin from Blaschke, Grigorian,
Voskresenky (2004)
Can reproduce observed Log N – Log S
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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
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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
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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
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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
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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
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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
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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
35
Model IX
No Pions Gaps from Takatsuka &
Tamagaki (2004) Ts-Tin from Blaschke,
Grigorian, Voskresenky (2004)
Can reproduce observed Log N – Log S
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HOORAY!!!!
Log N – Log S can select models!!!!!Only three (or even one!) passed the second test!
…….still………… is it possible just to update the temperature-age test???
May be Log N – Log S is not necessary?Let’s try!!!!
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Brightness constraint
Effects of the crust (envelope)
Fitting the crust it is possible to fulfill the T-t test …
…but not the second test: Log N – Log S !!!
(H. Grigorian astro-ph/0507052)
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Sensitivity of Log N – Log S
Log N – Log S is very sensitive to gaps Log N – Log S is not sensitive to the crust if it is applied to
relatively old objects (>104-5 yrs) Log N – Log S is not very sensitive to presence or
absence of pions
We conclude that the two test complement each other
39
Mass constraint
• Mass spectrum has to be taken into account when discussing data on cooling• Rare masses should not be used to explain the cooling data• Most of data points on T-t plot should be explained by masses <1.4 Msun
In particular:• Vela and Geminga should not be very massive
Phys. Rev .C (2006)nucl-th/0512098(published as a JINR preprint)
Cooling curves fromKaminker et al.
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Another attempt to test a set of models: hybrid stars
We studied several models for hybrid stars applying all possible tests: - T-t- Log N – Log S- Brightness constraint- Mass constraint
nucl-th/0512098
We also tried to present examples when a model successfully passesthe Log N – Log S test, but fails to pass the standard T-t test or fails tofulfill the mass constraint.
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Model I
Brightness - OKT-t - OKLog N – Log S - poorMass - NO
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Model II
Brightness - OK
T-t - No
Log N – Log S - OK
Mass - NO
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Model III
Brightness - OK
T-t - poor
Log N – Log S - OK
Mass - NO
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Model IV
Brightness - OK
T-t - OK
Log N – Log S - OK
Mass - OK
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Resume for HySs
One model among four was able to pass all tests.
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1. Spatial distribution of progenitor stars
a) Hipparcos stars up to 400 pc[Age: spectral type & cluster age (OB ass)]
b) Star associations: birth rate ~ Nstar
c) Field stars in the disc up to 3 kpc
Population sythesis – II.recent improvements
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3. Further improvements:
• Mass spectrum • fainter XMM EPIC PN count rates• cooling curves (Grigorian et al. 2005, Popov et al . 2006)
2. Spatial distribution of ISM (NH)
instead of : now :
+ new cross sections & abundances
1kpc
1kpc
Population synthesis – II.recent improvements
(by Bettina Posselt)
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b= +90°
b= -90°
First results First results The new initial distribution of progenitor stars:
For comparison: ROSAT, old ISM distribution, masses etc. as before
GB 500 pc
GB 300 pc
New
Popov et al. 2005
Outlook Outlook Different log N - log S curve for distinct sky regions
Population synthesis for fainter (XMM) sources
Count rate > 0.05 cts/s
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Age-distance diagram
(astro-ph/0407370)
Detectability of close-byyoung NSs stronglyDepends on their agesand distance from the Sun.
A toy-model: a localsphere (R=300 pc)and a flat disk.
Rate of NS formationin the sphere is235 Myr-1 kpc-3
(26-27 NS in Myr inthe whole sphere).
Rate in the disc is10 Myr-1 kpc-2
(280 NS in Myr up to3 kpc).
visibility
13 sources
1 source
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More realistic age-dist. diagram
Initial distributionfrom Popov et al. 2005.
Spatial evolution is notfollowed.
For the line of “visibility”(solid line in the middle)I assume the limitingflux 10-12 erg s-1 cm-2 and masses are <1.35(Yakovlev et al. curves).
In 4.3 Myr in 1 kpc around the Sun 200 NSsare expected to be born.
(astro-ph/0407370)
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Realistic age-distance diagram
Realistic initial distribution.
Spatial evolution is takeninto account.
The line of “visibility” isdrawn as the dotted line.
Five curves correspond to1, 4 , 13, 20 and 100 NSs.
At the moment in 1 kpconly about 10% of NSswith ages <4-5 Myrs areobserved.
(astro-ph/0407370)
visibility
100201 134
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Resume
We live in a very interesting region of the Milky Way! Log N – Log S test can include NSs with unknown ages, so additional sources (like the Magnificent Seven) can be used to test cooling curves. Two tests (LogN–LogS and Age-Temperature) are
perfect together. Additional considerations (brightness and mass constraints) have to be taken into account. More detailed PS models are welcomed. Age-distance diagram can be used as an additional tool.
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THAT’S ALL. THANK YOU!
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Radio detection
Malofeev et al. (2005) reported detection of 1RXS J1308.6+212708 (RBS 1223) in the low-frequency band (60-110 MHz) with the radio telescope in Pushchino.
In 2006 Malofeev et al. reported radio detectionof another one.
(back)
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NS+NS binaries
Pulsar Pulsar mass Companion mass
B1913+16 1.44 1.39B2127+11C 1.35 1.36B1534+12 1.33 1.35J0737-3039 1.34 1.25J1756-2251 1.40 1.18
(PSR+companion)/2
J1518+4904 1.35J1811-1736 1.30J1829+2456 1.25
(David Nice, talk at Vancouver 2005)
(Back)