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New adventures of UncatchablesNew adventures of Uncatchables
Sergei Popov, Bettina Posselt(astro-ph/0609275 and work in progress)
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Plan of the talkPlan of the talk
Intro. Pop. synthesis Some old results New improvements1. Initial distribution2. Mass spectrum and abundances3. ISM distribution Maps Age and distance distributions Where to search? Final conclusions
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Magnificent SevenMagnificent Seven
Name Period, sRX 1856 -RX 0720 8.39RBS 1223 10.31 RBS 1556 6.88?RX 0806 11.37RX 0420 3.45RBS 1774 9.44
Radioquiet (?)Close-byThermal emissionAbsorption featuresLong periods
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Population of close-by young NSsPopulation 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.
Where are the rest?UNCATCHABLES
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Population synthesis: ingredientsPopulation 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. Population synthesis – I.
© Bettina Posselt
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Solar vicinitySolar 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 BeltThe 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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Initial spatial distributionInitial 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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Mass spectrum of NSsMass 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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Log N – Log S 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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Some results of PS-I:Log N – Log S and spatial distribution
Some results of PS-I:Log N – Log S and 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
Log N – Log S for close-by ROSAT NSs can be explained by standard cooling curves taking into account the Gould Belt.
Log N – Log S can be used as an additional
test of cooling curves
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1. Spatial distribution of progenitor stars
a) Hipparcos stars up to 500 pc[Age: spectral type & cluster age (OB
ass)]b) 49 OB associations: birth rate ~
Nstar
c) Field stars in the disc up to 3 kpc
Population sythesis – II.recent improvementsPopulation sythesis – II.recent improvements
Solid – new initial XYZDashed – Rbelt = 500 pcDotted – Rbelt = 300 pc
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Population sythesis – II.recent improvementsPopulation sythesis – II.recent improvements
2. New cross sections & abundances and new mass spectrum
Solid – new abundances, old massDotted – old abundances, old massDashed – new abundances, new mass
Low mass stars are treated followingastro-ph/0409422
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3. Spatial distribution of ISM (NH)
instead of :
now :
Population synthesis – II.recent improvementsPopulation synthesis – II.recent improvements
Dot-dashed and dot-dot-dashed linesRepresent two new models of theISM distribution.
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b= +90°
b= -90°
Popov et al. 2005
Count rate > 0.05 cts/s
OriSco OB
Cep?Per?
PSRs+
Geminga+
M7
PSRs-
First results: new mapsFirst results: new maps
Clearly several richOB associations startto dominate in thespatial distribution
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INSs and local surroundingINSs and local surrounding
De Zeeuw et al. 1999 Motch et al. 2006
Massive star population in the Solar vicinity (up to 2 kpc) is dominated by OB associations. Inside 300-400 pc the Gould Belt is mostly important.
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Age and distance distributionsAge and distance distributions
Age
1 < cts/s < 10 0.1 < cts/s < 1 0.01 < cts/s < 0.1
Distance
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Where to search for more cowboys?Where to search for more cowboys?
We do not expect to find much more candidates at fluxes >0.1 cts/s.
Most of new candidates should be at fluxes 0.01< f < 0.1 cts/s.So, they are expected to be young NSs (<few 100 Mys) just outside the Belt.I.e., they should be in nearby OB associations and clusters.
Most probable candidates are Cyg OB7, Cam OB1, Cep OB2 and Cep OB3.Orion region can also be promising.
Name l- l+ b- b+ Dist., pc
Cyg OB7 84 96 -5 9 600-700
Cep OB2 96 108 -1 12 700
Cep OB3 108 113 1 7 700-900
Cam OB1 130 153 -3 8 800-900
0
10
-10
L=110 90130
(ads.gsfc.nasa.gov/mw/)
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Resume Resume
New more detailed population synthesis model for local population of isolated NS is made
New results provide a hint to search for new coolers. We predict that new objects can be identified at
0.01<cts/s<0.1 behind the Gould Belt in the directions of close-by rich OB associations, in particular Cep OB2.
These objects are expected to be younger and hotter than the Magnificent seven.
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The Magnificent Seven Vs. UncatchablesThe Magnificent Seven Vs. Uncatchables
Born in the Gould Belt.Bright. Middle-aged.Already observed.
Born behind the Belt.Dimmer. Younger.Wanted.
I thank all scientists with whom I collaborated during
different stages of work on INSs and had fruitful discussions:
D. Blaschke, M. Colpi, H. Grigorian, F. Haberl, V. Lipunov,
R. Neuhauser, M. Prokhorov, A. Treves, J. Trumper, ….
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Radio detectionRadio 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.
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