Dynamical formation of LMXBs in the inner bulge of M31 by Rasmus Voss with Marat Gilfanov X-rays...
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Transcript of Dynamical formation of LMXBs in the inner bulge of M31 by Rasmus Voss with Marat Gilfanov X-rays...
![Page 1: Dynamical formation of LMXBs in the inner bulge of M31 by Rasmus Voss with Marat Gilfanov X-rays from nearby galaxies ESAC September 2007.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649f0d5503460f94c21bf3/html5/thumbnails/1.jpg)
Dynamical formation of LMXBs
in the inner bulge of M31
by
Rasmus Vosswith
Marat Gilfanov
X-rays from nearby galaxies ESAC September 2007
![Page 2: Dynamical formation of LMXBs in the inner bulge of M31 by Rasmus Voss with Marat Gilfanov X-rays from nearby galaxies ESAC September 2007.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649f0d5503460f94c21bf3/html5/thumbnails/2.jpg)
OverviewOverview
Introduction: LMXBsWhat are they, how are they formed
Observations: LMXBs in M31The spatial distribution
Theory: Dynamical formation of LMXBs
Conclusions: Dynamical formation of LMXBs is important in the bulge of M31
![Page 3: Dynamical formation of LMXBs in the inner bulge of M31 by Rasmus Voss with Marat Gilfanov X-rays from nearby galaxies ESAC September 2007.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649f0d5503460f94c21bf3/html5/thumbnails/3.jpg)
LMXBsLMXBs
NS or BH accreting from a companion star < 1 Msol
Mass transfer driven by angular momentum lossfrom magnetic braking and gravitational radiation
![Page 4: Dynamical formation of LMXBs in the inner bulge of M31 by Rasmus Voss with Marat Gilfanov X-rays from nearby galaxies ESAC September 2007.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649f0d5503460f94c21bf3/html5/thumbnails/4.jpg)
Formation of (primordial) LMXBsFormation of (primordial) LMXBs
Only weaklydependent onthe stellarenvironment.
LMXBs trace the mass in galaxies
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ObservationsObservationsGilfanov (2004):
LMXBs do follow the stellar mass in nearby galaxies
![Page 6: Dynamical formation of LMXBs in the inner bulge of M31 by Rasmus Voss with Marat Gilfanov X-rays from nearby galaxies ESAC September 2007.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649f0d5503460f94c21bf3/html5/thumbnails/6.jpg)
ObservationsObservationsGilfanov (2004):
LMXBs do follow the stellar mass in nearby galaxies
Centaurus A Voss & Gilfanov (2006)with Chandra
![Page 7: Dynamical formation of LMXBs in the inner bulge of M31 by Rasmus Voss with Marat Gilfanov X-rays from nearby galaxies ESAC September 2007.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649f0d5503460f94c21bf3/html5/thumbnails/7.jpg)
LMXBs in globular clustersLMXBs in globular clusters
Out of ~150 LMXBs inthe Milky Way13 LMXBs reside in globular clusters
Globular clusters contain <0.1% of the mass of the Milky Way
Improbable that they can be primordial LMXBs
Due to stellar encounters(dynamical formationof LMXBs)
![Page 8: Dynamical formation of LMXBs in the inner bulge of M31 by Rasmus Voss with Marat Gilfanov X-rays from nearby galaxies ESAC September 2007.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649f0d5503460f94c21bf3/html5/thumbnails/8.jpg)
M31M31
![Page 9: Dynamical formation of LMXBs in the inner bulge of M31 by Rasmus Voss with Marat Gilfanov X-rays from nearby galaxies ESAC September 2007.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649f0d5503460f94c21bf3/html5/thumbnails/9.jpg)
M31M31
![Page 10: Dynamical formation of LMXBs in the inner bulge of M31 by Rasmus Voss with Marat Gilfanov X-rays from nearby galaxies ESAC September 2007.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649f0d5503460f94c21bf3/html5/thumbnails/10.jpg)
ObservationsObservations
M31 with Chandra
Something wrong!
Dynamical formation?
![Page 11: Dynamical formation of LMXBs in the inner bulge of M31 by Rasmus Voss with Marat Gilfanov X-rays from nearby galaxies ESAC September 2007.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649f0d5503460f94c21bf3/html5/thumbnails/11.jpg)
Dynamical LMXB formation channelsDynamical LMXB formation channelsTidal capture Exchange reactionCollision
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A few equationsA few equations
encounter rate per unit volume:
Two body encounters
Important: Gravitational focusing
![Page 13: Dynamical formation of LMXBs in the inner bulge of M31 by Rasmus Voss with Marat Gilfanov X-rays from nearby galaxies ESAC September 2007.](https://reader035.fdocuments.net/reader035/viewer/2022062517/56649f0d5503460f94c21bf3/html5/thumbnails/13.jpg)
A few equationsA few equations
Two body encounters
Kroupa IMF
Padova stellar isochrones (Girardi et al. 2002)
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M31 versus globular clustersM31 versus globular clusters
Density: 102 -5·105 Msol
/pc3 103-104 Msol
/pc3
Velocity dispersion: 1-20 km/s 150 km/s
Metallicity: 0.01-1.0 solar 1.5-2.0 solar
Globular clusters M31 inner bulge
Mass segregation: strong not effective
Black holes: No Yes
Neutron stars: 10% retention 100% retention
Mass <107 Msol
>1010Msol
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Dynamical LMXB formation channelsDynamical LMXB formation channelsTidal capture Exchange reactionCollision
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Predictions for M31Predictions for M31
•24 BH LMXBs• 5 NS LMXBs• 3 UCXBs
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Conclusions: M31Conclusions: M31•First evidence of dynamical formation of LMXBs in M31! •First theoretical investigation of DF in this environment! •Theory works •Mainly short period systems •Mainly BH accretors
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Predictions for globular clustersPredictions for globular clusters
Metal-rich With lifetimes:
•2 “normal” LMXB•3 LMXB with ~0.1 M
sol comp.
•1.5 UCXB
Observed:
•2 LMXB P>5hr•4 with P unknown•2 UCXB (P<1hr)
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An extra piece of evidenceAn extra piece of evidenceThe luminosity function of the LMXBs:The luminosity function of the LMXBs:
MW globularclusters
M31 globularclusters
M31 inner1 arcmin
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