1 / 23

Understanding LMXBs in Elliptical Galaxies

Vicky Kalogera . Understanding LMXBs in Elliptical Galaxies. CXC Image Archive. Low-Mass X-Ray Binaries. Accretors: NS or BH RLOF Donors: MS, RG, WD/degenerate low-mass: < 1M o Binary Periods: minutes to ~10 days Ages: old, ~ 0.1 - 10 Gyr Persistent X-rays:

yosef
Télécharger la présentation

Understanding LMXBs in Elliptical Galaxies

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Vicky Kalogera Understanding LMXBs in Elliptical Galaxies

  2. CXC Image Archive Low-Mass X-Ray Binaries Accretors: NS or BH RLOF Donors: MS, RG, WD/degenerate low-mass: < 1Mo Binary Periods: minutes to ~10 days Ages: old, ~ 0.1 - 10 Gyr Persistent X-rays: ~10 Myr - ~1 Gyr LMXBs form in both galactic fields (isolated binaries) globulars (dynamical interactions)

  3. primordial binary How do Low-Mass X-ray binaries form in galactic fields ? Common Envelope: orbital contraction and mass loss NS or BH formation X-ray binary at Roche Lobe overflow courtesy Sky & Telescope Feb 2003 issue

  4. LMXB Population Modeling Population Synthesis Calculations: necessary Basic Concept of a Statistical Description: evolution of an ensemble of binary and single stars with focus on XRB formation and their evolution through the X-ray phase (ideally in both galactic field and globulars).

  5. Population Synthesis Elements Star formation conditions: >time and duration, metallicity, IMF, binary properties

  6. Population Synthesis Elements Star formation conditions: >time and duration, metallicity, IMF, binary properties Modeling of single and binary evolution >mass, radius, core mass, wind mass loss > orbital evolution: e.g., tidal synchronization and circularization, mass loss, mass transfer > mass transfer modeling: stable driven by nuclear evolution or angular momentum loss thermally unstable or dynamically unstable > compact object formation: masses and supernova kicks > X-ray phase: evolution of mass-transfer rate and X-ray luminosity

  7. Population Synthesis Elements Star formation conditions: >time and duration, metallicity, IMF, binary properties Modeling of single and binary evolution >mass, radius, core mass, wind mass loss >orbital evolution:e.g., tidal synchronization and circularization, mass loss, mass transfer > mass transfer modeling: stable driven by nuclear evolution or angular momentum loss thermally unstable or dynamically unstable > compact object formation: masses and supernova kicks > X-ray phase: evolution of mass-transfer rate and X-ray luminosity

  8. Population Synthesis Elements Star formation conditions: >time and duration, metallicity, IMF, binary properties Modeling of single and binary evolution >mass, radius, core mass, wind mass loss >orbital evolution: e.g., tidal synchronization and circularization, mass loss, mass transfer >mass transfer modeling: stable driven by nuclear evolution or angular momentum loss thermally unstable or dynamically unstable > compact object formation: masses and supernova kicks > X-ray phase: evolution of mass-transfer rate and X-ray luminosity

  9. Population Synthesis Elements Star formation conditions: >time and duration, metallicity, IMF, binary properties Modeling of single and binary evolution >mass, radius, core mass, wind mass loss >orbital evolution: e.g., tidal synchronization and circularization, mass loss, mass transfer >mass transfer modeling: stable driven by nuclear evolution or angular momentum loss thermally unstable or dynamically unstable >compact object formation:masses and supernova kicks > X-ray phase: evolution of mass-transfer rate and X-ray luminosity

  10. Population Synthesis Elements Star formation conditions: >time and duration, metallicity, IMF, binary properties Modeling of single and binary evolution >mass, radius, core mass, wind mass loss >orbital evolution: e.g., tidal synchronization and circularization, mass loss, mass transfer >mass transfer modeling: stable driven by nuclear evolution or angular momentum loss thermally unstable or dynamically unstable >compact object formation: masses and supernova kicks >X-ray phase:evolution of mass-transfer rate and X-ray luminosity

  11. Population Synthesis Elements Star formation conditions: >time and duration, metallicity, IMF, binary properties Modeling of single and binary evolution >mass, radius, core mass, wind mass loss >orbital evolution: e.g., tidal synchronization and circularization, mass loss, mass transfer >mass transfer modeling: stable driven by nuclear evolution or angular momentum loss thermally unstable or dynamically unstable >compact object formation: masses and supernova kicks >X-ray phase: evolution of mass-transfer rate and X-ray luminosity Our population synthesis code: StarTrack Belcynski et al. 2006 including (simple) cluster dynamics: Ivanova et al. 2005

  12. XLFs in Elliptical Galaxies Fabbiano et al., Kim et al. 2006 (3-4)x1036 - (5-6)x1038 erg/s XLF slope: 0.9 +- 0.1

  13. Field LMXB models for NGC 3379 and NGC4278 Fragos, VK, Belczynski, et al. 2007 Star Formation: delta-function at t=0 Population Age: 9-10 Gyr Metallicity: Z=0.03 (1.5 x solar) Total Stellar Mass:3 x 1010 Mo Binary Fraction: 50% Initial Mass Fn: power-law index -2.7 (Scalo/Kroupa) also -2.35 (Salpeter) CE efficiency: 50% also: 100% See poster by Fragos et al. (#155.01)

  14. Field LMXB models for NGC 3379 and NGC4278 NS accretors dominate over BHs Transients in outburst more numerous than Persistent sources XLF shape depends on transient Duty Cycle: Lout=min (LX/DC, 2LEDD) i.e., empty disk mass accumulated during quiescence DC ~ 15-20% favored best-fit XLF slope: 0.9

  15. Field LMXB models for NGC 3379 and NGC 4278 NS accretors dominate over BHs Transients in outburst more numerous than Persistent sources Lout=min (LX/DC, 2LEDD) DC ~ 15-20% favored Lout dependent on Porb (claimed for MW BHs) clearly inconsistent with data

  16. Field LMXB models for NGC 3379 and NGC 4278 Dominant LMXB Donor Types: < ~5x1036 erg/s transient LMXBs with MS donors 5x1036 - 2x1037 persistent LMXBs with RG donors > ~2x1037 transient LMXBs with RG donors (not just transient RG as in Piro & Bildsten 2002)

  17. Field LMXB models for NGC 3379 and NGC 4278 LMXBs contributing to the observed XLF: LX > 5x1036 erg/s

  18. Field LMXB models for NGC 3379 and NGC 4278 Short & old (10Gyr ago) star formation episode does NOT lead to similar LMXB formation pattern LMXB formation rate: very high at ~500Myr but continues at lower levels for 10Gyr to present Short-lived LMXBs (e.g., persistent ultra-compacts) follow the LMXB formation rate pattern and NOT the star formation of the galaxy

  19. Field LMXB models for NGC 3379 and NGC 4278 Model Normalization depends on: assumed total galaxy mass (3x1010 Mo) assumed binary fraction (50%) Total Galaxy Mass depends on: total stellar light assumed mass-to-light ratio (uncertain by ~2) NGC 3379: 1-3 x 1010 Mo (uncertain by ~3) NGC 4278: same (within 25%) total stellar light Models favored based on XLF slope naturally give normalization consistent with observations: NGC 3379: within ~3 NGC 4278: within 15%

  20. LMXBs in Globular Clusters Bildsten & Deloye 2002: NS with WD donors in ultra-compact binaries ( ~10 min orbital periods) persistent, short-lived (1-10Myr), continually formed through dynamical interactions XLF slope (~ 0.8) and normalization consistent with observations (within uncertainties) up to ~5x1038 erg/s

  21. LMXBs Above the 'Break' ... ... @ (4-5)x1038 erg/s (i.e., NS Eddington limit for He) Sarazin et al. 2001: LMXBs with BH accretors Bright XRBs in GCs ?? Kalogera et al. 2004: 1-2 BH LMXBs per cluster BUT low detection probability (transients) King 2002: BH transients in outburst wide orbits, RG donors Ivanova & Kalogera 2006: BH transients in outburst RG or MS donors XLF slope possible tracer of BH mass spectrum

  22. LMXBs in Elliptical Galaxies Current Conclusions – Open Issues • Slope and Normalization of XLF in ~5x1036 – 5x1038 erg/s • can be explained by both: • Field NS-LMXBs with low-mass MS and RG donors (transient & persistent) • GC ultra-compact NS-LMXBs (persistent) • Q: Points to contributions from both field and clusters, but • how can different LMXB types give similar XLF slope &normalization? Bright-end XLF could be due to transient BH-LMXBs in outburst Field and GC XLFs similar, but note: small-N sample • Q: Given BH evolution in GCs and transient nature, • are there too many bright point sources in GCs ? • Q: Could bright sources in GCs be due to superposition ? • Q: Could all bright sources be simply super-Eddington NS-LMXBs (by x10!) ? • Where are the BH-LMXBs, similar to transients in the Milky Way?

  23. LMXBs in Elliptical Galaxies Current Conclusions – Open Issues • Models of Field NS-LMXBs are favored with: • Transient DC ~15% • Outburst Lx connected to long-term mass transfer rate and DC: • empty disk mass accumulated during quiescence • Moderate CE efficiencies • Shape changes at ~1x1037 erg/s could be connected to outburst Lx and DC Even in the field LXMB formation rate is sustained over long timescales after an early phase of enhanced formation

More Related