Black Hole bounty around Sgr A*

introduction to a paper: A density cusp of quiescent X-ray binaries in the central parsec of the Galaxy, Hailey et al. (2018)

Transcript

1. 1972 P. J. E. Peebles Distribution of stars near a massive compact object: n(r) ~ r^{-9/4} !1
2. 1972 1976—1977 P. J. E. Peebles Distribution of stars near a massive compact object: n(r) ~ r^{-9/4} John N. Bahcall & R. A. Wolf Consider diffusion, solve numerically Boltzmann Eq: n(r) ~ r^{-7/4} Density Cusp Growth of a Bahcall–Wolf cusp Figure from Wikipedia !2
3. 1972 1976—1977 P. J. E. Peebles Distribution of stars near a massive compact object: n(r) ~ r^{-9/4} John N. Bahcall & R. A. Wolf 2000 Jordi Miralda-Escude & Andrew Gould Prediction: ~25,000 stellar mass BH should be present within 1pc of the super-massive BH in the Milky Way. (Not detected.) Consider diffusion, solve numerically Boltzmann Eq: n(r) ~ r^{-7/4} Density Cusp !3
4. 1972 1976—1977 P. J. E. Peebles Distribution of stars near a massive compact object: n(r) ~ r^{-9/4} John N. Bahcall & R. A. Wolf 2000 Jordi Miralda-Escude & Andrew Gould Consider diffusion, solve numerically Boltzmann Eq: n(r) ~ r^{-7/4} Density Cusp 2018 Charles J. Hailey et al. !4 Prediction: ~25,000 stellar mass BH should be present within 1pc of the super-massive BH in the Milky Way. (Not detected.) Detect a density cusp of quiescent Black Hole binaries within 1pc from Sgr A*
5. Sgr A* A density cusp of quiescent X-ray binaries in the central parsec of the Galaxy Yuhan Yao 20191101@Journal Club Hailey et al. (2018) Chandra/ACIS-I (1.4x106 s) 1pc
6. Sgr A* Yuhan Yao 20191101@Journal Club b a 1pc 0.2pc A density cusp of quiescent X-ray binaries in the central parsec of the Galaxy Hailey et al. (2018) • 0.2—1 pc: 26 • 1—3.8 pc: 66 Number of point source with Count > 100 (2e-15 erg s-1 cm-2) Chandra/ACIS-I (1.4x106 s) 1 arcmin
7. Harder Softer Thermal spec (with Fe emission line) Non-thermal spec Absorbed power-law model Partially covered APEC model b a Astrophysical Plasma Emission Code 7 Chandra spectra of 2 sources within 1pc from Sgr A*
8. Harder Softer Chandra spectra of 2 sources within 1pc from Sgr A* Thermal spec (with Fe emission line) Non-thermal spec Absorbed power-law model Partially covered APEC model b a Astrophysical Plasma Emission Code Hardness ratio: CL: net Count 2–4 keV CH: net Count 4–8 keV HR2>0.3 HR2<0.3 8
9. 1pc 7.8x3.9pc 0.2pc HR2>0.3 HR2<0.3 More HR2<0.3 (non-thermal) sources within 1pc 1 arcmin
10. !10 More HR2<0.3 (non-thermal) sources within 1pc 26 sources 66 sources
11. 14 sources with HR2>0.3 12 sources with HR2<0.3 Stacked spectra of 26 sources within 1pc Magnetic CVs BH/NS binaries, pulsars Thermal emission Non-thermal emission !11
12. Hard, thermal X-ray sources: magnetic CVs Frank+2002 Perez+2016 NuSTAR 20—40 keV extended emission !12 Accretion column geometry for a magnetic white dwarf
13. 1pc 7.8x3.9pc 0.2pc HR2>0.3 HR2<0.3 More HR2<0.3 (non-thermal) sources within 1pc Magnetic CV ? 1 arcmin
14. Twelve Soft, non-thermal X-ray sources? !14 • Neutron-star low-mass X-ray binaries? • Quiescent black-hole low-mass X-ray binaries (qBH-LMXB)? • High-mass X-ray binaries? • Coronally active isolated stars and stellar binaries? • Rotation-powered millisecond pulsars (rMSP)? No outburst over a decade. O/B companion not detected by IR survey. Thermal spec, too faint to be detected. or Radiatively inefficient accretion flow (RIAF) or jet cooling break. or Magnetosphere or intra-binary shock.
15. Variability analysis !15 • Quiescent black-hole low-mass X-ray binaries (qBH-LMXB)? • Rotation-powered millisecond pulsars (rMSP)? ~30% show variability ~ days to years due to disk instability. No long-term variability. 6 with long term variability 6 without long term variability qBH-LMXB qBH-LMXB or rMSP
16. Surface density of non-thermal sources as a function of projected radius from Sgr A* !16 12 sources with Count > 100 18 sources with Count > 50 Cusp power-law index
17. A cumulative X-ray flux distribution of the qBH-LMXB candidates within 1 pc. !17 Total number estimate > 600—1000 qBH-LMXBs
18. Why don’t we see X-ray novae? Tanaka & Shibazaki+1996 Nearest BH-LMXB: A0620-00 @1kpc 40+ outburst should be detected! But only 1 transient BH was found Degenaar+2012, 2015 100 count = 2x10-15 erg s-1 cm-2 1 Crab = 2.4x10-8 erg s-1 cm-2 !18
19. Final remarks !19 • 60 known Galactic stellar mass black holes in X-ray binaries http://www.astro.puc.cl/BlackCAT/ • 12 qBH-LMXB candidates discovered within 1pc from Sgr A* Image credit: LIGO/Caltech • 3e+8 BHs in the Milky Way • Many ways to find them! http://www.astro.caltech.edu/ ~srk/BlackHoles/BlackHoles.html
20. Backup Slides
21. Photoelectric absorption in the interstellar medium. Hydrogen column density at which the absorption is 1/e at the photon energy Ea.
22. Break hardness ratio vs. column density degeneracy Color–color diagram of X-ray sources with C ≥ 100 !22 HR2 CL: 2–4 keV CH: 4–8 keV HR3 CL: 1–3 keV CH: 5–8 keV r<1pc sources r>1pc sources
23. Median photon energy in the spectrum versus hardness ratio of X-ray sources with C ≥ 100. !23 Break hardness ratio vs. column density degeneracy r<1pc sources r>1pc sources
24. !24 Hardness ratio for X-ray point sources with C>=100 as a function of the projected radial distance from Sgr A*