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P. Charles (SAAO) T. Shahbaz (IAC) C. Zurita (Obs. San Pedro Martir)

OBSERVATIONAL EVIDENCE FOR STELLAR-MASS BLACK HOLES Jorge Casares (IAC). P. Charles (SAAO) T. Shahbaz (IAC) C. Zurita (Obs. San Pedro Martir) R. Hynes (Lousiana State Univ.) D. Steeghs ( Harvard-Smithsonian Center for Astroph.). Impact in Astrophysics.

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P. Charles (SAAO) T. Shahbaz (IAC) C. Zurita (Obs. San Pedro Martir)

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  1. OBSERVATIONAL EVIDENCE FOR STELLAR-MASS BLACK HOLES Jorge Casares (IAC) P. Charles(SAAO) T. Shahbaz (IAC) C. Zurita(Obs. San Pedro Martir) R. Hynes(Lousiana StateUniv.) D. Steeghs(Harvard-Smithsonian Center for Astroph.)

  2. Impact in Astrophysics 1st observational evidence of BHs not until last 3 decades Fundamental objects throughout astrophysics (XRB, AGN…) Stellar-mass BH best opportunity for detailed studies • Test SNe models and evolution of massive stars e.g. V404Cyg, GRS 1915+105 • Chemical enrichment of the Galaxy e.g.GRO J1655-40, A0620-00, V4641 Sgr, XTE J1118+480 • Accretion physics, outflows and production of VHE radiation e.g. microquasars GRS 1915+105, GRO J1655-40, LS 5039 (:)

  3. Outline 1.- Introduction:dynamical evidence • 1st BHcandidatesin X-ray Binaries • From candidates to “confirmed” black holes 2.- Demography: • Population number • Masses, distribution and implications 3.- Conclusions

  4. 1.- Introduction Early History • 60’s: X-ray astronomy (UHURU, Ariel…) • Population of ~ 102 X-ray sources in the Galaxy with LX ~ 1038 erg/s and variability down to millisec • Compact object accreting ~ 10-9 M/yrfrom a close companion star (Shklovskii 1967)

  5. Two types of X-ray binaries 1) High Mass (HMXBs) • O-B I • Lopt/LX  10 2) Low Mass (LMXBs) • K-M V • Lopt/LX 10-2

  6. Cyg X-1 ( = HDE 226868) • O9.7 Iab • Velocity K= 64 km/s (latter refined to 75 km/s) and Porb= 5.6 d. Webster & Murdin 1972 Nature 235 37 Bolton 1972 Nature 240 124

  7. The mass function =0.25 M But donor likely undermassive (van den Heuvel & Ostriker 73) • MC >10 M • i < 65o MX > 4M Herrero et al. 1995 A&A 297 556 MC=12-19 M MX=4-15 M f (M) < MX Typically O9.7 Iab has ≈ 33 M(and then MX≈ 7 M, i=90º)

  8. Lattimer & Prakash (2004) EoS of Neutron Stars • Oppenheimer & Volkoff (1939):maximum mass for NS stable against gravitional collapse • Rhoades & Ruffini (1974):upper limit ~ 3.2 M assuming causality holds beyondρnm≈ 3x1014 g/cm3. • Kalogera & Baym (1996):~ 2.9 Mwith EoS accurate ~2ρnm

  9. A 0620-00 ( = N. Mon 75) OUTBURST: Companion  103 fainter than X-ray irradiated disc QUIESCENCE: companion dominates optical flux radial velocity studies X-ray Nova discovered by Ariel in 1975 with Fx≈ 50 Crabs

  10. A 0620-00 ( = N. Mon 75) P = 7.8 hr K = 457±8 km/sf(M)=3.18 ± 0.16 M McClintock & Remillard (1986): First spectroscopic detection of mid-K star Mx>maximum allowed mass for stable NS

  11. Black Hole Candidates • Historic debate about existence of BHs (80’s) • 3 candidates: • Cyg X-1 : f (M)=0.25 ± 0.01 M • LMC X-3: f (M)=2.3 ± 0.3 M • A0620-00: f (M)=3.2 ± 0.2 M • Alternative models • Multiple stars (Fabian, Pringle, Whelan 1974) • “Q stars” (Bahcall et al. 90) “Holy Grail would be f(M) > 5 M” (McClintock 86)

  12. V404 Cygni (=GS 2023+338) f (M)=6.3 ± 0.3 M Mx > 6.0 M independently of MC, i Casares, Charles & Naylor 1992 Nature 355 614 • XRT discovered in 1989 by Ginga with Lx 1039 erg/s • K0IV donor • P = 6.5 d. • K= 211 km/s

  13. GX 339-4: a novel technique AAT+NTT VLT Sco X-1 HeII NIII/CIII Shahbaz et al. 2001 Steeghs & Casares 2002 • Classic Black Hole candidate based on X-ray properties • Quiescence in 2000-01 but companion undetected • New outburst in 2002 NIII/CIIIemissionlines at λλ4630-40 Donor not detected but use irradiated lines to trace its orbit

  14. GX 339-4 Determine f (M) in new XRTs during outburst and increase number of BH discoveries. Kem=317 ±10 km/s  K2 f(M)5.8 ± 0.5 M Black Hole!! (Hynes et al. 2003 ApJ 583 L95) Multigausian fit to NIII lines Porb=1.76 d from HeII velocities

  15. Confirmed Black Holes with dynamical evidence System Porb f(M) Spect. Type Classification GRS 1915+105 33.5 d 9.5 ± 3.0 M K/MIII Transient V404 Cyg 6.470 d 6.08 ± 0.06 M K0IV ,, Cyg X-1 5.600 d 0.244 ± 0.005 M 09.7Iab Persistent LMC X-1 4.229 d 0.14 ± 0.05 M 07III ,, XTE J1819-254 2.817 d 2.74 ± 0.04 M B9III Transient GRO J1655-40 2.620 d 2.73 ± 0.09 M F3/5IV ,, BW Cir 2.545d 5.75 ± 0.30 M G5IV ,, GX 339-4 1.754 d 5.8 ± 0.5 M -- ,, LMC X-3 1.704 d 2.3 ± 0.3 M B3 V Persistent XTE J1550-564 1.542 d 6.86 ± 0.71 M G8/K8IV Transient 4U 1543-475 1.125 d 0.25 ± 0.01 M A2V ,, H1705-250 0.520 d 4.65 ± 0.21 M K3/7V ,, GS 1124-684 0.433 d 3.01 ± 0.15 M K3/5V ,, XTE J1859+226 0.382 d : 7.4 ± 1.1 M : -- ,, GS2000+250 0.345 d 5.01 ± 0.12 M K3/7V ,, A0620-003 0.325 d 2.72 ± 0.06 M K4V ,, XTE J1650-500 0.3205 d 2.73 ± 0.56 M K4V ,, GRS 1009-45 0.283 d 3.17 ± 0.12 M K7/M0V ,, GRO J0422+32 0.212 d 1.19 ± 0.02 M M2 V ,, XTE J1118+480 0.171 d 6.3 ± 0.2 M K5/M0V ,,

  16. Quiescent luminosities (Narayan et al. 1997, Menou et al. 1999) NS BH Further support: absence of a hard surface • Lack of pulses/X-ray bursts (Remillard et al. 2006) • Differences in X ray colour-colour diagram (Done & Gierlinski 2003) and Temperatures of the ultrasoft component at high accretion luminosities (e.g. Remillard et al. 2006).

  17. 2.- Demography: number, masses • Dynamical studies of XRTs indicate ~ 75% contain BHs ( f(M)>3 M) • Extrapolation of XRTs since the 60’s + assuming outburst duty cycle ~ 10-50 yrs suggest ~ 103 dormantBH XRTs (van den Heuvel 93). In good agreement with binary population models (Yungelson et al. 06). • Stellar evolution models predict ~ 108 (Brown & Bethe 94). How many are there and what is the mass-spectrum ? BH XRTs are the tip of iceberg of Galactic population

  18. Weighing BHs V404 Cyg (Casares & Charles 93) GRO J1655-40 (Orosz & Bailyn. 97) 1) 2) Measure Vrot sini 3) Fit ellipsoidal modulation Amplitude is strong function of inclination

  19. Mass spectrum of BHs 15 reliable masses of BHs: 4-14 M • Do BH masses cluster at a particular value? • What are the edges of the BH distribution? • Is there a continuum distribution between NS & BHs? Typical errors 30% Goals: • improve statistics • reduce errors to ≤10%

  20. Comparison with SNIb Models LS 5039 (Casares et al. 2005) 4U1700-37 (Clark et al. 2002) V395 Car (Shahbaz et al. 2004) GRS 1915+105 V404 CYG • 4U1700-37/V395 Car/LS 5039 masses of 2.2-5 M: Low mass BHs or massive NSs? Fryer & Kalogera (1999) • V404 Cyg/GRS1915+105 BH masses 12±2 M & 14±4 M just above mass cut: mass-loss during WR phase overestimated?

  21. Conclusions • Best observational evidence for stellar-mass BHs based on dynamical studies of X-ray binaries. • First BH candidates: Cyg X-1 (1972) & A0620-00 (1986). • BH candidatesconfirmed with discovery of f(M)≥6 M: V404 Cyg (1992)… • X-ray properties (lack pulsations/bursts, weak quiescent Lx…) supports presence of event horizon. • XRTs are best hunting ground for new BHs with 17 cases. Masses range between 4—14 M. • Tip of iceberg of hidden population of ~103 BH binaries and ~108 stellar-mass BHs in the Galaxy. • Better statistics needed to derive constraints to close binary evolution and SNe models.

  22. BH • Distinct evolution in colour-colour diagram (Done & Gierlinski 2003) Atoll Z-source Cir X-1 Further support: absence of a hard surface

  23. Israelian et al. 1999 Nature 401 142: Parecen estrellas “normales” pero deberían mostrar indicios de un pasado violento (explosión de SN, erupciones de rayos X...) XTE J1655-40 • enriquecimiento un factor 6-10 de elementos  en la compañera F6III (MC=2.3 M ) • Sólo se sintetizan en el interior de estrellas > 10 M La compañera fue enriquecida por la explosión de la SN que formó el AN en este sistema.

  24. X0921-63: ADC with K0III donor in P=9.0 d Shahbaz et al. 2004 ApJ 493 L39 Jonker et al. 2004 MNRAS 356 621 • Firts radial velocity curve (some evidence for irradiation?) • MX sin3 i > 1.9 ± 0.25 M i=70-90 (eclipses) Massive NS or low-mass BH?? Mx=2.0-4.3 M (no irradiation) Mx=1.9-2.9 M (irradiation model)

  25. New Technique for dynamical studies Allows to measure f(M) in X-ray active Binaries • Steeghs & Casares 2002 ApJ 568 273 • Sharp NIII & CIII Bowen lines in Sco X-1 • Doppler shift traces orbit of donor star

  26. X1822-371 M1  1.14(6) M M2  0.36(2) M Doppler Tomography Kem= 300 ± 8 km/s  K

  27. Proving the BH in BW Cir Faint X-ray Binary in quiescence at R=21 VLT + FORS2 at R = 4300 Porb=2.55 days K=279 ±5 km/s Vrot sin i=71 km/s Mc/MX =0.13 f(M)=5.8 ± 0.3M

  28. The latest BH: BW Cir (GS 1354-64) MX >7.8 M • Vrot sin i=71 km/s q = 0.13 • i < 70o (no eclipses) 65 % veiling

  29. The latest BH: BW Cir (GS 1354-64) D27 kpc Furthest BH in the Galaxy! • Companion is G0-8: Teff=5100-5700 K and veiled by 65% • R  3.6R set by size of Roche lobe L  10 L Radial velocity of Galactic rotation curve =104 km/s, consistent with measured -velocity

  30. OSIRIS BH Target: XTE J1859+226 Zurita et al. 2002 MNRAS 334 999 Ellipsoidal modulation at P=7.7 or 9.2 hr R=22.48 ± 0.07 Filipenko & Chornock (IAUC 7644) announced f(M)=7.4 ± 1.1 M Requires confirmation!! OSIRIS IN SPECTROSCOPIC MODE AT R~2000- 5000

  31. X0921-63: ADC with K0III donor in P=9.0 d Shahbaz et al. 2004 ApJ 493 L39 Jonker et al. 2004 MNRAS 356 621 • Firts radial velocity curve (some evidence for irradiation?) • MX sin3 i > 1.9 ± 0.25 M i=70-90 (eclipses) Massive NS or low-mass BH?? Mx=2.0-4.3 M (no irradiation) Mx=1.9-2.9 M (irradiation model)

  32. Gallo et al. (2003) found a correlation between radio and X-ray flux for Black Holes in the low/hard state. If the X-rays not beamed, then the Lorentz factors of the compact radio jets should be smaller than 2 to account for the small scattering of the correlation.

  33. Why should we expect microquasars to be γ-ray emitters? • Their extragalactic analogous, the quasars, are γ-ray emitters (analogy quasar-microquasar Mirabel & Rodríguez, Nature 1992,1994) • Theoretical models predict γ-rays from microquasars, i.e. Leptonic models: SSC Atoyan & Aharonian 1999, MNRAS 302, 253 Latham et al. 2005, AIP CP745, 323 EC Kaufman Bernadó et al. 2002, A&A 385, L10 Georganopoulos et al. 2002, A&A 388, L25 SSC+EC Bosch-Ramon et al. 2004 A&A 417, 1075 Synchrotron jet emission Markoff et al. 2003, A&A 397, 645 Hadronic models: Pion decay Romero et al. 2003, A&A 410, L1 Bosch-Ramon et al. 2005, A&A 432, 609

  34. We have obtained a radial velocity curve of LS 5039 with the INT (IDS) during 2 campaigns on 2002 and 2003 (Casares et al. 2005). The orbital period is found to be 3.906 d and the orbital parameters depend on the spectral lines used in the analysis. All Balmer and He lines included

  35. The results suggest that LS 5039 might be a black hole with 3-5 solar masses(Casares et al. 2005) (but optically thin radio spectrum). The orbit is eccentric.

  36. 3EG J1812-1316 GRO J1817-15 3EG J1823-1314 3EG J1826-1302 3EG J1824-1514 µ-quasar LS 5039 Reminder of different error box sizes. Importance of position accuracy from TeV observations.

  37. With the new orbital ephemerides (Casares et al. 2005), we have been able to see correlated TeV and X-ray orbital variability: • Accretion changes in an eccentric orbit. • VHE gamma-ray absorption by pair creation with photons of the companion. HESS RXTE

  38. We have enough information to build up a Spectral Energy Distribution…

  39. Radio, L0.1-100 GHz ~ 11031 erg/s Synchrotron Radiation e- e- e- g-ray, E > 100 MeV, Lg ~ 41035 erg/s Inverse Compton Scattering UV, E ~ 10 eV Lopt ~ 11039 erg/s e- ge ~ 103 X-ray L3-30 keV ~ 51034 erg/s O6.5V((f)) e- vjet 0.15c e- Proposed scenario

  40. We have enough information to build up a Spectral Energy Distribution… … to extract physical information. A leptonic model with external comptonization can explain the observations (Paredes et al. 2006).

  41. Current status on LS 5039: VLA observations covering several orbital cycles reveal no periodic variability, and a progressive cut-off towards high radio frequencies. The source is one order of magnitude brighterthan the correlation for BH in the low/hard state. New detailed observations have been conducted with HESS. Results challenging models will be published soon. We are analyzing further VLBI observations to better trace the inner jet structure and eventually measure the jet speed. New models including all angle dependencies (for IC scattering, gamma-ray absorption by photon-photon pair creation, cascading) are being produced, and will hopefully be tested soon against new data(seeDubus 2005, Paredes et al. 2006, Bednarek 2006). Alternative models based on the interaction between the relativistic wind of a non-accreting millisecond pulsar and the UV photons of the massive companion have also been proposed (Dubus 2006).

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