Observation of microquasars with the MAGIC telescope Observation of Cygnus X-1 with the MAGIC telescope Javier Rico Institut de Fisica d’Altes Energies (IFAE) Barcelona, SPAIN for the MAGIC collaboration

Cygnus X-1 Cygnus X-1 is binary system The distance to the system is 2 kpc The compact object is a black hole of M>13M☼ The optical companion is an O9.7 super-giant with M=30M☼ and a strong stellar wind The orbit is low-eccentric or circular with radius 0.2 AU and 5.6 days period. Modulation detected in radio and X-rays Different phase conventions. Here T0 adopted as companion star inferior conjunction (companion between observer and black hole) Inclination between 25 and 67 deg, 35 deg normally assumed 0.0 0.5 0.7 0.2 AU To observer 0.25 0.75

Observations with INTEGRAL Hard state Soft/intermediate state New probably non-thermal component emerges at 400 keV during the intermediate state (also seen by COMPTEL AT 1-10 MeV) The observed hard spectrum is well described by a model including: Thermal comptonization at corona Reflection on the accretion disk The observed soft spectrum is well described by a model including: Thermal disk Fe line Thermal comptonization at corona + reflection on disk

Giant outbursts Golenetskii et al. 2003 Between 1995 and 2003, 15 min to 8 hours outburst observed by Ulysses, Konus-Wind and/or BATSE Fluxes enhanced by a factor 3 to 10 up to luminosity ~1038 erg/s (2 kpc) Happening both in hard and soft states No change in the spectral shape Seems unrelated from accretion rate changes as hard/soft transitions (jet?)

Relativistic jet Stirling et al. 2001 ~15 mas 30 AU Gallo et al. 2005 Single-sided jet (microblazar?) resolved at milli-arcsec scales with VLBA in hard state. Opening angle <2°, bulk velocity is b>0.6c 1.4 GHz obs: 5 pc (8’) diameter ring-structure of bremsstrahlung emitting ionized gas at the shock between jet and ISM. Power released by the (dark) jet is of the same order or the bolometric x-ray luminosity and 2 orders of magnitude higher than what inferred from the radio spectrum

MAGIC observations Month (2006) Dates Zenith [degrees] Total [hours] Good [hours] June 30 0.1 0.0 July 1,25,26 5-30 2.1 1.1 August 16-22 15.5 11.9 September 17-20,23,25-29 5-35 19.6 19.1 October 12-15,21-23 20-35 5.9 5.3 November 10,11,14,18,19 24-35 3.0 2.5 Total 46.2 40.0 Data analized using MAGIC standard analysis. Cuts optimized for maximum sensitivity using Crab nebula observations same period and zenith angle range Search for: steady flux (using whole sample) fast varying signals (day by day and below) periodic flux (orbital folded)

Search for steady emission No significant signal is observed at any SIZE/energy cut Upper limits at the order of 1% Crab First limits at these energies

Daily searches 4.0s on 2006-09-25 between 20h58 and 23h41 UTC Sample subdivided until maximum significance is reached Correct probability by number of trials 4.9s (4.1s after 52 trials) from 79 minutes between 22h17 23h41

Signal significance and extension Background evaluated from 5 control regions from the same observation and close nights (Off/On =22) 4.9s

Source position Source location a = 19h58m17s, d = 35°12’8” ±1.5’ (stat) ± 2’ (syst) Compatible with the position of Cygnus X-1 and exclude radio ring

Spectrum Spectrum unfolded of detector effects Well fitted by power law with index -3.2±0.6 and ~10% Crab at 1 TeV

Search for orbital emission 3.8s at phase 0.9-1.0 (when the black hole is behind the star All (97%) data correspond to the same observation night

Correlation with X-rays Correlation MAGIC- X-rays (also INTEGRAL) MAGIC sees an excess right before the first Swift peak rise and zero flux in the decaying edge of second Swift peak Hard x-rays could be produced at the base of the jet and g-rays further away by interaction with stellar wind BUT… opacities are expected to be huge (10 at 1 TeV)

Conclusions With Cygnus X-1, the number of known g-ray binaries are 4, together with LS I +61 303 (MAGIC), LS 5039 and PSR B1959-63 (HESS). Paper accepted for publication at ApJL (2007-06-26) BUT… this is the first experimental evidence of VHE g-ray emission from a system powered by accretion this is the first experimental evidence of VHE g-ray emission from a system containing a stellar mass black hole the phenomenology is completely new: short time (<1day), intense flares probably not related to the orbital motion hints that the emission is produced far from the compact object