Bibcode
Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Arcaro, C.; Babić, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Berti, A.; Bhattacharyya, W.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Carosi, R.; Carosi, A.; Chatterjee, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Cumani, P.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Lotto, B.; de Oña Wilhelmi, E.; di Pierro, F.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D.; Elsaesser, D.; Engelkemeier, M.; Fallah Ramazani, V.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Gaug, M.; Giammaria, P.; Godinović, N.; Gora, D.; Guberman, D.; Hadasch, D.; Hahn, A.; Hassan, T.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Ishio, K.; Konno, Y.; Kubo, H.; Kushida, J.; Kuveždić, D.; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; Maggio, C.; Majumdar, P.; Makariev, M.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Minev, M.; Mirzoyan, R.; Moralejo, A.; Moreno, V.; Moretti, E.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Ninci, D.; Nishijima, K.; Noda, K.; Nogués, L.; Paiano, S.; Palacio, J. et al.
Bibliographical reference
Monthly Notices of the Royal Astronomical Society, Volume 472, Issue 3, p.3474-3485
Advertised on:
12
2017
Citations
13
Refereed citations
9
Description
The microquasar Cygnus X-1 displays the two typical soft and hard X-ray
states of a black hole transient. During the latter, Cygnus X-1 shows a
one-sided relativistic radio-jet. Recent detection of the system in the
high energy (HE; E ≳ 60 MeV) gamma-ray range with Fermi-LAT
associates this emission with the outflow. Former MAGIC observations
revealed a hint of flaring activity in the very high-energy (VHE; E
≳ 100 GeV) regime during this X-ray state. We analyse ∼97 h of
Cygnus X-1 data taken with the MAGIC telescopes between July 2007 and
October 2014. To shed light on the correlation between hard X-ray and
VHE gamma rays as previously suggested, we study each main X-ray state
separately. We perform an orbital phase-folded analysis to look for
variability in the VHE band. Additionally, to place this variability
behaviour in a multiwavelength context, we compare our results with
Fermi-LAT, AGILE, Swift-BAT, MAXI, RXTE-ASM, AMI and RATAN-600 data. We
do not detect Cygnus X-1 in the VHE regime. We establish upper limits
for each X-ray state, assuming a power-law distribution with photon
index Γ = 3.2. For steady emission in the hard and soft X-ray
states, we set integral upper limits at 95 per cent confidence level for
energies above 200 GeV at 2.6 × 10-12 photons
cm-2 s-1 and 1.0 × 10-11 photons
cm-2 s-1, respectively. We rule out steady VHE
gamma-ray emission above this energy range, at the level of the MAGIC
sensitivity, originating in the interaction between the relativistic jet
and the surrounding medium, while the emission above this flux level
produced inside the binary still remains a valid possibility.
Related projects
Particle Astrophysics
The MAGIC Collaboration is integrated by 20 research institutes and university departments from Armenia, Bulgaria, Finland, Germany, Italy, Poland, Spain, Switzerland and USA. The collaboration comprises two 17m diameter telescopes, located at the Roque de los Muchachos Observatory, designed to measure the Cherenkov radiation associated with
Ramón
García López