RT Journal Article T1 MAGIC constraints on gamma-ray emission from Cygnus X-3 A1 Antoranz Canales, Pedro A1 Barrio Uña, Juan Abel A1 Contreras González, José Luis A1 Fonseca González, María Victoria A1 Miranda Pantoja, José Miguel A1 Nieto Castaño, Daniel AB Cygnus X-3 is a microquasar consisting of an accreting compact object orbiting around a Wolf-Rayet star. It has been detected at radio frequencies and up to high-energy. rays (above 100 MeV). However, many models also predict a very high energy (VHE) emission (above hundreds of GeV) when the source displays relativistic persistent jets or transient ejections. Therefore, detecting such emission would improve the understanding of the jet physics. The imaging atmospheric Cherenkov telescope MAGIC observed Cygnus X-3 for about 70 hr between 2006 March and 2009 August in different X-ray/radio spectral states and also during a period of enhanced gamma-ray emission. MAGIC found no evidence for a VHE signal from the direction of the microquasar. An upper limit to the integral flux for energies higher than 250 GeV has been set to 2.2 x 10(-12) photons cm(-2) s(-1) (95% confidence level). This is the best limit so far to the VHE emission from this source. The non-detection of a VHE signal during the period of activity in the high-energy band sheds light on the location of the possible VHE radiation favoring the emission from the innermost region of the jets, where absorption is significant. The current and future generations of Cherenkov telescopes may detect a signal under precise spectral conditions. PB IOP Publishing SN 0004-637X YR 2010 FD 2010-09-20 LK https://hdl.handle.net/20.500.14352/43916 UL https://hdl.handle.net/20.500.14352/43916 LA eng NO © The American Astronomical Society. Supported by INFN Padova.We thank the Instituto de Astrofisica de Canarias for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. The support of the German BMBF and MPG, the Italian INFN, the Swiss National Fund SNF, and the Spanish MICINN are gratefully acknowledged. This work was also supported by the Polish MNiSzW Grant N N203 390834, by the YIP of the Helmholtz Gemeinschaft, and by grant DO02-353 of the Bulgarian National Science Fund. S. T. is grateful for the support of the RATAN observations and the Russian Foundation for Basic Research, grant N08-02-00504-a. NO INFN Padova NO German BMBF NO German MPG NO Italian INFN NO Swiss National Fund SNF NO Polish MNiSzW NO YIP of the Helmholtz Gemeinschaft NO Bulgarian National Science Fund NO RATAN observations NO Russian Foundation for Basic Research DS Docta Complutense RD 8 abr 2025