Observation of the crab pulsar wind nebula and microquasar candidates with MAGIC

Abstract

of the Imaging Atmospheric Cherenkov Telescopes (IACTs) in the exploration of the Very-_x000D_ High-Energy (VHE) band. The last generation of IACTs have been capable to increase the_x000D_ total number of known VHE emitting sources from a few to almost one hundred in just seven_x000D_ years of operation. This population comprises galactic and extragalactic objects. IACTs have_x000D_ proved to be very effective in both the discovery of new emitters, as well as in the fine analysis_x000D_ of the physics properties of well established sources. Among them, the Crab Pulsar Wind_x000D_ Nebula is probably the best studied astrophysical object and the archetypal PWN. Due to its_x000D_ brightness at almost all wavelenghts, it is considered as an astrophysical candle. Despite the_x000D_ Crab Nebula broad-band spectrum has been thoroughly studied across twenty orders of magnitudes,_x000D_ from radio frequencies to VHE, further effort is needed to resolve the contradictions_x000D_ in the combination of all the multiwavelenght results. With the commissioning of the second_x000D_ MAGIC telescope in 2009 and the beginning of the operations in stereoscopic mode, the_x000D_ performance of the instrument improved dramatically, allowing MAGIC to reach the lowest_x000D_ ever energy threshold among all the existing IACTs, and describe the Crab Nebula spectrum_x000D_ with unprecedented precision down to 50 GeV. This achievement is of crucial importance for_x000D_ the VHE !-ray astrophysics in the pre-CTA era, since it can cast new light on some of the_x000D_ unsolved mysteries of one of its most established sources._x000D_ On the other hand, MAGIC made a strong impact in the discovery of new VHE sources_x000D_ and, with the improved sensitivity of the stereoscopic mode, this will be even more so in_x000D_ the future. Among the galactic objects, Microquasars (MQs) constitute some of the best_x000D_ candidates for VHE emission, but despite several well accepted models predict such signal,_x000D_ it has not been detected. There are, in fact, evidences that the three binary systems which_x000D_ have been unambiguously detected at energies above few hundreds of GeV are binary pulsars_x000D_ rather than accreting microquasars. Nevertheless, the recent detection of the microquasar_x000D_ Cygnus X-3 above 100 MeV by both Agile and Fermi satellites, and the claim of short oneday_x000D_ flares from Cygnus X-1 reported by Agile confirmed that microquasars remain interesting_x000D_ targets for VHE telescopes. MAGIC made a strong effort in searching for VHE signals from_x000D_ microquasars, but found only a non-significant evidence of signal from Cygnus X-1 in 80_x000D_ minutes of observation on September 24, 2006. MAGIC tried to detect similar flares in the_x000D_ following four years but the subsequent hundred more hours of observations were unsuccessful._x000D_ Besides Cygnus X-1, MAGIC pointed at two other microquasar candidates, whose results are_x000D_ presented in this thesis: Cygnus X-3 and Scorpius X-1. The most constraining UL to the_x000D_ integral flux of these sources at the energy above few hundred GeV are provided. Further_x000D_ investigations are being planned to discover these sources at VHE in the next years.

Date of Award	16 Sept 2011
Original language	Undefined/Unknown
Supervisor	Enrique Fernández Sánchez (Co-director) & Juan Cortina Blanco (Director)