VERITAS 2008 - 2009 monitoring of the variable gamma-ray source M87

• Autores: Acciari, V. A.; Aliu, E.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Boltuch, D.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cannon, A.; Cesarini, A.; Chow, Y. C.; Ciupik, L.; Cogan, P.; Cui, W.; Dickherber, R.; Duke, C.; Finley, J. P.; Finnegan, G.; Fortin, P.; Furniss, A.; Galante, N.; Gall, D.; Gillanders, G. H.; Godambe, S.; Pichel, Ana Carolina; The Veritas Collaboration
• Año de publicación: 2010
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: galaxies: individual: M87 VER J1230+123; gamma rays: galaxies
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

M 87 is a nearby radio galaxy that is detected at energies ranging from radio to very high energy (VHE) gamma rays. Its proximity and its jet, misaligned from our line of sight, enable detailed morphological studies and extensive modeling at radio, optical, and X-ray energies. Flaring activity was observed at all energies, and multi-wavelength correlations would help clarify the origin of the VHE emission. In this paper, we describe a detailed temporal and spectral analysis of the VERITAS VHE gamma-ray observations of M 87 in 2008 and 2009. In the 2008 observing season, VERITAS detected an excess with a statistical significance of 7.2 standard deviations (σ) from M 87 during a joint multi-wavelength monitoring campaign conducted by three major VHE experiments along with the Chandra X-ray Observatory. In 2008 February, VERITAS observed a VHE flare from M 87 occurring over a 4 day timespan. The peak nightly flux above 250 GeV was (1.14 ± 0.26) × 10−11 cm−2 s−1, which corresponded to 7.7% of the Crab Nebula flux. M 87 was marginally detected before this 4 day flare period, and was not detected afterward. Spectral analysis of the VERITAS observations showed no significant change in the photon index between the flare and pre-flare states. Shortly after the VHE flare seen by VERITAS, the Chandra X-ray Observatory detected the flux from the core of M 87 at a historical maximum, while the flux from the nearby knot HST-1 remained quiescent. Acciari et al. presented the 2008 contemporaneous VHE gamma-ray, Chandra X-ray, and Very Long Baseline Array radio observations which suggest the core as the most likely source of VHE emission, in contrast to the 2005 VHE flare that was simultaneous with an X-ray flare in the HST-1 knot. In 2009, VERITAS continued its monitoring of M 87 and marginally detected a 4.2σ excess corresponding to a flux of ∼1% of the Crab Nebula. No VHE flaring activity was observed in 2009.
Fil: Acciari, V. A.. Harvard-Smithsonian Center for Astrophysics; Estados Unidos
Fil: Aliu, E.. Columbia University; Estados Unidos
Fil: Arlen, T.. University of California; Estados Unidos
Fil: Aune, T.. University of California; Estados Unidos
Fil: Beilicke, M.. University of Washington; Estados Unidos
Fil: Benbow, W.. Harvard-Smithsonian Center for Astrophysics; Estados Unidos
Fil: Boltuch, D.. University of Delaware; Estados Unidos
Fil: Bradbury, S. M.. University of Leeds; Reino Unido
Fil: Buckley, J. H.. University of Washington; Estados Unidos
Fil: Bugaev, V.. University of Washington; Estados Unidos
Fil: Byrum, K.. Argonne National Laboratory; Estados Unidos
Fil: Cannon, A.. University College Dublin; Irlanda
Fil: Cesarini, A.. National University of Ireland Galway; Irlanda
Fil: Chow, Y. C.. University of California; Estados Unidos
Fil: Ciupik, L.. Adler Planetarium and Astronomy Museum; Estados Unidos
Fil: Cogan, P.. McGill University; Canadá
Fil: Cui, W.. Purdue University; Estados Unidos
Fil: Dickherber, R.. University of Washington; Estados Unidos
Fil: Duke, C.. Grinnell College; Estados Unidos
Fil: Finley, J. P.. Purdue University; Estados Unidos
Fil: Finnegan, G.. University of Utah; Estados Unidos
Fil: Fortin, P.. Columbia University; Estados Unidos
Fil: Furniss, A.. University of California; Estados Unidos
Fil: Galante, N.. Harvard-Smithsonian Center for Astrophysics; Estados Unidos
Fil: Gall, D.. Purdue University; Estados Unidos
Fil: Gillanders, G. H.. National University of Ireland Galway; Irlanda
Fil: Godambe, S.. University of Utah; Estados Unidos
Fil: Pichel, Ana Carolina. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentina
Fil: The Veritas Collaboration.