PoS(MRU)106 http://pos.sissa.it/ ∗ [email protected] Speaker. CU Virginis is one of the(MCP) brightest class radio of emitting stars members and ofis the also unique magnetic one among chemically of stellar peculiar the radio fastestherent, sources 100% rotating. in right-hand generating polarised, We a radiation have from persistent, now oneacross highly confirmed (at the collimated, least) that sky beam of in CU its of a Vir magnetic co- wide polesThis emission that makes cone sweeps that the intercepts star the strikingly Earthobservation similar twice that to every time a the the pulsar. rotating star This period rotates. mechanism similarity probably of is related the further to star strengthened its isconfiguration). by very lengthening the strong at magnetic a field (and rapid possibly rate its due oblique to rotation a braking ∗ Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence. c

From Planets to Dark Energy: theOctober Modern 1-5 Radio 2007 Universe The University of Manchester, UK Rutherford Appleton Laboratory E-mail: Barry Kellett CU Virginis - A unique stellar pulsar? PoS(MRU)106 Barry Kellett 2 1.5 meters long and generates cyclotron maser radiation in the GHz ∼ AKR requires a low density cavity and an electron beam to enter this region. The electron This new mechanism naturally explains why the radio emission isThe 100% mechanism RCP works so and well why that it it is can be can and indeed has been tested in the laboratory, When simultaneous data on active stars from the radio and X-ray wavebands are compared a It was this last observation that suggested that the radio emission model assumed might be This is actually exactly like the magnetic field of the Earth. The Earth is known to emit radio beam is subjected to substantialmagnetic adiabatic dipole magnetic resulting compression in as the itelectron conversion descends of cyclotron into axial frequency. the momentum into planetary Theoretical rotationalcrescent or motion analysis horse-shoe at form indicates the of local that distribution function.of the radiation Such electron at a distribution the beam is cyclotron will unstable frequencycan to in form replace the the the emission a X-mode well [4,5]. known This loss-conegenerate new mechanism the cyclotron in maser new many mechanism situations radiation, because itbeam! it simply is requires much a simpler to converging dipole magnetic field and an electron from the auroral regions of the star, and also why the starin does not an require experiment GeV electrons. thatregime[6]. is 2. New Cyclotron Maser Mechanism remarkable correlation seems to applycovering - 8-10 ranging orders from of solarall? magnitude flares Then, [1]. to in active 1998, But dwarf the whyemission first and was resolved should giant radio coming the stars picture from X-ray of the a andorbit). polar star regions radio This was of fluxes obtained is the [2]. correlate quite star This unlikeemission at (as showed the was determined that Sun. compiled. by the the The For plane 15 finalto of of piece be the highly 17 of binary right-hand radio the circularly flares puzzle polarizedwere from was (RCP) 100% the found upto left-hand star when 100% polarized, UV in the but many Ceti, very radio cases. intense the flare and (The emission short two was lived exceptions found bursts [3].) inapplicable. The model assumes that theand emission a is gyrosynchrotron magnetic produced field. bystar GeV The can electrons simultaneous X-rays produce only copious require amountsa of keV keV new electrons and radio GeV and electrons emission it at mechanismabout seems the be same the hard time. 100% found to Could right-hand that believe circular would thatprocess, polarization? work a such The with as answer just a seemed keV cyclotron torelatively electrons? simple maser, be magnetic but a And field how coherent geometry what was generation for it the star, excited/driven? a toriodal The dipole answer magnetic wasemission, field. to and assume it a emanatesEarth’s from Auroral the Kilometric polar Radiation (or (AKR)UV is auroral) Ceti, remarkably except regions, for similar and the to it wavelengthsimply the of reflects is radio the the 100% emission, flare vastly cm different RCP. emission for magnetic In of field the fact, strengths star of the and the km two for sources. the Earth. But this CU Virginis - A unique stellar pulsar? 1. Background PoS(MRU)106 A Barry Kellett Physica Scripta Astronomy and Cyclotron Maser Radiation from Can late-type active stars be explained by a 3 Microwave emission from X-ray bright solar-like stars: Coherent cyclotron maser radiation from UV Ceti. Astronomy and Astrophysics 302, 775, 1995. First VLBI image of a main-sequence star Generation of auroral kilometric radiation by electron horseshoe Monthly Notices of the Royal Astronomical Society 329, 102-108, 2002. Astrophysical Journal 595, 279-284, 2003. Physics of Plasmas 7, 3089-3092, 2000. the F-G main sequence and beyond. Astrophysics 331, 596, 1998. dipole magnetic trap? distributions. Astronomy and Astrophysics 370, 1000-1003, 2001. Cyclotron Maser Instability with Application toVolume T Space 116, and 23-26, Laboratory Plasmas. 2005. Astrophysical Shocks. CU Virginis is a magnetic chemically peculiar star. This means it possesses a strong dipole We have now observed the star with MERLIN and confirmed that CU Vir produces repeating, [2] Benz, A. O., Conway, J., Gudel, M. magnetic field and we know thisour is offset view from of the the rotational magnetic axishours) field of we the changes. pass star. through So, That as the means themagnetic magnetic that star poles. equator for rotates, VLA twice each observations and in rotation our 1998 ofemission, showed line-of-sight in the that also short CU star passes “bursts”. Vir (about can close This produce 12.5 strongly to highly suggestedradiation both polarized to via radio us our that new the mechanism. star is generating cyclotron maser narrow, 100% right-hand circularly polarised (RCP)narrow emission emission at peaks 1.6GHz. are We the believepoles two that of sides the the of two star. an Another openthe possible emission intense application cone radio of emission from the from just new quasar one radio jets, of emission in the mechanism particular magnetic from is blazars[7]. to explain References [1] Gudel, M., Schmitt, J.H.M.M., Benz, A. O. [3] Kellett, B. J., Bingham, R., Cairns, R. A., Tsikoudi, V. CU Virginis - A unique stellar pulsar? 3. New Cyclotron Star [4] Bingham, R., Cairns, R. A. [5] Bingham, R., Cairns, R. A., Kellett, B. J. [6] Cairns, R. A., Speirs, D. C., Ronald, K., Vorgul, I., Kellett, B. J., Phelps, A. D. R., Bingham, R. [7] Bingham, R., Kellett, B. J., Cairns, R. A., Tonge, J., Mendonça, J. T.