J/ApJ/921/9ivo://CDS.VizieR/J/ApJ/921/9doi:10.26093/cds/vizier.19210009CDSDas B.Chandra P.2023-07-03T14:36:38Z2023-03-20T15:40:15ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.frvariable-starspeculiar-variable-starsradio-astronomypolarimetryThe presence of a large-scale surface magnetic field in early-type stars leads to several unique electromagnetic phenomena producing radiation over X-ray to radio bands. Among them, the rarest type of emission is electron cyclotron maser emission (ECME) observed as periodic, circularly polarized radio pulses. The phenomenon was first discovered in the hot magnetic star CU Vir. Past observations of this star led to the consensus that the star produces only right circularly polarized ECME, suggesting that only one magnetic hemisphere takes part in the phenomenon. Here we present the first ultra-wideband (0.4-4GHz) study of this star using the upgraded Giant Metrewave Radio telescope and the Karl G. Jansky Very Large Array, which led to the surprising discovery of ECME of both circular polarizations up to around 1.5GHz. The GHz observations also allowed us to infer that the upper ECME cutoff frequency is at >=5GHz. The sub-GHz observation led to the unexpected observation of more than two pairs of ECME pulses per rotation cycle. In addition, we report the discovery of a "giant pulse" and transient enhancements, which are potentially the first observational evidence of "centrifugal breakout" of plasma from the innermost part of the stellar magnetosphere. The stark contrast between the star's behavior at GHz and sub-GHz frequencies could either be due to propagation effects, a manifestation of varying magnetic field topology as a function of height, or a signature of an additional "ECME engine."2021ApJ...921....9Dhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/921/9CatalogResearchIsServedByTAP VizieR generic servicerelated-toB/gcvs : General Catalogue of Variable Stars (Samus+, 2007-2017)B/vsx : AAVSO International Variable Star Index VSX (Watson+, 2006-)B/polarbase : PolarBase spectropol. database (ESPaDOnS, NARVAL) (Petit+, 2014)J/A+AS/117/335 : Optical positions of radio emitting stars (Assafin+, 1996)J/A+AS/130/215 : Effective temperatures of Ap stars (Sokolov, 1998)J/A+A/383/1062 : Opt. positions of 55 radio stars at Yunnan Obs. (Hu+, 2002)J/A+A/493/931 : MAD observations of {sigma} Ori (Bouy+, 2009)J/MNRAS/431/2106 : CU Vir Stroemgren differential photometry (Pyper+, 2013)J/MNRAS/431/2240 : Activity in A-type stars from Kepler (Balona, 2013)J/PASP/126/469 : PolarBase catalogue of stellar spectra (Petit+, 2014)J/A+A/625/A34 : Photometry of CU Vir (Krticka+, 2019)J/MNRAS/499/5379 : Longitudinal magnetic field of 6 B stars (Shultz+, 2020)J/MNRAS/504/3730 : Synthetic RGB photometry of bright stars (Cardiel+, 2021)J/A+A/652/A31 : Stellar magnetic rot. phase curves. II (Bychkov+, 2021)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/921/9https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/ApJ/921/9http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/ApJ/921/9https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/ApJ/921/9https://vizier.iucaa.in/viz-bin/votable?-source=J/ApJ/921/9http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/ApJ/921/9GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapRadiodefaultJ/ApJ/921/9/fluxesFlux density measurements at uGMRT band 3 (300-500MHz) and band 4 (550-900MHz) and at VLA L band (1000-2000MHz) and S band (2000-4000MHz), tables 2-5recnoRecord number assigned by the VizieR team. Should Not be used for identification.meta.recordintHJD1Heliocentric Julian Day, observation startdtime.start;obsdoubleHJD2Heliocentric Julian Day, observation enddtime.end;obsdoubleFlux[-1.9/184] Flux density in BandmJyphot.flux.density;em.radiofloate_Flux[0.2/19] Uncertainty in Flux (1)mJystat.error;phot.fluxfloatPolPolarization type ("RCP"; "LCP") (2)meta.codecharnu0[347/3947] Central frequency of a bandMHzem.freqfloatdnu[22/1128] BandwidthMHzinstr.bandwidthfloatBanduGMRT (3=300-500MHz; 4=550-900MHz) or VLA (L=1-2GHz; S=2-4GHz) observation bandinstr.bandpasschar