Multiwavelength Observations of AB Doradus

Abstract

We have observed the bright, magnetically active multiple star AB Doradus in a multiwavelength campaign centring around two large facility allocations in November 2006 and January, 2007. Our observations have covered at least three large flares. These flares were observed to produce significant hardening of the X-ray spectra during their very initial stages. We monitored flare-related effects using the Suzaku X-ray satellite and the Australia Telescope Compact Array (ATCA) at 3.6 and 6 cm. Observations at 11 and 21 cm were also included, but they were compromised by interference. Optical monitoring was also provided by broadband B and V photometry and some high-dispersion spectrograms. From this multiwavelength coverage we find that the observed flare effects can be mainly associated with a large active region near longitude zero. The second major X-ray and microwave flare of Jan 8, 2007 was observed with a favourable geometry that allowed its initial high-energy impulsive phase to be observed in the higher frequency range of Suzaku's XIS detectors. The fractional circular polarisation (Stokes V/I) was measured in the uv data for the complete runs, for 25 min integrations and, at 4.80 GHz, for 5 min integrations, using the radio data of Nov 21 2006 and Jan 08 2007. Most of the full data sets showed V/I fractions from AB Dor B that were significant at greater than the 3σ level. In several of the 5 min integrations at 4.80 and 8.64 GHz this fraction reached a significance level between 3 and 9σ . Lack of angular resolution prevented identification of these high V/I values with one or other of the two low-mass red-dwarf components of AB Dor B.

AB Dor: Coronal Imaging and Activity Cycles

“…The resulting fluxes were converted to luminosity using the distance of 14.85 pc. The quiescent fluxes in 0.3-10.0 keV using Suzaku data during the years 2006 and 2007 are taken from Slee et al (2014). The evolution of quiescent luminosity is summarized in Table B1 in Appendix B and is plotted in Figure 3.…”

Preparing for solar and heliospheric science with the SKAO: An Indian perspective

“…Indian scientists have been playing a leading role in establishing solar and heliospheric science as one of the key science objectives of the MWA and continue to lead it (Oberoi & Kasper 2004;Oberoi & Benkevitch 2010;Bowman et al 2013;Beardsley et al 2020). Though the bulk of the work by the Indian community has been at frequencies overlapping with the SKAO-Low, the future plans involve making use of the SKAO-Mid frequencies as well.…”

Stellar flares observed by LOFT: implications for the physics of coronae and for the "space weather" environment of extrasolar planets

“…Multi-wavelength flare studies can be (and have been) used to derive information on flare physical parameters, the properties of the nonthermal electrons and the coronal magnetic field strengths, etc., which are unobtainable from X-ray data alone. For more information, see White et al (2011), who review the extensive studies of solar flares done using simultaneous radio and hard X-ray bands, and Slee et al (2014) for a recent example of such a multi-wavelength campaign which observed 3 flares from the nearby young star AB Dor.…”