CFHT UM2025 - Presentation Details
Abstract Details
Title: Mapping HD 54879's complex magnetic field
Presenter: Christi Erba
Abstract:
Authors: C. Erba and C. P. Folsom Abstract: The O-type star HD 54879 (O9.7 V) has attracted much attention since the presence of a strong (>2kG) circumstellar magnetic field was confirmed in 2015. Routine spectropolarimetric monitoring with ESPaDOnS at CFHT provided evidence for an extremely long rotation period of at least 7 yr, placing HD 54879 as the second most slowly-rotating magnetic O-type star currently known. We now confirm that a complete rotation period of the star has been observed. Least-squares deconvolution profiles were extracted with SpecpolFlow and were used to provide measurements of the longitudinal magnetic field Bz. The best-fit to the Bz data provides a rotation period of P = 2562 63/−58 d (about 7.02 yr). We also present the first detailed magnetic map HD 54879, constructed using a modified Zeeman Doppler Imaging technique. The ZDI map reveals a complex magnetic topology with an average surface magnetic field strength of 2954 G, a strength for the dipole component of 3939 G, and a significant amount of magnetic energy in the quadrupole components of the field (23%). The number of magnetic massive stars identified as having complex field topologies is still extremely small; thus, the monitoring and characterization of any one of these objects improves an ever-expanding picture of how magnetism contributes to massive stellar evolution.