Magnetic fields have now been detected in stars in several parts of the Hertzsprung-Russell diagram. Roughly dipolar fields ranging in strength between 3× 102 and 3×104 G are found in many chemically peculiar A and B main sequence stars. Dipolar fields are also found in some 2–3% of white dwarfs, but with strengths between 1×106 and 5×108 G. In both these types of stars, the observed fields vary as the underlying star turns, but do not change in a secular manner. In solartype stars, structurally complex fields of a few kG are found with filling factors of the order of 0.1 to 0.8. Further indirect evidence of fields in cool main sequence stars is provided by detection of visible and ultraviolet line emission (chromospheric activity), x radiation (coronal matter), and giant starspots. In this review, we survey the observations of stellar magnetism in all these types of stars, as well as efforts to model the observed magnetic fields and associated photospheric peculiarities and activity.

Magnetic fields at the surfaces of stars

This paper presents a catalogue and the method of determining averaged quadratic effective magnetic fields (Be) for 1212 main-sequence and giant stars, and 11 white dwarf stars. The catalogue includes stars that are members of several open clusters. We have compiled measurements of the longitudinal magnetic field for those stars, which were scattered in the existing literature. A new parameter, magnetization (MA), has been defined, and we present values of MA for stars of various spectral classes. Our sample includes a subset of 610 chemically peculiar early-type stars. We confirm the conclusion of our previous study that the number distribution of all chemically peculiar stars versus the averaged magnetic field strength is described by a decreasing exponential function. Relations of this type also hold for stars of all the analysed subclasses of chemical peculiarity. Magnetization tends to correlate with the effective temperature only at high MA, for He-weak and He-rich stars.

Catalogue of averaged stellar effective magnetic fields -II. Re-discussion of chemically peculiar A and B stars

This paper presents the catalogue and the method of determination of averaged quadratic effective magnetic fields $\langle B_{\rm e} \rangle$ for 596 main sequence and giant stars. The catalogue is based on measurements of the stellar effective (or mean longitudinal) magnetic field strengths B e , which were compiled from the existing literature. We analysed the properties of 352 chemically peculiar A and B stars in the catalogue, including Am, ApSi, He-weak, He-rich, HgMn, ApSrCrEu, and all ApSr type stars. We have found that the number distribution of all chemically peculiar (CP) stars vs. averaged magnetic field strength is described by a decreasing exponential function. Relations of this type hold also for stars of all the analysed subclasses of chemical peculiarity. The exponential form of the above distribution function can break down below about 100 G, the latter value representing approximately the resolution of our analysis for A type stars.

https://www.aanda.org/articles/aa/pdf/2003/32/aa3253.pdf

Catalogue of averaged stellar effective magnetic fields - I. Chemically peculiar A and B type stars

Magnetized stars usually exhibit periodic variations of the effective (longitudinal) magnetic field B e caused by their rotation. We present a catalog of magnetic rotational phase curves, B e vs. the rotational phase ϕ , and tables of their parameters for 136 stars on the main sequence and above it. Phase curves were obtained by the least squares fitting of sine wave or double wave functions to the available B e measurements, which were compiled from the existing literature. Most of the catalogued objects are chemically peculiar A and B type stars (127 stars). For some stars we also improved or determined periods of their rotation. We discuss the distribution of parameters describing magnetic rotational phase curves in our sample.

/pdf/a-catalog-of-stellar-magnetic-rotational-phase-curves-3jyjqtutaj.pdf

A catalog of stellar magnetic rotational phase curves

This is the first paper of the series dedicated to the analysis of the magnetism of chemically peculiar (CP) stars of the upper Main Sequence. We use our own measurements and published data to compile a catalog of magnetic CP stars containing a total of 326 objects with confidently detected magnetic fields and 29 stars which are very likely to possess magnetic field. We obtained the data on the magnetism of the overwhelming majority of the stars solely based on the analysis of longitudinal field component Be. The surface magnetic field, Bs, has been measured for 49 objects. Our analysis shows that the number of magnetic CP stars decreases with increasing field strength in accordance with exponential law, and stars with Be exceeding 5kG occur rarely (about 3% objects of our list).

A. H. Vaughan

Papers

High-resolution polarization observations inside the spectral lines of magnetic Ap stars. II. Observations of alpha 2 Canum Venaticorum.