Searching for links between magnetic fields and stellar evolution. I. A survey of magnetic fields in open cluster A- and B-type stars with FORS1

TL;DR

This study surveys magnetic fields in 235 early-type stars in open clusters to understand their evolution and origin, detecting magnetic fields in 41 stars, most of which were previously unknown as magnetic.

Contribution

It provides the first large-scale spectropolarimetric survey of magnetic fields in open cluster A- and B-type stars, expanding knowledge of magnetic field occurrence and properties.

Findings

Magnetic fields detected in 41 stars, 37 newly identified.

No magnetic fields found in 138 normal A and B-type stars.

Median measurement error was about 80 G for magnetic stars.

Abstract

About 5% of upper main sequence stars are permeated by a strong magnetic field, the origin of which is still matter of debate. With this work we provide observational material to study how magnetic fields change with the evolution of stars on the main sequence, and to constrain theory explaining the presence of magnetic fields in A and B-type stars. Using FORS1 in spectropolarimetric mode at the ESO VLT, we have carried out a survey of magnetic fields in early-type stars belonging to open clusters and associations of various ages. We have measured the magnetic field of 235 early-type stars with a typical uncertainty of about 100 G. In our sample, 97 stars are Ap or Bp stars. For these targets, the median error bar of our field measurements was about 80 G. A field has been detected in about 41 of these stars, 37 of which were not previously known as magnetic stars. For the 138 normal A and B-type stars, the median error bar was 136 G, and no field was detected in any of them.