Update on Research of Massive Magnetic Stars


As I described in my previous blog “Magnetic Fields of Massive Stars”, I am doing research for Professor Véronique Petit. Originally I was only doing it for my senior seminar class, but this semester I got a college roll position for it as well, so I’ve added quite a few more hours on the project. I will briefly go over the background again and then give an update of my research.

Ever since a magnetic field was discovered on our sun, scientists have searched for and found many other stars with magnetic fields. Some stars classified as O or B stars (meaning they are relatively young and very massive) are included in this search, although OB magnetic stars are a lot rarer than magnetic stars with mass similar to the sun’s. One particular OB magnetic star named tau Sco was observed with an unusually complex magnetic field. Tau Sco’s magnetic field was discovered when scientists were looking for a cause of the stellar wind anomalies observed in the star’s spectra, but for a while, tau Sco was the only star exhibiting these properties, so not many conclusions could be made.

But then two other stars, HD66665 and HD64325, were observed with very similar spectra to tau Sco’s. Petit et al. did some analysis on these stars and discovered many of their properties are indeed very similar to tau Sco. A magnetic field was detected, too, but the question remains whether it’s as complex as tau Sco’s. My research project is working with new data from these stars to determine their magnetic fields and compare them with normal magnetic massive stars.



















Tau Sco’s magnetic field lines (top) vs. a more typical massive magnetic star’s fields lines (bottom).


I started by writing an algorithm with the program Interactive Data Language (IDL) to read in the data from HD66665 and plot the flux and polarization data. The polarization data was then used to calculate the magnetic field values using an equation from an article by Landstreet and Donati . To compare with a normal magnetic field from a massive star, a sine curve was attempted to fit the data. The fact the points don’t follow the theoretical curve very well is a good indicator that HD66665 might have a more complex magnetic field, although perhaps not as complex as tau Sco. The next steps will be to do a more in-depth error analysis and use this same method for the other star, HD64325.

Polarization data of HD66665.

Polarization data of HD66665.


Calculated magnetic field values plotted against time. The solid sine curve represents the magnetic field of a normal massive star.

Calculated magnetic field values plotted against time. The solid sine curve represents the magnetic field of a normal massive star.

This research has been good for me, especially programming-wise. While I did learn IDL for my internship last summer, a couple of months really is not long enough to know everything about it. Using it for the past seven months is not enough to know everything, either, but I definitely feel like I have a better grasp on it now. Petit also had me make a research website , which introduced me to HTML, so that’s also a great plus from this experience. I hope to get some analysis done on the other star before leaving for summer break. I highly recommend all students to get involved in some kind of undergraduate research. It can earn you a little income and, even more importantly, give you experiences to put on your resume!


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