Chandra
Orion Ultradeep Project
X-ray evolution
It has long been known that younger stars are more magnetically active than older stars, and it was thought to occur because younger stars are more rapidly rotating. This is called the activity-age-rotation connection. However, it was established only for main sequence stars older than ~50 Myr, and it was not clear whether the trends continued into the younger, pre-main sequence phases of evolution. Due to various difficulties with ultraviolet, optical & radio measurements, X-rays provide the most effective tool for measuring magnetic activity in pre-main sequence stars.
The thick line shows the integrated distribution of X-ray luminosities for COUP Orion stars (ages~0.1-10) Myr) in a narrow mass range. Comparison distributions are the Pleiades cluster (dashed line, age~100 Myr), Hyades cluster (dotted line, age~500 Myr), and solar neighborhood stars (thin line, ages~1-5 Gyr). We clearly establish that the activity-age relation continues through the pre-main sequence phases. In a puzzling fashion, we also show that age-rotation relation does not hold for these youngest stars.
The full paper on COUP X-ray evolution is:
The evolution of X-ray emission in young stars
Thomas Preibisch and Eric D. Feigelson
Back to the COUP home page
X-ray evolution
It has long been known that younger stars are more magnetically active than older stars, and it was thought to occur because younger stars are more rapidly rotating. This is called the activity-age-rotation connection. However, it was established only for main sequence stars older than ~50 Myr, and it was not clear whether the trends continued into the younger, pre-main sequence phases of evolution. Due to various difficulties with ultraviolet, optical & radio measurements, X-rays provide the most effective tool for measuring magnetic activity in pre-main sequence stars.
The thick line shows the integrated distribution of X-ray luminosities for COUP Orion stars (ages~0.1-10) Myr) in a narrow mass range. Comparison distributions are the Pleiades cluster (dashed line, age~100 Myr), Hyades cluster (dotted line, age~500 Myr), and solar neighborhood stars (thin line, ages~1-5 Gyr). We clearly establish that the activity-age relation continues through the pre-main sequence phases. In a puzzling fashion, we also show that age-rotation relation does not hold for these youngest stars.
The full paper on COUP X-ray evolution is:
The evolution of X-ray emission in young stars
Thomas Preibisch and Eric D. Feigelson
Back to the COUP home page