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Measuring the density structure of an accretion hot spot
C C Espaillat1, C E Robinson2, M M Romanova3
1Institute for Astrophysical Research, Department of Astronomy, Boston University, Boston, MA, USA. cce@bu.edu.
Nature
|September 2, 2021
Summary
Accretion onto young stars creates hot spots with density gradients. New observations reveal a radial density gradient in these hot spots, impacting star formation and planetary system development.
Area of Science:
- Astrophysics
- Stellar evolution
- Exoplanet research
Background:
- Magnetospheric accretion models predict funnel flows from protoplanetary disks onto stars.
- These flows create stellar surface hot spots with density gradients, crucial for understanding accretion processes.
- Previous observations lacked sensitivity to the radial density distribution within these hot spots.
Purpose of the Study:
- To investigate the radial density distribution in stellar hot spots using ultraviolet and optical light curves.
- To test predictions of magnetospheric accretion models regarding hot spot structure.
- To understand how hot spot properties influence the early stages of star and planet formation.
Main Methods:
- Obtained periodic ultraviolet and optical light curves of the accreting star GM Aurigae.
- Analyzed the time lag between ultraviolet and optical emission peaks.
- Interpreted light curve variations within the framework of magnetospheric accretion models.
Main Results:
- Detected a periodicity in ultraviolet and optical light curves of GM Aurigae.
- Observed a time lag of approximately one day between the peaks of ultraviolet and optical emission.
- The observed time lag indicates a difference in the spatial distribution of ultraviolet and optical brightness, implying a radial density gradient in the hot spot.
Conclusions:
- The findings provide observational evidence for a radial density gradient in a stellar hot spot.
- This gradient affects the temperature and emission characteristics of different regions within the hot spot.
- The study refines our understanding of magnetospheric accretion and its role in early stellar evolution and planet formation.
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