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Stellar Characterization & Variability | Center for Exoplanets and …
Table of Contents
Overview
Our understanding of exoplanets is directly dependent on our understanding of their host stars. We measure planetary masses in terms of their host stars‘ masses, we infer elemental abundance ratios from those in the atmosphere of their host star, and we infer surface temperatures and conditions informed by their host stars’ luminosities.
Variability of Kepler Solar-like Stars Harboring Small Exoplanets
Our Kepler small exoplanet host star sample is presented again in this pseudo H-R diagram, but now with variability facts provided for each star. Plotted are .25-day light-curve standard deviations that are >0.002 mag (red points), between 0.001 and 0.002 mag (green points), and those with values <0.001 mag (blue points). Source
Stellar Variability noise Floor for Transiting Exoplanet Photometry
In principle, space-based photometry of transiting exoplanets contains information about the host star and the exoplanet. An additional advantage of observing in the infrared would be quieter variability of the star, and a stronger variation of the transit light curve at ingress and egress that most suit their data, comparing the models that contributed to star variability with a simpler model that did not.They found that data for six planets from 20 analyzed had a better compatibility with a model that was adapted to the variability of stars and six other planets may experience small contamination of their host stars.
They analyze light at the wavelengths that are visible, near-infrastructure and near-ultraviolet, using the fact that the distortion of the activity of the star is much clearer in the area near-UV and visible (optics) than on a longer wavelength in infrared.
The team describes two ways to judge if star variability may affect the planet data.
Dr. Saba explained: ”One of them is looking at the overall spectrum shape – that is,the pattern of light at different wavelengths that have passed this planet from stars – to see whether this can be explained by this planet itself or if the activity of the star is needed.”
Alex Thomson added: “The risk of misinterpretation can be managed with the coverage of the right wavelength. Shorter wavelengths, optical observations as used in this study are very helpful, because this is where the effect of the most obvious star contamination.”
Contact Information
Mark greaves
- M.Greaves [at] ucl.ac.uk
- +44 (0) 20 3108 9485
University College London
- Gower Street, London, WC1E 6BT
- +44 (0) 20 7679 2000
An Interview with Mark Greaves on Exoplanet Research
Q: Can you explain why exoplanet researchers measure planetary masses in terms of their host stars’ masses?
A: When studying exoplanets, we frequently enough use our host stars as a reference point to better understand the planets’ characteristics. Measuring planetary masses in terms of their host stars’ masses provides a standardized framework. This allows for comparative analyses across different planetary systems,offering insights into scaling laws and the formation processes of exoplanets.
Q: How do we infer elemental abundance ratios from the atmospheric composition of host stars?
A: We infer elemental abundance ratios from the atmosphere of the host star because the material from which the star and its planets formed would be chemically similar. By analyzing the star’s atmosphere through spectroscopy, we can detect the presence and concentration of various elements. These abundance ratios can then provide data about the potential chemical makeup and formation processes of the planets orbiting the star.
Q: What role do host stars’ luminosities play in determining the surface temperatures and conditions of exoplanets?
A: The luminosity of a host star is a key factor in determining the surface temperatures and conditions of its orbiting exoplanets. The energy output from the star heats the planet’s surface, and higher luminosities will tend to create hotter and potentially more active planetary atmospheres. By understanding the star’s luminosity and its variability, we can model the surface conditions of the exoplanets more accurately.
Variability of Kepler Solar-like Stars Harboring Small Exoplanets
Q: What insights have you gained from analyzing the variability of Kepler solar-like stars that host small exoplanets?
A: By studying the variability of Kepler solar-like stars hosting small exoplanets, we can gain insights into how stellar activity affects our ability to detect and characterize exoplanets. The different variability ranges plotted in the H-R diagram help us understand which stars are more stable and thus better suited for precise photometric observations. This information is crucial for selecting targets for follow-up studies and confirming the presence of exoplanets.
Stellar Variability Noise Floor for Transiting Exoplanet Photometry
Q: How does stellar variability impact the photometry of transiting exoplanets, and what are the implications for observations?
A: Stellar variability can introduce noise into the photometry of transiting exoplanets, making it more challenging to detect and characterize these distant worlds. In principle, observing in the infrared can help mitigate this issue by reducing stellar variability noise. Comparative studies of photometric data in different wavelengths can reveal whether star activity substantially impacts the observed transit light curves. Managing the risk of misinterpretation through appropriate wavelength coverage is essential for accurate assessments of exoplanet characteristics.
contact Information
Mark Greaves
- M.Greaves [at] ucl.ac.uk
- +44 (0) 20 3108 9485
University College London
- Gower Street, London, WC1E 6BT
- +44 (0) 20 7679 2000
