Spots and faculae in V1298 Tau. The paper: “Spot Modeling through Multiband Photometry Analysis of V1298 Tau” of A. Biagini (INAF-OAPA/UNIPA) appeared on A&A
Most stars behave like enormous dynamos, producing intense magnetic fields within them. These magnetic fields then interact with the plasma that constitutes the star’s interior and atmosphere, in a constant tug of war where the prevailing force dominates the dynamics. In the outer region of stars, from the photosphere to the corona, the pressure exerted by the gas is less intense than the magnetic force. This phenomenon is the basis for a series of time-varying processes known as “magnetic activity”, which includes, for example, photospheric spots, flares, and faculae.
The Sun is the only star where magnetic phenomena can be observed with great spatial detail. For the other stars, it is necessary to analyze time series of observations in various bands and make use of the lessons learned from studying the Sun. These studies are important for various reasons. For example, they allow us to understand how the magnetic activity of stars changes depending on their properties and over the course of their evolution. Moreover, magnetic phenomena such as photospheric spots have a significant impact on the search for and characterization of exoplanets around stars, as they can interfere with signals caused by the presence of planets or with observations that are essential for analyzing exoplanetary atmospheres. This is particularly relevant for young, fast-rotating stars, which are characterized by intense magnetic activity.
To determine the physical properties of spots and faculae (regions respectively cooler and hotter than the stellar photosphere caused by magnetic activity) in a young star, the team of researchers led by astrophysicist A. Biagini (INAF – Palermo Astronomical Observatory and University of Palermo) analyzed a series of optical band observations of the star V1298 Tau. It is a 1.1 solar mass star, 23 million years old, located just 360 light-years away from us. V1298 Tau is one of the few stars under 30 million years old around which planets have been identified.
The observations analyzed by the team were collected over four different periods between 2021 and 2022, using the Ritchey-Chretien telescope of the Chianti Multifunctional Observatory. The analysis of the variability in stellar emission in these bands allowed them to model the presence of spots and faculae on the photosphere of V1298 Tau. The spots are always about polar, and, averaging the contributions of spots and faculae, the temperatures of the active regions during the observations ranged from about 3900 to 4800 degrees K, compared to the star’s effective temperature of 4970 degrees K. The study, which also involved astronomers A. Petralia, C. di Maio, and G. Micela from INAF – Palermo Astronomical Observatory, is described in the article “Spot Modeling through Multiband Photometry Analysis of V1298 Tau“, recently published in Astronomy & Astrophysics.
The cover image (click here to view it in full) shows the polar view of the active regions (both spots and faculae) of V1298 Tau as reconstructed from the observations acquired on February 23rd.
Mario Giuseppe Guarcello
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