Colloquium
Analysis of the Balmer jump in B-type stars with and without emission lines.
Abstract
B-type stars have temperatures ranging from 10000 to 30000 Kelvin and masses between 3 and 20 Mo. They exhibit radiation-driven stellar winds that lead to significant mass loss throughout their evolution, influencing the chemical enrichment of the interstellar medium. A key feature of this stellar group is its high degree of heterogeneity, including a wide variety of peculiar objects such as stars with high rotational velocities, circumstellar envelopes, or chemical anomalies (e.g., Be, B[e], HAeBe, and LBVs). In these cases, determining fundamental parameters like effective temperature (Teff) and surface gravity (logg) is particularly challenging, as both line intensities and profiles can be strongly affected by circumstellar material or rotation.
An alternative and robust methodology for estimating these parameters is the BCD (Barbier-Chalonge-Divan) Spectrophotometric Classification System. Based on the analysis of the Balmer discontinuity (or Balmer jump) at 3700 Å, this method was developed as a quantitative equivalent to the MK and Yerkes systems using measurable observable parameters. The BCD system offers a straightforward approach to determining Teff and logg, even in stars with prominent emission lines, while also providing independent estimates of color excess and distance.
In this seminar, I will discuss the application of the BCD method to a diverse sample of objects, ranging from B-type stars in open clusters to emission-line stars and objects in transitional evolutionary phases, such as sgB[e], LBV, and HAeBe stars.
About the talk
Instituto de Astrofísica de La Plata
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About the speaker
Dr. Yael Aidelman holds a PhD in Astronomy, and she is a CONICET researcher at the La Plata Institute of Astrophysics (Argentina) and a member of the “Models of Peculiar Stars” research group, where her work focuses on the spectrophotometric study of massive stars, particularly Be stars and blue supergiants. She also serves as a lecturer at the Faculty of Astronomical and Geophysical Sciences of the National University of La Plata (Argentina). She coordinates the spectroscopy area of the Historical Observational Data Recovery Project, which is dedicated to the recovery, digitisation, and preservation of spectroscopic observations recorded on glass plates. She also serves as the UNLP representative on the Scientific Committee of the CASLEO Observatory (San Juan, Argentina). She is currently a visiting researcher at the Instituto de Astrofísica de Canarias, where she collaborates with Sergio Simón Díaz and his research team.