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Chemically peculiar stars investigated by the BRITE Mission

Teja Begari, Klaus Bernhard, Ernst Paunzen, Prapti Mondal

TL;DR

This study analyzes BRITE nanosatellite photometry for 85 chemically peculiar (CP) stars to refine or determine their rotational periods. It employs a uniform time-series pipeline based on the Generalized Lomb-Scargle periodogram, with iterative cleaning and pre-whitening to extract significant signals in a wide frequency range, cross-validated against archival TESS data. The authors identify 47 stars with robust periods, uncover six clear multiperiodic cases suggesting misclassification (e.g., Be/shell or SPB stars) among CP2/CP4 targets, and note 11 apparently constant stars within BRITE precision. The results demonstrate BRITE’s effectiveness for period verification and misclassification detection among bright CP stars, especially when complemented by TESS data, and place the objects reliably on the Hertzsprung-Russell diagram.

Abstract

We present a comprehensive analysis of BRITE photometry for 85 chemically peculiar stars, aimed at refining or determining their rotational periods. Utilizing a uniform Lomb-Scargle-based pipeline, we derived significant periods for 47 targets. A comparison with existing literature periods reveals generally good agreement, although several stars exhibit discrepant or previously unrecognized behavior. Notably, six targets display clear multiperiodicity, which, when combined with archival TESS data, suggests that these six candidates are likely misclassified, for example, as a magnetic CP2 or a CP4 star and instead exhibit characteristics consistent with a Be/shell star. Furthermore, eleven stars show no detectable periodic variations within the precision limits of BRITE. Our analysis demonstrates the effectiveness of long-term nanosatellite photometry, particularly when complemented by TESS data, in verifying catalogue periods, identifying multiperiodic behavior, and detecting potential misclassifications among bright CP stars.

Chemically peculiar stars investigated by the BRITE Mission

TL;DR

This study analyzes BRITE nanosatellite photometry for 85 chemically peculiar (CP) stars to refine or determine their rotational periods. It employs a uniform time-series pipeline based on the Generalized Lomb-Scargle periodogram, with iterative cleaning and pre-whitening to extract significant signals in a wide frequency range, cross-validated against archival TESS data. The authors identify 47 stars with robust periods, uncover six clear multiperiodic cases suggesting misclassification (e.g., Be/shell or SPB stars) among CP2/CP4 targets, and note 11 apparently constant stars within BRITE precision. The results demonstrate BRITE’s effectiveness for period verification and misclassification detection among bright CP stars, especially when complemented by TESS data, and place the objects reliably on the Hertzsprung-Russell diagram.

Abstract

We present a comprehensive analysis of BRITE photometry for 85 chemically peculiar stars, aimed at refining or determining their rotational periods. Utilizing a uniform Lomb-Scargle-based pipeline, we derived significant periods for 47 targets. A comparison with existing literature periods reveals generally good agreement, although several stars exhibit discrepant or previously unrecognized behavior. Notably, six targets display clear multiperiodicity, which, when combined with archival TESS data, suggests that these six candidates are likely misclassified, for example, as a magnetic CP2 or a CP4 star and instead exhibit characteristics consistent with a Be/shell star. Furthermore, eleven stars show no detectable periodic variations within the precision limits of BRITE. Our analysis demonstrates the effectiveness of long-term nanosatellite photometry, particularly when complemented by TESS data, in verifying catalogue periods, identifying multiperiodic behavior, and detecting potential misclassifications among bright CP stars.
Paper Structure (11 sections, 2 equations, 5 figures, 8 tables)

This paper contains 11 sections, 2 equations, 5 figures, 8 tables.

Table of Contents

  1. Introduction
  2. data sources and target selection
  3. Time series analysis
  4. Instrumental effects and data cleaning
  5. Variable stars
  6. Apparently constant stars
  7. Notes on misclassified CP2 and CP4 candidates
  8. Astrophysical Parameters and the Hertzsprung-Russell Diagram
  9. Conclusions
  10. The used data sets from the BRITE mission
  11. Essential data for our sample stars

Figures (5)

  • Figure 1: Example TESS Light curves of the three of the six multiperiodic stars.
  • Figure 2: Histogram of the $V$ magnitudes for our target star sample.
  • Figure 3: A comparison of BRITE-derived periods with literature values is presented for our sample stars. The plot includes lines indicating perfect agreement (unity line) as well as half- and double-period relationships. Three extreme outlier stars (HD 15633, HD 59635 and HD 81188), discussed in the text, are denoted by unique symbols.
  • Figure 4: Phased light curves of four sample stars observed by BRITE, showcasing diverse periods and light-curve characteristics.
  • Figure 5: Positions of our target stars in the Hertzsprung-Russell diagram, which is provided in the form of $\log T_\mathrm{eff}$ versus $\log L/L_\odot$ (Table \ref{['table_master1']}). Also shown are stellar evolutionary models for the indicated logarithmic ages by 2012MNRAS.427..127B.