BRITE-Constellation Mission Update

par Catherine Lovekin (Canadian PI for BRITE)
(Cassiopeia – hivers 2020)

BRITE-Constellation is an international space astronomy mission consisting of a fleet of 20x20x20 cm nanosatellites dedicated to precision optical photometry of bright stars in two photometric colours. The mission continues in full science operations, with 45 datasets available in the public domain from the BRITE public archive. As of April of 2020, all data is made public as soon as decorrelation is complete, with no proprietary period.

The BRITE mission is a collaboration between Canadian, Austrian and Polish astronomers and space scientists. The Canadian partners represent University of Toronto, Université de Montréal, Mount Allison University, Royal Military College of Canada, University of British Columbia, and Bishop’s University. The mission was built, and the Canadian satellites operated by, the University of Toronto Institute for Aerospace Studies Space Flight Lab (UTIAS-SFL). The Canadian Space Agency funded the construction of the Canadian satellites, and continues to support their day-to-day operations.

Operations

There are five BRITE satellites in the Constellation, which work together to obtain well-sampled, long term continuous (~6 months) light curves in both red and blue band passes across a variety of sky fields.

As this issue of Cassiopeia went to press, the assignments of the BRITE nanosats was:

  • BRITE Toronto (Canada): This satellite observes with a red filter. It is currently observing the Orion/Taurus III field, revisiting this field for the third time.
  • BRITE Lem (Poland): Lem observes with a blue filter, but is currently idle due to unresolved stability issues.
  • BRITE Heweliusz (Poland): Heweliusz observes with a red filter. It is currently observing the Vela/Pictorus V field.
  • BRITE Austria (Austria): BRITE Austria observes with a blue filter. It is currently observing the Orion VII field.
  • UniBRITE (Austria): Currently out of order.

The BRITE Constellation observing program is currently set through November of 2021. Details of the observing plan are available on the BRITE photometry Wiki page.

Recent Science Results

“β Cas: The first δ Scuti star with a dynamo magnetic field” (Zwintz et al., 2020, A&A, 643, A110)

This study investigates the pulsational and magnetic field properties of β Cas, as well as the star’s apparent fundamental parameters and chemical abundances.

Based on photometric time series obtained from three different space missions (BRITE-Constellation, SMEI, and TESS), we conduct a frequency analysis and investigate the stability of the pulsation amplitudes over four years of observations. We investigate the presence of a magnetic field and its properties using spectropolarimetric observations taken with the Narval instrument by applying the least-squares deconvolution and Zeeman-Doppler imaging techniques.

The star β Cas shows only three independent p-mode frequencies down to the few ppm-level; its highest amplitude frequency is suggested to be an n = 3, ℓ = 2, m = 0 mode. Its magnetic field structure is quite complex and almost certainly of a dynamo origin. The atmosphere of β Cas is slightly deficient in iron peak elements and slightly overabundant in C, O, and heavier elements.

Atypically for δ Scuti stars, we can only detect three pulsation modes down to exceptionally low noise levels for β Cas. The star is also one of very few δ Scuti pulsators known to date to show a measurable magnetic field and the first δ Scuti star with a dynamo magnetic field. These characteristics make β Cas an interesting target for future studies of dynamo processes in the thin convective envelopes of F-type stars, the transition region between fossil and dynamo fields, and the interaction between pulsations and magnetic field.

Figure 1. BRITE photometric time series obtained by UBr (panel a) and BAb in 2016 (panel b) to the same Y-axis scale and with a time base of 170 days on both X axes. Panels c and d show 4-days subsets of the UBr and BAb 2016 light curves binned to 5-minute intervals and the corresponding multi-sine fit with the two identified pulsation frequencies again to the same Y-axis scale and with a time base of 4 days on both X axes. From Zwintz et al. (2020).

Conferences, Resources, and Social Media

Conferences

The BRITE team did not host any conferences this year. The proceedings from the 2019 conference “Stars and their Variability Observed from Space” has now been published and all papers are available at brite.camk.edu.pl/pub/index.html.

The mission Wiki (including information on past, current and future fields) can be accessed here.

BRITE Constellation is on Facebook, at @briteconstellation.

The BRITE International Advisory Science Team

The BRITE International Advisory Science Team (BIAST), which consists of BRITE scientific PIs, technical authorities, amateur astronomers, and mission fans, advises the mission executive on scientific and outreach aspects of the mission. If you’re interested in joining BIAST, contact Konstanze Zwintz, the chair of BEST at konstanze.zwintz@uibk.ac.at.

Pour marque-pages : Permaliens.

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