BRITE-Constellation Mission Update

By / par Gregg Wade (on behalf of the Canadian BRITE Team)
(Cassiopeia – Spring / printemps 2022)

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 38 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, and Royal Military College of Canada. 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 were:

  • BRITE Toronto (Canada): This satellite observes with a red filter. It is currently observing the Vel-Pup VIII field. (As indicated by the roman numeral, Vel-Pup is a BRITE legacy field being observed for the 8th 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 has recently finished observing the Orion VIII field and is being set up on the Cru-Car IV field.
  • BRITE Austria (Austria): BRITE Austria observes with a blue filter. It has recently completed observing the Orion VIII field.
  • UniBRITE (Austria): Currently out of order.

The BRITE Constellation observing program is currently set through mid-2022. Details of the observing plan will be available on the BRITE photometry Wiki page.

Recent Science Results

“A study of stochastic photometric variability in the winds of Galactic Wolf-Rayet stars” (Lenoir-Craig et al., ApJ 925, 79)

In order to explore how the ubiquitous short-term stochastic variability in the photometric observations of Wolf-Rayet (WR) stars is related to various stellar characteristics, we examined a sample of 50 Galactic WR stars using 122 lightcurves obtained by the BRIght Target Explorer-Constellation, Transiting Exoplanet Survey Satellite and Microvariability and Oscillations of Stars satellites. We found that the periodograms resulting from a discrete Fourier transform of all our detrended lightcurves are characterized by a forest of random peaks showing an increase in power starting from ~0.5 day-1 down to ~0.1 day-1. After fitting the periodograms with a semi-Lorentzian function representing a combination of white and red noise, we investigated possible correlations between the fitted parameters and various stellar and wind characteristics. Seven correlations were observed, the strongest and only significant one being between the amplitude of variability, α0, observed for hydrogen-free WR stars, while WNh stars exhibit correlations between α0 and the stellar temperature, T, and also between the characteristic frequency of the variations, νchar, and both T and v. We report that stars observed more than once show significantly different variability parameters, indicating an epoch-dependent measurement. We also find that the observed characteristic frequencies for the variations generally lie between -0.5 < log n < 0.5, and that the values of the steepness of the amplitude spectrum are typically found in the range -0.1 < log g < 0.5. We discuss various physical processes that can lead to this correlation.

BRITE orbital-mean magnitudes of WR24 from the 36-Car-II field as a function of the Heliocentric Julian Date, after subtraction of the median, showing the stochastic photometric variability of this star.

Conferences, Resources, and Social Media

Conferences

The BRITE team does not plan to host any conferences at this time.

Resources

The BRITE Public Data Archive, based in Warsaw, Poland, at the Nikolaus Copernicus Astronomical Centre, can be accessed here.

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 Dr. Catherine Lovekin, the chair of BEST.

Pour marque-pages : Permaliens.

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