BRITE-Constellation Mission Update

By / par Gregg Wade (Canadian PI for BRITE)
(Cassiopeia – Summer / été 2019)

BRITEpatch

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 25 data releases to BRITE target PIs having already taken place, and many datasets available in the public domain from the BRITE public archive.

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, Bishop’s 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 operating BRITE satellites in the Constellation, collecting data on various sky fields in a coordinated programme to obtain well-sampled, longterm continuous (~6 months) light curves in both red and blue bandpasses.

As this issue of Cassiopeia went to press, here was the status of the sky assignments for the BRITE nanosats:

  • BRITE Toronto (Canada): Toronto observes with a red filter. It is currently observing the Car III field. As implied by the numeral ‘III’, the current campaign on this field represents a revisit of a previously-observed field. Attempts have also been initiated to begin observing the CygLyr III field as a switch field.
  • BRITE Lem (Poland): Lem observes with a blue filter. It is observing the Sco II field.
  • BRITE Heweliusz (Poland): Heweliusz observes with a red filter. This satellite is also observing the Sco II field.
  • BRITE Austria (Austria): BRITE Austria observes with a blue filter. It is observing the Sag V field after having recently completed the Vel/Pup V field.
  • UniBRITE (Austria): UniBRITE observes with a red filter. This satellite is also observing the Sag V field after having recently completed the Vel/Pup V field.

The BRITE Constellation observing programme complete to mid-2020 has been planned by the BRITE Executive Science Team (BEST), and details are available on the BRITE photometry Wiki page.

Recent Science Results

« Revisiting the pulsational characteristics of the exoplanet host star beta Pictoris », by K. Zwintz et al. (A&A, in press). Zwintz et al. revisit the pulsational properties of beta Pic – host to a gas giant planet – and identify its pulsation modes from normalised amplitudes in five different passbands. They conducted a frequency analysis using three seasons of BRITE-Constellation observations in the BRITE blue and red filters, in addition to a long bRing light curve and nearly 8 years of photometric measurements from the SMEI mission. Using 2D rotating models, they fit the normalised amplitudes and frequencies through Monte Carlo Markov Chains, identifying 15 pulsation frequencies in the range from 34 to 55c/d, where two display clear amplitude variability. Using the normalised amplitudes in up to five passbands, they identify the associated modes as three l = 1, six l = 2 and six l = 3 modes. Multiple fits to the frequencies and normalised amplitudes are obtained including one with a near equator-on inclination for beta Pic, which corresponds to expectations based on the orbital inclination of beta Pic b and the orientation of the circumstellar disk. This solution leads to a rotation rate of 27% of the Keplerian break-up velocity, a radius of 1.497+-0.025 RSun, and a mass of 1.797+-0.035 MSun. The ~2% errors in radius and mass do not account for uncertainties in the models and a potentially erroneous mode-identification.


Figure 1 – Frequency analysis of the BRITE 2016/17 data in the red filter (left) and the blue filter (right): spectral window (panels a and e), original amplitude spectrum from 0 to 100 d−1 (panels b and f), zoom into the original amplitude spectrum (panels c and g) and residual amplitude spectrum after prewhitening the corresponding pulsation frequencies (panels d and h) with the residual noise level marked as horizontal dashed lines. The identified pulsation frequencies (as listed in Table 2) are marked in panels b and c as red (for the BRITE red filter) and in panels f and g as blue (for the BRITE blue filter) lines. The triangles mark the frequencies found in the ASTEP data by Mékarnia et al. (2017). Vertical dashed lines mark the positions of the respective satellite’s orbital frequency (i.e., BTr on the left and BLb on the right) and its multiples. From Zwintz et al. (in press).

Conferences, Resources and Social Media

Conferences

The BRITE team is spearheading the organization of a conference entitled “Stars and their Variability, Observed from Space”, to occur in Vienna, Austria from August 19 – 23, 2019. Preregistration is available on the conference website.

Resources

The BRITE Public Data Archive, based in Warsaw, Poland, at the Nikolaus Copernicus Astronomical Centre, can be accessed at brite.camk.edu.pl/pub/index.html.

The mission Wiki (including information on past, current and future fields) can be accessed at brite.craq-astro.ca/.

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 to join BIAST, contact Canadian BRITE PI Gregg Wade: wade-g@rmc.ca.

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