par Gregg Wade (on behalf of the Canadian BRITE team)
(Cassiopeia – été 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.
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 Cyg V field. (As indicated by the roman numeral, Cygnus is a BRITE legacy field being observed for the 5th time.) The pointing performance of the satellites on this field has been poor, and an alternative field may be considered.
- 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 Cru-Car IV field with good performance.
- BRITE Austria (Austria): BRITE Austria observes with a blue filter. It is currently observing the Sgr 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
“5 yr of BRITE-Constellation photometry of the luminous blue variable P Cygni: properties of the stochastic low-frequency variability” (Elliot et al. 2022, MNRAS 509, 4246)
The BRITE flux of P Cyg, after subtracting off the global mean, with units of parts per thousand (ppt) (left) and the Fourier amplitude spectrum (right) for the 2015 data. Each peak used in the analysis is highlighted with a different color in the Fourier spectrum, and then the fit is overplotted on the photometry with the corresponding colour for that term and all previous terms. The final multi-frequency fit is then used to calculate the (? − ?) that is shown on the bottom panel of the photometry.
Luminous Blue Variables (LBVs) are massive stars that are likely to be a transitionary phase between O stars and hydrogen-free classical Wolf-Rayet stars. The variability of these stars has been an area of study for both professional and amateur astronomers for more than a century. In this paper, we present 5 yr of precision photometry of the classical LBV P Cygni taken with the BRITE-Constellation nanosatellites. We have analyzed these data with Fourier analysis to search for periodicities that could elucidate the drivers of variability for these stars. These data show some long-time-scale variability over the course of all six calendar years of observations, but the frequencies needed to reproduce the individual light curves are not consistent from 1 yr to the next. These results likely show that there is no periodic phenomenon present for P Cygni, meaning that the variability is largely stochastic. We interpret the data as being caused by internal gravity waves similar to those seen in other massive stars, with P Cygni exhibiting a larger amplitude and lower characteristic frequency than the main-sequence or blue supergiant stars previously studied. These results show evidence that LBVs may be an extrapolation of the blue supergiants, which have previously been shown to be an extension of main-sequence stars in the context of the stochastic low-frequency photometric variability.
Conferences, Resources, and Social Media
The BRITE team will be holding their annual face-to-face strategic planning meeting during the TASC6/KASC13 meeting in Leuven in early July.
Resources and Social Media
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 Catherine Lovekin, the chair of BEST.