BRITEning up the Be Phenomenon

Baade, D.; Rivinius, Th.; Pigulski, A.; Panoglou, D.; Carciofi, A.; Handler, G.; Kuschnig, R.; Martayan, Ch.; Mehner, A.; Moffat, A. F. J.; Pablo, H.; Popowicz, A.; Rucinski, S. M.; Wade, G. A.; Weiss, W. W.; Zwintz, K.

doi:10.48550/arxiv.1708.08413

Cited by 2 publications

(13 citation statements)

References 16 publications

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“…This was confirmed by Pápics et al (2017) in the same data. In the early-type Be star 25 Ori, Baade et al (2017b, an extended version of this work with additional BRITE and revised SMEI observations is in preparation) tentatively identified an extremely rich pattern of grouped combination frequencies.…”

Section: Introductionmentioning

confidence: 83%

“…During the monitoring period with Kepler, also KIC 11971405 underwent some small outbursts. As Baade et al (2017b) showed, the spacing in time of some of these events can be related to difference frequencies of some NRP modes with the highest amplitudes. Such coupling had previously been found in BRITE, Kepler, and CoRoT observations of several early-type Be stars (Baade et al 2016;Rivinius et al 2016;Baade et al 2017b, Rivinius et al, in prep.).…”

Section: Introductionmentioning

confidence: 94%

“…While BRITE can be effective at detecting photometric signatures of outbursts (Baade et al 2017b(Baade et al , 2018, the extensive clipping applied to the SMEI observations of ν Pup may well have led to the removal also of genuinely stellar events 5 mmag. For the BRITE data of ν Pup, the detection threshold is lower but not by much because, for the stitching together of the numerous short data strings, it was assumed that between consecutive datasets there were no jumps intrinsic to the star.…”

Section: Mass Lossmentioning

confidence: 99%

“…Evidence is broadly increasing (Rivinius et al 1998;Baade et al 2017b) that multi-mode nonradial pulsation (NRP) plays a central role in the conditioning of the stellar atmosphere for outbursts. Which specific conditions do lead to an outburst is entirely unknown except that temporarily much increased NRP amplitudes can have triggering power.…”

Section: Introductionmentioning

confidence: 99%

“…Interacting NRP modes may operate the valves of the angular-momentum-loss process. Baade et al (2017b) have presented a scheme of nested clocks with hierarchically decreasing frequencies, which all derive from stellar pulsation frequencies and govern the opening and closing of the angular-momentum-loss valves. More massive stars may have to open these valves more often and/or more widely because they evolve more rapidly.…”

Section: Introductionmentioning

confidence: 99%

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Short-term variability and mass loss in Be stars IV. Two groups of closely spaced, approximately equidistant frequencies in three decades of space photometry of $ν$ Puppis (B7-8 IIIe)

Baade,

Pigulski,

Rivinius

et al. 2018

Preprint

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Context. In early-type Be stars, groups of nonradial pulsation (NRP) modes with numerically related frequencies may be instrumental for the release of excess angular momentum through mass-ejection events. Difference and sum/harmonic frequencies often form additional groups.Aims. The purpose is to find out whether a similar frequency pattern occurs in the cooler third-magnitude B7-8 IIIe shell star ν Pup. Methods. Time-series analyses are performed of space photometry with BRITE-Constellation (2015, 2016/17, and 2017/18), SMEI (2003-2011), and Hipparcos (1989-1993. Two IUE SWP and 27 optical echelle spectra spanning 20 years were retrieved from various archives. Results. The optical spectra exhibit no anomalies or well-defined variabilities. A magnetic field was not detected. All three photometry satellites recorded variability near 0.656 c/d which is resolved into three features separated by ∼0.0021 c/d. First harmonics form a second frequency group, also spaced by ∼0.0021 c/d. The frequency spacing is very nearly but not exactly equidistant. Variability near 0.0021 c/d was not detected. The long-term frequency stability could be used to derive meaningful constraints on the properties of a putative companion star. The IUE spectra do not reveal the presence of a hot subluminous secondary. Conclusions. ν Pup is another Be star exhibiting an NRP variability pattern with long-term constancy and underlining the importance of combination frequencies and frequency groups. The star is a good target for efforts to identify an effectively single Be star.

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Section: Introductionmentioning

confidence: 83%

Section: Introductionmentioning

confidence: 94%

Section: Mass Lossmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Short-term variability and mass loss in Be stars IV. Two groups of closely spaced, approximately equidistant frequencies in three decades of space photometry of $ν$ Puppis (B7-8 IIIe)

Baade,

Pigulski,

Rivinius

et al. 2018

Preprint

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Short-term variability and mass loss in Be stars VI. Frequency groups in $γ$ Cas detected by TESS

Labadie-Bartz,

Baade,

Carciofi

et al. 2020

Preprint

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In photometry of 𝛾 Cas (B0.5 IVe) from the SMEI and BRITE-Constellation satellites, indications of low-order non-radial pulsation have recently been found, which would establish an important commonality with the class of classical Be stars at large. New photometry with the TESS satellite has detected three frequency groups near 1.0 (𝑔1), 2.4 (𝑔2), and 5.1 (𝑔3) d −1 , respectively. Some individual frequencies are nearly harmonics or combination frequencies but not exactly so. Frequency groups are known from roughly three quarters of all classical Be stars and also from pulsations of 𝛽 Cep, SPB, and 𝛾 Dor stars and, therefore, firmly establish 𝛾 Cas as a non-radial pulsator. The total power in each frequency group is variable. An isolated feature exists at 7.57 d −1 and, together with the strongest peaks in the second and third groups ordered by increasing frequency (𝑔2 and 𝑔3), is the only one detected in all three TESS sectors. The former long-term 0.82 d −1 variability would fall into 𝑔1 and has not returned at a significant level, questioning its attribution to rotational modulation. Low-frequency stochastic variability is a dominant feature of the TESS light curve, possibly caused by internal gravity waves excited at the core-envelope interface. These are known to be efficient at transporting angular momentum outward, and may also drive the oscillations that constitute 𝑔1 and 𝑔2. The hard X-ray flux of 𝛾 Cas is the only remaining major property that distinguishes this star from the class of classical Be stars.

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BRITEning up the Be Phenomenon

Cited by 2 publications

References 16 publications

Short-term variability and mass loss in Be stars IV. Two groups of closely spaced, approximately equidistant frequencies in three decades of space photometry of $ν$ Puppis (B7-8 IIIe)

Short-term variability and mass loss in Be stars IV. Two groups of closely spaced, approximately equidistant frequencies in three decades of space photometry of $ν$ Puppis (B7-8 IIIe)

Short-term variability and mass loss in Be stars VI. Frequency groups in $γ$ Cas detected by TESS

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