TESS light curves of γ Cas stars

Nazé, Yaël; Rauw, Grégor; Pigulski, A.

doi:10.1093/mnras/staa2553

Cited by 22 publications

(32 citation statements)

References 49 publications

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“…The shorter period is reminiscent of the photometric periodicity reported by Labadie-Bartz et al ( 2017) and Nazé et al (2020c). In the latter reference, those photometric changes were interpreted as signatures from eclipses in a system unrelated to the Be star.…”

Section: Discovery Of a Double Periodicitysupporting

confidence: 58%

“…the component contributes 10-15% of the total light of V782 Cas. This rules out the possibility considered by Nazé et al (2020c) that the short-period binary might correspond to one of the neighbouring sources resolved by GAIA, as these objects would contribute much less than ∼40% to the combined light.…”

Section: V782 Cas B the Short-period Binarymentioning

confidence: 89%

“…For V782 Cas, additional photometric data have been obtained by TESS since those presented in Nazé et al (2020c) hence we reextracted the whole dataset. The 30 min lightcurves of both sectors (18 and 25) were derived through aperture photometry using the Python package Lightkurve 1 .…”

Section: Tessmentioning

confidence: 99%

“…Since the TESS lightcurve of V782 Cas indicates an eclipsing binary in an overcontact configuration (see Nazé et al 2020c, and below), the stars in the short-period binary must be in co-rotation. We can then use the formula of Eggleton (1983) to express the radius of Figure 9.…”

Section: V782 Cas B the Short-period Binarymentioning

confidence: 99%

“…Therefore, the secondary component of the short-period binary likely has a mass of 6 +1.5 −1.2 M ⊙ , which would correspond to an B5 star with an uncertainty of one or two spectral substypes. We also revisited the analysis of the photometric lightcurve presented by Nazé et al (2020c), taking advantage of the better knowledge of the short-period binary. Adopting the improved ephemerides of the short-period binary (Table 2) 4 , we built an updated lightcurve consisting of 100 normal points computed as the mean magnitude per 0.01 phase bin.…”

Section: V782 Cas B the Short-period Binarymentioning

confidence: 99%

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Velocity monitoring of γ Cas stars reveals their binarity status

Nazé

Rauw

Czesla

et al. 2022

Monthly Notices of the Royal Astronomical Society

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The binary status of γ Cas stars has been discussed while theoretically examining the origin of their peculiar X-ray emission. However, except in two cases, no systematic radial velocity monitoring of these stars had been undertaken yet to clarify their status. We now fill this gap using TIGRE, CARMENES, and UVES high-resolution spectroscopy. Velocities were determined for 16 stars, revealing shifts and/or changes in line profiles. The orbit of six new binaries could be determined: the long periods (80–120 d) and small velocity amplitudes (5–7 km s−1) suggest low mass companions (0.6–1 M⊙). The properties of the known γ Cas binaries appear similar to those of other Be systems, with no clear-cut separation between them. One of the new systems is a candidate for a rare case of quadruple system involving a Be star. Five additional γ Cas stars display velocity variations compatible with the presence of companions, but no orbital solution could yet be formally established for them hence they only receive the status of “binary candidate”.

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Section: Discovery Of a Double Periodicitysupporting

confidence: 58%

Section: V782 Cas B the Short-period Binarymentioning

confidence: 89%

Section: Tessmentioning

confidence: 99%

Section: V782 Cas B the Short-period Binarymentioning

confidence: 99%

Section: V782 Cas B the Short-period Binarymentioning

confidence: 99%

See 3 more Smart Citations

Velocity monitoring of γ Cas stars reveals their binarity status

Nazé

Rauw

Czesla

et al. 2022

Monthly Notices of the Royal Astronomical Society

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Making waves in massive star asteroseismology

Bowman

2023

Astrophys Space Sci

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Massive stars play a major role not only in stellar evolution but also galactic evolution theory. This is because of their dynamical interaction with binary companions, but also because their strong winds and explosive deaths as supernovae provide chemical, radiative and kinematic feedback to their environments. Yet this feedback strongly depends on the physics of the supernova progenitor star. It is only in recent decades that asteroseismology – the study of stellar pulsations – has developed the necessary tools to a high level of sophistication to become a prime method at the forefront of astronomical research for constraining the physical processes at work within stellar interiors. For example, precise and accurate asteroseismic constraints on interior rotation, magnetic field strength and geometry, mixing and angular momentum transport processes of massive stars are becoming increasingly available across a wide range of masses. Moreover, ongoing large-scale time-series photometric surveys with space telescopes have revealed a large diversity in the variability of massive stars, including widespread coherent pulsations across a large range in mass and age, and the discovery of ubiquitous stochastic low-frequency (SLF) variability in their light curves. In this invited review, I discuss the progress made in understanding the physical processes at work within massive star interiors thanks to modern asteroseismic techniques, and conclude with a future outlook.

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The historical active episodes of the disks around γ Cassiopeiae (B0.5 IVe) and 59 Cygni (B1 IVe) revisited

Baade,

Labadie-Bartz,

Rivinius

et al. 2023

A&A

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The observations of all known major activity phases of the disks around the classical Be stars γ Cas and 59 Cyg with low-mass companions are comprehensively reviewed and purely qualitatively evaluated again, though taking advantage of new insights gained over the past 25 yr into the physics of Be disks. Both stars have exhibited activity cycles in the violet-to-red (V/R) flux ratio of emission lines with two peaks. This activity is indistinguishable from those of the vast majority of Be stars and so probably were caused by one-armed (m = 1) disk oscillations. The anomalous high-activity phases from 1932 to 1942 in γ Cas and between 1972 and 1976 in 59 Cyg were distinguished from m = 1 density waves by large variations in the separations of pairs of emission peaks. In two consecutive cycles, shell phases during which the emission peaks were maximally separated alternated with single (blended) emission peaks. The amplitude in peak separation of more than a factor of two implies a high-amplitude variation in the disk aspect angle. When the peaks were blended and the disk was viewed closest to face-on, local maxima in visual brightness probably occurred in γ Cas, and the visibility of the stellar absorption lines was reduced, as is expected from increased free-bound emission into the line of sight (there is no time-resolved photometry for 59 Cyg from the event in the 1970s). In y Cas, the pre-event V/R variability (pre-event observations of 59 Cyg do not exist) was practically identical to m = 1 variability. In spite of the subsequent rapid rise in amplitude (up to ~4), the V/R variations connected smoothly in phase but may require an explanation involving the 3D structure of the disk. The phasing of single-peak and shell stages relative to the V/R activity was the same in both cycles of γ Cas, whereas this is not clear for 59 Cyg. During both high-activity cycles of γ Cas, but at different phases, transient additional pairs of emission lines appeared in γ Cas that were much sharper than the main ones and they also had different peak separations and V/R ratios. In the second instance, their velocities were up to ~+500 km s−1. The extremely rapid excitation of the activity phases and their short duration of only two cycles in both stars may indicate a resonant behavior of an unidentified nature. In both stars, the line emission was strongly developed at the onset of the high-activity phases but it basically disappeared at the end of them, and the disks may have been dynamically destroyed. The atypical disk variations were presumably triggered by enhanced interactions between a disk and companion star. In both systems, there seems to be less evidence for a mass-loss outburst than for a reduced mass-injection rate into the disk. The resulting lower viscous coupling between a disk and star would have facilitated the tilting of the disk.

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TESS light curves of γ Cas stars

Cited by 22 publications

References 49 publications

Velocity monitoring of γ Cas stars reveals their binarity status

Velocity monitoring of γ Cas stars reveals their binarity status

Making waves in massive star asteroseismology

The historical active episodes of the disks around γ Cassiopeiae (B0.5 IVe) and 59 Cygni (B1 IVe) revisited

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