(Sub)stellar companions shape the winds of evolved stars

Decin, L.; Montargès, M.; Richards, A. M. S.; Gottlieb, C. A.; Homan, W.; McDonald, Iain; Mellah, I. El; Danilovich, T.; Wallström, Sofia; Zijlstra, A. A.; Baudry, A.; Bolte, John; Cannon, Emily; Beck, E. De; Ceuster, Frederik De; Koter, A. de; Ridder, J. De; Etoka, S.; Gobrecht, David; Gray, M. D.; Herpin, Fabrice; Jeste, Manali; Lagadec, E.; Kervella, P.; Khouri, T.; Menten, K. M.; Millar, T. J.; Müller, H. S. P.; Plane, J. M. C.; Sahai, Raghvendra; Sana, H.; Sande, M. Van de; Waters, L. B. F. M.; Wong, K. T.; Yates, J.

doi:10.1126/science.abb1229

Cited by 86 publications

(61 citation statements)

References 160 publications

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“…Information on the terminal outflow velocity of the gas can be obtained from the analysis of CO thermal radio emission and/or by maser emission. The velocity profile of our model with dust is consistent with the observations, which show a spread between 10 and 20 km/s (see, e.g., [39][40][41]). The values obtained are also consistent with the typical expansion velocity derived for stars in our Galaxy [42][43][44] and in the Large Magellanic Cloud [45,46].…”

Section: Resultssupporting

confidence: 88%

AGB Stars and Their Circumstellar Envelopes. I. the VULCAN Code

et al. 2021

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The interplay between AGB interiors and their outermost layers, where molecules and dust form, is a problem of high complexity. As a consequence, physical processes like mass loss, which depend on the chemistry of the circumstellar envelope, are often oversimplified. The best candidates to drive mass-loss in AGB stars are dust grains, which trap the outgoing radiation and drag the surrounding gas. Grains build up, however, is far from being completely understood. Our aim is to model both the physics and the chemistry of the cool expanding layers around AGB stars in order to characterize the on-going chemistry, from atoms to dust grains. This has been our rationale to develop ab initio VULCAN, a FORTRAN hydro code able to follow the propagation of shocks in the circumstellar envelopes of AGB stars. The version presented in this paper adopts a perfect gas law and a very simplified treatment of the radiative transfer effects and dust nucleation. In this paper, we present preliminary results obtained with our code.

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Section: Resultssupporting

confidence: 88%

AGB Stars and Their Circumstellar Envelopes. I. the VULCAN Code

et al. 2021

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“…Then, we fine-tuned the LSPs of our sample using the TATRY code, which implements the multiharmonic analysis of variance algorithm (Schwarzenberg-Czerny 1996). The classification of the LMC and SMC variables was additionally verified by the inspection of the near-infrared (NIR) period-luminosity diagrams for both galaxies, namely the P log -W JK diagram (Figure 2), where W JK = K s − 0.686(J − K s ) is the extinction-free Wesenheit index, while J-and K s -band magnitudes were taken from the IRSF Magellanic Clouds Point Source Catalog (Kato et al 2007) or (if not available) from the 2MASS All-Sky Catalog of Point Sources (Cutri et al 2003). Objects located outside sequence D (Wood et al 1999) in the period-luminosity diagram were removed from our list of LSP stars.…”

Section: Sample Selectionmentioning

confidence: 99%

“…Each epoch consists of 10-24 single-exposure observations obtained within one to a few days. We converted these individual measurements into fluxes, averaged (with outlier rejection) within each epoch, and converted back to the Cutri et al 2003). The period-luminosity sequences are labeled with letters according to the Wood et al (1999) nomenclature.…”

Section: Mid-ir Photometrymentioning

confidence: 99%

“…Period-Wesenheit index diagrams for long-period variables in the LMC (left panel) and SMC (right panel). The NIR Wesenheit index is an extinction-free quantity defined as W JK = K s − 0.686(J − K s ), where J-and K s -band magnitudes originate from the IRSF Catalog(Kato et al 2007) or from the 2MASS Catalog(Cutri et al 2003). The period-luminosity sequences are labeled with letters according to theWood et al (1999) nomenclature.…”

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Binarity as the Origin of Long Secondary Periods in Red Giant Stars

Soszyński

Olechowska

Ratajczak

et al. 2021

ApJL

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Long secondary periods (LSPs), observed in a third of pulsating red giant stars, are the only unexplained type of large-amplitude stellar variability known at this time. Here we show that this phenomenon is a manifestation of a substellar or stellar companion orbiting the red giant star. Our investigation is based on a sample of about 16,000 well-defined LSP variables detected in the long-term OGLE photometric database of the Milky Way and Magellanic Clouds, combined with the mid-infrared data extracted from the NEOWISE-R archive. From this collection, we selected about 700 objects with stable, large-amplitude, well-sampled infrared light curves and found that about half of them exhibit secondary eclipses, thus presenting an important piece of evidence that the physical mechanism responsible for LSPs is binarity. Namely, the LSP light changes are due to the presence of a dusty cloud orbiting the red giant together with the companion and obscuring the star once per orbit. The secondary eclipses, visible only in the infrared wavelength, occur when the cloud is hidden behind the giant. In this scenario, the low-mass companion is a former planet that has accreted a significant amount of mass from the envelope of its host star and grown into a brown dwarf.Unified Astronomy Thesaurus concepts: Asymptotic giant branch stars (2100); Long period variable stars (935); Close binary stars (254); Circumstellar dust (236); Brown dwarfs (185)

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“…The physical effects of companion objects may also be imprinted on the density structure of the CSE gas. Thus the beautiful spiral patterns detected in IRC+10216 58 and R Sculptoris 59 , LL Peg 60 and the equatorial density enhancement in L 2 Pup 61,62 , as well as the complex density structures seen in all O-rich AGB stars studied at high spatial resolution in the ALMA Large Programme ATOMIUM 63 , can all be interpreted in terms of an orbiting stellar or planetary companion that perturbs the radial outflow from the AGB star. Recently, Homan et al 64 used ALMA to study the CO and SiO emission in the CSE of the O-rich AGB star EP Aqr at high angular resolution.…”

Section: Internal (Companion) Uv Photonsmentioning

confidence: 97%

The role of ultraviolet photons in circumstellar astrochemistry

Millar

2020

Chinese Journal of Chemical Physics

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Stars with masses between 1 and 8 solar masses (M ) lose large amounts of material in the form of gas and dust in the late stages of stellar evolution, during their Asymptotic Giant Branch phase. Such stars supply up to 35% of the dust in the interstellar medium and thus contribute to the material out of which our solar system formed.In addition, the circumstellar envelopes of these stars are sites of complex, organic chemistry with over 80 molecules detected in them. We show that internal ultraviolet photons, either emitted by the star itself or from a close-in, orbiting companion, can significantly alter the chemistry that occurs in the envelopes particularly if the envelope is clumpy in nature. At least for the cases explored here, we find that the presence of a stellar companion, such as a white dwarf star, the high flux of UV photons destroys H 2 O in the inner regions of carbon-rich AGB stars to levels below those observed and produces species such as C + deep in the envelope in contrast to the expectations of traditional descriptions of circumstellar chemistry.

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(Sub)stellar companions shape the winds of evolved stars

Cited by 86 publications

References 160 publications

AGB Stars and Their Circumstellar Envelopes. I. the VULCAN Code

AGB Stars and Their Circumstellar Envelopes. I. the VULCAN Code

Binarity as the Origin of Long Secondary Periods in Red Giant Stars

The role of ultraviolet photons in circumstellar astrochemistry

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