Standing on the Shoulders of Giants: New Mass and Distance Estimates for Betelgeuse through Combined Evolutionary, Asteroseismic, and Hydrodynamic Simulations with MESA

Abstract

We conduct a rigorous examination of the nearby red supergiant Betelgeuse by drawing on the synthesis of new observational data and three different modeling techniques. Our observational results include the release of new, processed photometric measurements collected with the space-based Solar Mass Ejection Imager instrument prior to Betelgeuse's recent, unprecedented dimming event. We detect the first radial overtone in the photometric data and report a period of 185±13.5 days. Our theoretical predictions include self-consistent results from multitimescale evolutionary, oscillatory, and hydrodynamic simulations conducted with the Modules for Experiments in Stellar Astrophysics software suite. Significant outcomes of our modeling efforts include a precise prediction for the star's radius:-+ R 764 62 116 . In concert with additional constraints, this allows us to derive a new, independent distance estimate of-+ 168 15 27 pc and a parallax of p =-+ 5.95 0.85 0.58 mas, in good agreement with Hipparcos but less so with recent radio measurements. Seismic results from both perturbed hydrostatic and evolving hydrodynamic simulations constrain the period and driving mechanisms of Betelgeuse's dominant periodicities in new ways. Our analyses converge to the conclusion that Betelgeuse's ≈400 day period is the result of pulsation in the fundamental mode, driven by the κ-mechanism. Grid-based hydrodynamic modeling reveals that the behavior of the oscillating envelope is mass-dependent, and likewise suggests that the nonlinear pulsation excitation time could serve as a mass constraint. Our results place α Orionis definitively in the early core helium-burning phase of the red supergiant branch. We report a present-day mass of 16.5-19 M e-slightly lower than typical literature values.

Atmosphere of Betelgeuse before and during the Great Dimming event revealed by tomography

“…Interferometric observations of Betelgeuse by Haubois et al (2009), Chiavassa et al (2010), Ohnaka et al (2011), and Montargès et al (2016) have shown evidence for the presence of large convective cells in its atmosphere, which is in accordance with predictions by Schwarzschild (1975). The photometric periodicity of Betelgeuse is characterized by two main periods: a short one of about 400 days and a long one of about 2000 days (Kiss et al 2006;Joyce et al 2020). Mechanisms such as atmospheric pulsations in the fundamental or low-overtone modes and oscillations excited by convection cells were invoked to explain the short photometric period (Kiss et al 2006;Joyce et al 2020).…”

“…The photometric periodicity of Betelgeuse is characterized by two main periods: a short one of about 400 days and a long one of about 2000 days (Kiss et al 2006;Joyce et al 2020). Mechanisms such as atmospheric pulsations in the fundamental or low-overtone modes and oscillations excited by convection cells were invoked to explain the short photometric period (Kiss et al 2006;Joyce et al 2020). The long photometric variations were proposed to be due to binarity or magnetic activity (Wood et al 2004), or turnover of giant convection cells (Stothers 2010).…”

A dusty veil shading Betelgeuse during its Great Dimming

“…Measurements 40 obtained in June-July 2020 showed that Betelgeuse experienced another dimming not corresponding to the 400 days period, but it has recovered since 41 . These successive dimmings fall within the irregular pattern of light curve variability of the star, and can be attributed to pulsation/convective activity 6 . Our results confirm that the Great Dimming is not an indication of Betelgeuse's imminent explosion as a supernova 6,24 (SN).…”

“…These successive dimmings fall within the irregular pattern of light curve variability of the star, and can be attributed to pulsation/convective activity 6 . Our results confirm that the Great Dimming is not an indication of Betelgeuse's imminent explosion as a supernova 6,24 (SN). Interpretation of the early behavior of core-collapse SNe light curves and post collapse spectral line variation point to enhanced pre-SN mass loss in the final weeks to centuries of the stars' life 42 , in at least part of the progenitor population.…”

Az optikai interferometria 100 éve a csillagászatban • 100 Years of Optical Interferometry in Astronomy

“…Az akkori mérések szerint úgy gondolták, a Betelgeuze távolsága 181 fényév, ebből pedig kiszámítható, hogy a csillag átmérője 2,6 CSE (a csillagászati egység a Nap és a Föld közötti átlagos távolság, 150 millió km). Többek között magyar hozzájárulásnak (Molnár László) is köszönhetően ma már tudjuk, hogy a csillag háromszor messzebb van, mint Michelsonék hitték (Joyce et al, 2020). A látszó méretére kapott érték viszont ma is pontosnak számít, az új távolságértékkel tehát a csillag átmérője mintegy 7 CSE.…”