arXiv subjects

M. Wavasseur

Publications and source records attributed to M. Wavasseur.

3 recordsLinked to original sources

arXiv2026

Comparative Study of Two Luminous Red Novae I. Progenitor Modeling and Dust Formation

Luminous red novae are astrophysical transients associated with unstable mass transfer in interacting binaries and are commonly interpreted as outcomes of common-envelope evolution, possibly ending in merger. These interactions can liberate large amounts of gas, part of which may later condense into dust. We study the luminous red novae AT2021biy and AT2021blu to constrain their binary progenitors, estimate the mass ejected during the outbursts, and infer the dust mass from the infrared evolution of their remnants. We computed two grids of binary stellar-evolution tracks with the MESA binary module, constrained by pre-outburst photometry. We applied mass-transfer instability criteria to select progenitors able to merge on timescales compatible with archival observations. From these models, we estimated the gas mass lost during the mass-transfer phase and lower and upper bounds on the envelope mass that could be ejected during common-envelope evolution using the available orbital energy. We compared these ejecta-mass estimates with values inferred from light-curve models. Finally, we modeled mid-infrared NEOWISE data to derive dust masses up to ~3 years post-outburst, providing an additional lower limit on the total ejecta mass. We constrained the donor masses to Md = 18-23 Msun for AT2021biy and Md = 14 +/- 0.5 Msun for AT2021blu. Lower limits on the ejected envelope mass are 0.03-2.98 Msun for AT2021biy and 0.02-0.1 Msun for AT2021blu. Comparison with light-curve models favors intermediate mass ratios, q = 3-10 for AT2021biy and q = 5-15 for AT2021blu. The inferred dust masses are 1-5 orders of magnitude below the estimated ejected envelope masses, implying that only a small fraction of the gas condenses into dust. Their evolution is consistent with shock interaction and suggests pre-existing circumstellar material, in line with the pre-outburst mass loss predicted by our MESA models.

astro-ph.SR↗

arXiv2023

The height of convective plumes in the red supergiant $μ$ Cep

Aims. We seek to understand convection in red supergiants and the mechanisms that trigger the mass loss from cool evolved stars. Methods. Linear spectropolarimetry of the atomic lines of the spectrum of $μ$ Cep reveals information well outside the wavelength range expected from previous models. This is interpreted as structures in expansion that are visible in the front hemisphere and sometimes also in the back hemisphere. We model the plasma distribution together with its associated velocities through an inversion algorithm to fit the observed linear polarization. Results. We find that supposing the existence of plasma beyond the limb rising high enough to be visible above it can explain the observed linear polarization signatures as well as their evolution in time. From this we are able to infer the geometric heights of the convective plumes and establish that this hot plasma rises to at least 1.1 R*. Conclusions. $μ$ Cep appears to be in an active phase in which plasma rises often above 1.1 R* . We generalize this result to all red supergiants in a similarly evolved stage, which at certain epochs may easily send plasma to greater heights, as $μ$ Cep appears to be doing at present. Plasma rising to such heights can easily escape the stellar gravity.

astro-ph.SR↗

arXiv2022

Three-dimensional imaging of convective cells in the photosphere of Betelgeuse

Understanding convection in red supergiants and the mechanisms that trigger the mass loss from these evolved stars are the general goals of most observations of Betelgeuse and its inner circumstellar environment. Linear spectropolarimetry of the atomic lines of the spectrum of Betelgeuse reveals information about the three-dimensional (3D) distribution of brightness in its atmosphere. We model the distribution of plasma and its velocities and use inversion algorithms to fit the observed linear polarization. We obtain the first 3D images of the photosphere of Betelgeuse. Within the limits of the used approximations, we recover vertical convective flows and measure the velocity of the rising plasma at different heights in the photosphere. In several cases, we find this velocity to be constant with height, indicating the presence of forces other than gravity acting on the plasma and counteracting it. In some cases, these forces are sufficient to maintain plasma rising at 60\,\kms to heights where this velocity is comparable to the escape velocity. Forces are present in the photosphere of Betelgeuse that allow plasma to reach velocities close to the escape velocity. These mechanisms may suffice to trigger mass loss and sustain the observed large stellar winds of these evolved stars.

astro-ph.SR↗