Astronomie et Astrophysique

Autor: Rachael M. Roettenbacher, Fabien Baron, Norman Vargas, John B. Lester, Judit Sturmann, Arturo O. Martinez, Olli Majoinen, Chris Farrington, Ettore Pedretti, Nicholas J. Scott, Hilding R. Neilson, Claudia Paladini, T. ten Brummelaar, Miguel Montargès, Gail H. Schaefer, Stephen T. Ridgway, Nathalie D. Thureau, Douglas R. Gies, Xiao Che, Ryan P. Norris, Andrea Chiavassa, Matthew D. Anderson, John D. Monnier, Michael S. Connelley, Laszlo Sturmann, László L. Kiss
Přispěvatelé: Joseph Louis LAGRANGE (LAGRANGE), Université Côte d'Azur (UCA)-Université Nice Sophia Antipolis (... - 2019) (UNS), COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Observatoire de la Côte d'Azur, COMUE Université Côte d'Azur (2015-2019) (COMUE UCA)-Université Côte d'Azur (UCA)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National de la Recherche Scientifique (CNRS), Chiavassa, Andrea
Jazyk: angličtina
Rok vydání: 2021
Předmět:
Zdroj: The Astrophysical journal letters
The Astrophysical journal letters, Bristol : IOP Publishing, In press
ISSN: 2041-8205
2041-8213
Popis: We present H-band interferometric observations of the red supergiant (RSG) AZ Cyg made with the Michigan Infra-Red Combiner (MIRC) at the six-telescope Center for High Angular Resolution Astronomy (CHARA) Array. The observations span 5 years (2011-2016), offering insight into the short and long-term evolution of surface features on RSGs. Using a spectrum of AZ Cyg obtained with SpeX on the NASA InfraRed Telescope Facility (IRTF) and synthetic spectra calculated from spherical MARCS, spherical PHOENIX, and SAtlas model atmospheres, we derive $T_{\text{eff}}$ is between $3972 K$ and $4000 K$ and $\log~g$ between $-0.50$ and $0.00$, depending on the stellar model used. Using fits to the squared visibility and Gaia parallaxes we measure its average radius $R=911^{+57}_{-50}~R_{\odot}$. Reconstructions of the stellar surface using our model-independent imaging codes SQUEEZE and OITOOLS.jl show a complex surface with small bright features that appear to vary on a timescale of less than one year and larger features that persist for more than one year. 1D power spectra of these images suggest a characteristic size of $0.52-0.69~R_{\star}$ for the larger, long lived features. This is close to the values of $0.51-0.53~R_{\star}$ derived from 3D RHD models of stellar surfaces. We conclude that interferometric imaging of this star is in line with predictions of 3D RHD models but that short-term imaging is needed to more stringently test predictions of convection in RSGs.
31 pages, 8 tables, 14 figures, accepted to ApJ
Databáze: OpenAIRE
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