Mid-infrared circumstellar emission of the long-period Cepheid l Carinae resolved with VLTI/MATISSE
Creators: name: Hocdé, V.
name: Nardetto, N.
name: Matter, A.
name: Lagadec, E.
name: Mérand, A.
name: Cruzalèbes, P.
name: Meilland, A.
name: Millour, F.
name: Lopez, B.
name: Berio, P.
name: Weigelt, G.
name: Petrov, R.
name: Isbell, J. W.
name: Jaffe, W.
name: Kervella, P.
name: Glindemann, A.
name: Schöller, M.
name: Allouche, F.
name: Gallenne, A.
name: de Souza, A. Domiciano
name: Niccolini, G.
name: Kokoulina, E.
name: Varga, J.
name: Lagarde, S.
name: Augereau, J. -C.
name: van Boekel, R.
name: Bristow, P.
name: Henning, Th.
name: Hofmann, K. -H.
name: Zins, G.
name: Danchi, W. -C.
name: Delbo, M.
name: Dominik, C.
name: Rosas, V. Gámez
name: Klarmann, L.
name: Hron, J.
name: Hogerheijde, M. R.
name: Meisenheimer, K.
name: Pantin, E.
name: Paladini, C.
name: Robbe-Dubois, S.
name: Schertl, D.
name: Stee, P.
name: Waters, R.
name: Lehmitz, M.
name: Bettonvil, F.
name: Heininger, M.
name: Bristow, P.
name: Woillez, J.
name: Wolf, S.
name: Yoffe, G.
name: Szabados, L.
name: Chiavassa, A.
name: Borgniet, S.
name: Breuval, L.
name: Javanmardi, B.
name: Ábrahám, P.
name: Abadie, S.
name: Abuter, R.
name: Accardo, M.
name: Adler, T.
name: Agócs, T.
name: Alonso, J.
name: Antonelli, P.
name: Böhm, A.
name: Bailet, C.
name: Bazin, G.
name: Beckmann, U.
name: Beltran, J.
name: Boland, W.
name: Bourget, P.
name: Brast, R.
name: Bresson, Y.
name: Burtscher, L.
name: Buter, R.
name: Castillo, R.
name: Chelli, A.
name: Cid, C.
name: Clausse, J. -M.
name: Connot, C.
name: Conzelmann, R. D.
name: De Haan, M.
name: Ebert, M.
name: Elswijk, E.
name: Fantei, Y.
name: Frahm, R.
name: Rosas, V. Gámez
name: Gabasch, A.
name: Garces, E.
name: Girard, P.
name: Glazenborg, A.
name: Gonté, F. Y. J.
name: Herrera, J. C. González
name: Graser, U.
name: Guajardo, P.
name: Guitton, F.
name: Hanenburg, H.
name: Haubois, X.
name: Hubin, N.
name: Huerta, R.
name: Idserda, J.
name: Ives, D.
name: Jakob, G.
name: Jaskó, A.
name: Jochum, L.
name: Klein, R.
name: Kragt, J.
name: Kroes, G.
name: Kuindersma, S.
name: Labadie, L.
name: Laun, W.
name: Poole, R. Le
name: Leinert, C.
name: Lizon, J. -L.
name: Lopez, M.
name: Marcotto, A.
name: Mauclert, N.
name: Maurer, T.
name: Mehrgan, L. H.
name: Meisner, J.
name: Meixner, K.
name: Mellein, M.
name: Mohr, L.
name: Morel, S.
name: Mosoni, L.
name: Navarro, R.
name: Neumann, U.
name: Nußbaum, E.
name: Pallanca, L.
name: Pasquini, L.
name: Percheron, I.
name: Duc, T. Phan
name: Pott, J. -U.
name: Pozna, E.
name: Ridinger, A.
name: Rigal, F.
name: Riquelme, M.
name: Rivinius, Th.
name: Roelfsema, R.
name: Rohloff, R. -R.
name: Rousseau, S.
name: Schuhler, N.
name: Schuil, M.
name: Shabun, K.
name: Soulain, A.
name: Stephan, C.
name: ter Horst, R.
name: Tromp, N.
name: Vakili, F.
name: van Duin, A.
name: Venema, L. B.
name: Vinther, J.
name: Wittkowski, M.
name: Wrhel, F.
Publisher: name: arXiv
Year: 2021
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Astrophysics of Galaxies (astro-ph.GA)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: The nature of circumstellar envelopes (CSE) around Cepheids is still a matter of debate. The physical origin of their infrared (IR) excess could be either a shell of ionized gas, or a dust envelope, or both. This study aims at constraining the geometry and the IR excess of the environment of the long-period Cepheid $\ell$ Car (P=35.5 days) at mid-IR wavelengths to understand its physical nature. We first use photometric observations in various bands and Spitzer Space Telescope spectroscopy to constrain the IR excess of $\ell$ Car. Then, we analyze the VLTI/MATISSE measurements at a specific phase of observation, in order to determine the flux contribution, the size and shape of the environment of the star in the L band. We finally test the hypothesis of a shell of ionized gas in order to model the IR excess. We report the first detection in the L band of a centro-symmetric extended emission around l Car, of about 1.7$R_\star$ in FWHM, producing an excess of about 7.0\% in this band. In the N band, there is no clear evidence for dust emission from VLTI/MATISSE correlated flux and Spitzer data. On the other side, the modeled shell of ionized gas implies a more compact CSE ($1.13\pm0.02\,R_\star$) and fainter (IR excess of 1\% in the L band). We provide new evidences for a compact CSE of $\ell$ Car and we demonstrate the capabilities of VLTI/MATISSE for determining common properties of CSEs. While the compact CSE of $\ell$ Car is probably of gaseous nature, the tested model of a shell of ionized gas is not able to simultaneously reproduce the IR excess and the interferometric observations. Further Galactic Cepheids observations with VLTI/MATISSE are necessary for determining the properties of CSEs, which may also depend on both the pulsation period and the evolutionary state of the stars.
description: 13 pages, 8 figures, accepted in Astronomy and Astrophysics