1. Mid-infrared circumstellar emission of the long-period Cepheid l Carinae resolved with VLTI/MATISSE
- Author
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Hocdé, V., Nardetto, N., Matter, A., Lagadec, E., Mérand, A., Cruzalèbes, P., Meilland, A., Millour, F., Lopez, B., Berio, P., Weigelt, G., Petrov, R., Isbell, J. W., Jaffe, W., Kervella, P., Glindemann, A., Schöller, M., Allouche, F., Gallenne, A., de Souza, A. Domiciano, Niccolini, G., Kokoulina, E., Varga, J., Lagarde, S., Augereau, J. -C., van Boekel, R., Bristow, P., Henning, Th., Hofmann, K. -H., Zins, G., Danchi, W. -C., Delbo, M., Dominik, C., Rosas, V. Gámez, Klarmann, L., Hron, J., Hogerheijde, M. R., Meisenheimer, K., Pantin, E., Paladini, C., Robbe-Dubois, S., Schertl, D., Stee, P., Waters, R., Lehmitz, M., Bettonvil, F., Heininger, M., Woillez, J., Wolf, S., Yoffe, G., Szabados, L., Chiavassa, A., Borgniet, S., Breuval, L., Javanmardi, B., Ábrahám, P., Abadie, S., Abuter, R., Accardo, M., Adler, T., Agócs, T., Alonso, J., Antonelli, P., Böhm, A., Bailet, C., Bazin, G., Beckmann, U., Beltran, J., Boland, W., Bourget, P., Brast, R., Bresson, Y., Burtscher, L., Buter, R., Castillo, R., Chelli, A., Cid, C., Clausse, J. -M., Connot, C., Conzelmann, R. D., De Haan, M., Ebert, M., Elswijk, E., Fantei, Y., Frahm, R., Gabasch, A., Garces, E., Girard, P., Glazenborg, A., Gonté, F. Y. J., Herrera, J. C. González, Graser, U., Guajardo, P., Guitton, F., Hanenburg, H., Haubois, X., Hubin, N., Huerta, R., Idserda, J., Ives, D., Jakob, G., Jaskó, A., Jochum, L., Klein, R., Kragt, J., Kroes, G., Kuindersma, S., Labadie, L., Laun, W., Poole, R. Le, Leinert, C., Lizon, J. -L., Lopez, M., Marcotto, A., Mauclert, N., Maurer, T., Mehrgan, L. H., Meisner, J., Meixner, K., Mellein, M., Mohr, L., Morel, S., Mosoni, L., Navarro, R., Neumann, U., Nußbaum, E., Pallanca, L., Pasquini, L., Percheron, I., Duc, T. Phan, Pott, J. -U., Pozna, E., Ridinger, A., Rigal, F., Riquelme, M., Rivinius, Th., Roelfsema, R., Rohloff, R. -R., Rousseau, S., Schuhler, N., Schuil, M., Shabun, K., Soulain, A., Stephan, C., ter Horst, R., Tromp, N., Vakili, F., van Duin, A., Venema, L. B., Vinther, J., Wittkowski, M., and Wrhel, F.
- Subjects
Astrophysics - Solar and Stellar Astrophysics ,Astrophysics - Astrophysics of Galaxies - Abstract
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., Comment: 13 pages, 8 figures, accepted in Astronomy and Astrophysics
- Published
- 2021
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