Circumstellar emission of Cepheids across the instability strip: Mid-infrared observations with VLTI/MATISSE
| Autor: | Hocdé, V., Matter, A., Nardetto, N., Gallenne, A., Kervella, P., Mérand, A., Pietrzyński, G., Gieren, W., Leftley, J., Robbe-Dubois, S., Lopez, B., Bailleul, M. C., Bras, G., Smolec, R., Wielgórski, P., Hajdu, G., Afanasiev, A. |
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| Rok vydání: | 2024 |
| Předmět: | |
| Druh dokumentu: | Working Paper |
| Popis: | The circumstellar envelopes (CSE) of Cepheids are still not well characterized despite their potential impact on distance determination via both the period-luminosity relation and the parallax-of-pulsation method. This paper aims to investigate Galactic Cepheids across the instability strip in the mid-infrared with MATISSE/VLTI in order to constrain the geometry and physical nature (gas and/or dust) of their CSEs. We secured observations of eight Galactic Cepheids from short up to long period of pulsation, with MATISSE/VLTI in $L$, $M$ and $N$-bands. The SED analysis in the mid-IR confirms the absence of dust spectral signature for all the star sample. For each star in $L$, $M$ and $N$-band we observe closure phases which are consistent with centro-symmetric geometry for the different targets. Finally, the visibilities in $L$, $M$ and $N$ bands are in agreement with the expected star angular diameter, although the observations are compatible with the presence of compact CSEs within the uncertainties. We provide 2$\,\sigma$ upper limits on the CSE flux contribution based on model residuals for several CSE radius, which yield to exclude models simultaneously large and bright ($R_\mathrm{CSE}\approx10\,R_\star$ and $f_\mathrm{CSE}\approx10\%$) for all the stars of the sample. Last, the visibilities in the $N$-band rule out CSE models with significant amount of different type of dust. The MATISSE observations of eight Cepheids with different pulsation period (from 7 up to 38$\,$day) and evolution stage, provide for the first time a comprehensive picture of Cepheids from mid-IR interferometry. We present additional evidences that circumstellar dust emission is negligible or absent around Cepheids for a wide range of stellar parameters in the instability strip. Further interferometric observations in the visible and the near-infrared will be necessary to disentangle the star and the CSE. Comment: 22 pages, 17 figures, accepted in Astronomy and Astrophysics |
| Databáze: | arXiv |
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