A snapshot of the inner dusty regions of a R CrB-type variable
Context. R Coronae Borealis (R CrB) variable stars are suspected to sporadically eject optically thick dust clouds causing, when one of them lies on the line-of-sight, a huge brightness decline in visible light. Direct detections with 8-m class adaptive optics of such clouds located at about 0.2–0.3...
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ri-123456789-289872020-06-03T17:39:23Z A snapshot of the inner dusty regions of a R CrB-type variable Leão, Izan de Castro Laverny, P. de Chesneau, O. Mékarnia, D. Medeiros, José Renan de Stars: AGB and post-AGB Stars: variables: general Stars: individual: RY Sagittarii Stars: mass-loss Stars: circumstellar matter Stars: techniques: interferometric Context. R Coronae Borealis (R CrB) variable stars are suspected to sporadically eject optically thick dust clouds causing, when one of them lies on the line-of-sight, a huge brightness decline in visible light. Direct detections with 8-m class adaptive optics of such clouds located at about 0.2–0.3 arcsec from the center (∼1000 stellar radii) were recently reported for RY Sgr, the brightest R CrB of the southern hemisphere. Aims. Mid-infrared interferometric observations of RY Sgr allowed us to explore the circumstellar regions much closer to the central star (∼20–40 mas) to look for the signature of any heterogeneities and to characterize them. Methods. Using the VLTI/MIDI instrument, five dispersed visibility curves in the N-band were recorded in May and June 2005 with different projected baselines oriented towards two roughly perpendicular directions. The large spatial frequencies’ visibility curves exhibit a sinusoidal shape, whereas, at shorter spatial frequencies’ visibility curves follow a Gaussian decrease. These observations are well interpreted with a geometrical model consisting of a central star surrounded by an extended circumstellar envelope in which one bright cloud is embedded. Results. Within this simple geometrical scheme, the inner 110 AU dusty environment of RY Sgr is dominated at the time of observations by a single dusty cloud, which at 10 µm represents ∼10% of the total flux of the whole system, slightly less that the star flux. The cloud is located at about 100 stellar radii (or ∼30 AU) from the center toward the East-North-East direction (or the symmetric direction with respect to center) within a circumstellar envelope whose FWHM is about 120 stellar radii. This first detection of a cloud so close to the central star supports the classical scenario of the R CrB brightness variations in the optical spectral domain and demonstrates the feasibility of a temporal monitoring of the dusty environment of this star on a monthly scale. 2020-05-15T14:31:23Z 2020-05-15T14:31:23Z 2007-05 article MEDEIROS, Jose Renan de et al. A snapshot of the inner dusty regions of a R CrB-type variable. Astronomy & Astrophysics (Berlin), v. 466, n. 2, p. L1-L4, 2007. ISSN 1432-0746 versão online. DOI https://doi.org/10.1051/0004-6361:20077128. Disponível em: https://www.aanda.org/articles/aa/abs/2007/17/aa7128-07/aa7128-07.html. Acesso em: 27 maio 2020. Reproduzido com permissão da Astronomy & Astrophysics, © ESO. 0004-6361 (print); 1432-0746 (online) https://repositorio.ufrn.br/jspui/handle/123456789/28987 10.1051/0004-6361:20077128 en application/pdf Astronomy & Astrophysics |
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English |
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Stars: AGB and post-AGB Stars: variables: general Stars: individual: RY Sagittarii Stars: mass-loss Stars: circumstellar matter Stars: techniques: interferometric |
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Stars: AGB and post-AGB Stars: variables: general Stars: individual: RY Sagittarii Stars: mass-loss Stars: circumstellar matter Stars: techniques: interferometric Leão, Izan de Castro Laverny, P. de Chesneau, O. Mékarnia, D. Medeiros, José Renan de A snapshot of the inner dusty regions of a R CrB-type variable |
| description |
Context. R Coronae Borealis (R CrB) variable stars are suspected to sporadically eject optically thick dust clouds causing, when one of them lies on the line-of-sight, a huge brightness decline in visible light. Direct detections with 8-m class adaptive optics of such clouds located at about 0.2–0.3 arcsec from the center (∼1000 stellar radii) were recently reported for RY Sgr, the brightest R CrB of the southern hemisphere.
Aims. Mid-infrared interferometric observations of RY Sgr allowed us to explore the circumstellar regions much closer to the central star (∼20–40 mas) to look for the signature of any heterogeneities and to characterize them. Methods. Using the VLTI/MIDI instrument, five dispersed visibility curves in the N-band were recorded in May and June 2005 with different projected baselines oriented towards two roughly perpendicular directions. The large spatial frequencies’ visibility curves exhibit a sinusoidal shape, whereas, at shorter spatial frequencies’ visibility curves follow a Gaussian decrease. These observations are well interpreted with a geometrical model consisting of a central star surrounded by an extended circumstellar envelope in which
one bright cloud is embedded. Results. Within this simple geometrical scheme, the inner 110 AU dusty environment of RY Sgr is dominated at the time of observations by a single dusty cloud, which at 10 µm represents ∼10% of the total flux of the whole system, slightly less that the star flux. The cloud is located at about 100 stellar radii (or ∼30 AU) from the center toward the East-North-East direction (or the symmetric direction with respect to center) within a circumstellar envelope whose FWHM is about 120 stellar radii. This first detection of a cloud so close to the central star supports the classical scenario of the R CrB brightness variations in the optical spectral domain and demonstrates the feasibility of a temporal monitoring of the dusty environment of this star on a monthly scale. |
| format |
article |
| author |
Leão, Izan de Castro Laverny, P. de Chesneau, O. Mékarnia, D. Medeiros, José Renan de |
| author_facet |
Leão, Izan de Castro Laverny, P. de Chesneau, O. Mékarnia, D. Medeiros, José Renan de |
| author_sort |
Leão, Izan de Castro |
| title |
A snapshot of the inner dusty regions of a R CrB-type variable |
| title_short |
A snapshot of the inner dusty regions of a R CrB-type variable |
| title_full |
A snapshot of the inner dusty regions of a R CrB-type variable |
| title_fullStr |
A snapshot of the inner dusty regions of a R CrB-type variable |
| title_full_unstemmed |
A snapshot of the inner dusty regions of a R CrB-type variable |
| title_sort |
snapshot of the inner dusty regions of a r crb-type variable |
| publisher |
Astronomy & Astrophysics |
| publishDate |
2020 |
| url |
https://repositorio.ufrn.br/jspui/handle/123456789/28987 |
| work_keys_str_mv |
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1773958330038878208 |