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Mid-infrared evolution of eta Carinae from 1968 to 2018

Mid-infrared evolution of eta Carinae from 1968 to 2018
Mid-infrared evolution of eta Carinae from 1968 to 2018
η Car is one of the most luminous and massive stars in our Galaxy and is the brightest mid-IR source in the sky outside our solar system. Since the late 1990s, the central source has dramatically brightened at UV and optical wavelengths. This might be explained by a decrease in circumstellar dust extinction. We aim to establish the mid-IR flux evolution and further our understanding of the star’s UV and optical brightening. Mid-IR images from 8−20 μm were obtained in 2018 with VISIR at the Very Large Telescope. Archival data from 2003 and 2005 were retrieved from the ESO Science Archive Facility, and historical records were collected from publications. We present mid-IR images of η Car with the highest angular resolution to date at the corresponding wavelengths (≥0.22″). We reconstruct the mid-IR evolution of the spectral energy distribution of the spatially integrated Homunculus nebula from 1968 to 2018 and find no long-term changes. The bolometric luminosity of η Car has been stable over the past five decades. We do not observe a long-term decrease in the mid-IR flux densities that could be associated with the brightening at UV and optical wavelengths, but circumstellar dust must be declining in our line of sight alone. Short-term flux variations within about 25% of the mean levels could be present.
0004-6361
Mehner, A.
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de Wit, W.-J.
f1ef9803-ec69-4469-89bf-c80c059c722e
Asmus, D.
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Morris, P.W.
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Agliozzo, C.
a2621d52-7d2c-4ad3-a003-a4b30e05488b
Barlow, M.J.
a1a4afcc-0ce6-4274-b3ce-3e89ac8a04bc
Gull, T.R.
3926a56e-b895-4db1-a755-e4deb9fd28ae
Hillier, D.J.
6a6d05c4-ee02-471c-8198-d871d5d3e01e
Weigelt, G.
bd0be979-0519-484f-b489-e3e44467bf57
Mehner, A.
0238555b-f5ea-4253-869b-c32b420291a9
de Wit, W.-J.
f1ef9803-ec69-4469-89bf-c80c059c722e
Asmus, D.
f783516a-c74c-4912-b68e-4e896e4317b2
Morris, P.W.
68f28d8f-bce4-4060-9763-ed274490968b
Agliozzo, C.
a2621d52-7d2c-4ad3-a003-a4b30e05488b
Barlow, M.J.
a1a4afcc-0ce6-4274-b3ce-3e89ac8a04bc
Gull, T.R.
3926a56e-b895-4db1-a755-e4deb9fd28ae
Hillier, D.J.
6a6d05c4-ee02-471c-8198-d871d5d3e01e
Weigelt, G.
bd0be979-0519-484f-b489-e3e44467bf57

Mehner, A., de Wit, W.-J., Asmus, D., Morris, P.W., Agliozzo, C., Barlow, M.J., Gull, T.R., Hillier, D.J. and Weigelt, G. (2019) Mid-infrared evolution of eta Carinae from 1968 to 2018. Astronomy & Astrophysics, 630 (L6). (doi:10.1051/0004-6361/201936277).

Record type: Letter

Abstract

η Car is one of the most luminous and massive stars in our Galaxy and is the brightest mid-IR source in the sky outside our solar system. Since the late 1990s, the central source has dramatically brightened at UV and optical wavelengths. This might be explained by a decrease in circumstellar dust extinction. We aim to establish the mid-IR flux evolution and further our understanding of the star’s UV and optical brightening. Mid-IR images from 8−20 μm were obtained in 2018 with VISIR at the Very Large Telescope. Archival data from 2003 and 2005 were retrieved from the ESO Science Archive Facility, and historical records were collected from publications. We present mid-IR images of η Car with the highest angular resolution to date at the corresponding wavelengths (≥0.22″). We reconstruct the mid-IR evolution of the spectral energy distribution of the spatially integrated Homunculus nebula from 1968 to 2018 and find no long-term changes. The bolometric luminosity of η Car has been stable over the past five decades. We do not observe a long-term decrease in the mid-IR flux densities that could be associated with the brightening at UV and optical wavelengths, but circumstellar dust must be declining in our line of sight alone. Short-term flux variations within about 25% of the mean levels could be present.

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Mid-infrared evolution of n car from 1968 to 2018 - Accepted Manuscript
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Accepted/In Press date: 23 August 2019
e-pub ahead of print date: 30 September 2019

Identifiers

Local EPrints ID: 435295
URI: http://eprints.soton.ac.uk/id/eprint/435295
ISSN: 0004-6361
PURE UUID: 36179563-20eb-47f3-8261-15bbf295da4c

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Date deposited: 30 Oct 2019 17:30
Last modified: 23 Jan 2020 17:35

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Contributors

Author: A. Mehner
Author: W.-J. de Wit
Author: D. Asmus
Author: P.W. Morris
Author: C. Agliozzo
Author: M.J. Barlow
Author: T.R. Gull
Author: D.J. Hillier
Author: G. Weigelt

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