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Post Info TOPIC: 49 Ceti
Blobrana


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HD 9672
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Title: Volatile-Rich Circumstellar Gas in the Unusual 49 Ceti Debris Disk
Author: Aki Roberge, Barry Y. Welsh, Inga Kamp, Alycia J. Weinberger, Carol A. Grady

We present Hubble Space Telescope STIS far-UV spectra of the edge-on disk around 49 Ceti, one of the very few debris disks showing sub-mm CO emission. Many atomic absorption lines are present in the spectra, most of which arise from circumstellar gas lying along the line-of-sight to the central star. We determined the line-of-sight CI column density, estimated the total carbon column density, and set limits on the OI column density. Surprisingly, no line-of-sight CO absorption was seen. We discuss possible explanations for this non-detection, and present preliminary estimates of the carbon abundances in the line-of-sight gas. The C/Fe ratio is much greater than the solar value, suggesting that 49 Cet harbours a volatile-rich gas disk similar to that of Beta Pictoris.

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Blobrana


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49 Ceti
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Comet collisions every six seconds explain 17-year-old stellar mystery

Every six seconds, for millions of years, comets have been colliding with one another near a star in the constellation Cetus called 49 CETI, which is visible to the naked eye.
Over the past three decades, astronomers have discovered hundreds of dusty disks around stars, but only two - 49 CETI is one - have been found that also have large amounts of gas orbiting them.
Young stars, about a million years old, have a disk of both dust and gas orbiting them, but the gas tends to dissipate within a few million years and almost always within about 10 million years. Yet 49 CETI, which is thought to be considerably older, is still being orbited by a tremendous quantity of gas in the form of carbon monoxide molecules, long after that gas should have dissipated.
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Position (J2000): R.A. 01 34 37.77884 |  Dec. -15° 40' 34.8979''



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Blobrana


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Title: A 40 Myr Old Gaseous Circumstellar Disk at 49 Ceti: Massive CO-Rich Comet Clouds at Young A-Type Stars
Authors: B. Zuckerman, Inseok Song

The gaseous molecular disk that orbits the main sequence A-type star 49 Ceti has been known since 1995, but the stellar age and the origin of the observed carbon monoxide molecules have been unknown. We now identify 49 Ceti as a member of the 40 Myr old Argus Association and present a colliding comet model to explain the high CO concentrations seen at 49 Ceti and the 30 Myr old A-type star HD 21997. The model suggests that massive -- 400 Earth mass -- analogues of the Sun's Kuiper Belt are in orbit about some A-type stars, that these large masses are composed primarily of comet-like objects, and that these objects are rich in CO and perhaps also CO2. We identify additional early-type members of the Argus Association and the Tucana/Horologium and Columba Associations; some of these stars display excess mid-infrared emission as measured with the Widefield Infrared Survey Explorer (WISE).

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Position (J2000): R.A. 01 34 37.77884  |  Dec. -15° 40' 34.8979''



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