* Astronomy

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RE: BP Piscium

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Title: Chandra X-ray Detection of the Enigmatic Field Star BP Psc
Authors: Joel H. Kastner, Rodolfo Montez Jr. (RIT Center for Imaging Science), David Rodriguez (UCLA Dept. of Physics and Astronomy), Nicolas Grosso (Observatoire astronomique de Strasbourg), B. Zuckerman, Marshall D. Perrin (UCLA Dept. of Physics and Astronomy), Thierry Forveille (Laboratoire d'Astrophysique de Grenoble), James R. Graham (Astronomy Dept., University of California, Berkeley)

BP Psc is a remarkable emission-line field star that is orbited by a dusty disk and drives a parsec-scale system of jets. We report the detection by the Chandra X-ray Observatory of a weak X-ray point source coincident with the centroids of optical/IR and submillimetre continuum emission at BP Psc. As the star's photosphere is obscured throughout the visible and near-infrared, the Chandra X-ray source likely represents the first detection of BP Psc itself. The X-rays most likely originate with magnetic activity at BP Psc and hence can be attributed either to a stellar corona or to star-disk interactions. The log of the ratio of X-ray to bolometric luminosity (log(L_X/L_{bol}) lies in the range -5.8 to -4.2. This is smaller than log(L_X/L_{bol}) ratios typical of low-mass, pre-main sequence stars, but is well within the log(L_X/L_{bol}) range observed for rapidly-rotating (FK Com-type) G giant stars. Hence, the Chandra results favour an exotic model wherein the disk/jet system of BP Psc is the result of its very recently engulfing a companion star or giant planet, as the primary star ascended the giant branch.

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Title: Gas and Dust Associated with the Strange, Isolated, Star BP Piscium
Authors: B. Zuckerman, C. Melis, Inseok Song, David S. Meier, Marshall D. Perrin, Bruce Macintosh, Christian Marois, Alycia J. Weinberger, Joseph H. Rhee, James R. Graham, Joel H. Kastner, Patrick Palmer, T. Forveille, E.E. Becklin, D. J. Wilner, T. S. Barman, G. W. Marcy, M. S. Bessell
(Version v2)

We have carried out a multiwavelength observational campaign demonstrating some of the remarkable properties of the infrared-bright variable star BP Psc. Surrounded by a compact dusty, gaseous disk, this little-studied late-G (or early-K) type star emits about 75% of its detected energy flux at infrared wavelengths. Evidence for accretion of gas in conjunction with narrow bi-polar jets and Herbig-Haro objects is apparently consistent with classification of BP Psc as a pre-main sequence star, as postulated in most previous studies. If young, then BP Psc would be one of the nearest and oldest known classical T Tauri stars. However, such an evolutionary classification encounters various problems that are absent or much less severe if BP Psc is instead a luminosity class III post-main sequence star. In this case, it would be the first known example of a first ascent giant surrounded by a massive molecular disk with accompanying rapid gas accretion and prominent jets and HH objects. In this model, the genesis of the massive dusty gaseous disk could be a consequence of the envelopment of a low mass companion star. Properties in the disk may be conducive to the current formation of planets, a gigayear or more after the formation of BP Psc itself.

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Blobrana · L

An unusual star may have swallowed its stellar companion and burped out a planet-forming cloud as a result, a new study reports.
The star, called BP Piscium, is surrounded by a thick disc of gas and dust from which it appears to be sucking up new material at a prodigious rate.
These properties are typical of young stars, but BP Piscium appears to be much older, based on the weak signs of lithium in its light spectrum. Younger stars have plenty of lithium, but it gets destroyed as stars age.
A team of scientists led by Carl Melis of the University of California in Los Angeles (UCLA), US, reported the unusual star at a meeting of the American Astronomical Society in Austin, Texas, US, in January.

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Two old stars appear to be gearing up for a second generation of planet formation, a phenomenon astronomers say they have never seen before.

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Tycho 4144 329 2

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RE: BP Piscium

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Two old stars may be undergoing a second episode of planet formation, long after their initial window of opportunity.
Astronomers believe the stars once had orbiting companions, but that these were engulfed when the stars expanded.
This caused matter to be ejected from the stars, forming a disc of gas and dust from which planets can form.
Details were presented at the 211th American Astronomical Society meeting in Austin, Texas.

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Old Stars Piscium and Tycho Give New Births
Hundreds of millions or even billions of years after planets would have initially formed around two unusual stars, a second wave of planetesimal and planet formation appears to be taking place, UCLA astronomers and colleagues believe.

"This is a new class of stars, ones that display conditions now ripe for formation of a second generation of planets, long, long after the stars themselves formed. If we took a rocket to one of these stars and discovered there were two totally distinct ages for their planets and more minor bodies like asteroids, that would blow scientists' minds away," said Benjamin Zuckerman, UCLA professor of physics and astronomy and co-author of the research, which has not yet been published. "We're seeing stars with characteristics that have never been seen before" - UCLA astronomy graduate student Carl Melis, who reported the findings today at the American Astronomical Society meeting in Austin, Texas

The stars, which Melis says possess "amazing" properties for their age, are known as BP Piscium, in the constellation Pisces, and TYCHO 4144 329 2, in the constellation Ursa Major.
These two stars have many characteristics of very young stars, Melis said, including rapid accretion of gas, extended orbiting disks of dust and gas, a large infrared excess emission and, in the case of BP Piscium, jets of gas that are being shot into space. Planetesimals, like comets and asteroids, along with planets, form from the gas and dust particles that orbit young stars; planetesimals are small masses of rock or ice that merge to form larger bodies.

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