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HE 0437-5439 -- an unbound hyper-velocity main-sequence B-type star
Astrophysics · Submitted 10 Nov 2005
abstract compiled · 2026-09-23 · no language-model review
The authors' main claim Its galactic rest frame velocity is at least 563km/s, almost twice the local Galactic escape velocity, indicating that the star is unbound to the Galaxy.
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The abstract, sentence by sentence
We report the discovery of a 16th magnitude star, HE0437-5439, with a heliocentric radial velocity of +723+-3km/s. A quantitative spectral analysis of high-resolution optical spectra obtained with the VLT and the UVES spectrograph shows that HE0437-5439 is a main sequence B-type star with Teff=20350K, log g=3.77, solar within a factor of a few helium abundance and metal content, rotating at v sin i=54km/s. Using appropriate evolutionary tracks we derive a mass of 8 Msun and a corresponding distance of 61 kpc. Its galactic rest frame velocity is at least 563km/s, almost twice the local Galactic escape velocity, indicating that the star is unbound to the Galaxy. Numerical kinematical experiments are carried out to constrain its place of birth. It has been suggested that such hyper-velocity stars can be formed by the tidal disruption of a binary through interaction with the super-massive black hole at the Galactic center (GC). HE0437-5439 needs about 100Myrs to travel from the GC to its presentposition, much longer than its main sequence lifetime of 25Myrs. This can only be reconciled if HE0437-5439 is a blue straggler star. In this case, the predicted proper motion is so small that it can only be measured by future space missions. Since the star is much closer to the Large Magellanic Cloud (LMC, 18kpc) than to the GC, it can reach its position from the center of the LMC. The proper motion predicted in this case is about 2mas/y (relative to the LMC), large enough to be measurable with conventional techniques from the ground. The LMC origin could also be tested by a high-precision abundance analysis.
background contribution method result interpretation main claim
| # | sentence | role | the authors' own work | states the main conclusion | strength |
|---|---|---|---|---|---|
| s0 | We report the discovery of a 16th magnitude star, HE0437-5439, with a heliocentric radial velocity of +723+-3km/s. | result 0.50 | 0.95 | 0.07 | asserted 1.00 |
| s1 | A quantitative spectral analysis of high-resolution optical spectra obtained with the VLT and the UVES spectrograph shows that HE0437-5439 is a main sequence B-type star with Teff=20350K, log g=3.77, solar within a factor of a few helium abundance and metal content, rotating at v sin i=54km/s. | result 0.84 | 0.96 | 0.04 | asserted 1.00 |
| s2 | Using appropriate evolutionary tracks we derive a mass of 8 Msun and a corresponding distance of 61 kpc. | result 0.99 | 0.95 | 0.05 | asserted 1.00 |
| s3 | Its galactic rest frame velocity is at least 563km/s, almost twice the local Galactic escape velocity, indicating that the star is unbound to the Galaxy. | interpretation 0.67 | 0.88 | 0.79 | asserted 0.50 |
| s4 | Numerical kinematical experiments are carried out to constrain its place of birth. | method 0.85 | 0.91 | 0.03 | asserted 0.87 |
| s5 | It has been suggested that such hyper-velocity stars can be formed by the tidal disruption of a binary through interaction with the super-massive black hole at the Galactic center (GC). | background 0.99 | 0.05 | 0.05 | hedged possibility 0.94 |
| s6 | HE0437-5439 needs about 100Myrs to travel from the GC to its presentposition, much longer than its main sequence lifetime of 25Myrs. | result 0.55 | 0.75 | 0.07 | asserted 1.00 |
| s7 | This can only be reconciled if HE0437-5439 is a blue straggler star. | interpretation 0.98 | 0.56 | 0.22 | asserted 0.94 |
| s8 | In this case, the predicted proper motion is so small that it can only be measured by future space missions. | interpretation 0.40 | 0.58 | 0.05 | asserted 0.87 |
| s9 | Since the star is much closer to the Large Magellanic Cloud (LMC, 18kpc) than to the GC, it can reach its position from the center of the LMC. | interpretation 0.88 | 0.50 | 0.12 | hedged possibility 0.78 |
| s10 | The proper motion predicted in this case is about 2mas/y (relative to the LMC), large enough to be measurable with conventional techniques from the ground. | result 0.48 | 0.74 | 0.08 | asserted 0.94 |
| s11 | The LMC origin could also be tested by a high-precision abundance analysis. | future work 0.98 | 0.14 | 0.06 | hedged possibility 0.99 |
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The paper
Original abstract
We report the discovery of a 16th magnitude star, HE0437-5439, with a heliocentric radial velocity of +723+-3km/s. A quantitative spectral analysis of high-resolution optical spectra obtained with the VLT and the UVES spectrograph shows that HE0437-5439 is a main sequence B-type star with Teff=20350K, log g=3.77, solar within a factor of a few helium abundance and metal content, rotating at v sin i=54km/s. Using appropriate evolutionary tracks we derive a mass of 8 Msun and a corresponding distance of 61 kpc. Its galactic rest frame velocity is at least 563km/s, almost twice the local Galactic escape velocity, indicating that the star is unbound to the Galaxy. Numerical kinematical experiments are carried out to constrain its place of birth. It has been suggested that such hyper-velocity stars can be formed by the tidal disruption of a binary through interaction with the super-massive black hole at the Galactic center (GC). HE0437-5439 needs about 100Myrs to travel from the GC to its presentposition, much longer than its main sequence lifetime of 25Myrs. This can only be reconciled if HE0437-5439 is a blue straggler star. In this case, the predicted proper motion is so small that it can only be measured by future space missions. Since the star is much closer to the Large Magellanic Cloud (LMC, 18kpc) than to the GC, it can reach its position from the center of the LMC. The proper motion predicted in this case is about 2mas/y (relative to the LMC), large enough to be measurable with conventional techniques from the ground. The LMC origin could also be tested by a high-precision abundance analysis.
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2 arXiv papers cite this in 3 sentences
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Cites it as background 1 paper
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The term hypervelocity star, however, has been used for all stars unbound to the Galaxy, irrespective of their place of origin [ref] , and even their evolutionary state [ref] .
Intermediate-mass runaway and hypervelocity star candidates in DESI DR1 · Introduction · 0.82
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