Cesium detected in the atmosphere of a hot white dwarf

By analyzing the information from the Far Ultraviolet Spectroscopic Explorer (FUSE) telescope, a world staff of astronomers has found cesium within the ambiance of a scorching white dwarf often called HD 149499B. The discovering, reported November 3 on the arXiv pre-print server, marks the primary time this component has been recognized within the ambiance of a scorching white dwarf.

White dwarfs (WDs) are stellar cores left behind after a star has exhausted its nuclear fuel. Because of their excessive gravity, they’re identified to have atmospheres of both pure hydrogen or pure helium. Nonetheless, a small fraction of WDs exhibits traces of heavier parts.

So far, solely 18 trans-iron parts (with an atomic quantity better than 28) have been recognized up to now within the atmospheres of scorching white dwarfs. Generally, these trans-iron parts have been discovered to be overabundant in WDs.

Now, a gaggle of astronomers led by Pierre Chayer of the Area Telescope Science Institute in Baltimore, Maryland, studies the discovering of cesium (Cs), with an atomic number 55, within the ambiance of HD 149499B—a vibrant helium-rich white dwarf with an effective temperature of 49,500 Okay. The detection is a results of observations of this star with FUSE between 2000 and 2006.

“We report the primary detection of cesium (Z = 55) within the ambiance of a white dwarf. Round a dozen absorption traces of Cs _IV, Cs _V, and Cs _VI have been recognized within the Far Ultraviolet Spectroscopic Explorer spectrum of the He-rich white dwarf HD 149499B,” the researchers wrote within the paper.

All in all, 13 cesium traces have been detected within the FUSE spectrum with equal widths within the vary 2.3–26.9 mÅ. The astronomers added that every one these transitions come up from low-energy ranges starting from ten thousand to some tens of 1000’s of cm⁻¹.

Based on the authors of the examine, cesium detection within the ambiance of HD 149449B is no surprise, on condition that the checklist of trans-iron parts recognized within the atmospheres of WDs has grown significantly for the reason that detection of germanium in 2005.

The abundance of cesium within the ambiance of HD 149449B was calculated to be −5.45 (cesium to helium abundance ratio), which is -3.95 when it comes to the mass fraction. This consequence makes cesium essentially the most ample trans-iron component noticed in HD 149499B.

Summing up the outcomes, the researchers attempt to discover essentially the most believable speculation explaining the presence of cesium within the atmosphere of this white dwarf.

“Radiative levitation is essentially the most believable pure phenomenon to clarify its presence…. Though radiative levitation complicates the interpretation of the supply of trans-iron parts, it allows the buildup of huge abundances, and due to this fact, the detection of these parts that in any other case wouldn’t be detected,” the authors of the paper concluded.

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