Cesium detected in the atmosphere of a hot white dwarf

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

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

So far, solely 18 trans-iron components (with an atomic quantity larger than 28) have been recognized to date within the atmospheres of scorching white dwarfs. Usually, these trans-iron components have been discovered to be overabundant in WDs.

Now, a bunch 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 environment of HD 149499B—a brilliant 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 environment of a white dwarf. Round a dozen absorption strains 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 strains have been detected within the FUSE spectrum with equal widths within the vary 2.3–26.9 mÅ. The astronomers added that each one these transitions come up from low-energy ranges starting from ten thousand to a couple tens of hundreds of cm⁻¹.

In response to the authors of the examine, cesium detection within the environment of HD 149449B isn’t a surprise, on condition that the record of trans-iron components recognized within the atmospheres of WDs has grown significantly because the detection of germanium in 2005.

The abundance of cesium within the environment of HD 149449B was calculated to be −5.45 (cesium to helium abundance ratio), which is -3.95 by way of the mass fraction. This end result makes cesium essentially the most considerable trans-iron ingredient 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 components, it allows the buildup of enormous abundances, and subsequently, the detection of these components that in any other case wouldn’t be detected,” the authors of the paper concluded.

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