LP 40-365: An unusual white dwarf star may be a surviving remnant of a subluminous Type Ia supernova
In: Science - Aug 18, 2017 - Vol. 357, Issue 6352, pp. 680-683 - DOI: 10.1126/science.aam8378
(Astroserver project reference: NWKZKA)
(Copyright and image credit: Russell Kightley, www.scientific.pictures, Used with permission.)
These findings are presented in the August 18th (2017) issue of Science, published by the American Association for the Advancement of Science (AAAS).
The class of supernovae known as Type Ia are the brightest explosions in the Universe and are fundamental to measure its huge dimension. The recent discovery of dark energy rests almost entirely on our current understanding of these powerful explosions.
To understand the nature of these explosions cosmologists adhere to a behaviorist approach concentrating mainly on environmental factors and the nature of the galaxies hosting these events. Following that approach it is possible to calibrate the true luminosity of these supernovae and use them as standard candle lights to measure distances. But then we know nothing of the explosions themselves. Stellar astrophysicists follow a constructivist approach and build models aimed at a deeper understanding of the engine powering these explosions.
(Copyright and image credit: Sardi Pax, https://www.youtube.com/c/SardiPax, Used with permission.)
"Such a cataclysmic binary star has never been caught feeding and getting ready for the explosion," commented Stephane Vennes, leading author of the Science article. "All we ever witness is the aftermath of the explosion, that is the bright flash in the distant Universe that even outshines the galaxy hosting that event. But now, with the discovery of a surviving remnant of the white dwarf itself, we have direct clues to the nature of the most important actor involved in these events.
"For a remnant to survive, it is necessary to invoke a special class of uncommon supernovae that do not completely destroy the white dwarf at the heart of the explosion. The new class of models developed in recent years by multiple teams is able under narrow circumstances to leave a partially burnt bound remnant that is instantly ejected at an exceedingly high velocity. This is the model favored by the research team. "Indeed, the white dwarf LP 40-365 is escaping the Milky Way", commented Lilia Ferrario from the Australian National University.
(Image source: ESO Online DSS; astroserver.org)
"We selected this object for observation with the spectrograph at the four-meter telescope because of its large apparent motion across the celestial sphere. Thousands of objects like this one are known, but the sky was partly cloudy on that night and we had to go for the brightest star available which turned out to be LP 40-365," said team member Adela Kawka, underpinning the importance of serendipity in astronomy.
"We alerted team members J.R. Thorstensen and E. Alper at Dartmouth College, and P. Nemeth at the Karl Remeis Observatory for urgent follow-up observations."
A final, crowning data set was obtained with the help of team member V. Khalack at the Université de Moncton using the CFHT/GRACES spectrograph fed by an optical fiber hooked to its neighbor, the eight-meter Gemini-North telescope located on Mauna Kea. The data were analyzed with state-of-the-art computer codes. The analysis proved the compact nature of the star and its exotic chemical composition.
"The extreme peculiarity of the atmosphere required a lengthy and complex model atmosphere analysis which crunched several weeks of computing time. But the results proved very exciting. Such a peculiar atmosphere devoid of hydrogen and helium is rare indeed", commented team member Peter Nemeth.
(Copyright and image credit: Russell Kightley, www.scientific.pictures, Used with permission.)
Many more of these objects are lurking in the Milky Way and awaiting discovery. The recent ESA/Gaia mission may well help us discover many more of these objects and help us understand the white dwarf stars at the heart of supernova explosions.
Science contact
- Dr Stephane Vennes
- Astronomical Institute of the Czech Academy of Sciences
- Fricova 298; 251 65 Ondrejov; Czech Republic
- Phone: +420 323620217
- Email: vennes @asu.cas.cz
Related links
-
Synthetic Spectrum Covering The Optical Range (3000 To 10000 Angstroms).
The file NWKZKA.spr lists in two columns a surface stellar model flux (Eddington flux):
column (1) wavelength in units of angstrom, and column (2) the flux in units of erg/cm2/s/angstrom/steradian.
https://doi.org/10.5281/zenodo.826139 - Research paper preprint on Astro-ph
- Science article preview at Sciencemagazinedigital.org
- Australian National University (ANU) press release
- Canada-France-Hawaii Telescope (CFHT) press release
- Gemini Observatory press release, GRACES instrument science highlight
- Animations on the Astroserver Youtube Channel
- Wikipedia article on LP 40-365
- LP 40-365 (GD 492) on SIMBAD
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