Title: On the origin of the ultramassive white dwarf GD50
Authors: P. D. Dobbie (1), R. Napiwotzki (2), N. Lodieu (1), M. R. Burleigh (1), M. A. Barstow (1), R. F. Jameson (1) ((1) University of Leicester, UK, (2) University of Hertfordshire, UK)
We argue on the basis of astrometric and spectroscopic data that the ultramassive white dwarf GD50 is associated with the star formation event that created the Pleiades and is possibly a former member of this cluster. Its cooling age (~60Myrs) is consistent with it having evolved essentially as a single star from a progenitor with a mass M>6Msun so we find no need to invoke a white dwarf-white dwarf binary merger scenario to account for its existence. This result may represent the first direct observational evidence that single star evolution can produce white dwarfs with M>1.1Msun, as predicted by some stellar evolutionary theories. On the basis of its tangential velocity we also provisionally identify the ultramassive (M~1.2Msun) white dwarf PG0136+251 as being related to the Pleiades. These findings may help to alleviate the difficulties in reconciling the observed number of hot nearby ultramassive white dwarfs with the smaller number predicted by binary evolution models under the assumption that they are the products of white dwarf mergers.
Read more (22kb, PDF)
Quote:
|
The `lost Pleiad' legend came about to explain why only six are easily visible to the unaided eye. This sister is variously said to be Electra, who veiled her face at the burning of Troy, appearing to mortals afterwards only as a comet; or Merope, who was shamed for marrying a mortal; or Celæno, who was struck by a thunderbolt. Missing Pleiad myths also appear in other cultures, prompting Burnham to speculate stellar variability (Pleione?) as a physical basis. It is difficult to know if the modern naming pays attention to any of this. Celæno is the faintest at present, but the "star" Asterope is actually two stars, each of which is fainter than Celæno if considered separately.
|
http://www.naic.edu/~gibson/pleiades/pleiades_myth.html