Epoch J2000 Equinox J2000
|Right ascension||05h 38m 39.147s|
|Declination||−69° 06′ 21.20″|
|Apparent magnitude (V)||13.70|
|Evolutionary stage||Wolf-Rayet star|
|B−V color index||-0.10|
|Distance||165,000 ly |
|Absolute magnitude (MV)||-8.11|
|Luminosity (visual, LV)||141,000 L☉|
|Age||~2 Myr|
BAT99-98 is a star in the Large Magellanic Cloud. It is located near the R136 cluster in the 30 Doradus nebula. At 226 M☉ and 5,000,000 L☉ it is the third most massive and the fifth most luminous star known.
A 1978 survey carried out by J. Melnick covered the 30 Doradus region and found six new W-R stars, all belonging to the WN sequence. The survey observed stars that were above magnitude 14 and that were within two arcminutes of the centre of the 30 Doradus nebula, and BAT99-98 was labelled as star J. It was found to have an apparent magnitude of 13.5 and a spectral type of WN-5.
The following year, 13 new Wolf Rayet stars in the LMC were reported, one of which was Mel J. It was numbered 12, referred to as AB 12, or LMC AB 12 to distinguish it from the better-known SMC AB stars.
Neither the AB12 nor Mel J designations are in common use, although Melnick 49 is sometimes seen. More commonly, LMC Wolf Rayet stars are referred to by R (Radcliffe Observatory) numbers, Brey (Breysacher catalogue) numbers, or BAT99 numbers.
The star is located near the R136 cluster and shares similar mass-luminosity properties to the massive stars in R136. It is estimated that at its birth that the star held 250 M☉ and has since lost 20 M☉. It sheds a large amount of mass through a stellar wind that moves at 1,600 km/s. The star has a surface temperature of 45,000 K and a luminosity of 5,000,000 L☉. Although the star is very luminous due to its high temperature, it is only 141,000 times brighter than the sun visually. It is classified as a WN6 star.
The future of BAT99-98 depends on its mass loss. It is thought that stars this massive will never lose enough mass to avoid a catastrophic end. The result is likely to be a supernova, hypernova, gamma-ray burst, or perhaps almost no visible explosion, and leaving behind a black hole or neutron star. The exact details depend heavily on the timing and amount of the mass loss, with current models not fully reproducing observed stars, but the most massive stars in the local universe are expected to produce type Ib or Ic supernovae, sometimes with a gamma-ray burst, and leave behind a black hole.
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