S Doradus variables (LBVs) show distinct quiescent and outburst states.
 During the quiescent phase, LBVs lie along a diagonal band in the H–R diagram called the S Doradus Instability Strip, with the more luminous examples having hotter temperatures.

The standard theory is that LBV outbursts occur when the mass loss increases and an extremely dense stellar wind creates a pseudo-photosphere.
 The temperature drops until the wind opacity starts to decrease, meaning all LBV outbursts reach a temperature around 8,000–9,000 K. The bolometric luminosity during outbursts is considered to remain largely unchanged, but the visual luminosity increases as radiation shifts from the ultraviolet into the visual range.
Detailed investigations have shown that some LBVs appear to change luminosity from minimum to maximum.
S Doradus has been calculated to be less luminous at maximum brightness (minimum temperature), possibly as a result of potential energy going into expansion of a substantial portion of the star.
AG Carinae and HR Carinae show similar luminosity decreases in some studies, but in the most convincing case AFGL 2298 increased its luminosity during its outbursts.

Rare larger eruptions can appear as long-lasting under-luminous supernovae, and have been termed supernova impostors.
 The cause of the eruptions is unknown, but the star survives and may experience multiple eruptions.
Eta Carinae and P Cygni are the only known examples in the Milky Way galaxy, and S Doradus has not shown such an eruption.
S Doradus variables (LBVs) show distinct quiescent and outburst states.  During the quiescent phase, LBVs lie along a diagonal band in the H–R diagram called the S Doradus Instability Strip, with the more luminous examples having hotter temperatures.
The standard theory is that LBV outbursts occur when the mass loss increases and an extremely dense stellar wind creates a pseudo-photosphere.  The temperature drops until the wind opacity starts to decrease, meaning all LBV outbursts reach a temperature around 8,000–9,000 K. The bolometric luminosity during outbursts is considered to remain largely unchanged, but the visual luminosity increases as radiation shifts from the ultraviolet into the visual range. Detailed investigations have shown that some LBVs appear to change luminosity from minimum to maximum. S Doradus has been calculated to be less luminous at maximum brightness (minimum temperature), possibly as a result of potential energy going into expansion of a substantial portion of the star. AG Carinae and HR Carinae show similar luminosity decreases in some studies, but in the most convincing case AFGL 2298 increased its luminosity during its outbursts.
Rare larger eruptions can appear as long-lasting under-luminous supernovae, and have been termed supernova impostors.  The cause of the eruptions is unknown, but the star survives and may experience multiple eruptions. Eta Carinae and P Cygni are the only known examples in the Milky Way galaxy, and S Doradus has not shown such an eruption.
S Doradus