L dwarf

[4] If a young exoplanet or planetary-mass companion is detected via direct imaging, it can also have an L spectral type, such as Kappa Andromedae b.

With the discovery of 20 new late-type objects it was necessary to define the L-type and T-type spectral types.

[6] M-dwarfs show absorption due to water vapor (H2O) in their near-infrared spectrum.

In particular, the collision induced absorption of hydrogen molecules leads to a suppression of the H- and K-band, which causes L-type subdwarfs to have blue near-infrared colors.

[12] The hydrogen burning minimum mass lies at 0.075 M☉ (78.5 MJ) for objects with a solar metallicity.

[13] The table of ultracool fundamental parameters lists several objects with an infrared spectral type of L0 to L4 and a mass above 78.5 MJ.

[14] The same team found that ⅓ of known L-subdwarfs are substellar objects and ⅔ are low-mass stars.

[17] In the table of ultracool fundamental parameters there are currently 422 objects with an infrared spectral type of L and a mass range of 14-78.5 MJ.

Beyond 100 AU, it is referred to as a planetary-mass companion since theories predict that these objects form on their own and not from material of a protoplanetary disk.

A lower-mass object has for example a lower surface gravity, which leads to a more extended atmosphere and more vertical mixing.

This will affect the depth of certain spectral features and can lead to red near-infrared colors.

The so-called "lithium test" is less reliable to determine a low mass for young L-dwarfs.

[26] An example for a low gravity object is CWISE J0506+0738, which has a spectral type between L8γ and T0γ and probably a mass of 7±2 MJ.

Radio pulses from brown dwarfs are highly circular polarized and likely come from electron cyclotron maser instability (ECMI), which is connected to aurorae.

One suggestion is the breakdown of the co-rotation with a plasma disk, which also powers the main aurora on Jupiter.

Systems with an L-dwarf as a primary have a binary fraction of 24+6−2% with a typical separation of 5–8 astronomical units (AU).