Editing Brown dwarf (section)

==== Secondary features ====
{| class="wikitable floatright" style="width: 26em"
|+ Brown dwarf spectral types
|-
! colspan="2" |Secondary features
|-
|pec
|This suffix (e.g. L2pec) stands for "peculiar".<ref>{{cite web|url=http://simbad.u-strasbg.fr/simbad/sim-display?data=sptypes|title=Spectral type codes|website=simbad.u-strasbg.fr|access-date=2020-03-06}}</ref>
|-
|sd
|This prefix (e.g. sdL0) stands for [[subdwarf]] and indicates a low metallicity and blue color.<ref name=":5">{{cite journal |last1=Burningham |first1=Ben |last2=Smith |first2=Leigh |last3=Cardoso |first3=Cátia V. |last4=Lucas |first4=Philip W. |last5=Burgasser |first5=Adam J. |last6=Jones |first6=Hugh R. A. |last7=Smart |first7=Richard L. |date=May 2014 |title=The discovery of a T6.5 subdwarf |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=440 |issue=1 |pages=359–364 |doi=10.1093/mnras/stu184 |doi-access=free |arxiv=1401.5982 |bibcode=2014MNRAS.440..359B |s2cid=119283917 |issn=0035-8711 }}</ref>
|-
|β
|Objects with the beta (β) suffix (e.g. L4β) have an intermediate surface gravity.<ref name=":6">{{cite journal |last1=Cruz |first1=Kelle L. |last2=Kirkpatrick |first2=J. Davy |last3=Burgasser |first3=Adam J. |date=February 2009 |title=Young L Dwarfs Identified in the Field: A Preliminary Low-Gravity, Optical Spectral Sequence from L0 to L5 |journal=The Astronomical Journal |volume=137 |issue=2 |pages=3345–3357 |doi=10.1088/0004-6256/137/2/3345 |arxiv=0812.0364 |bibcode=2009AJ....137.3345C |s2cid=15376964 |issn=0004-6256 }}</ref>
|-
|γ
|Objects with the gamma (γ) suffix (e.g. L5γ) have a low surface gravity.<ref name=":6"/>
|-
|red
|The red suffix (e.g. L0red) indicates objects without signs of youth, but high dust content.<ref name=":7">{{cite journal |last1=Looper |first1=Dagny L. |last2=Kirkpatrick |first2=J. Davy |last3=Cutri |first3=Roc M. |last4=Barman |first4=Travis |last5=Burgasser |first5=Adam J. |last6=Cushing |first6=Michael C. |last7=Roellig |first7=Thomas |last8=McGovern |first8=Mark R. |last9=McLean |first9=Ian S. |last10=Rice |first10=Emily |last11=Swift |first11=Brandon J. |date=October 2008 |title=Discovery of Two Nearby Peculiar L Dwarfs from the 2MASS Proper-Motion Survey: Young or Metal-Rich? |journal=Astrophysical Journal |volume=686 |issue=1 |pages=528–541 |doi=10.1086/591025 |arxiv=0806.1059 |bibcode=2008ApJ...686..528L |s2cid=18381182 |issn=0004-637X }}</ref>
|-
|blue
|The blue suffix (e.g. L3blue) indicates unusual blue near-infrared colors for L dwarfs without obvious low metallicity.<ref name=":8">{{cite journal |last1=Kirkpatrick |first1=J. Davy|last2=Looper |first2=Dagny L. |last3=Burgasser |first3=Adam J. |last4=Schurr |first4=Steven D. |last5=Cutri |first5=Roc M. |last6=Cushing |first6=Michael C. |last7=Cruz |first7=Kelle L. |last8=Sweet |first8=Anne C. |last9=Knapp |first9=Gillian R. |last10=Barman |first10=Travis S. |last11=Bochanski |first11=John J. |date=September 2010 |title=Discoveries from a Near-infrared Proper Motion Survey Using Multi-epoch Two Micron All-Sky Survey Data |journal=Astrophysical Journal Supplement Series |volume=190 |issue=1 |pages=100–146 |doi=10.1088/0067-0049/190/1/100 |arxiv=1008.3591 |bibcode=2010ApJS..190..100K |s2cid=118435904 |issn=0067-0049 }}</ref>
|}
Young brown dwarfs have low [[Surface gravity|surface gravities]] because they have larger radii and lower masses than the field stars of similar spectral type. These sources are noted by a letter ''beta'' (β) for intermediate surface gravity or ''gamma'' (γ) for low surface gravity. Indicators of low surface gravity include weak CaH, K I and Na I lines, as well as a strong VO line.<ref name=":6"/> ''Alpha'' (α) denotes normal surface gravity and is usually dropped. Sometimes an extremely low surface gravity is denoted by a delta (δ).<ref name=":8"/> The suffix "pec" stands for "peculiar"; this suffix is still used for other features that are unusual, and summarizes different properties, indicating low surface gravity, subdwarfs and unresolved binaries.<ref name="Faherty 10">{{cite journal |last1=Faherty |first1=Jacqueline K. |last2=Riedel |first2=Adric R. |last3=Cruz |first3=Kelle L. |last4=Gagne |first4=Jonathan |last5=Filippazzo |first5=Joseph C. |last6=Lambrides |first6=Erini |last7=Fica |first7=Haley |last8=Weinberger |first8=Alycia |last9=Thorstensen |first9=John R. |last10=Tinney |first10=Chris G. |last11=Baldassare |first11=Vivienne |date=July 2016 |title=Population Properties of Brown Dwarf Analogs to Exoplanets |journal=Astrophysical Journal Supplement Series |volume=225 |issue=1 |pages=10 |doi=10.3847/0067-0049/225/1/10 |arxiv=1605.07927 |bibcode=2016ApJS..225...10F |s2cid=118446190 |issn=0067-0049 |doi-access=free }}</ref> The prefix sd stands for [[subdwarf]] and only includes cool subdwarfs. This prefix indicates a low [[metallicity]] and kinematic properties that are more similar to [[Galactic halo|halo]] stars than to [[Thin disk|disk]] stars.<ref name=":5"/> Subdwarfs appear bluer than disk objects.<ref>{{cite web |url=http://www.stsci.edu/~inr/cmd.html |title=Colour-magnitude data |first=Neill |last=Reid <!-- |date=15/07/02 (unless a typo, dates to ca. 2004, otherwise 2002 --> |website=www.stsci.edu |access-date=2020-03-06 }}</ref> The red suffix describes objects with red color, but an older age. This is not interpreted as low surface gravity, but as a high dust content.<ref name=":7"/><ref name=":8"/> The blue suffix describes objects with blue [[near-infrared]] colors that cannot be explained with low metallicity. Some are explained as L+T binaries, others are not binaries, such as [[2MASS J11263991−5003550]] and are explained with thin and/or large-grained clouds.<ref name=":8"/>