Editing Cepheid variable (section)

=== Type II Cepheids ===
{{Main|Type II Cepheid}}
[[File:Kappa Pavonis TESS lightcurve.png|thumb|Light curve of [[κ Pavonis]], a Type II cepheid, recorded by NASA's [[Transiting Exoplanet Survey Satellite]] (TESS)]]
Type II Cepheids (also termed Population II Cepheids) are [[population II]] variable stars which pulsate with periods typically between 1 and 50 days.<ref name=wallerstein02>{{cite journal |bibcode=2002PASP..114..689W |doi=10.1086/341698 |title=The Cepheids of Population II and Related Stars |date=2002 |last1=Wallerstein |first1=George |journal=[[Publications of the Astronomical Society of the Pacific]] |volume=114 |issue=797 |pages=689–699|s2cid=122225966 }}</ref><ref name=so08>{{cite journal |arxiv=0811.3636 |bibcode=2008AcA....58..293S |title=The Optical Gravitational Lensing Experiment. The OGLE-III Catalog of Variable Stars. II.Type II Cepheids and Anomalous Cepheids in the Large Magellanic Cloud |author1=Soszyński, I. |author2=Udalski, A. |author3=Szymański, M. K. |author4=Kubiak, M. |author5=Pietrzyński, G. |author6=Wyrzykowski, Ł. |author7=Szewczyk, O. |author8=Ulaczyk, K. |author9=Poleski, R. |volume=58 |date=2008 |pages=293 |journal=[[Acta Astronomica]] }}</ref> Type II Cepheids are typically [[metallicity|metal]]-poor, old (~10 Gyr), low mass objects (~half the mass of the Sun). Type II Cepheids are divided into several subgroups by period. Stars with periods between 1 and 4 days are of the [[BL Herculis variable|BL Her subclass]], 10–20 days belong to the [[W Virginis variable|W Virginis subclass]], and stars with periods greater than 20 days belong to the [[RV Tauri variable|RV Tauri subclass]].<ref name="wallerstein02" /><ref name="so08" />

Type II Cepheids are used to establish the distance to the [[Galactic Center]], [[globular clusters]], and [[galaxies]].<ref name="majaess2009" /><ref name=ku02>{{cite journal |arxiv=astro.ph/0306567 |bibcode=2003AcA....53..117K |title=The Optical Gravitational Lensing Experiment. Population II Cepheids in the Galactic Bulge |author1=Kubiak, M. |author2=Udalski, A. |volume=53 |date=2003 |pages=117 |journal=[[Acta Astronomica]]}}</ref><ref name=mat06>{{cite journal |arxiv=astro.ph/0606609 |bibcode=2006MNRAS.370.1979M |doi=10.1111/j.1365-2966.2006.10620.x |title=The period-luminosity relation for type II Cepheids in globular clusters |date=2006 |last1=Matsunaga |first1=Noriyuki |last2=Fukushi |first2=Hinako |last3=Nakada |first3=Yoshikazu |last4=Tanabé |first4=Toshihiko |last5=Feast |first5=Michael W. |last6=Menzies |first6=John W. |last7=Ita |first7=Yoshifusa |last8=Nishiyama |first8=Shogo |last9=Baba |first9=Daisuke |last10=Naoi |first10=Takahiro |last11=Nakaya |first11=Hidehiko |last12=Kawadu |first12=Takahiro |last13=Ishihara |first13=Akika |last14=Kato |first14=Daisuke |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=370 |issue=4 |pages=1979–1990 |doi-access=free |s2cid=25991504 |display-authors=8 }}</ref><ref name=feast08>{{cite journal |arxiv=0803.0466 |bibcode=2008MNRAS.386.2115F |doi=10.1111/j.1365-2966.2008.13181.x |title=The luminosities and distance scales of type II Cepheid and RR Lyrae variables |date=2008 |last1=Feast |first1=Michael W. |last2=Laney |first2=Clifton D. |last3=Kinman |first3=Thomas D. |last4=Van Leeuwen |first4=Floor |last5=Whitelock |first5=Patricia A. |journal=[[Monthly Notices of the Royal Astronomical Society]] |volume=386 |issue=4 |pages=2115–2134 |doi-access=free |s2cid=14459638 }}</ref><ref name="majaess2009b" /><ref name=majaess09c>{{cite journal |arxiv=0912.2928 |bibcode=2010JAVSO..38..100M |title=RR Lyrae and Type II Cepheid Variables Adhere to a Common Distance Relation |author1=Majaess, D. J. |volume=38 |issue=1 |date=2010 |pages=100–112 |journal=[[The Journal of the American Association of Variable Star Observers]]}}</ref><ref name=mat09>{{cite journal |arxiv=0904.4701 |bibcode=2009MNRAS.397..933M |doi=10.1111/j.1365-2966.2009.14992.x |title=Period-luminosity relations for type II Cepheids and their application |date=2009 |last1=Matsunaga |first1=Noriyuki |last2=Feast |first2=Michael W. |last3=Menzies |first3=John W. |journal=[[Monthly Notices of the Royal Astronomical Society ]]|volume=397 |issue=2 |pages=933–942 |doi-access=free |s2cid=13912466 }}</ref>