Editing Subgiant (section)

==Variability==
Several types of [[variable star]] include subgiants:
* [[Beta Cephei variable]]s, early B main sequence and subgiant stars
* [[Slowly pulsating B-type star]]s, mid to late B main sequence and subgiant stars
* [[Delta Scuti variable]]s, late A and early F main sequence and subgiant stars

Subgiants more massive than the sun cross the [[Cepheid variable|Cepheid]] [[instability strip]], called the ''first crossing'' since they may cross the strip again later on a [[blue loop]]. In the {{solar mass|2 – 3}} range, this includes Delta Scuti variables such as [[Beta Cassiopeiae|β Cas]].<ref name=ayres1084>{{cite journal|bibcode=1984iue..prop.1747A|title=A Far-Ultraviolet Study of the Bright Delta Scuti Variable Beta Cassiopeia|journal=IUE Proposal ID #DSGTA|last1=Ayres|first1=Thomas R.|year=1984|page=1747}}</ref>  At higher masses the stars would pulsate as [[Classical Cepheid variables]] while crossing the instability strip, but massive subgiant evolution is very rapid and it is difficult to detect examples. [[SV Vulpeculae]] has been proposed as a subgiant on its first crossing<ref name=luck>{{cite journal|bibcode=2001A&A...373..589L|title=SV Vulpeculae: A first crossing Cepheid?|journal=Astronomy and Astrophysics|volume=373|issue=2|pages=589|last1=Luck|first1=R. E.|last2=Kovtyukh|first2=V. V.|last3=Andrievsky|first3=S. M.|year=2001|doi=10.1051/0004-6361:20010615|doi-access=free}}</ref> but was subsequently determined to be on its second crossing <ref name=turner>{{cite journal|bibcode=2004A&A...423..335T|title=On the crossing mode of the long-period Cepheid SV Vulpeculae|journal=Astronomy and Astrophysics|volume=423|last1=Turner|first1=D. G.|last2=Berdnikov|first2=L. N.|year=2004|doi=10.1051/0004-6361:20040163|pages=335–340|doi-access=free}}</ref>