9 Cephei

{{Short description|Star in the constellation Cepheus}}

{{Starbox begin

| name = 9 Cephei

}}

{{Starbox image

| image=

{{Location mark

|image=Cepheus constellation map.svg|alt=|float=center|width=260

|label=|position=right

|mark=Red circle.svg|mark_width=10|mark_link=9 Cep

|x=760|y=922

}}

|caption=Location of 9 Cephei (circled)

}}

{{Starbox observe

| epoch = J2000.0

| constell = Cepheus

| ra= {{RA|21|37|55.22469}}

| dec= {{DEC|+62|04|54.9825}}

| appmag_v = 4.69 - 4.78

}}

{{Starbox character

| class = B2 Ib

| b-v = +0.30

| u-b = −0.54

| variable = α Cyg

}}

{{Starbox astrometry

| radial_v = −13.50 ± 0.8

| prop_mo_ra = −1.64 ± 0.17

| prop_mo_dec = −3.02 ± 0.16

| parallax = 0.48

| p_error = 0.14

| parallax_footnote =

| dist_pc = 950

| absmag_v = −6.44

}}

{{Starbox detail

| component1 = Searle et al 2008

| mass = 21

| radius = 39.8

| gravity = 2.50

| luminosity = 151,000

| temperature = 18,000

| metal =

| rotation =

| rotational_velocity = 73

| age =

| age_gyr =

| component2 = Markova & Puls 2008{{cite journal|bibcode=2008A&A...478..823M|arxiv=0711.1110|title=Bright OB stars in the Galaxy. IV. Stellar and wind parameters of early to late B supergiants|journal=Astronomy and Astrophysics|volume=478|issue=3|pages=823|last1=Markova|first1=N.|last2=Puls|first2=J.|year=2008|doi=10.1051/0004-6361:20077919|s2cid=14510634}}

| mass2 = 12

| radius2 = 32

| gravity2 = 2.50

| luminosity2 = 129,000

| temperature2 = 19,200

| metal2 =

| rotation2 =

| rotational_velocity2 = 45

| age2 =

| age_gyr2 =

}}

{{Starbox catalog

| names = 9 Cephei, V337 Cephei, HD 206165, HR 8279, HIP 106801, BD+61°2169, 2MASS J21375521+6204548, GSC 04253-02243

}}

{{Starbox reference

| Simbad=HD+206165

}}

{{Starbox end}}

9 Cephei (9 Cep), also known as V337 Cephei, is a variable star in the constellation Cepheus. It is visible to the naked eye.

File:V337CepLightCurve.png for V337 Cephei, plotted from TESS data]]

In 1967, Graham Hill announced his discovery that 9 Cephei is a variable star. 9 Cephei was given the name V337 Cephei and classified as an α Cygni variable in 1979.{{cite journal|bibcode=1979IBVS.1581....1K|title=64th Name-List of Variable Stars|journal=Information Bulletin on Variable Stars|volume=1581|pages=1|last1=Kholopov|first1=P. N.|last2=Kukarkina|first2=N. P.|last3=Perova|first3=N. B.|year=1979}} It varies irregularly between magnitude 4.69 and 4.78. A study of the Hipparcos satellite photometry showed an amplitude of 0.56 magnitudes, but could find no periodicity.{{cite journal|bibcode=2009A&A...507.1141L|title=A systematic study of variability among OB-stars based on HIPPARCOS photometry|journal=Astronomy and Astrophysics|volume=507|issue=2|pages=1141|last1=Lefèvre|first1=L.|last2=Marchenko|first2=S. V.|last3=Moffat|first3=A. F. J.|last4=Acker|first4=A.|year=2009|doi=10.1051/0004-6361/200912304|doi-access=free}}

9 Cephei is considered to be a member of the Cepheus OB2 stellar association, a scattering of massive bright stars around a thousand parsecs away in the southern part of the constellation Cepheus.

Calculations of the physical properties of 9 Cephei vary considerably even from broadly similar observational data. Modelling using the non-LTE line-blanketed CMFGEN atmospheric code gives a temperature of 18,000 K, radius of {{solar radius|40}}, luminosity of {{solar luminosity|151,000}}, and mass of {{solar mass|21}}. Calculations using the FASTWIND model give gives a temperature of 19,200 K, radius of {{solar radius|32}}, luminosity of {{solar luminosity|129,000}}, and mass of {{solar mass|12}}.