27 Cygni

{{about|b¹ Cygni|other stars with this Bayer designation|b Cygni}}

{{Starbox begin

| name = 27 Cygni

}}

{{Starbox image

| image = 250px

| caption = A light curve for V2008 Cygni, plotted from Hipparcos data

}}

{{Starbox observe

| epoch = J2000

| constell = Cygnus

| ra = {{RA|20|06|21.76743}}

| dec = {{DEC|+35|58|20.8875}}

| appmag_v = 5.38

}}

{{Starbox character

| type = subgiant

| class = G8.5 IVa

| b-v = +0.85

| u-b =

| variable = RS CVn

}}

{{Starbox astrometry

| radial_v = {{Val|−32.98|0.09}}

| prop_mo_ra = −225.032

| prop_mo_dec = −440.042

| parallax = 41.7718

| p_error = 0.0845

| parallax_footnote =

| absmag_v = 3.48

}}

{{Starbox detail

| source =

| mass = {{Val|1.26|0.03}}

| radius = {{Val|2.51|0.05}}

| luminosity = {{Val|4.07|0.50|0.44}}

| temperature = {{Val|5108|26|fmt=commas}}

| gravity = {{Val|3.74|0.07}}

| metal_fe = {{Val|−0.02|0.05}}

| rotational_velocity = {{Val|1.78|0.23}}

| age_gyr = {{Val|4.34|0.40}}

}}

{{Starbox catalog

| names = {{odlist | V=V2008 Cygni | B=b¹ Cygni | F=27 Cygni | BD=+35°3959 | HD=191026 | HIP=99031 | HR=7689 | SAO=69413 | WDS=J20064+3558A }}

}}

{{Starbox reference

| Simbad=27+Cyg

}}

27 Cygni is a subgiant star in the northern constellation of Cygnus. It is faintly visible to the naked eye with an apparent visual magnitude of 5.38. The distance to this system, as estimated from its annual parallax shift of {{Val|41.77|ul=mas}}, is 78.1 light-years. At that distance, the visual magnitude is diminished by an extinction of 0.05 due to interstellar dust. It is moving closer to the Earth with a heliocentric radial velocity of −33 km/s, and has a relatively high proper motion, traversing the celestial sphere at the rate of {{Val|0.495|ul=arcsecond}} per year.

27 Cygni is a G-type subgiant with a stellar classification of G8.5 IVa, a star that has used up its core hydrogen and is starting to expand. It was found to be slightly variable by Percy et al. (1986), changing by up to 0.05 in visual magnitude with a characteristic time scale of 50–60 days. Further observations suggested a possible rotation period of around 42 days. Samus et al. (2017) classify it as a suspected RS Canum Venaticorum variable, meaning that it is a close binary star whose components have star-spots that cause rotationally-modulated variations in brightness. It has been given the variable star designation V2008 Cygni.

27 Cygni is listed in multiple star catalogues with three faint companions within one arc-minute. The two closer ones are unrelated background objects, while the third has a similar distance and space motion and is described as a common proper motion companion.

References

{{reflist|refs=

{{cite web |title=Hipparcos Tools Interactive Data Access |url=https://www.cosmos.esa.int/web/hipparcos/interactive-data-access |website=Hipparcos |publisher=ESA |access-date=8 December 2021}}

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{{citation

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| volume=71 | pages=245 | year=1989 | postscript=.

| bibcode=1989ApJS...71..245K | doi=10.1086/191373 }}

{{citation

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| last3=Bozic | first3=H. | last4=Harmanec | first4=P.

| last5=Horn | first5=J. | last6=Koubsky | first6=P.

| last7=Kriz | first7=S. | last8=Kelsey | first8=L. A.

| last9=Hoff | first9=D. B. | last10=Landis | first10=H. J.

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| display-authors=1 | journal=Information Bulletin on Variable Stars

| volume=2891 | page=1 | date=May 1986

| bibcode=1986IBVS.2891....1P | postscript=. }}

{{citation

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| journal=The Journal of the American Association of Variable Star Observers

| volume=18 | issue=1 | pages=36–38 | date=June 1989

| bibcode=1989JAVSO..18...36E | postscript=. }}

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| journal=Monthly Notices of the Royal Astronomical Society

| volume=389 | issue=2 | pages=869–879 | date=September 2008

| doi=10.1111/j.1365-2966.2008.13596.x | doi-access=free | bibcode=2008MNRAS.389..869E

| arxiv=0806.2878 | s2cid=14878976 | postscript=. }}

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| title=Stellar parameters and chemical abundances of 223 evolved stars with and without planets

| display-authors=1 | journal=Astronomy & Astrophysics

| volume=574 | pages=A50 | year=2015

| bibcode=2015A&A...574A..50J | arxiv=1410.6422

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| title=A Catalog of Northern Stars with Annual Proper Motions Larger than 0.15" (LSPM-NORTH Catalog)

| journal=The Astronomical Journal

| volume=129 | issue=3 | pages=1483–1522 | date=March 2005

| doi=10.1086/427854 | bibcode=2005AJ....129.1483L

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}}

Category:G-type subgiants

Category:RS Canum Venaticorum variables

Category:Cygnus (constellation)

Cygni, b1

Cygni, 27

Category:Durchmusterung objects