Epsilon Octantis

{{Short description|Variable star in the constellation Octans}}

{{Starbox begin

| name = ε Octantis

}}

{{Starbox image

| image=

{{Location mark

|image=Octans constellation map.svg|alt=|float=center|width=280

|label=|position=right

|mark=Red circle.svg|mark_width=10|mark_link=Epsilon Octantis

|x=463|y=455

}}

| caption=Location of ε Octantis (circled)

}}

{{Starbox observe

| epoch = J2000

| constell = Octans

| ra = {{RA|22|20|01.67970}}{{cite journal | arxiv=0708.1752 | bibcode=2007A&A...474..653V | doi=10.1051/0004-6361:20078357 | title=Validation of the new Hipparcos reduction | journal=Astronomy and Astrophysics | volume=474 | issue=2 | pages=653–664 | year=2007 | last1=Van Leeuwen | first1=F. | s2cid=18759600 }} [http://vizier.u-strasbg.fr/viz-bin/VizieR-S?HIP%20110256 Vizier catalog entry]

| dec = {{DEC|-80|26|23.0947}}

| appmag_v = 4.58 - 5.30

}}

{{Starbox character

| class = M5III{{cite journal | bibcode=1995yCat.5050....0H | title=VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991) | journal=VizieR On-line Data Catalog: V/50. Originally Published in: 1964BS....C......0H | volume=5050 | last1=Hoffleit | first1=D. | last2=Warren | first2=W. H. | year=1995 }}

| b-v = +1.47{{cite journal | bibcode=2006yCat.2168....0M | title=VizieR Online Data Catalog: Homogeneous Means in the UBV System (Mermilliod 1991) | journal=VizieR On-line Data Catalog: II/168. Originally Published in: Institut d'Astronomie | volume=2168 | last1=Mermilliod | first1=J. C. | year=2006 }}[http://vizier.u-strasbg.fr/viz-bin/VizieR-4?-source=II/168/ubvmeans&LID=%2B100210967 Vizier catalog entry]

| u-b = +1.18

| variable = SRb{{cite journal | bibcode=2009yCat....102025S |title=VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)|journal=VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S|volume=1|display-authors=etal|last1=Samus|first1=N. N.|last2=Durlevich|first2=O. V.|year=2009}}

}}

{{Starbox astrometry

| radial_v = +11.70{{Cite journal | doi=10.1134/S1063773706110065 | bibcode=2006AstL...32..759G| title=Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system| journal=Astronomy Letters| volume=32| issue=11| pages=759–771| year=2006| last1=Gontcharov| first1=G. A.|arxiv = 1606.08053 | s2cid=119231169}}

| prop_mo_ra = +56.81

| prop_mo_dec = −43.47

| parallax = 11.22

| p_error = 0.23

| parallax_footnote =

| absmag_v = +0.34{{cite journal | bibcode=2012AstL...38..331A | doi=10.1134/S1063773712050015 | arxiv=1108.4971 | title=XHIP: An extended hipparcos compilation | journal=Astronomy Letters | volume=38 | issue=5 | pages=331 | year=2012 | last1=Anderson | first1=E. | last2=Francis | first2=Ch. | s2cid=119257644 }} [http://vizier.u-strasbg.fr/viz-bin/VizieR-4?-source=V/137D/XHIP&HIP=110256 Vizier catalog entry]

}}

{{Starbox detail

| mass = 1.34{{cite journal | bibcode=1999A&A...352..555A | arxiv=astro-ph/9911002 | title=Fundamental parameters of nearby stars from the comparison with evolutionary calculations: Masses, radii and effective temperatures | journal=Astronomy and Astrophysics | volume=352 | pages=555–562 | last1=Allende Prieto | first1=C. | last2=Lambert | first2=D. L. | year=1999 }} [http://vizier.u-strasbg.fr/viz-bin/VizieR-4?-source=J/A%2bA/352/555/table1&Name=HIP110256 Vizier catalog entry]

| radius = {{Val|112|15}}{{citation | title=VLTI/AMBER observations of cold giant stars: atmospheric structures and fundamental parameters | display-authors=1 | last1=Arroyo-Torres | first1=B. | last2=Martí-Vidal | first2=I. | last3=Marcaide | first3=J. M. | last4=Wittkowski | first4=M. | last5=Guirado | first5=J. C. | last6=Hauschildt | first6=P. H. | last7=Quirrenbach | first7=A. | last8=Fabregat | first8=J. | journal=Astronomy & Astrophysics | volume=566 | id=A88 | pages=11 | date=June 2014 | doi=10.1051/0004-6361/201323264 | bibcode=2014A&A...566A..88A | arxiv=1404.7384 | s2cid=16778588 }}

| temperature = {{Val|3560|264|fmt=commas}}

| luminosity = 1,819

| gravity = 2.15

}}

{{Starbox catalog

| names = {{odlist | name=BO Oct | B=ε Oct | CD=−81°831 | FK5=839 | HD=210967 | HIP=110256 | HR=8481 | SAO=258928 | GC=31166 }}

}}

{{Starbox reference

| Simbad = Epsilon+Octantis

}}

{{Starbox end}}

Epsilon Octantis, Latinized from ε Octantis, is a star in the southern circumpolar constellation of Octans. It is a faintly visible to the naked eye with an apparent visual magnitude of about 5. The annual parallax shift of 11.22 mas yields a distance estimate of around 291 light years. It is moving further from the Sun with a radial velocity of +11.7 km/s.

File:EpsOctLightCurve.png for Epsilon Octantis, plotted from Hipparcos data{{cite web

| url=https://cdsarc.cds.unistra.fr/viz-bin/ftp-index?/ftp/cats/more/HIP/cdroms/cats

| website=Centre de Données astronomiques de Strasbourg | title=/ftp/cats/more/HIP/cdroms/cats

| publisher=Strasbourg astronomical Data Center | access-date=15 October 2022}}]]

This is an evolved, cool red giant star with a stellar classification of class M5III. It is a semiregular variable with a magnitude range of 4.58 to 5.30 and a (poorly defined) period around 55 days. The star has 1.34 times the mass of the Sun and has expanded to around 112 times the Sun's radius. It is radiating 1,819 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,560 K.

Epsilon Octantis was found to be variable on a survey of the southern sky conducted by the Bamberg observatory, which was reported in 1966.{{cite journal |bibcode=1966IBVS..120....1S |title=Bright Southern BV-Stars |last1=Strohmeier |first1=W. |last2=Fischer |first2=H. |last3=Ott |first3=H. |journal=Information Bulletin on Variable Stars |year=1966 |volume=120 |page=1 }} In 1972, it was assigned the variable star designation BO Octantis,{{cite journal | last1=Kukarkin | first1=B. V. | last2=Kholopov | first2=P. N. | last3=Kukarkina | first3=N. P. | last4=Perova | first4=N. B. | title=58th Name-List of Variable Stars | journal=Information Bulletin on Variable Stars | date=1 September 1972 | issn=0374-0676 | volume=717 | pages=1 | bibcode=1972IBVS..717....1K }} although this is now recognised as a mistake since stars with Bayer designations are not given a separate variable star designation.

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