b Persei
{{Short description|Star in the constellation Perseus}}
{{about|b Persei|β Persei|Algol}}
{{lowercasetitle}}
{{Starbox begin
| name = b Persei
}}
{{Starbox image
|image=
{{Location mark
|image=Perseus constellation map.svg|alt=|float=center|width=280
|label=|position=right
|mark=Red circle.svg|mark_width=10|mark_link=b Persei
|x=314|y=398
}}
|caption=Location of b Persei (circled)
}}
{{Starbox observe
| epoch = J2000.0
| equino = J2000.0
| constell = Perseus
}}
{{Starbox character
| variable = Ellipsoidal{{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 = {{val|19.8|0.9}}{{cite journal | last=Wilson | first=R. E. | year=1953 | title=General Catalogue of Stellar Radial Velocities | journal=Carnegie Institute Washington D.C. Publication | publisher=Carnegie Institution for Science | bibcode=1953GCRV..C......0W | lccn=54001336 }}
| prop_mo_ra = {{val|45.42|0.40}}
| prop_mo_dec = {{val|-56.72|0.32}}
| parallax = 10.40
| p_error = 0.35
| dist_pc =
}}
{{Starbox orbit
|primary=A or Aa
|name=B or Ab
|period_unitless={{val|1.52735997|0.00000036}} days
|eccentricity=0.0
|inclination={{val|22|3}} or {{val|55|3}}
|periastron={{val|2450001.0931|0.003}}
}}
{{Starbox orbit
|primary=AB
|name=C or Ac
|period_unitless={{val|703.06|0.07}} days
|axis_unitless={{val|26.22|0.06}} mas
|inclination={{val|90.5|0.1}}
|node={{val|120.0|0.1}}
|periastron={{val|2440080|3}}
|eccentricity={{val|0.185|0.003}}
|periarg={{val|212|1}}
}}
{{Starbox detail
| component1 = A or Aa
| gravity =
| age_gyr =
}}
{{Starbox detail|no_heading=y
| component1 = B or Ab
| component2 = C or Ac
}}
{{Starbox catalog
| names = BD+49°1150, GC 5174, HD 26961, HR 1324, HIP 20070, SAO 24531
}}
{{Starbox reference
| Simbad = b+Persei
}}
{{Starbox end}}
File:BPerLightCurve.pngs for b Persei. The top panel, plotted from TESS data,{{cite web |title=MAST: Barbara A. Mikulski Archive for Space Telescopes |url=https://mast.stsci.edu/portal/Mashup/Clients/Mast/Portal.html |publisher=Space Telescope Science Institute |access-date=14 September 2022}} shows the variability of the inner binary pair. The lower panels, plotted from AAVSO data,{{cite web |title=Download Data |url=https://www.aavso.org/data-download |website=aavso.org |publisher=AAVSO |access-date=14 September 2022}} show two eclipses.]]
b Persei (also known as HD 26961) is a spectroscopic triple star in the constellation Perseus. Its apparent magnitude is 4.60, making it visible to the naked eye. It is about 320 light years away.
In addition to the primary, an A-type giant, there is a smaller and cooler companion in a 1.53 day orbit, probably an F-class star around absolute magnitude 3.0, and a more distant companion (star C or Ac) in an orbit calculated to be 702 days long. The close binary pair forms a rotating ellipsoidal variable with a 1.53 day period. Star C forms an Algol-type variable system with the close binary, showing both primary eclipses (when star C passes in front of the inner pair) and secondary eclipses (when the inner pair passes in front of star C).{{cite web |title=b Per |url=https://www.aavso.org/vsx/index.php?view=detail.top&oid=26212 |website=The International Variable Star Index |publisher=AAVSO |access-date=15 September 2022}} Timings of the eclipses show a 704.5-day period.{{cite web |url=https://mintaka.aavso.org/aavso-alert-notice-791 |title=Alert Notice 791: Anticipated secondary eclipse of b Per centered on September 29 2022 UT |website=AAVSO |access-date=2022-09-15 }}
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