1 Persei


1 Persei (1 Per) is an eclipsing binary[3] star in the constellation Perseus. Its uneclipsed apparent magnitude is 5.49. The binary star consists of two B2 type main-sequence stars in a 25.9 day eccentric orbit.[5] The stars are surrounded by a faint cloud of gas visible in mid-infrared, although whether they are the origin of the gas or simply passing through it is unclear.

1 Persei
Perseus constellation map.svg
Red circle.svg
Location of 1 Persei (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Perseus
Right ascension 01h 51m 59.32008s[1]
Declination +55° 08′ 50.5837″[1]
Apparent magnitude (V) 5.49 - 5.74 - 5.85[2]
Spectral type B1.5V[2]
Variable type eclipsing binary[3]
Proper motion (μ) RA: 12.716(74)[1] mas/yr
Dec.: −8.410(79)[1] mas/yr
Parallax (π)2.6944 ± 0.0888 mas[1]
Distance1,210 ± 40 ly
(370 ± 10 pc)
Absolute magnitude (MV)−1.37/−1.77[4]
Primary1 Persei A
Companion1 Persei B
Period (P)25.935951±0.000003 d
Eccentricity (e)0.3768±0.0014
Inclination (i)88.048±0.002°
Periastron epoch (T)2443563.466±0.005 HJD
Argument of periastron (ω)
Semi-amplitude (K1)
97.4±0.1 km/s
Semi-amplitude (K2)
91.2±0.1 km/s
Mass6.95 M
Radius3.29 R
Luminosity2,188 L
Surface gravity (log g)4.25 cgs
Temperature21,500 K
Rotation1.45 days
Rotational velocity (v sin i)115 km/s
Mass7.42 M
Radius3.86 R
Luminosity3,311 L
Surface gravity (log g)4.14 cgs
Temperature22,000 K
Rotation1.40 days
Rotational velocity (v sin i)140 km/s
Other designations
V436 Persei, BD+54 396, HD 11241, HIP 8704, HR 533, SAO 22690
Database references

Observational historyEdit

A visual band light curve for V436 Persei, adapted from Janik et al. (2003)[4]

The possible eclipsing binary nature of 1 Persei was first noticed by Donald Kurtz in 1977 when it was used as a comparison star to test for photometric variability of HD 11408.[6] In 1979 French amateur observers succeeded in determining an orbital period of 25.9 days.[7] During the primary eclipse, the brightness drops to magnitude 5.85. In the secondary eclipses, the brightness drops to magnitude 5.74. The eclipses each last for approximately 25 hours.[2]


  1. ^ a b c d e Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. Gaia EDR3 record for this source at VizieR.
  2. ^ a b c Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S.
  3. ^ a b North, P.; et al. (1981). "1 Per: a new eclipsing binary with a long period and an elliptical orbit" (PDF). Information Bulletin on Variable Stars. 2036: 1. Bibcode:1981IBVS.2036....1N.
  4. ^ a b c d Janík, J.; et al. (2003). "Search for forced oscillations in binaries. IV. The eclipsing binary V436 Per revisited". Astronomy and Astrophysics. 408 (2): 611–619. Bibcode:2003A&A...408..611J. doi:10.1051/0004-6361:20030960.
  5. ^ Harmanec, P.; et al. (1997). "Search for forced oscillations in binaries. I. The eclipsing and spectroscopic binary V436 Persei = 1 Persei". Astronomy and Astrophysics. 319 (2): 867–880. Bibcode:1997A&A...319..867H.
  6. ^ Kurtz, D. W. (1977). "The photometric variability of 1 Per". Publications of the Astronomical Society of the Pacific. 89: 939–940. Bibcode:1977PASP...89..939K. doi:10.1086/130251.
  7. ^ Figer, Alain; Maurin, Luc (1979). "1 Persei, a low amplitude eclipsing binary, has a period of 25.939 days and an elliptical orbit". GEOS Circular on Eclipsing Binaries. 2 (EB 2). Bibcode:1979GEOCE...2.....F.