LS I +61 303

LS I +61 303 is a microquasar, a binary system containing a massive star and a compact object. The compact object is a black hole candidate and is around 7,000 light-years away.

LS I +61 303
Observation data
Epoch J2000      Equinox J2000
Constellation Cassiopeia
Right ascension 02h 40m 31.6643s[1]
Declination +61° 13′ 45.592″[1]
Apparent magnitude (V) 10.61–10.83[2]
Characteristics
Spectral type B0Ve[3]
U−B color index −0.34[4]
B−V color index +0.86[4]
Variable type High-mass X-ray binary[2]
Astrometry
Radial velocity (Rv)−41.41 km/s
Proper motion (μ) RA: 0.27[5] mas/yr
Dec.: 2.38[5] mas/yr
Parallax (π)0.45 ± 0.23[1] mas
Distanceapprox. 7,000 ly
(approx. 2,000 pc)
Other designations
V615 Cas, 1RXS J024033.5+611358, TYC 4047-1917-1, HIP 12469
Database references
SIMBADdata

Discovery

LS I +61 303 is an 11th-magnitude star that was recognised as a luminous object and catalogued as an OB star in 1959.[6] It was included in the Hipparcos survey as HIP 12469 and had its parallax measured at 5.65±2.28 milliarcseconds (mas), revised to −0.29±2.99 mas in the new reduction.[5] The first Gaia data release gave a parallax of 0.45±0.23 mas.[1]

The galactic radio source GT 0236+610 was found at the same position as LS I +61 303. A gamma-ray source 2CG 135+01 was found within a degree of its position, and the MAGIC telescope confirmed that LS I +61 303 was the source of the gamma rays. Periodic X-ray outbursts also occur.[7]

Binary system

LS I +61 303 shows the spectrum of a Be star, a B0 main sequence star with disk that produces emission lines in its spectrum. Variations in its radial velocity show that it is in orbit with an unseen compact object having a mass between 1 and 4 M☉. The pair orbit every 26.496 days.[7] Although the uncertain mass of the compact object would allow it to be a neutron star, it is thought likely to be a black hole.[8]

Variability

LS I +61 303 varies slightly at optical wavelengths, but measurements going back to 1887 show no obvious period. It also shows regular X-ray outbursts coinciding with its orbital period, and strong radio variability.[9] It was given the variable star designation V615 Cassiopeiae.[2]

Microquasar

LS I +61 303 emits HE and VHE (High Energy and Very High Energy) gamma rays.[3][7] It is only one of several known star systems that produce such energetic rays. Other two systems are PSR B1259–63, LS 5039 and HESS J0632+057.

References
  1. Gaia Collaboration (2016). "Gaia Data Release 1". Astronomy & Astrophysics. 595: A2. arXiv:1609.04172. Bibcode:2016A&A...595A...2G. doi:10.1051/0004-6361/201629512. S2CID 1828208.
  2. 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. Paredes, Josep M; Ribó, Marc; Bosch-Ramon, Valentí; West, Jennifer R; Butt, Yousaf M; Torres, Diego F; Martí, Josep (2007). "Chandra Observations of the Gamma-Ray Binary LS I +61 303: Extended X-Ray Structure?". The Astrophysical Journal Letters. 664 (1): L39–L42. arXiv:0706.0877. Bibcode:2007ApJ...664L..39P. doi:10.1086/520674. S2CID 9974663.
  4. Reig, P; Fabregat, J (2015). "Long-term variability of high-mass X-ray binaries. I. Photometry". Astronomy & Astrophysics. 574: A33. arXiv:1411.7163. Bibcode:2015A&A...574A..33R. doi:10.1051/0004-6361/201425008. S2CID 119183277.
  5. van Leeuwen, F.; et al. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357. S2CID 18759600.
  6. Hardorp, J; Rohlfs, K; Slettebak, A; Stock, J (1959). "Luminous stars in the Northern Milky Way. Part I". Hamburger Sternw. 01. Bibcode:1959LS....C01....0H.
  7. Albert, J; et al. (2006). "Variable Very-High-Energy Gamma-Ray Emission from the Microquasar LS I +61 303". Science. 312 (5781): 1771–3. arXiv:astro-ph/0605549. Bibcode:2006Sci...312.1771A. doi:10.1126/science.1128177. PMID 16709745. S2CID 20981239.
  8. Massi, M; Migliari, S; Chernyakova, M (2017). "The black hole candidate LS I +61°0303". Monthly Notices of the Royal Astronomical Society. 468 (3): 3689. arXiv:1704.01335. Bibcode:2017MNRAS.468.3689M. doi:10.1093/mnras/stx778. S2CID 118894005.
  9. Gregory, P. C; Taylor, A. R; Crampton, D; Hutchings, J. B; Hjellming, R. M; Hogg, D; Hvatum, H; Gottlieb, E. W; Feldman, P. A; Kwok, S (1979). "The radio, optical, X-ray, gamma-ray star LSI +61 deg 303". Astronomical Journal. 84: 1030. Bibcode:1979AJ.....84.1030G. doi:10.1086/112508.

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