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HD 256

From Wikipedia, the free encyclopedia
Binary star system in the constellation Cetus
HD 256
Observation data
Epoch J2000      Equinox J2000
ConstellationCetus
Right ascension00h 07m 18.26172s[1]
Declination−17° 23′ 13.2424″[1]
Apparent magnitude (V)6.20[2]
Characteristics
Spectral typeA3Vn sh[3]
Apparent magnitude (B)6.33[4]
Apparent magnitude (J)5.858[5]
Apparent magnitude (H)5.83[5]
Apparent magnitude (K)5.747[5]
B−Vcolor index0.133±0.005[2]
Astrometry
Radial velocity (Rv)−10.2±0.9[6] km/s
Proper motion (μ)RA: −7.217[1]mas/yr
Dec.: 21.155[1]mas/yr
Parallax (π)6.8882±0.1184 mas[1]
Distance474 ± 8 ly
(145 ± 2 pc)
Absolute magnitude (MV)0.01[2]
Orbit[7]
Period (P)747.6 days
Semi-major axis (a)3.08 AU
Eccentricity (e)0.23
Inclination (i)93.34°
Details[7]
A
Mass1.94±0.15 M☉
Luminosity57.3±2.0 L☉
Surface gravity (log g)3.8±0.1 cgs
Temperature9,000±100 K
Rotational velocity (v sin i)294±9 km/s
Age530±50 Myr
B
Mass1.62±0.13 M☉
Luminosity13.7±0.5 L☉
Surface gravity (log g)4.2±0.1 cgs
Temperature8,250±100 K
Rotational velocity (v sin i)200±20 km/s
Other designations
BD−18°6428,Gaia DR2 2414558084699665920,GC 103,HD 256,HIP 602,HR 10,SAO 147090,PPM 208364,2MASS J00071825-1723132[4]
Database references
SIMBADdata

HD 256 is abinary star[7] system in theequatorialconstellation ofCetus. It has a white hue and is dimly visible to the naked eye with anapparent visual magnitude of 6.20.[2] Based uponparallax measurements, the system is located at a distance of approximately 474 light years from theSun.[1] It is drifting closer with aradial velocity of −10 km/s.[6]

Originally considered a single star, it was reported to be ashell star in 1982. Circumstellar absorption lines were then found to be variable, showing a similarity to the edge-ondebris disk surroundingBeta Pictoris.[8] Thestellar classification of A2 IV/V matched anA-type star near the end of itsmain sequence lifetime, showing traits of an emergingsubgiant star phase.[9]

A 2019 study usingPIONIER (VLTI) and 32 years ofradial velocity measurements concluded that HD 256 is instead abinary star. The variable component of thespectral lines do not come fromexocomets according to this study, but rather from the binarity. Each individual star holds its own circumstellar shell. The pair have an orbital period of 2.05 years, an eccentricity of around 0.23, and a semimajor axis of3.08 AU.[7] The adjusted classification is of a rapidly rotatingmain sequence shell star of type A3Vn sh.[3]

References

[edit]
  1. ^abcdefBrown, A. G. A.; et al. (Gaia collaboration) (August 2018)."Gaia Data Release 2: Summary of the contents and survey properties".Astronomy & Astrophysics.616. A1.arXiv:1804.09365.Bibcode:2018A&A...616A...1G.doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source atVizieR.
  2. ^abcdAnderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation".Astronomy Letters.38 (5): 331.arXiv:1108.4971.Bibcode:2012AstL...38..331A.doi:10.1134/S1063773712050015.S2CID 119257644.
  3. ^abAbt, Helmut A.; Morrell, Nidia I. (1995)."The Relation between Rotational Velocities and Spectral Peculiarities among A-Type Stars".Astrophysical Journal Supplement.95: 135.Bibcode:1995ApJS...99..135A.doi:10.1086/192182.
  4. ^ab"HR 10".SIMBAD.Centre de données astronomiques de Strasbourg. Retrieved2015-03-01.
  5. ^abcCutri, Roc M.; Skrutskie, Michael F.; Van Dyk, Schuyler D.; Beichman, Charles A.; Carpenter, John M.; Chester, Thomas; Cambresy, Laurent; Evans, Tracey E.; Fowler, John W.; Gizis, John E.; Howard, Elizabeth V.; Huchra, John P.; Jarrett, Thomas H.; Kopan, Eugene L.; Kirkpatrick, J. Davy; Light, Robert M.; Marsh, Kenneth A.; McCallon, Howard L.; Schneider, Stephen E.; Stiening, Rae; Sykes, Matthew J.; Weinberg, Martin D.; Wheaton, William A.; Wheelock, Sherry L.; Zacarias, N. (2003)."VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)".CDS/ADC Collection of Electronic Catalogues.2246: II/246.Bibcode:2003yCat.2246....0C.
  6. ^abGontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system".Astronomy Letters.32 (11):759–771.arXiv:1606.08053.Bibcode:2006AstL...32..759G.doi:10.1134/S1063773706110065.S2CID 119231169.
  7. ^abcdMontesinos, B.; et al. (September 2019). "HR 10: A main-sequence binary with circumstellar envelopes around both components. Discovery and analysis".Astronomy & Astrophysics.629: A19.arXiv:1907.12441.Bibcode:2019A&A...629A..19M.doi:10.1051/0004-6361/201936180.hdl:10150/634605.ISSN 0004-6361.S2CID 198967613.
  8. ^Lagrange-Henri, A. M.; et al. (January 1990). "HR 10 : a new beta Pictoris-like star ?".Astronomy & Astrophysics.227:L13 –L16.Bibcode:1990A&A...227L..13L.ISSN 0004-6361.
  9. ^Houk, N.; Smith-Moore, M. (1988).Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Vol. 4.Bibcode:1988mcts.book.....H.
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