HD 41004

HD 41004 is a visual binary[4] star system in the southern constellation of Pictor. It is too faint to be visible to the naked eye, having a combined apparent visual magnitude of 8.65.[2] The two components have a magnitude difference of 3.7, and share a common proper motion[4] with an angular separation of 0.30″, as of 2018.[3] The distance to this system is approximately 136 light years based on parallax.[1] It is drifting further away from the Sun with a radial velocity of +42.5 km/s, having come to within 44.5 ly some 831,000 years ago.[2]

HD 41004
Observation data
Epoch J2000      Equinox J2000
Constellation Pictor
Right ascension 05h 59m 49.64736s[1]
Declination −48° 14′ 22.8058″[1]
Apparent magnitude (V) 8.65[2] (8.82 + 12.51)[3]
Characteristics
Spectral type K1V + M2V[4]
B−V color index 0.887±0.013[2]
Astrometry
Radial velocity (Rv)+42.5±0.5[2] km/s
Proper motion (μ) RA: −41.520±0.485[1] mas/yr
Dec.: +59.652±0.556[1] mas/yr
Parallax (π)24.0437 ± 0.2635[1] mas
Distance136 ± 1 ly
(41.6 ± 0.5 pc)
Absolute magnitude (MV)5.60[2]
Details[5]
A
Mass0.89±0.07 M☉
Radius1.04+0.02
−0.03[1] R☉
Luminosity0.629±0.008[1] L☉
Surface gravity (log g)4.34±0.11 cgs
Temperature5,255±52 K
Metallicity [Fe/H]0.15±0.03 dex
Rotational velocity (v sin i)1.0±1.2[6] km/s
B
Mass0.4[7] M☉
Other designations
CD−48°2083, HD 41004, HIP 28393, SAO 217660, PPM 310291, WDS J05598-4814[8]
Database references
SIMBADdata

The primary, component A, is a K-type main-sequence star with a stellar classification of K1V[4] and a visual magnitude of 8.82.[3] Torres et al. (2006) classed it as a K1IV star,[6] suggesting it is a subgiant star that is evolving off the main sequence. It has 89%[4] of the mass of the Sun and 104%[1] of the Sun's radius. The star is radiating 63%[1] of the Sun's luminosity from its photosphere at an effective temperature of 5,255 K.[4] Its smaller companion, designated component B, is a red dwarf with spectral type M2V[4] and apparent magnitude 12.33. It has a projected separation of 23 AU from the primary.[4]

Companions

A planet, HD 41004 Ab, was discovered by Zucker et al., in but not published until 2004. It has a mass >2.56 times that of Jupiter. It orbits the primary star at a separation of 1.70 astronomical units, taking 2.64 years with a high eccentricity of 0.74.

The HD 41004 A planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b >2.56 MJ 1.70 963 0.74 — —
HD 41004 Bb
Discovery
Discovered byZucker et al.
Discovery date2004
radial velocity
Orbital characteristics
Periastron0.0163 AU
Apoastron0.0191 AU
0.0177 AU
Eccentricity0.081±0.012
1.3283±1.2e-5 d
145 km/s
0.411 mas
178.5±7.8°
2452434.88±0.0029 JD
Semi-amplitude6114±71 m/s
Physical characteristics
Mass~16 MJ (most probable)[4]
< ~25 MJ[4]

    HD 41004 Bb is a brown dwarf that at the time of the discovery was orbiting closer to the secondary star than any known extrasolar planet or brown dwarf (a=0.0177 AU), at only 145 km/s, because of its low-mass parent star, taking 1.3 days. Its orbit is circular despite the gravitational effect of HD 41004 A because of the tidal effect of the nearby star HD 41004 B.[9] A search for cyclotron radiation from the magnetosphere of Bb in 2020 did not find any, indicating the planet is either weakly magnetized, or the emission cone did not point to Earth at the time of observation.[10]

    References
    1. Brown, 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 at VizieR.
    2. Anderson, 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. Mason, B. D.; et al. (2014). "The Washington Visual Double Star Catalog". Bibcode:2001AJ....122.3466M. doi:10.1086/323920. Retrieved 2015-07-22. Cite journal requires |journal= (help)
    4. Zucker, S.; et al. (November 2004). "Multi-order TODCOR: Application to observations taken with the CORALIE echelle spectrograph. II. A planet in the system HD 41004". Astronomy and Astrophysics. 426 (2): 695–698. Bibcode:2004A&A...426..695Z. doi:10.1051/0004-6361:20040384.
    5. Sousa, S. G.; et al. (November 2018). "SWEET-Cat updated. New homogenous spectroscopic parameters". Astronomy & Astrophysics. 620: 13. arXiv:1810.08108. Bibcode:2018A&A...620A..58S. doi:10.1051/0004-6361/201833350. S2CID 119374557. A58.
    6. Torres, C. A. O.; et al. (December 2006). "Search for associations containing young stars (SACY). I. Sample and searching method". Astronomy and Astrophysics. 460 (3): 695–708. arXiv:astro-ph/0609258. Bibcode:2006A&A...460..695T. doi:10.1051/0004-6361:20065602. S2CID 16080025.
    7. Quarles, Billy; Li, Gongjie; Kostov, Veselin; Haghighipour, Nader (2020), "Orbital Stability of Circumstellar Planets in Binary Systems", The Astronomical Journal, 159 (3): 80, arXiv:1912.11019, Bibcode:2020AJ....159...80Q, doi:10.3847/1538-3881/ab64fa, S2CID 209444271
    8. "HD 41004". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-07-13.
    9. Santos, N. C.; et al. (2002). "The CORALIE survey for southern extra-solar planets. IX. A 1.3-day period brown dwarf disguised as a planet". Astronomy and Astrophysics. 392 (1): 215–229. arXiv:astro-ph/0206213. Bibcode:2002A&A...392..215S. doi:10.1051/0004-6361:20020876. S2CID 14195872.
    10. In search of radio emission from exoplanets: GMRT observations of the binary system HD 41004, 2020, arXiv:2011.06843
    • "HD 41004 A". The Extrasolar Planets Encyclopaedia. Retrieved 2008-07-21.
    • "HD 41004 B". The Extrasolar Planets Encyclopaedia. Retrieved 2008-07-21.

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