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
Other designations
CD−48°2083, HD 41004, HIP 28393, SAO 217660, PPM 310291, WDS J05598-4814[7]
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

In 2003 a planet HD 41004 Ab was first discovered by Zucker et al., 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.[8]

    gollark: I also wonder why most hatcheries are closed-source.
    gollark: I mean it wouldn't be that bad.
    gollark: Not really, no.
    gollark: Oh, yes, they would lose the stored dragons, wouldn't they.
    gollark: If they don't have backups, they're idiots anyway.

    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.
    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: 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. 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.
    7. "HD 41004". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-07-13.
    8. 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.
    • "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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