# HD 114613

Observation data Constellation Epoch J2000.0      Equinox J2000.0 A star chart of the constellation of Centaurus showing the position of HD 114613. Centaurus 13h 12m 03.19s[1] −37° 48′ 10.89″[1] 4.852 ± 0.011[2] G3IV[3][note 1] 0.659 ± 0.020[2] Radial velocity (Rv) -15.0 ± 0.9 km/s Proper motion (μ) RA: -381.72 ± 0.31[1] mas/yr Dec.: 45.75 ± 0.20[1] mas/yr Parallax (π) 48.38 ± 0.29[1] mas Distance 67.4 ± 0.4 ly (20.7 ± 0.1 pc) Absolute magnitude (MV) 3.276 ± 0.024[note 2] Mass 1.25 ± 0.03[4] M☉ Radius 2.01 ± 0.06[4] R☉ Luminosity 4.057 ± 0.014[5] L☉ Surface gravity (log g) 3.97 ± 0.02[5] cgs Temperature 5729 ± 17[5] K Metallicity [Fe/H] 0.19 ± 0.01[5] dex Rotation 34.1 ± 3.5 days[6] Rotational velocity (v sin i) 2.4 ± 0.5[7] km/s Age 5.20 ± 0.24[4] Gyr HIP 64408, Gliese 501.2, HR 4979 SIMBAD data

HD 114613 (Gliese 501.2) is a fifth magnitude yellow subgiant that lies approximately 67 light-years away in the constellation of Centaurus. The star is host to a long-period giant planet, and may possibly be orbited by more.

## Stellar characteristics

The position of HD 114613 on the Hertzsprung-Russell diagram. The star lies significantly above the main sequence.

HD 114613 is a bright star that lies about eight arcminutes south-east of Iota Centauri, towards the middle of Centaurus. Though it is fairly easily observable with the naked eye, the star does not have a Bayer or Flamsteed designation as the constellation of Centaurus contains many brighter stars.

The B-V colour and spectroscopic temperature of HD 114613 indicate that it has a spectral type of G3. This means that the star is only 50 kelvin cooler than the Sun, giving it the yellow hue typical of G-type stars. On the Hertzsprung-Russell diagram (left) the star lies significantly above the main sequence, and is close to the subgiant branch; this means that HD 114613 has depleted the hydrogen in its core through nuclear fusion, and is increasing in luminosity and radius while decreasing in temperature as it moves towards the giant branch. The cooling of the star as it evolves means that it had an earlier spectral type when on the main sequence, probably close to the F9V Iota Horologii.

As HD 114613 is ending hydrogen fusion, the star must be fairly old. When combined with a spectroscopically-derived mass of 1.25 ± 0.03 M and a surface gravity of log 3.95 ± 0.03 g the implied age of the star is 5.20 ± 0.24 billion years,[4] making it slightly older than the Sun. Though stellar metallicities typically decrease with increasing stellar age, within the age range of the thin disk a wide range of metallicities are common; HD 114613's high iron abundance of 0.19 ± 0.01 dex (155 ± 4% of the solar abundance) is therefore not unusual. The rate of giant planet occurrence for Fe/H = 0.2 dex stars is about 15%,[8] which makes it fairly unsurprising that the star hosts a giant planet.

Somewhat peculiarly for a star that both had an earlier spectral type than the Sun and is currently a subgiant, HD 114613 has a magnetic cycle.[6] With a period of 897 ± 61 days, the star's magnetic cycle is about four-and-a-half times shorter than the Solar magnetic cycle and is one of the shortest magnetic cycles known.

## Planet searches

Being bright and solar-type, HD 114613 is an attractive target for radial velocity (RV)-based planet searches.

HD 114613 was one of the 37 targets of the first RV-based planet search in the southern hemisphere, the ESO-CES survey that spanned between 1992 and 1998.[9] This survey did not detect any companion with several Jovian masses out to a few AU. An extension of this survey to the HARPS spectrograph provides further constraint, suggesting that there are no Jupiter-mass companions out to about 5 AU.[10]

HD 114613 is included in the samples of the ESO-CORALIE[8] and AAT-UCLES[11] planet searches that both began in 1998. Seemingly finding the star to be RV-stable and suitable for higher precision, HD 114613 was included in a subset of the CORALIE sample that became the sample of the ESO-HARPS high precision planet search that began in 2004,[5] while the star was elevated in importance in the AAT sample in 2005.[12][13] Though apparently not included in its main sample, HD 114613 is included in the sample of the Keck-HIRES Eta-Earth low-mass planet search that also began in 2004.[14]

### Planetary system

In Wittenmyer et al. 2012,[15] HD 114613 is indicated to be a low-mass planet host. Though this references a Tuomi et al. 2012 (Tuomi, M., et al. 2012, MNRAS, submitted), no such paper was published that year. More recently, in a Tuomi et al. 2013,[16] Tau Ceti is noted to have a similar activity index distribution to HD 114613. Again, a Tuomi et al. 2012 is referenced, though somewhat more completely (Tuomi, M., Jones, H. R. A., Jenkins, J. S., et al. 2012, MNRAS, submitted). No paper announcing HD 114613 as a low-mass planet host has been published as of 2014.

However, that does not mean the star is not a planet host. Wittenmyer et al. (2014) found HD 114613 to show a moderate-amplitude variation in its radial velocity with a period of 10.5 years, indicative of a long-period companion.[17] The radial velocity semi-amplitude of 5.5 m/s translates to a planet with a minimum mass about half a Jupiter mass. The planet has an intermediate orbital eccentricity of 0.25, which means that it can be somewhat loosely considered a Jupiter analogue.

The HD 114613 planetary system[17]
Companion
(in order from star)
Mass Semimajor axis
(AU)
Orbital period
(days)
b ≥0.48 ± 0.04 MJ 5.16 ± 0.13 3827 ± 105 0.25 ± 0.08

## Notes

1. ^ Though SIMBAD references the star as G3V, The star is significantly over-luminous for a dwarf: on the Hertzsprung-Russell diagram (see image) the star lies on the subgiant band, so it is listed as a subgiant here.
2. ^ The relevant calculation for absolute magnitude is $\scriptstyle M = m - 5 \log_{10} \left( \frac{100}{\mathrm{parallax\ (mas)}} \right)$, where $M\!\,$ is absolute magnitude and $m\!\,$ is apparent magnitude.

## References

1. van Leeuwen, F. (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.
2. ^ a b Høg, E. et al. (2000). "The Tycho-2 catalogue of the 2.5 million brightest stars". Astronomy and Astrophysics 355: 27–30. Bibcode:2000A&A...355L..27H. doi:10.1888/0333750888/2862.
3. ^ A Modern Mean Stellar Color and Effective Temperatures (Teff) # Sequence for O9V-Y0V Dwarf Stars, E. Mamajek, 2011, website
4. ^ a b c d Takeda, Genya et al. (2007). "Structure and Evolution of Nearby Stars with Planets. II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog". The Astrophysical Journal Supplement Series 168 (2): 297–318. arXiv:astro-ph/0607235. Bibcode:2007ApJS..168..297T. doi:10.1086/509763.
5. Sousa, S. G. et al. (August 2008). "Spectroscopic parameters for 451 stars in the HARPS GTO planet search program. Stellar [Fe/H] and the frequency of exo-Neptunes.". Astronomy and Astrophysics 487 (1): 373–381. arXiv:0805.4826. Bibcode:2008A&A...487..373S. doi:10.1051/0004-6361:200809698.
6. ^ a b Lovis, C. et al. (2011). "The HARPS search for southern extra-solar planets. XXXI. Magnetic activity cycles in solar-type stars: statistics and impact on precise radial velocities". arXiv:1107.5325 [astro-ph.SR].
7. ^ Valenti, J. A. et al. (2005). "Spectroscopic Properties of Cool Stars (SPOCS). I. 1040 F, G, and K Dwarfs from Keck, Lick, and AAT Planet Search Programs". The Astrophysical Journal Supplement Series 159 (1): 141–166. Bibcode:2005ApJS..159..141V. doi:10.1086/430500.
8. ^ a b Mortier, A. et al. (2013). "On the functional form of the metallicity-giant planet correlation". Astronomy & Astrophysics 551. arXiv:1302.1851. Bibcode:2013A&A...551A.112M. doi:10.1051/0004-6361/201220707.
9. ^ Endl, M. et al. (2002). "The planet search program at the ESO Coudé Echelle spectrometer. III. The complete Long Camera survey results". Astronomy & Astrophysics 392: 671–690. arXiv:astro-ph/0207512. Bibcode:2002A&A...392..671E. doi:10.1051/0004-6361:20020937.
10. ^ Zechmeister, M. et al. (2013). "The planet search programme at the ESO CES and HARPS. IV. The search for Jupiter analogues around solar-like stars". Astronomy & Astrophysics 592. arXiv:1211.7263. Bibcode:2013A&A...552A..78Z. doi:10.1051/0004-6361/201116551.
11. ^ Jones, Hugh R. A. et al. (2002). "Extrasolar planets around HD 196050, HD 216437 and HD 160691". Monthly Notices of the Royal Astronomical Society 337 (4): 1170–1178. arXiv:astro-ph/0206216. Bibcode:2002MNRAS.337.1170J. doi:10.1046/j.1365-8711.2002.05787.x.
12. ^ Wittenmyer, Robert A. et al. (2010). "The Frequency of Low-mass Exoplanets. II. The "Period Valley"". The Astrophysical Journal 722 (2). arXiv:1008.5232. Bibcode:2010ApJ...722.1854W. doi:10.1088/0004-637X/722/2/1854.
13. ^ Wittenmyer, Robert A. et al. (2011). "The Frequency of Low-mass Exoplanets. III. Toward η at Short Periods". The Astrophysical Journal 738 (1). arXiv:1103.4186. Bibcode:2011ApJ...738...81W. doi:10.1088/0004-637X/738/1/81.
14. ^ Howard, Andrew A. et al. (2010). "The Occurrence and Mass Distribution of Close-in Super-Earths, Neptunes, and Jupiters". Science 330. arXiv:1011.0143. Bibcode:2010Sci...330..653H. doi:10.1126/science.1194854.
15. ^ Wittenmyer, Robert A. et al. (2012). "The Anglo-Australian Planet Search. XXII. Two New Multi-planet Systems". The Astrophysical Journal 753 (2). 169. arXiv:1205.2765. Bibcode:2012ApJ...753..169W. doi:10.1088/0004-637X/753/2/169.
16. ^ Tuomi, M. et al. (2013). "Signals embedded in the radial velocity noise. Periodic variations in the τ Ceti velocities.". Astronomy & Astrophysics 551. arXiv:1212.4277. Bibcode:2013A&A...551A..79T. doi:10.1051/0004-6361/201220509.
17. ^ a b Wittenmyer, Robert A. et al. (2014). "The Anglo-Australian Planet Search. XXIII. Two New Jupiter Analogs". The Astrophysical Journal. arXiv:1401.5525. Bibcode:2014ApJ...783..103W. doi:10.1088/0004-637X/783/2/103.