HD 215152

HD 215152 is a star in the zodiac constellation of Aquarius. It has an apparent visual magnitude of 8.13,^[2] meaning it is too faint to be seen with the naked eye. Parallax measurements provide distance estimates of around 70 light years.^[1] The star has a relatively high proper motion,^[7] moving across the sky at an estimated 0.328 arc seconds per year along a position angle of 205°.^[8]

HD 215152

Observation data Epoch J2000.0      Equinox J2000.0
Constellation	Aquarius
Right ascension	22h 43m 21.3028s[1]
Declination	−06° 24′ 02.953″[1]
Apparent magnitude (V)	8.13[2]
Characteristics
Spectral type	K3 V[3]
B−V color index	0.968[4]
Astrometry
Radial velocity (Rv)	−13.88±0.13[1] km/s
Proper motion (μ)	RA: −154.095[1] mas/yr Dec.: −289.915[1] mas/yr
Parallax (π)	46.3324 ± 0.0238 mas[1]
Distance	70.39 ± 0.04 ly (21.58 ± 0.01 pc)
Details
Mass	0.756±0.016[5] M☉
Surface gravity (log g)	4.26±0.15[5] cgs
Temperature	4,803±52[5] K
Metallicity [Fe/H]	−0.08±0.02[5] dex
Rotation	36.5±1.6 d[6]
Rotational velocity (v sin i)	3.35[4] km/s
Age	5.207±4.069[5] Gyr
Other designations
BD−07° 5839, GJ 4291, HD 215152, HIP 112190, SAO 146275, 2MASS J22432131-0624025[7]
Database references
SIMBAD	data

A 2015 survey ruled out the existence of any additional stellar companions at projected distances from 6 to 145 astronomical units.^[9]

This star has a stellar classification of K3 V,^[3] which indicates that it is an ordinary K-type main sequence star. Based upon observation of regular variations in chromospheric activity, it has a rotation period of 36.5±1.6 days.^[10] Stellar models give an estimated mass of around 76% of the Sun.^[5] It has a slightly lower metallicity than the Sun,^[5] and thus has a lower abundance of elements other than hydrogen and helium. The effective temperature of the stellar atmosphere is about 4,803 K, giving it the orange-hued glow of an ordinary K-type star.^[11]

HD 215152 is a candidate for possessing a debris disk—a circumstellar disk of orbiting dust and debris. This finding was made through the detection of an infrared excess at a wavelength of 70 μm by the Spitzer Space Telescope. The detection has a 3σ level of certainty.^[12]

Planetary system

HD 215152 has a total of four confirmed sub-Neptune mass planets, all of which are potentially rocky. With all of the planets orbiting within 0.154 AU, it is a very compact system. The inner two are separated by only 0.0098 AU, or about four times the distance between the Earth and the Moon. This is unusual for systems discovered by radial velocity measurements.^[13] In 2011, it was reported that two planetary candidates (c and d) had been detected in close orbit around this star. The planets were discovered through Doppler spectroscopy using the HARPS spectrograph at La Silla Observatory in Chile. Their presence was revealed by periodic variations in the radial velocity of the host star due to gravitational perturbations by the orbiting objects.^[14] In 2018, two more planets were confirmed.^[13] All planets have brief orbital periods: the four planets orbit every 5.76, 7.28, 10.86 and 25.2 days respectively.^[13] Their minimum masses range between 1.7 and 2.9 Earth masses.

There is a gap between orbits of HD 215152 d and HD 215152 e, which may contain a fifth, yet-undetected terrestrial low-mass planet.^{[citation needed]}

Artist's impression and size comparison of the four known planets of HD 215152 system with Earth, assuming Earth-like composition

The HD 215152 planetary system^[13]

Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
b	≥1.819+0.501 −0.629 M🜨	0.057638+0.000739 −0.000759	5.75999+0.00157 −0.00175	Probably ≤0.03	—	—
c	≥1.720+0.618 −0.725 M🜨	0.067393+0.000860 −0.000893	7.28243+0.00451 −0.00827	Probably ≤0.03	—	—
d	≥2.801+0.809 −0.923 M🜨	0.08799+0.00113 −0.00116	10.86499+0.00564 −0.00613	Probably ≤0.03	—	—
e	≥2.877+1.063 −1.481 M🜨	0.15417+0.00199 −0.00204	25.1967+0.0476 −0.0505	Probably ≤0.03	—	—

References

1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
2. Santos, N. C.; et al. (2013), "SWEET-Cat: A catalogue of parameters for Stars With ExoplanETs", Astronomy and Astrophysics, 556, A150, arXiv:1307.0354, Bibcode:2013A&A...556A.150S, doi:10.1051/0004-6361/201321286, S2CID 55237847.
3. Gray, R. O.; et al. (2003), "Contributions to the Nearby Stars (NStars) Project: Spectroscopy of Stars Earlier than M0 within 40 Parsecs: The Northern Sample. I", The Astronomical Journal, 126 (4): 2048–2059, arXiv:astro-ph/0308182, Bibcode:2003AJ....126.2048G, doi:10.1086/378365, S2CID 119417105.
4. Martínez-Arnáiz, R.; et al. (September 2010), "Chromospheric activity and rotation of FGK stars in the solar vicinity. An estimation of the radial velocity jitter", Astronomy and Astrophysics, 520: A79, arXiv:1002.4391, Bibcode:2010A&A...520A..79M, doi:10.1051/0004-6361/200913725, S2CID 43455849.
5. Tsantaki, M.; et al. (July 2013), "Deriving precise parameters for cool solar-type stars. Optimizing the iron line list", Astronomy & Astrophysics, 555: A150, arXiv:1304.6639, Bibcode:2013A&A...555A.150T, doi:10.1051/0004-6361/201321103, S2CID 118388752.
6. Suárez Mascareño, A.; et al. (2015), "Rotation periods of late-type dwarf stars from time series high-resolution spectroscopy of chromospheric indicators", Monthly Notices of the Royal Astronomical Society, 452 (3): 2745–2756, arXiv:1506.08039, Bibcode:2015MNRAS.452.2745S, doi:10.1093/mnras/stv1441.
7. "HD 215152". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved March 14, 2016.{{cite web}}: CS1 maint: postscript (link)
8. Carney, Bruce W.; et al. (June 1994), "A survey of proper motion stars. XII. An expanded sample", The Astronomical Journal, 107 (6): 2240–2289, Bibcode:1994AJ....107.2240C, doi:10.1086/117035.
9. Mugrauer, M.; Ginski, C. (12 May 2015), "High-contrast imaging search for stellar and substellar companions of exoplanet host stars", Monthly Notices of the Royal Astronomical Society, 450 (3): 3127–3136, Bibcode:2015MNRAS.450.3127M, doi:10.1093/mnras/stv771, hdl:1887/49340, retrieved 19 June 2020.
10. Suárez Mascareño, A.; et al. (September 2015), "Rotation periods of late-type dwarf stars from time series high-resolution spectroscopy of chromospheric indicators", Monthly Notices of the Royal Astronomical Society, 452 (3): 2745–2756, arXiv:1506.08039, Bibcode:2015MNRAS.452.2745S, doi:10.1093/mnras/stv1441.
11. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 18, 2012, retrieved 2012-01-16.
12. Koerner, D. W.; et al. (February 2010), "New Debris Disk Candidates Around 49 Nearby Stars" (PDF), The Astrophysical Journal Letters, 710 (1): L26–L29, Bibcode:2010ApJ...710L..26K, doi:10.1088/2041-8205/710/1/L26, S2CID 122844702.
13. Delisle, J.-B.; et al. (June 2018), "The HARPS search for southern extra-solar planets. XLIII. A compact system of four super-Earth planets orbiting HD 215152", Astronomy & Astrophysics, 614: 9, arXiv:1802.04631, Bibcode:2018A&A...614A.133D, doi:10.1051/0004-6361/201732529, A133
14. Mayor, M.; et al. (September 2011), The HARPS search for southern extra-solar planets XXXIV. Occurrence, mass distribution and orbital properties of super-Earths and Neptune-mass planets, arXiv:1109.2497, Bibcode:2011arXiv1109.2497M.