HD 98649

HD 98649
Observation data; Epoch J2000.0 Equinox J2000.0
Constellation	Crater
Right ascension	11h 20m 51.76855s[1]
Declination	−23° 13′ 02.4295″[1]
Apparent magnitude (V)	+8.00[2]
Characteristics
Spectral type	G4V
B−V color index	+0.658 ± 0.003[3]
Astrometry
Radial velocity (Rv)	4.25±0.12[1] km/s
Proper motion (μ)	RA: −199.735±0.022 mas/yr[1] ; Dec.: −177.620±0.017 mas/yr[1]
Parallax (π)	23.7206 ± 0.0216 mas[1]
Distance	137.5 ± 0.1 ly ; (42.16 ± 0.04 pc)
Absolute magnitude (MV)	+4.91[2]
Details
Mass	0.97±0.02[4] M☉
Radius	~1[2] R☉
Luminosity (bolometric)	0.968±0.019[4] L☉
Luminosity (visual, LV)	0.83[note 1] L☉
Surface gravity (log g)	4.38 ± 0.08[2] cgs
Temperature	5759 ± 35[2] K
Metallicity [Fe/H]	–0.02 ± 0.03[2] dex
Rotation	27 ± 4.0 days[2]
Rotational velocity (v sin i)	1.19[2] km/s
Age	4.44+0.68; −0.58[4] Gyr
Other designations
	BD−22° 3121, HIP 55409, SAO 179793, LTT 4199
Database references
SIMBAD	data
Exoplanet Archive	data
Extrasolar Planets; Encyclopaedia	data

HD 98649 is a G-type yellow dwarf star, classified as a G4V, that has approximately the same mass and diameter as the Sun, but has only 86% of its luminosity. It is considered a solar analog.[4] HD 98649 is about 138 light-years from earth. HD 98649 is found in the Crater constellation.[2]

Planetary system

From 1998 to 2012, the star was under observance from the CORALIE echelle spectrograph at La Silla Observatory.

In 2012, a long-period, wide-orbiting planet was deduced by radial velocity. This was published in November.

The discoverers noted, "HD 98649b is in the top five of the most eccentric planetary orbit and the most eccentric planet known with a period larger than 600 days." The reason for this eccentricity is unknown. They also submit it as a candidate for direct imaging, once it gets out to 10.4 AU at apoastron and 250 milliarcseconds of separation relative to Earth.[2]

Using astrometry from Gaia, astronomers were able to deduce the true mass of HD 98649 b as 9.7 M_J, somewhat higher than its minimum mass from radial velocity.[4][5]

The HD 98649 planetary system[4]
Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (years)	Eccentricity	Inclination	Radius
b	9.7+2.3 −1.9 M_J	5.97+0.24 −0.21	14.74+0.88 −0.75	0.852+0.033 −0.022	43.7+13 −8.1°	—

References

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.
Marmier, M.; et al. (2013). "The CORALIE survey for southern extrasolar planets XVII. New and updated long period and massive planets". Astronomy and Astrophysics. 551. A90. arXiv:1211.6444. Bibcode:2013A&A...551A..90M. doi:10.1051/0004-6361/201219639. S2CID 59467665.
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. S2CID 18759600.Vizier catalog entry
Li, Yiting; Brandt, Timothy D.; Brandt, G. Mirek; Dupuy, Trent J.; Michalik, Daniel; Jensen-Clem, Rebecca; Zeng, Yunlin; Faherty, Jacqueline; Mitra, Elena L. (2021). "Precise Masses and Orbits for Nine Radial-velocity Exoplanets". The Astronomical Journal. 162 (6): 266. arXiv:2109.10422. Bibcode:2021AJ....162..266L. doi:10.3847/1538-3881/ac27ab. S2CID 237592581.
Feng, Fabo; Butler, R. Paul; et al. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series. 262 (21): 21. arXiv:2208.12720. Bibcode:2022ApJS..262...21F. doi:10.3847/1538-4365/ac7e57. S2CID 251864022.

Notes

Taking the absolute visual magnitude of HD 98649 $\scriptstyle M_{V_{\ast }}=4.91$ and the absolute visual magnitude of the Sun $\scriptstyle M_{V_{\odot }}=4.83$ , the visual luminosity can be calculated by $\scriptstyle {\frac {L_{V_{\ast }}}{L_{V_{\odot }}}}=10^{0.4\left(M_{V_{\odot }}-M_{V_{\ast }}\right)}$

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[GaiaDR3-1] 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.

[Marmier2013-2] Marmier, M.; et al. (2013). "The CORALIE survey for southern extrasolar planets XVII. New and updated long period and massive planets". Astronomy and Astrophysics. 551. A90. arXiv:1211.6444. Bibcode:2013A&A...551A..90M. doi:10.1051/0004-6361/201219639. S2CID 59467665.

[van_Leeuwen2007-3] 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. S2CID 18759600.Vizier catalog entry

[Li2021-4] Li, Yiting; Brandt, Timothy D.; Brandt, G. Mirek; Dupuy, Trent J.; Michalik, Daniel; Jensen-Clem, Rebecca; Zeng, Yunlin; Faherty, Jacqueline; Mitra, Elena L. (2021). "Precise Masses and Orbits for Nine Radial-velocity Exoplanets". The Astronomical Journal. 162 (6): 266. arXiv:2109.10422. Bibcode:2021AJ....162..266L. doi:10.3847/1538-3881/ac27ab. S2CID 237592581.

[Feng2022-6] Feng, Fabo; Butler, R. Paul; et al. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series. 262 (21): 21. arXiv:2208.12720. Bibcode:2022ApJS..262...21F. doi:10.3847/1538-4365/ac7e57. S2CID 251864022.

[luminosity_visual-5] Taking the absolute visual magnitude of HD 98649 $\scriptstyle M_{V_{\ast }}=4.91$ and the absolute visual magnitude of the Sun $\scriptstyle M_{V_{\odot }}=4.83$ , the visual luminosity can be calculated by $\scriptstyle {\frac {L_{V_{\ast }}}{L_{V_{\odot }}}}=10^{0.4\left(M_{V_{\odot }}-M_{V_{\ast }}\right)}$