R Leonis

R Leonis is a red giant Mira-type variable star located approximately 370 light years away in the constellation Leo.

R Leonis
Location of R Leonis (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Leo
Right ascension 09h 47m 33.4840s[1]
Declination +11° 25′ 43.823″[1]
Apparent magnitude (V) 4.4 - 11.3[2]
Characteristics
Spectral type M6e-M8IIIe-M9.5e[2]
Apparent magnitude (J) −0.7[3]
B−V color index 1.26
Variable type Mira
Astrometry
Proper motion (μ) RA: 6.132[1] mas/yr
Dec.: −53.097[1] mas/yr
Parallax (π)14.0566 ± 0.8378[1] mas
Distance372 ly
(114[4] pc)
Details
Mass0.7[5] M☉
Radius299,[6] 320-350[7] R☉
Luminosity3,537[4] L☉
Temperature2,890[6] (2,930 - 3,080)[7] K
Other designations
R Leo, HIP 48036, HD 84748, HR 3882, BD+12°2096, SAO 98769
Database references
SIMBADdata

The apparent magnitude of R Leonis varies between 4.31 and 11.65 with a period of 312 days. At maximum it can be seen with the naked eye, while at minimum a telescope of at least 7 cm is needed. The star's effective temperature is estimated 2,890 kelvins and radius spans 299 solar radii (208,000,000 kilometres; 1.39 astronomical units),[6] roughly Mars's orbital zone.

Possible planet
Artistic rendering of R Leonis's putative evaporating planetary companion

In 2009 Wiesemeyer et al.[5] proposed that quasi-periodic fluctuations observed for the star R Leonis may be due to the presence of an evaporating substellar companion, probably an extrasolar planet. They have inferred a putative mass for the orbiting body of twice the mass of Jupiter, orbital period of 5.2 years and likely orbital separation of 2.7 astronomical units. If confirmed such a planetary object could likely be an evaporating planet, with a long comet-like trail as hinted by intense SiO maser emissions.

The R Leonis planetary system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b (unconfirmed) ≥2 MJ ≥2.7 1898 0 — —

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. "GCVS Query=R Leo". General Catalogue of Variable Stars @ Sternberg Astronomical Institute, Moscow, Russia. Retrieved 2012-08-22.
  3. "V* R Leo". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2012-08-21.
  4. McDonald, I.; De Beck, E.; Zijlstra, A. A.; Lagadec, E. (2018). "Pulsation-triggered dust production by asymptotic giant branch stars". Monthly Notices of the Royal Astronomical Society. 481 (4): 4984. arXiv:1809.07965. Bibcode:2018MNRAS.481.4984M. doi:10.1093/mnras/sty2607. S2CID 118969263.
  5. Wiesemeyer; et al. (2009). "Precessing planetary magnetospheres in SiO stars?. First detection of quasi-periodic polarization fluctuations in R Leonis and V Camelopardalis". Astronomy and Astrophysics. 498 (3): 801–810. arXiv:0809.0359. Bibcode:2009A&A...498..801W. doi:10.1051/0004-6361/200811242. S2CID 14531031.
  6. De Beck, E.; Decin, L.; De Koter, A.; Justtanont, K.; Verhoelst, T.; Kemper, F.; Menten, K. M. (2010). "Probing the mass-loss history of AGB and red supergiant stars from CO rotational line profiles. II. CO line survey of evolved stars: Derivation of mass-loss rate formulae". Astronomy and Astrophysics. 523: A18. arXiv:1008.1083. Bibcode:2010A&A...523A..18D. doi:10.1051/0004-6361/200913771. S2CID 16131273.
  7. Fedele; et al. (2005). "The K -Band Intensity Profile of R Leonis Probed by VLTI/VINCI". Astronomy and Astrophysics. 431 (3): 1019–1026. arXiv:astro-ph/0411133. Bibcode:2005A&A...431.1019F. doi:10.1051/0004-6361:20042013. S2CID 15500217.
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