EV Lacertae

EV Lacertae

Artist's conception of a flare explosion on EV Lacertae.
Observation data
Epoch J2000      Equinox J2000
Constellation Lacerta
Right ascension 22h 46m 49.7323s[1]
Declination +44° 20′ 02.368″[1]
Apparent magnitude (V) 10.09[2]
Characteristics
Spectral type M3.5[3]
U−B color index +0.83[4]
B−V color index +1.36[4]
Variable type Flare star
Astrometry
Radial velocity (Rv)–1.5[5] km/s
Proper motion (μ) RA: –704.65[1] mas/yr
Dec.: –459.41[1] mas/yr
Parallax (π)199.3 ± 0.93[6] mas
Distance16.37 ± 0.08 ly
(5.02 ± 0.02 pc)
Details
Mass0.35[7] M☉
Radius0.36[7] R☉
Temperature3,400 ± 18[8] K
Metallicity [Fe/H]–0.01 ± 0.17[8] dex
Rotation4.376 days[9]
Rotational velocity (v sin i)4.5[7] km/s
Other designations
GJ 873, BD+43 4305, LHS 3853, LTT 16695, HIP 112460, PLX 5520
Database references
SIMBADdata

EV Lacertae (EV Lac, Gliese 873, HIP 112460) is a faint red dwarf star 16.5 light years away in the constellation Lacerta. It is the nearest star to the Sun in that region of the sky, although with an apparent magnitude of 10, it is only barely visible with binoculars. EV Lacertae is spectral type M3.5 flare star that emits X-rays.[10]

On 25 April 2008, NASA's Swift satellite picked up a record-setting flare from EV Lacertae.[11] This flare was thousands of times more powerful than the largest observed solar flare. Because EV Lacertae is much farther from Earth than the Sun, the flare did not appear as bright as a solar flare. The flare would have been visible to the naked eye if the star had been in an observable part of the night sky at the time. It was the brightest flare ever seen from a star other than the Sun.

EV Lacertae is much younger than our Sun, and still spinning rapidly. The fast spin, together with its convective interior, produces a magnetic field that is much more powerful than the Sun's. This strong magnetic field is believed to play a role in the star's ability to produce such bright flares. After the flare, the star was blue.

Distance

EV Lacertae distance estimates

Source Parallax, mas Distance, pc Distance, ly Distance, Pm Ref.
Woolley et al. (1970) 195±3 5.13±0.08 16.73+0.26
−0.25		 158.2+2.5
−2.4		 [12]
Gliese & Jahreiß (1991) 197.0±2.5 5.08+0.07
−0.06		 16.56±0.21 156.6±2 [13]
Gatewood et al. (1993) 199.3±0.93 5.018+0.024
−0.023		 16.37±0.08 154.8±0.7 [6]
van Altena et al. (1995) 198.0±2.6 5.05±0.07 16.47+0.22
−0.21		 155.8+2.1
−2		 [14]
Perryman et al. (1997) (Hipparcos) 198.07±2.05 5.05±0.05 16.47±0.17 155.8±1.6 [15]
Perryman et al. (1997) (Tycho) 235.40±31.00 4.2+0.6
−0.5		 13.9+2.1
−1.6		 131.1+19.9
−15.3		 [16]
van Leeuwen (2007) 195.22±1.87 5.12±0.05 16.71±0.16 158.1±1.5 [17]
RECONS TOP100 (2012) 198.21±0.84[nb 1] 5.045±0.021 16.46±0.07 155.7±0.7 [18]

Non-trigonometric distance estimates are marked in italic. The most precise estimate is marked in bold.

References

  1. ↑ 1.0 1.1 1.2 1.3 Perryman, M. A. C. et al. (April 1997). "The HIPPARCOS Catalogue". Astronomy & Astrophysics 323: L49–L52. Bibcode:1997A&A...323L..49P.
  2. ↑ "V* EV Lac -- Flare Star". SIMBAD. Centre de Données astronomiques de Strasbourg. Retrieved 2010-06-12.
  3. ↑ Montes, D.; López-Santiago, J.; Gálvez, M. C.; Fernández-Figueroa, M. J.; De Castro, E.; Cornide, M. (November 2001). "Late-type members of young stellar kinematic groups - I. Single stars". Monthly Notices of the Royal Astronomical Society 328 (1): 45–63. arXiv:astro-ph/0106537. Bibcode:2001MNRAS.328...45M. doi:10.1046/j.1365-8711.2001.04781.x.
  4. ↑ 4.0 4.1 Erro, B. I. (1971). "Infrared photometry of UV CET stars". Boletin Del Instituto De Tonantzintla 6: 143. Bibcode:1971BITon...6..143E.
  5. ↑ Wilson, Ralph Elmer (1953). General Catalogue of Stellar Radial Velocities. Washington: Carnegie Institution of Washington. Bibcode:1953QB901.W495.....
  6. ↑ 6.0 6.1 Gatewood, George; de Jonge, Kiewiet Joost; Stephenson, Bruce (1993). "One-milliarsecond precision parallax studies in the regions of Delta Cephei and EV Lacertae". Publications of the Astronomical Society of the Pacific 105 (692): 1101–1106. Bibcode:1993PASP..105.1101G. doi:10.1086/133287.
  7. ↑ 7.0 7.1 7.2 Phan-Bao, Ngoc; Martín, Eduardo L.; Donati, Jean-François; Lim, Jeremy (July 2006). "Magnetic Fields in M Dwarfs: Rapid Magnetic Field Variability in EV Lacertae". The Astrophysical Journal 646 (1): L73–L76. arXiv:astro-ph/0603480. Bibcode:2006ApJ...646L..73P. doi:10.1086/506591.
  8. ↑ 8.0 8.1 Rojas-Ayala, Bárbara et al. (April 2012). "Metallicity and Temperature Indicators in M Dwarf K-band Spectra: Testing New and Updated Calibrations with Observations of 133 Solar Neighborhood M Dwarfs". The Astrophysical Journal 748 (2): 93. arXiv:1112.4567. Bibcode:2012ApJ...748...93R. doi:10.1088/0004-637X/748/2/93.
  9. ↑ Testa, Paola; Drake, Jeremy J.; Peres, Giovanni (December 2004). "The Density of Coronal Plasma in Active Stellar Coronae". The Astrophysical Journal 617 (1): 508–530. arXiv:astro-ph/0405019. Bibcode:2004ApJ...617..508T. doi:10.1086/422355.
  10. ↑ Schmitt JHMM, Fleming TA, Giampapa MS (Sep 1995). "The X-ray view of the low-mass stars in the solar neighborhood". Ap J. 450 (9): 392–400. Bibcode:1995ApJ...450..392S. doi:10.1086/176149.
  11. ↑ Dunbar, Brian (May 20, 2008). Smith, Yvette, ed. "Pipsqueak Star Unleashes Monster Flare". NASA. Retrieved 2010-06-12.
  12. ↑ Woolley R.; Epps E. A.; Penston M. J.; Pocock S. B. (1970). "Woolley 873". Catalogue of stars within 25 parsecs of the Sun. Retrieved 2014-11-22.
  13. ↑ Gliese, W. and Jahreiß, H. (1991). "Gl 873". Preliminary Version of the Third Catalogue of Nearby Stars. Retrieved 2014-11-22.
  14. ↑ Van Altena W. F., Lee J. T., Hoffleit E. D. (1995). "GCTP 5520". The General Catalogue of Trigonometric Stellar Parallaxes (Fourth ed.). Retrieved 2014-11-22.
  15. ↑ Perryman et al. (1997). "HIP 112460". The Hipparcos and Tycho Catalogues. Retrieved 2014-11-22.
  16. ↑ Perryman et al. (1997). "HIP 112460". The Hipparcos and Tycho Catalogues. Retrieved 2014-11-22.
  17. ↑ van Leeuwen F. (2007). "HIP 112460". Validation of the new Hipparcos reduction. Retrieved 2014-11-22.
  18. ↑ "RECONS TOP100". THE ONE HUNDRED NEAREST STAR SYSTEMS brought to you by RECONS (Research Consortium On Nearby Stars). 2012. Retrieved 2014-11-22.

Notes

  1. ↑ Weighted parallax based on parallaxes from Gatewood et al. (1993), van Altena et al. (1995) and van Leeuwen (2007).