Coordinated observations of the red dwarf flare star EV LAC in 1994 and 1995

Abranin, E. P.; Alekseev, I. Yu.; Avgoloupis, S.; Bazelyan, L. L.; Berdyugina, S. V.; Cutispoto, G.; Гершберг, Р. Е.; Larionov, V. M.; Leto, G.; Lisachenko, V. N.; Marino, G.; Mavridis, L. N.; Messina, S.; Melnik, V. N.; Pagano, I.; Pustil'nik, S. V.; Rodonò, M.; Roizman, G. S.; Seiradakis, J. H.; Sigal, G. P.; Shakhovskaya, N. I.; Shakhovskoy, D. N.; Щербаков, В. А.

doi:10.1080/10556799808232093

Cited by 25 publications

(10 citation statements)

References 15 publications

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“…The He II 4686 Å line is not commonly observed in UV Ceti-type stars but is present in our spectrum F1. Abranin et al (1998) also detected it in spectra of a flare on EV Lac and noted that it behaved in the same way as the He II 1640 Å line in AD Leo (Byrne & Gary 1988). Zirin & Hirayama (1985) discuss the formation of this line in solar flares and conlcude that it is only formed in very deep regions of the chromosphere during the most intense flares.…”

Section: Other Chromospheric Linesmentioning

confidence: 81%

Optical Spectroscopy of a Flare on Barnard’s Star

Paulson

Allred

Anderson

et al. 2006

PUBL ASTRON SOC PAC

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ABSTRACT. We present optical spectra of a flare on Barnard's star. Several photospheric and chromospheric species were enhanced by the flare heating. An analysis of the Balmer lines shows that their shapes are best explained by Stark broadening rather than chromospheric mass motions. We estimate the temperature of the flaring region in the lower atmosphere to be ≥8000 K and the electron density to be ∼10 14 cm Ϫ3 , similar to values observed in other dM flares. Because Barnard's star is considered to be one of our oldest neighbors, a flare of this magnitude is probably quite rare.

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Section: Other Chromospheric Linesmentioning

confidence: 81%

Optical Spectroscopy of a Flare on Barnard’s Star

Paulson

Allred

Anderson

et al. 2006

PUBL ASTRON SOC PAC

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“…In addition to these 20 young stars, we also included in our sample the well studied single M dwarf flare star GJ 873 (EV Lac). GJ 873 is the second brightest M dwarf X-ray source in the Röntgensatellit All-Sky Survey (Hünsch et al 1999;Osten et al 2006), has one of the strongest surface magnetic field strengths measured on an M dwarf (Johns-Krull & Valenti 1996;Reiners & Basri 2007), and a differential star spot covering factor of 4-11% (Abranin et al 1998). While its activity suggests a young age, its dwarf-like gravity and the absence of lithium in its atmosphere (Pettersen et al 1984) indicate it is not pre-main sequence.…”

Section: Comparison Field Starsmentioning

confidence: 99%

Precise Infrared Radial Velocities From Keck/Nirspec and the Search for Young Planets

Bailey

White

Blake

et al. 2012

ApJ

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We present a high-precision infrared radial velocity study of late-type stars using spectra obtained with NIRSPEC at the W. M. Keck Observatory. Radial velocity precisions of 50 m/s are achieved for old field mid-M dwarfs using telluric features for precise wavelength calibration. Using this technique, 20 young stars in the β Pic (age ∼ 12 Myr) and TW Hya (age ∼ 8 Myr) Associations were monitored over several years to search for low mass companions; we also included the chromospherically active field star GJ 873 (EV Lac) in this survey. Based on comparisons with previous optical observations of these young active stars, radial velocity measurements at infrared wavelengths mitigate the radial velocity noise caused by star spots by a factor of ∼ 3. Nevertheless, star spot noise is still the dominant source of measurement error for young stars at 2.3 µm, and limits the precision to ∼ 77 m/s for the slowest rotating stars (vsini < 6 km/s), increasing to ∼ 168 m/s for rapidly rotating stars (vsini > 12 km/s). The observations reveal both GJ 3305 and TWA 23 to be single-lined spectroscopic binaries; in the case of GJ 3305, the motion is likely caused by its 0. ′′ 09 companion, identified after this survey began. The large amplitude, short-timescale variations of TWA 13A are indicative of a hot Jupiter-like companion, but the available data are insufficient to confirm this. We label it as a candidate radial velocity variable. For the remainder of the sample, these observations exclude the presence of any 'hot' (P < 3 days) companions more massive than 8 M Jup , and any 'warm' (P < 30 day) companions more massive than 17 M Jup , on average. Assuming an edge-on orbit for the edge-on disk system AU Mic, these observations exclude the presence of any hot Jupiters more massive than 1.8 M Jup or warm Jupiters more massive than 3.9 M Jup .

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“…References: 2,Vogt (1981); 7, O'Neal et al (2004); 8, O'Neal et al (2001), 9, Rodonò et al (1986 16, Dorren & Guinan (1994); 17, Strassmeier & Rice (1998); 18, Marsden et al (2005); 19,Amado et al (2000); 20,Chugajnov (1975); 21,Torres & Ribas (2002); 22,Torres & Ferraz Mello (1973); 23,Abranin et al (1998); 24,Scholz et al (2005); 25,Berdyugina (2005); 26, Sanchis Ojeda, private communication; 27,Terndrup et al (1999); 28, Savanov & Dmitrienko (2012); 29, Varga (2014) * indicates that these values are also included in theBerdyugina (2005) review.…”

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confidence: 99%

Stellar activity as noise in exoplanet detection – II. Application to M dwarfs

Andersen

Korhonen

2015

Monthly Notices of the Royal Astronomical Society

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The ubiquity of M dwarf stars combined with their low masses and luminosities make them prime targets in the search for nearby, habitable exoplanets. We investigate the effects of starspot-induced radial velocity (RV) jitter on detection and characterization of planets orbiting M dwarfs. We create surface spot configurations with both random spot coverage and active regions. Synthetic stellar spectra are calculated from a given spot map, and RV measurements are obtained using cross-correlation technique. We add the RV signal of an orbiting planet to these jitter measurements, and reduce the data to "measure" the planetary parameters. We investigate the detectability of planets around M dwarfs of different activity levels, and the recovery of input planetary parameters. When studying the recovery of the planetary period we note that while our original orbital radius places the planet inside the HZ of its star, even at a filling factor of 2% a few of our measurements fall outside the "conservative Habitable Zone". Higher spot filling factors result in more and higher deviations. Our investigations suggest that caution should be used when characterizing planets discovered with the RV method around stars that are (or are potentially) active.in the habitable zone should be just 5 pc away, although Mann et al. (2013) contests that this estimate might be too high based on their revised values of R * , L * , M * for a sample of Kepler stars, which resulted in some of the formerly HZ planets no longer orbiting within the HZ.The HZ is most loosely defined as the area around a star in which liquid water could exist on the planet's surface. According to the model developed by Kopparapu et al. (2013), the inner and outer HZ limits for our Solar System are 0.99 AU and 1.70 AU, respectively. Kopparapu et al. (2013) point out that their model does not include the radiative effects of clouds, so the boundaries could extend farther. M dwarfs are much less massive and less luminous than solar-type stars, which means the HZ is significantly closer to the star (for example, for an M dwarf of mass M ≈ 0.5M⊙, and R ≈ 0.5R⊙, the HZ is between ∼0.1 and ∼0.2 AU). This makes small planets orbiting in the HZ around M dwarfs easier to detect than their counterparts orbiting more massive stars for a few reasons: (1) Transits are more likely to be detected due to the the HZ being significantly closer to the

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Coordinated observations of the red dwarf flare star EV LAC in 1994 and 1995

Cited by 25 publications

References 15 publications

Optical Spectroscopy of a Flare on Barnard’s Star

Optical Spectroscopy of a Flare on Barnard’s Star

Precise Infrared Radial Velocities From Keck/Nirspec and the Search for Young Planets

Stellar activity as noise in exoplanet detection – II. Application to M dwarfs

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