Lithium in Stars X-Ray Selected by EXOSAT

Tagliaferri, G.; Randich, S.; Pallavicini, R.; Cutispoto, G.

doi:10.1007/978-94-011-1964-1_38

Cited by 9 publications

(21 citation statements)

References 5 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…This agrees with the temperature maps, which show that the spot is larger and cooler in 2010 -although we recall that the phase coverage during 2010 is incomplete. The derived values agree well with the result byTagliaferri et al (1994), implying that AF Lep is a young object. Furthermore, the literature gives varying values for the equivalent width (EW) of the lithium line on AF Lep.…”

supporting

confidence: 89%

“…The simulations show that the places of the spots (or spot groups) are correct, but the temperature contrast suffers from the lack of resolution. Tagliaferri et al (1994) have reported a lithium abundance of log N(Li) = 3.2 for AF Lep. Our 2005 observations do not cover the lithium line, but for the later observations this region is covered.…”

Section: Surface Spot Configurationmentioning

confidence: 99%

“…aa24229-14 young object. Furthermore, it has an unusually high intrinsic Xray luminosity of ∼ 1.6 × 10 30 ergs s −1 for a single, late-F-type star (Tagliaferri et al 1994).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Doppler images and the underlying dynamo. The case of AF Leporis

Järvinen,

Arlt,

Hackman

et al. 2014

Preprint

View full text Add to dashboard Cite

Context. The (Zeeman-)Doppler imaging studies of solar-type stars very often reveal large high-latitude spots. This also includes F stars that possess relatively shallow convection zones, indicating that the dynamo operating in these stars differs from the solar dynamo. Aims. We aim to determine whether mean-field dynamo models of late-F type dwarf stars can reproduce the surface features recovered in Doppler maps. In particular, we wish to test whether the models can reproduce the high-latitude spots observed on some F dwarfs. Methods. The photometric inversions and the surface temperature maps of AF Lep were obtained using the Occamian-approach inversion technique. Low signal-to-noise spectroscopic data were improved by applying the least-squares deconvolution method. The locations of strong magnetic flux in the stellar tachocline as well as the surface fields obtained from mean-field dynamo solutions were compared with the observed surface temperature maps. Results. The photometric record of AF Lep reveals both long-and short-term variability. However, the current data set is too short for cycle-length estimates. From the photometry, we have determined the rotation period of the star to be 0.9660 ± 0.0023 days. The surface temperature maps show a dominant, but evolving, high-latitude (around +65 • ) spot. Detailed study of the photometry reveals that sometimes the spot coverage varies only marginally over a long time, and at other times it varies rapidly. Of a suite of dynamo models, the model with a radiative interior rotating as fast as the convection zone at the equator delivered the highest compatibility with the obtained Doppler images.

show abstract

supporting

confidence: 89%

Section: Surface Spot Configurationmentioning

confidence: 99%

See 1 more Smart Citation

Doppler images and the underlying dynamo. The case of AF Leporis

Järvinen,

Arlt,

Hackman

et al. 2014

Preprint

View full text Add to dashboard Cite

show abstract

“…For the Columba association, to which κ And purportedly belongs, the only stars from published membership lists (Torres et al 2008;Malo et al 2013 Valenti & Fischer 2005), HD 31647 (-0.12; Hill 1995), HD 39206 (0.06; Lemke 1989), and HD 40216 (0.00; Tagliaferri et al 1994). Hence, thus Columba members have spectroscopic metallicities consistent with being approximately solar (mean [Fe/H] = 0.01 ± 0.05), and the spectroscopic [Fe/H] estimates for κ And would appear to make the star chemically peculiar if it is truly associated with Columba.…”

Section: Stellar Parametersmentioning

confidence: 99%

The Κ ANDROMEDAE SYSTEM: NEW CONSTRAINTS ON THE COMPANION MASS, SYSTEM AGE, AND FURTHER MULTIPLICITY

Hinkley

Pueyo

Faherty

et al. 2013

ApJ

View full text Add to dashboard Cite

κ Andromedae is a B9IVn star at 52 pc for which a faint substellar companion separated by 55±2 AU was recently announced. In this work, we present the first spectrum of the companion, "κ And B," using the Project 1640 high-contrast imaging platform. Comparison of our low-resolution Y JH-band spectra to empirical brown dwarf spectra suggests an early-L spectral type. Fitting synthetic spectra from PHOENIX model atmospheres to our observed spectrum allows us to constrain the effective temperature to ∼2000 K, as well as place constraints on the companion surface gravity. Further, we use previously reported log(g) and T eff measurements of the host star to argue that the κ And system has an isochronal age of 220±100 Myr, older than the 30 Myr age reported previously. This interpretation of an older age is corroborated by the photometric properties of κ And B, which appear to be marginally inconsistent with other 10-100 Myr low-gravity L-dwarfs for the spectral type range we derive. In addition, we use Keck aperture masking interferometry combined with published radial velocity measurements to rule out the existence of any tight stellar companions to κ And A that might be responsible for the system's overluminosity. Further, we show that luminosity enhancements due to a nearly "pole-on" viewing angle coupled with extremely rapid rotation is unlikely. κ And A is thus consistent with its slightly evolved luminosity class (IV) and we propose here that κ And, with a revised age of 220 ± 100 Myr, is an interloper to the 30 Myr Columba association with which it was previously associated. The photometric and spectroscopic evidence for κ And B combined with our re-assesment of the system age implies a substellar companion mass of 50 +16 −13 M Jup , consistent with a brown dwarf rather than a planetary mass companion.

show abstract

“… (1) the membership lists given by Eggen in his four decades of research on SKGs (Eggen 1958a,b, 1960a,b, 1975, 1983a–c, 1984a–c, 1989, 1991, 1992a–c, 1994, 1995a,b, 1996, 1998a–c), and additional lists given by Soderblom & Mayor (1993a); (2) the study by Agekyan & Orlov (1984) and Orlov et al (1995), which searched for kinematic groups in the solar neighbourhood (see also Popović, Ninković & Pavlović 1995); (3) the study of ages of spotted late‐type stars by Chugainov (1991); (4) X‐ray‐ and EUV‐selected active stars and lithium‐rich stars (Favata et al 1993, 1995, 1998; Jeffries & Jewell 1993; Mullis & Bopp 1994; Tagliaferri et al 1994; Jeffries 1995; Schachter et al 1996; Hünsch, Schmitt & Voges 1998a,b; Hünsch et al 1999; Cutispoto et al 1999; 2000); (5) single rapidly rotating stars such as AB Dor, PZ Tel, HD 197890, RE J1816+541, BD+224409 (LO Peg), HK Aqr, V838 Cen, V343 Nor and LQ Hya, previously assigned membership of the Local Association; (6) chromospherically active late‐type dwarfs in the solar neighbourhood with studied kinematic properties (Soderblom & Clements 1987; Young, Sadjadi & Harlan 1987; Upgren 1988; Soderblom 1990; Ambruster et al 1998); (7) flare stars with studied kinematic properties (Poveda et al 1996); (8) the study of field M dwarfs with high‐resolution spectra by Delfosse et al (1998), including the recently identified M9V star DENIS , which is the closest star later than M7V (Delfosse et al 2001); (9) other chromospherically active stars (Henry, Fekel & Hall 1995; Henry et al 1996; Soderblom et al 1998); (10) late‐type stars included in the list of the nearest 100 stellar systems given by the Research Consortium on Nearby Stars (RECONS 1 ); (11) the study of nearby young solar analogues by Gaidos (1998) and Gaidos, Henry & Henry (2000); (12) the sample of nearby, single, solar‐type stars selected as proxies for the Sun at different stages in the project the ‘Sun in Time’ by Bochanski et al (2000); (13) the study of nearby young X ‐ray‐active low‐mass stars with well‐measured parallaxes by Wichmann & Schmitt (2001), and (14) the active stars included in the Vienna‐KPNO search for Doppler‐imaging candidate stars (Strassmeier et al 2000). …”

Section: Selection Of the Samplementioning

confidence: 99%

Late-type members of young stellar kinematic groups - I. Single stars

Montes

López‐Santiago

Gálvez

et al. 2001

Monthly Notices of the Royal Astronomical Society

418

507

View full text Add to dashboard Cite

This is the first paper of a series aimed at studying the properties of late‐type members of young stellar kinematic groups. We concentrate our study on classical young moving groups such as the Local Association (Pleiades moving group, , IC 2391 supercluster (35 Myr), Ursa Major group (Sirius supercluster, 300 Myr), and Hyades supercluster (600 Myr), as well as on recently identified groups such as the Castor moving group (200 Myr). In this paper we compile a preliminary list of single late‐type possible members of some of these young stellar kinematic groups. Stars are selected from previously established members of stellar kinematic groups based on photometric and kinematic properties as well as from candidates based on other criteria such as their level of chromospheric activity, rotation rate and lithium abundance. Precise measurements of proper motions and parallaxes taken from the Hipparcos Catalogue, as well as from the Tycho‐2 Catalogue, and published radial velocity measurements are used to calculate the Galactic space motions (U, V, W) and to apply Eggen's kinematic criteria in order to determine the membership of the selected stars to the different groups. Additional criteria using age‐dating methods for late‐type stars will be applied in forthcoming papers of this series. A further study of the list of stars compiled here could lead to a better understanding of the chromospheric activity and their age evolution, as well as of the star formation history in the solar neighbourhood. In addition, these stars are also potential search targets for direct imaging detection of substellar companions.

show abstract

Lithium in Stars X-Ray Selected by EXOSAT

Cited by 9 publications

References 5 publications

Doppler images and the underlying dynamo. The case of AF Leporis

Doppler images and the underlying dynamo. The case of AF Leporis

The Κ ANDROMEDAE SYSTEM: NEW CONSTRAINTS ON THE COMPANION MASS, SYSTEM AGE, AND FURTHER MULTIPLICITY

Late-type members of young stellar kinematic groups - I. Single stars

Contact Info

Product

Resources

About