J/MNRAS/431/2240ivo://CDS.VizieR/J/MNRAS/431/2240doi:10.26093/cds/vizier.74312240CDSBalona L.A.2024-07-21T20:14:45Z2014-07-10T15:05:50ZCDS support team

CDS, Observatoire de Strasbourg, 11 rue de l'Universite, F-67000 Strasbourg, France

cds-question@unistra.fra-starsvariable-starsTwo years of Kepler data are used to investigate low-frequency variations in A-type stars. In about 875 (40%) A-type stars, the periodogram shows a simple peak and its harmonic. If we assume that the photometric period is the period of rotation, we can derive the equatorial rotational velocity from a suitable radius estimate. It turns out that the distribution of equatorial velocities derived in this way is similar to the distribution of equatorial velocities of A-type main-sequence stars in the general field derived from spectroscopic line broadening, verifying our initial assumption. We suggest that the light variation is due to rotational modulation caused by starspots or some other corotating structure. In many stars the rotation peak in the periodogram has a characteristic shape which is not understood. The light amplitudes are highly variable. We deduce from the amplitude distribution that the sizes of starspots in A-type stars are similar to the largest sunspots. From the widths of the peaks in the periodogram we deduce that differential rotation in these stars is similar to that in the Sun. We find that the period-colour relationship used for gyrochronology in late-type stars extends to early F-type and probably late A-type stars as well. Flares in A-type stars have been recently detected. We add 13 additional A-type flare stars to this sample, which means that about 1.5% of A-type stars in the Kepler field show flares. We conclude that A-type stars are active and, like cooler stars, have starspots and flares.2013MNRAS.431.2240Bhttps://cdsarc.cds.unistra.fr/viz-bin/cat/J/MNRAS/431/2240CatalogResearchIsServedByTAP VizieR generic serviceIsServedByConesearch servicerelated-toV/133 : Kepler Input Catalog (Kepler Mission Team, 2009)https://cds.unistra.fr/vizier-org/licences_vizier.htmlhttps://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/MNRAS/431/2240https://vizier.iucaa.in/viz-bin/VizieR-2?-source=J/MNRAS/431/2240http://vizieridia.saao.ac.za/viz-bin/VizieR-2?-source=J/MNRAS/431/2240https://vizier.cds.unistra.fr/viz-bin/votable?-source=J/MNRAS/431/2240https://vizier.iucaa.in/viz-bin/votable?-source=J/MNRAS/431/2240http://vizieridia.saao.ac.za/viz-bin/votable?-source=J/MNRAS/431/2240GETtext/xml+votablehttps://tapvizier.cds.unistra.fr/TAPVizieR/tapCone search capability for table J/MNRAS/431/2240/Astars (List of rotation frequencies in A-type stars: {delta}Sct (table A1), {gamma}Dor (table A2), and rotational variables (table A3))https://vizier.cds.unistra.fr/viz-bin/conesearch/J/MNRAS/431/2240/Astars?https://vizier.iucaa.in/viz-bin/conesearch/J/MNRAS/431/2240/Astars?http://vizieridia.saao.ac.za/viz-bin/conesearch/J/MNRAS/431/2240/Astars?GETtext/xml+votable180.050000true290.9547436.938221110.0055555555555555564/922-923 933 945 5/3645-3647 3683 3704 3706 3731 3740-3741 3776 3778-3779 3784 3789 3792 6/14559 14567 14573 14575 14577-14579 14730-14731 14738 14744 14746 14749-14751 14792 14794 14828 14830 14915-14918 14921-14923 14948 14950-14952 14955-14956 14958-14959 14968-14969 14971-14972 14974-14975 15041 15044 15108-15110 15140-15141 15143 15145 15148-15150 15152-15153 15155 15172-15174 15200 15232https://cdsarc.cds.unistra.fr/viz-bin/moc/J/MNRAS/431/2240?format=asciiOpticaldefaultJ/MNRAS/431/2240/AstarsList of rotation frequencies in A-type stars: {delta}Sct (table A1), {gamma}Dor (table A2), and rotational variables (table A3)TypeType of star; dSct={delta}Sct (table A1), gDor={gamma}Dor (table A2), rot=rotational variables (table A3)meta.code;src.varcharKICKIC number (Cat. V/133)meta.id;meta.mainintprimaryn_KIC[p] "p" for stars having the characteristic periodogram described in the main articlemeta.notecharf0Rotation frequencyd**-1em.freq;src.varfloatA0Amplitude of the frequencymmagphot.magfloatS/N0Local signal-to-noise (ratio of the amplitude to mean local background noise in the periodogram)pos.lg;pos.lsrfloatA1Amplitude of first harmonicmmagphot.magfloatS/N1First harmonic signal-to-noisestat.snrfloatsA/A[0/1.5]? Fractional amplitude variation between quarters (1)phot.mag;arith.ratiofloatnullable_RAPositions from KIC (V/133) (right ascension part)degpos.eq.ra;meta.main_DEPositions from KIC (V/133) (declination part)degpos.eq.dec;meta.main