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Further images of α Persei G dwarfs
We present two images of intermediate and low axial inclination G dwarfs(AP 149 and AP 193) in the young open cluster α Persei, andcompare these with previous images of intermediate and high axialinclination objects in this cluster. All stars show starspots at highlatitudes, with one star exhibiting a strong polar spot. Althoughlow-latitude features are found on all stars to some degree, thedetection of spots on AP 193 is marginal. The apparent difference instarspot morphology from one object to the next is probably the resultof a stellar magnetic cycle, although the exact effect on the starspotdistribution throughout a cycle is unknown. Polar spots are found inmany Doppler images of rapidly rotating cool stars. In the past, theirexistence has been called into question, and it has been suggested thatthey could be the manifestations of NLTE (e.g. chromospheric filling inof line profiles) effects rather than real photospheric features. Weassume the polar spots to be real photospheric features, and concludethat the flat-bottomed nature of the profile shape can be attributed tophotospheric polar spots. The degree of truncation of the profiledepends not only on spot size and strength, but also on the effectiveforeshortening of the polar region, a function of axial inclination.Hα is in emission on AP 149 which shows a double peak at mostphases. The time-series of the profile shows an s-wave pattern as theposition of these peaks changes throughout the rotation cycle. Weattribute this to coronal clouds located above the stellar surface insynchronous orbit. A maximum-entropy tomogram is derived revealing fourdistinct emission regions located near and above the corotation radius.
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Osservazione e dati astrometrici
| Costellazione: | Vergine |
| Ascensione retta: | 13h15m24.63s |
| Declinazione: | +03°13'09.8" |
| Magnitudine apparente: | 9.024 |
| Moto proprio RA: | -120.6 |
| Moto proprio Dec: | -100.1 |
| B-T magnitude: | 9.753 |
| V-T magnitude: | 9.085 |
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