Bluer colour of UX Arietis at fainter
 visual magnitudes

Rosario, M. J.; Raveendran, A. V.; Mekkaden, M. V.

doi:10.1051/0004-6361:20078429

Cited by 6 publications

(13 citation statements)

References 18 publications

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“…4 that the active star has to be redder when fainter if the composite colour has to remain nearly constant and that even a constant (B − V) for the active star during its brightness variation would make the composite colour appreciably bluer when it becomes fainter. Rosario et al (2008) reported that the differential V mag of UX Ari available from 1972 to 2008, when folded over the orbital period, has a spread of about 0.48 mag around 0.50p against a spread of only 0.18 mag around 0.0p; we find that the most recent data are also consistent with this. The 0.0p corresponds to the conjunction with the active star in front.…”

Section: (B -V) Colour Variationsupporting

confidence: 84%

“…4, however, shows that there is a slight tendency for the star to become redder as it becomes fainter. The Δ(B − V) shows a scatter of about 0.1 mag, which is significantly larger than the observational errors, as in the case of the other active RS CVn binaries, UX Ari, II Peg, and DM UMa (Rosario et al 2007). …”

Section: (B -V) Colour Variationmentioning

confidence: 66%

“…The comparatively larger orbit (1.7 times larger) probably weakens the varying gravitational coupling between the component stars because of the changing quadrupole moment of the active star, thereby, producing changes in the orbital period that are difficult to detect. Rosario et al (2008) pointed out that the apparent longitudinal asymmetry in spot activity that is fixed in the orbital reference frame observed in UX Ari would mean that differential rotation in the active component is either absent, or negligibly small, and that the presence of the companion significantly modulates the surface distribution of spots on the active star. The V magnitudes plotted in Fig.…”

Section: Discussionmentioning

confidence: 99%

“…Apart from weakening the differential rotation, it is likely that the companion also significantly affects the surface distribution of spots on the active star. Rosario et al (2007) pointed that all the chromospherically active binaries that are known to show or suspected to show bluer colours at fainter visual magnitudes, UX Ari, V711 Tau, RS CVn (Ulvas & Henry 2005), and MM Her (Tas et al 1999), are double-lined spectroscopic binaries. Since there is no apparent reason for the spots on the active components of double-lined binaries to differ from those on the corresponding components in single-lined systems, we conclude that the near-constancy of the composite (B − V) colour of V711 Tau as it becomes fainter is caused by the higher fractional contribution by the hotter component to the total light of the system in the blue spectral region.…”

Section: Discussionmentioning

confidence: 99%

“…In the case of the double-lined RS CVn binary UX Ari, which becomes appreciably bluer when fainter, Ulvas & Engvold (2003) also suggested a similar mechanism. However, Rosario et al (2007) pointed out that the unreasonably high brightness ratio of the components of UX Ari used by them in their modelling affected this conclusion, and that the greater contribution by the hotter secondary to the total light in the blue spectral region is definitely responsible for the star becoming bluer when it is fainter.…”

Section: Introductionmentioning

confidence: 99%

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Orbital period modulation and spot activity in the RS CVn binary V711 Tauri

Muneer

Jayakumar

Rosario

et al. 2010

A&A

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Aims. We attempt to establish the real nature of the orbital period variation and its relation to the spot activity of V711 Tau, and determine why the (B − V) colour of the star appears to be nearly independent of its V magnitude. We wish to verify whether existing predictions in the literature for the long-term spot activity of the star are true or not by making extended photometric observations, and whether the broad component of Hα emission originates in more localised active regions, as suggested by some chromospheric models, by searching for any correlation between the base-line width of the emission and the light modulation. Methods. We obtained new radial velocities of the G-type component of V711 Tau on 42 nights during 2004−09, and BV photometry of V711 Tau on 202 nights during the years 1993−2009. We measured the equivalent widths of two well resolved lines of the G-type component from 13 of the spectra obtained by us. We also measured the equivalent widths and base-line widths of Hα emission from 21 spectra obtained during 2008−09. We analyse these along with relevant information available in the literature. Results. The available radial velocity data of V 711 Tau are consistent with a sinusoidal modulation of its orbital period; the period of modulation is found to be 36.3 ± 1.9 yr. The fractional light-loss over a photometric cycle is found to vary with an average period of 14.1 ± 0.3 yr. It appears that physical processes linked to the magnetic activity of the spotted star are responsible for the variation in the orbital period. The excess reduction in the B band flux relative to that in V band caused by spot activity is almost compensated for by the fractional increase in the contribution by the hotter companion to the total light in the blue spectral region, and thereby makes the (B − V) colour of the binary system nearly independent of its V magnitude. We find that the ratio of the radii of the components derived from their v sin i values, which is usually quoted in the literature, is substantially larger than that implied by the ratio of their brightnesses in V band. There is a slight indication from the V band data that the spot activity in V711 Tau has a component that is fixed in the orbital frame of reference. The equivalent width and base-line width of Hα emission do not show any obvious correlation with the V band light curve.

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Section: (B -V) Colour Variationsupporting

confidence: 84%

Section: (B -V) Colour Variationmentioning

confidence: 66%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Orbital period modulation and spot activity in the RS CVn binary V711 Tauri

Muneer

Jayakumar

Rosario

et al. 2010

A&A

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Three-Component Model of Spottedness in the Classical RS CVn System UX Ari

Alekseev

2014

Astrophysics

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It is shown that the hypothesis of a complex (cold spots and hot flares) structure for the active regions on UX Ari reproduces well the photometric behavior of the star. According to the model the spots are colder than the quiescent atmosphere at 1300 K, while the flares are hotter than the photosphere at 750 K. These estimates are in good agreement with Doppler mapping of the star, with calculations of its photometric behavior, and with observations of OH molecular bands. The effective area of the spotted regions approaches half the total surface of the star. Our estimates show that the flares form about a third of the spotted area. The time variation in the star's brightness and in the effective area of the spots is probably cyclical with a characteristic time of 8-9 years. The switching of the active latitudes shows no obvious cyclicity.

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AKARI's infrared view on nearby stars

Ita

Matsuura

Ishihara

et al. 2010

A&A

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Context. The AKARI, a Japanese infrared space mission, has performed an All-Sky Survey in six infrared-bands from 9 to 180 μm with higher spatial resolutions and better sensitivities than IRAS. Aims. We investigate the mid-infrared (9 and 18 μm) point source catalog (PSC) obtained with the infrared camera (IRC) onboard AKARI, in order to understand the infrared nature of the known objects and to identify previously unknown objects. Methods. Color-color diagrams and a color-magnitude diagram were plotted with the AKARI-IRC PSC and other available all-sky survey catalogs. We combined the Hipparcos astrometric catalog and the 2MASS all-sky survey catalog with the AKARI-IRC PSC. We furthermore searched literature and SIMBAD astronomical database for object types, spectral types, and luminosity classes. We identified the locations of representative stars and objects on the color−magnitude and color−color diagram schemes. The properties of unclassified sources can be inferred from their locations on these diagrams. Results. We found that the (B − V) vs. (V − S 9W) color−color diagram is useful for identifying the stars with infrared excess emerged from circumstellar envelopes or disks. Be stars with infrared excess are separated well from other types of stars in this diagram. Whereas (J − L18W) vs. (S 9W − L18W) diagram is a powerful tool for classifying several object types. Carbon-rich asymptotic giant branch (AGB) stars and OH/IR stars form distinct sequences in this color−color diagram. Young stellar objects (YSOs), pre-main sequence (PMS) stars, post-AGB stars, and planetary nebulae (PNe) have the largest mid-infrared color excess and can be identified in the infrared catalog. Finally, we plot the L18W vs. (S 9W − L18W) color−magnitude diagram, using the AKARI data together with Hipparcos parallaxes. This diagram can be used to identify low-mass YSOs and AGB stars. We found that this diagram is comparable to the [24] vs. ([8.0] − [24]) diagram of Large Magellanic Cloud sources using the Spitzer Space Telescope data. Our understanding of Galactic objects will be used to interpret color-magnitude diagram of stellar populations in the nearby galaxies that Spitzer Space Telescope observed. Conclusions. Our study of the AKARI color−color and color−magnitude diagrams will be used to explore properties of unknown objects in the future. In addition, our analysis highlights a future key project to understand stellar evolution with a circumstellar envelope, once the forthcoming astronometrical data with GAIA are available.

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Bluer colour of UX Arietis at fainter visual magnitudes

Cited by 6 publications

References 18 publications

Orbital period modulation and spot activity in the RS CVn binary V711 Tauri

Orbital period modulation and spot activity in the RS CVn binary V711 Tauri

Three-Component Model of Spottedness in the Classical RS CVn System UX Ari

AKARI's infrared view on nearby stars

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