- ID:
- ivo://CDS.VizieR/J/MNRAS/381/602
- Title:
- BV differential light curves of EQ Tau
- Short Name:
- J/MNRAS/381/602
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present two new sets of complete light curves of EQ Tauri (EQ Tau) observed in 2000 October and 2004 December. These were analysed, together with the light curves obtained by Yang & Liu (2002AJ....124.3358Y) in 2001 December, with the 2003 version of the Wilson-Devinney code. In the three observing seasons, the light curves show a noticeable variation in the time-scale of years. The more massive component of EQ Tau is a solar-type star (G2) with a very deep convective envelope, which rotates about 80 times as fast as the Sun. Therefore, the change can be explained by dark-spot activity on the common convective envelope. The assumed unperturbed part of the light curve and the radial velocities published by Rucinski et al. (2001AJ....122.1974R) were used to determine the basic parameters of the system, which were kept fixed for spot modelling in the three sets of light curves. The results reveal that the total spotted area on the more massive component covers 18, 3 and 20 per cent of the photospheric surface in the three observing seasons, respectively. Polar spots and high-latitude spots are found. The analysis of the orbital period has demonstrated that it undergoes cyclical oscillation, which is due to either a tertiary component or periodic magnetic activity in the more massive component.
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Search Results
- ID:
- ivo://CDS.VizieR/J/AJ/133/1421
- Title:
- BV differential photometry of 11 gamma Dor stars
- Short Name:
- J/AJ/133/1421
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have used precise photometric and high-dispersion spectroscopic observations to study 11 gamma Doradus stars, 10 of them newly confirmed. Only five of these 11 gamma Doradus stars appear to be single; two are primaries of double-lined spectroscopic binaries, one is the secondary of a double-lined binary, two are primaries of visual binaries and, in the case of the double-lined binary (HD 86371), either or both components could be a pulsating gamma Doradus star. We have determined a preliminary orbital period of 5.32 days for the double-lined binary HD 41547. Several of the stars show spectroscopic line-profile and low-amplitude radial velocity variability indicative of pulsation. All 11 stars are photometrically variable with amplitudes between 4 and 94 mmag in Johnson B and periods between 0.38 and 1.86 days. The 11 stars have between two and five independent periods.
- ID:
- ivo://CDS.VizieR/J/A+A/499/567
- Title:
- BV differential photometry of HR 7224
- Short Name:
- J/A+A/499/567
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Although photometric variations of chemically peculiar (CP) stars are frequently used to determine their rotational periods, the detailed mechanism of their light variability remains poorly understood. We simulate the light variability of the star HR 7224 using the observed surface distribution of silicon and iron. We used the TLUSTY model atmospheres calculated for the appropriate silicon and iron abundances to obtain the emergent flux and to predict the rotationally modulated light curve of the star. We also obtained additional photometric measurements and employed our own regression procedure to derive a more precise estimate of the light elements. We show that the light variation of the star can be explained as a result of i) the uneven surface distribution of the elements, ii) the flux redistribution from the ultraviolet to the visible part of the spectrum, and iii) rotation of the star. We show that the silicon bound-free transitions and iron bound-bound transitions provide the main contribution to the flux redistribution, although an additional source of opacity is needed. We confirm that numerous iron lines significantly contribute to the well-known depression at 5200{AA} and discuss the connection between iron abundance and the value of peculiarity index a. The uneven surface distribution of silicon and iron is able to explain most of the rotationally modulated light variation in the star HR 7224.
- ID:
- ivo://CDS.VizieR/J/A+A/420/1039
- Title:
- 2001-2003 BV differential photometry of SW Lac
- Short Name:
- J/A+A/420/1039
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- In the present study, the activity of the eclipsing binary of the W UMa-type system SW Lac is examined by analysing the new BV photoelectric observations obtained in 2001, 2002 and 2003 at the Ankara University Observatory. During this period, the seasonal light curves show significant differences and asymmetries. A simultaneous analysis of the light curves is made using Djurasevic's inverse-problem method.
- ID:
- ivo://CDS.VizieR/J/A+A/521/A36
- Title:
- BV differential photometry of V711 Tau
- Short Name:
- J/A+A/521/A36
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- 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 H{alpha} 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.
- ID:
- ivo://CDS.VizieR/J/A+A/465/943
- Title:
- BVI and RV curves of 5 eclipsing binaries
- Short Name:
- J/A+A/465/943
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We detected tertiary components of close binaries from spectroscopy and light curve modelling, investigated the light-travel time effect and the possibility of magnetic activity cycles, measured mass ratios for unstudied systems, and derived absolute parameters. We carried out new photometric and spectroscopic observations of five bright close eclipsing binaries, predominantly in the southern skies. We obtained full Johnson BV light curves, which were modelled with the Wilson-Devinney code. Radial velocities were measured with the cross-correlation method using IAU radial velocity standards as spectral templates. Period changes were studied with the O-C method, utilising published epochs of minimum light (XY Leo) and ASAS photometry (VZ Lib). For three objects (DX Tuc, QY Hya, V870 Ara), absolute parameters have been determined for the first time. We spectroscopically detected the tertiary components in XY Leo and VZ Lib and discovered one in QY Hya. For XY Leo we updated the light-time effect parameters and detected a secondary periodicity of about 5100d in the O-C diagram that may hint at the existence of short-period magnetic cycles. A combination of recent photometric data shows that the orbital period of the tertiary star in VZ Lib is likely to be over 1500d. QY Hya is a semi-detached X-ray active binary in a triple system with K and M-type components, while V870 Ara is a contact binary with the third smallest spectroscopic mass ratio for a W UMa star to date. Being close to the theoretical minimum for contact binaries, this small mass ratio suggests that V870 Ara has the potential of constraining evolutionary scenarios of binary mergers. The inferred distances to these systems are compatible with the Hipparcos parallaxes.
- ID:
- ivo://CDS.VizieR/J/ApJ/483/826
- Title:
- BVI CCD photometry of Berkeley 17
- Short Name:
- J/ApJ/483/826
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Faint magnitude BVI CCD photometry of the central region of the old open cluster Berkeley 17 (Be 17) has been undertaken to investigate the claim that it is the oldest open cluster yet discovered (Phelps, Janes, & Montgomery, 1994AJ....107.1079P). This study reveals Be 17 to have a metallicity -0.30<=[Fe/H]<=0.00; a reddening 0.52<=E(B-V)<=0.68 or 0.61<=E(V-I)<=0.71; a distance modulus, (m-M)_0_=12.15+/-0.10, corresponding to a distance of 2.7+/-0.1kpc; a diameter of ~10pc; a minimum mass of 400 Msun; and an age of 10-13Gyr. With an adopted age of 12(+1)(-2)Gyr, these results suggest that Be 17 is indeed the oldest open cluster yet discovered. The inferred old age for Be 17 indicates that the cluster is an important one for studies of the differences between open and globular clusters, the transition from the halo/thick disk to the thin disk of the Galaxy, and even for establishing the minimum age of the universe.
- ID:
- ivo://CDS.VizieR/J/MNRAS/250/683
- Title:
- BVI CCD photometry of NGC 7510
- Short Name:
- J/MNRAS/250/683
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- CCD observations in B, V and I passbands have been used to generate deep V, (B-V) and V, (V-I) colour-magnitude diagrams for the open cluster NGC 7510. The sample consists of 592 stars reaching down to V=21mag. There appears to be non- uniform extinction over the face of the cluster with the value of colour excess, E(B-V), ranging from 1.0 to 1.3mag. The law of interstellar extinction in the direction of the cluster is found to be normal. A broad main sequence is clearly visible in both colour-magnitude diagrams. From the bluest part of the colour-magnitude diagrams, the true distance modulus to the cluster has been estimated as 12.5+/-0.3mag and an upper limit of 10 Myr has been assigned for the cluster age.
- ID:
- ivo://CDS.VizieR/J/AJ/126/2840
- Title:
- BVI CCD photometry of Sextans dSph galaxy
- Short Name:
- J/AJ/126/2840
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present deep wide-field VI CCD photometry of the Sextans dwarf spheroidal galaxy (dSph) in the Local Group, covering a field of 42'x28' located at the center of the galaxy (supplemented by short B photometry). The limiting magnitudes with 50% completeness are V=24.4mag and I=23.6mag.
- ID:
- ivo://CDS.VizieR/J/A+A/478/865
- Title:
- BVIc differential photometry of GSC 0762-110
- Short Name:
- J/A+A/478/865
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Photometry of the triple-mode radially pulsating variable GSC 0762-0110 has been performed. The star has a fundamental period of 0.1945d and period ratios of 0.7641 and 0.8012. In addition two non-radial modes were found, for which the amplitude diminished considerably over the last few years. The data presented here are the B, V and Ic differential instrumental magnitudes of GSC 0762-0110 with respect to GSC 0766-2426. The V data are from four different observatories, the B and Ic data from a single observatory. Instrumental details are given in the paper.
