- ID:
- ivo://CDS.VizieR/J/AJ/129/2026
- Title:
- Differential photometry of HD 8801
- Short Name:
- J/AJ/129/2026
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have discovered the first example of a star pulsating intrinsically with both {gamma} Doradus and {delta} Scuti frequencies. HD 8801 is an Am metallic-line star that appears to be single. Since the vast majority of Am stars are members of binary systems with periods less than 1000 days and also do not pulsate, HD 8801 possesses a very unusual, if not unique, combination of physical properties. Our photometry, acquired with an automatic telescope at Fairborn Observatory, resolves six independent pulsation periods between 0.048 and 0.404 days. The two longest periods lie within the range of {gamma} Dor variables, while the four shorter periods are within the range of {delta} Sct stars.
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- ID:
- ivo://CDS.VizieR/J/ApJ/688/1345
- Title:
- Differential photometry of the SB* BD+20 307
- Short Name:
- J/ApJ/688/1345
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Field star BD+20 307 is the dustiest known main-sequence star, based on the fraction of its bolometric luminosity, ~4%, that is emitted at infrared wavelengths. The particles that carry this large infrared luminosity are unusually warm, comparable to the temperature of the zodiacal dust in the solar system, and their existence is likely to be a consequence of a fairly recent collision of large objects such as planets or planetary embryos. Thus, the age of BD+20 307 is potentially of interest in constraining the era of terrestrial planet formation. The present project was initiated with an attempt to derive this age using the Chandra X-Ray Observatory to measure the X-ray flux of BD+20 307 in conjunction with extensive photometric and spectroscopic monitoring observations from Fairborn Observatory. However, the recent realization that BD+20 307 is a short-period, double-line, spectroscopic binary whose components have very different lithium abundances vitiates standard methods of age determination. We find the system to be metal-poor; this, combined with its measured lithium abundances, indicates that BD+20 307 may be several to many Gyr old. BD+20 307 affords astronomy a rare peek into a mature planetary system in orbit around a close binary star (because such systems are not amenable to study by the precision radial velocity technique).
- ID:
- ivo://CDS.VizieR/J/A+A/469/285
- Title:
- Differential Stroemgren photometry of U Oph
- Short Name:
- J/A+A/469/285
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We aim to determine absolute dimensions for the mid B-type eclipsing binary U Ophiuchi and compare the inferred ages and chemical compositions to those of other binary stars with masses near 5M_{sun}_. We determine masses, radii, logg, logT_eff_, and luminosities for the stars in U Oph from new radial velocities and uvby light curves. By improving the Wilson-Devinney code, we also derive precise apsidal-motion and light-time orbits of this triple system, using 353 times of minimum over 120 years. Finally, we compare the data for U Oph and similar systems with the predictions of stellar models.
- ID:
- ivo://CDS.VizieR/J/A+A/480/187
- Title:
- Differential Stromgren photometry of 15 And
- Short Name:
- J/A+A/480/187
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The {lambda} Bootis stars are a chemically peculiar subgroup of main sequence A/F stars. Several of these fall into the instability strip of the {delta} Scuti stars and the whole spectroscopic group shows a high incidence of pulsational variability. We investigated the pulsational behaviour of the {lambda} Bootis star 15 And (HD 221756) to determine as many intrinsic mode frequencies as possible for asteroseismic applications.
- ID:
- ivo://CDS.VizieR/J/A+A/456/261
- Title:
- Differential uvby photometry of HD 239276
- Short Name:
- J/A+A/456/261
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The variability of HD 239276 was suspected photometrically nearly twenty years ago, but was confirmed with new observations obtained in 2001 during a two-site photometric campaign carried out from Spain, in uvby{beta} Stroemgren-Crawford photometry, and China, using the Johnson V filter. Two low-dispersion spectra were also collected. The results establish this star as a new multiperiodic gamma Dor-type pulsator with deficiency in metallicity.
- ID:
- ivo://CDS.VizieR/J/A+A/450/715
- Title:
- Differential uvby photometry of HD 218427
- Short Name:
- J/A+A/450/715
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Table 1 contents 845 simultaneous measurements collected in each of the four uvby colours of the Stromgren photometric system for the Gamma Doradus variable HD 218427. The data are magnitude differences (Du, Dv, Db, Dy, D(b-y), Dm1, Dc1) of the variable star minus comparison star in the standard system versus Heliocentric Julian Date. The comparison star is HD 219874. The origin in time is the Julian Day 2452839. The observations were carried out by the authors through the year 2003 using the 0.90m telescope at Sierra Nevada Observatory, Spain (Julian Days:0 to 69 in the table) and the 1.50m telescope at San Pedro Martir Observatory, Mexico (Julian Days: 122 to 128). Both telescopes are equipped with identical six-channel uvby-Hbeta spectrograph photometers for simultaneous measurements in uvby or in the narrow and wide H{beta} channels, respectively. Please note that a technical problem arose with the "u" filter in the 1.50m telescope, which made the "u" data collected with that telescope useless and they are named as 99.
- ID:
- ivo://CDS.VizieR/J/A+A/309/787
- Title:
- DX Eri variability
- Short Name:
- J/A+A/309/787
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present results of nearly simultaneous monitoring of uvby light and HeI667.81nm line-profile variations of the equatorial Be star DX Eri in November 1991. They are analysed along with numerous uvby photometry in the period 1986-1995.
- ID:
- ivo://CDS.VizieR/J/A+A/326/1044
- Title:
- Eclipsing binaries uvbyHbeta photometry
- Short Name:
- J/A+A/326/1044
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Systematic differences in photometric stellar surface gravity determination are studied by means of the comparison with empirical values derived from detached double-lined eclipsing binaries. Photometric gravities were computed using Moon & Dworetsky (1985MNRAS.217..305M) grids based on Kurucz (1979ApJS...40....1K) atmosphere models, and empiric al gravities were taken from Andersen (1991A&ARv...3...91A). Individual Stroemgren colours and {beta} indices of each component of the binary system have to be taken into account to correctly analyze the observed differences. A compilation of data on a sample containing 30 detached double-lined eclipsing binaries with accurate (=~1-2%) determination of mass and radius and available uvbyH_{beta}_ photometric data is also presented. Correction of the differences in terms of T_eff_ and logg for the range 11000K<T_eff_<20000K reduces the mean residuals from 0.13dex to 0.07dex. For the range 7000K<T_eff_<8500K, the consideration of metallicity effects by means of {delta}m_o_ index improves the accuracy from 0.20dex to 0.09dex.
- ID:
- ivo://CDS.VizieR/V/14
- Title:
- Estimated astrophysical parameters from uvby
- Short Name:
- V/14
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Observed values of the Stroemgren uvby colors were collected from the literature. A computer program calculated the reddening for each star. This value was used to compute the unreddened value of (b-v), c1, and m1. These were then used to compute [c(1)], [m(1)], and [u-b] for the star. Except for the H beta index, the observed quantities are not included.
- ID:
- ivo://CDS.VizieR/J/A+A/511/A22
- Title:
- EW Ori differential uvby light curves
- Short Name:
- J/A+A/511/A22
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Recent studies of inactive and active solar-type binaries suggest that chromospheric activity, and its effect on envelope convection, is likely to cause significant radius and temperature discrepancies. Accurate mass, radius, and abundance determinations from additional solar-type binaries exhibiting various levels of activity are needed for a better insight into the structure and evolution of these stars. We aim to determine absolute dimensions and abundances for the G0 V detached eclipsing binary EW Ori, and to perform a detailed comparison with results from recent stellar evolutionary models.
