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29 frequencies for the δ Scuti variable BI CMi: the 1997-2000 multisite campaigns
A multisite campaign of BI CMi was carried out with excellent frequencyresolution and high photometric accuracy from 1997 to 2000, includingtwo long observing seasons. 29 pulsation frequencies could be extractedfrom the 1024h (177 nights) of photometry used. The detected frequenciesinclude 20 pulsation modes in the main pulsation frequency range from4.8 to 13.0cycled-1 (55 to 150μHz), eight linearcombinations of these frequencies, and a very low frequency at1.66cycled-1. Since the value of the low frequency at1.66cycled-1 cannot be identified with a linear combinationof other frequencies, g-mode pulsation is suspected, but rotationalmodulation of abundance spots cannot be ruled out. BI CMi, which issituated near the cool edge of the classical instability strip, may beboth a δ Scuti and a γ Doradus star. Another outstandingproperty of BI CMi is the presence of a number of close frequency pairsin the power spectrum with separations as small as0.01cycled-1. A rotational velocity ofvsini=76+/-1kms-1 was determined from a high-dispersionspectrum. From phase differences, the dominant modes can be identifiedwith l values from 0 to 2. The spectral type and evolutionary status ofBI CMi are examined.
| YY Canis Minoris: Contact or near contact system?
New V photoelectric observations of the eclipsing system YY CMi,obtained at La Silla, Chile, and Merate Observatory, Italy, arepresented. New times of minima and ephemeris based on our observationsare also given. The V light curve was analysed by using the WD code toderive the geometrical and physical parameters of the system. Since nospectroscopic mass ratio is available, the q-search method was appliedto yield the preliminary range of the mass ratio in order to search forthe final solution. First the unspotted solution was carried out byusing the unperturbed parts of the light curve and applying the DCprogram of the WD code. The solution was performed by assuming contact(mode 3) and semi-detached (mode 4) configuration, since noclassification of the system is possible from the shape of the lightcurve. The solution in mode 4 does not lead to an acceptable model,since the secondary was found to be slightly overcontact. Therefore thecontact solution was finally adopted. Moreover the light curvepeculiarities (Max II fainter than Max I and excess of light around thephase 0.32) were explained by assuming a cool and a hot spot on thesurface of the secondary (cooler) component. The degree of contact isvery small (f~ 3%) and the thermal contact is poor (T_1-T_2)~ 650 K.These results together with the high photometric mass ratio q~ 0.89indicate that YY CMi is very probably a system at the beginning or theend of the contact phase. Based on observations partly made at theEuropean Southern Observatory (ESO). Table 1 is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html
| Vitesses radiales. Catalogue WEB: Wilson Evans Batten. Subtittle: Radial velocities: The Wilson-Evans-Batten catalogue.
We give a common version of the two catalogues of Mean Radial Velocitiesby Wilson (1963) and Evans (1978) to which we have added the catalogueof spectroscopic binary systems (Batten et al. 1989). For each star,when possible, we give: 1) an acronym to enter SIMBAD (Set ofIdentifications Measurements and Bibliography for Astronomical Data) ofthe CDS (Centre de Donnees Astronomiques de Strasbourg). 2) the numberHIC of the HIPPARCOS catalogue (Turon 1992). 3) the CCDM number(Catalogue des Composantes des etoiles Doubles et Multiples) byDommanget & Nys (1994). For the cluster stars, a precise study hasbeen done, on the identificator numbers. Numerous remarks point out theproblems we have had to deal with.
| The delta Scuti star BI Canis Minoris (identically equals HD 66853): Pulsational behavior and a critical discussion of physical parameter determination
A two site photometric campaign on the delta Scuti star BI CMi (2302 Vobservations over 16 nights) has allowed us to detect unambiguously fourpulsation frequencies nul = 8.246, nu2 = 8.865,nu3 = 7.433 and nu4 = 8.515 c/d) with amplitudesbetween 22 and 5 mmag. The data also show the presence of the nonlinearcoupling term nu1 + nu2, the 2 nu1 termand the possible presence of two other frequencies with amplitudes of2-3 mmag. Other components with further smaller amplitudes are probablypresent, but the data do not allow reliable identifications. We discussthe identification of the pulsation modes in term of nonradical p modes,and we also point out the uncertainties on these identificationassociated to the physical parameter estimates. The possiblemicrovariability of HD 67028, one of the two comparison stars, is alsodiscussed.
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Observation and Astrometry data
| Constellation: | Canis Minor |
| Right ascension: | 08h05m47.71s |
| Declination: | +02°09'54.3" |
| Apparent magnitude: | 6.821 |
| Distance: | 448.43 parsecs |
| Proper motion RA: | -2.2 |
| Proper motion Dec: | -5.7 |
| B-T magnitude: | 6.815 |
| V-T magnitude: | 6.821 |
Catalogs and designations:
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INHABITED SKY
