The Nainital-Cape Survey. II. Report for pulsation in five chemically peculiar A-type stars and presentation of 140 null results
Aims.We search for photometric variability in chemically peculiar A typestars in the northern hemisphere. Methods: .High-speed photometricobservations of Ap and Am star candidates have been carried out fromARIES (Manora Peak, Nainital) using a three-channel fast photometerattached to the ARIES 104-cm Sampurnanand telescope. Results:.This paper presents three new variables: HD 113878, HD 118660 and HD207561. During the time span of the survey (1999 December to 2004January) pulsations of the δ Sct type were also found for the twoevolved Am stars HD 102480 and HD 98851, as reported in Joshi et al.(2002, 2003). Additionally, we present 140 null results of the surveyfor this time span. Conclusions: .The star HD 113878 pulsates witha period of 2.31 h, which is typical of δ Sct stars. HD 118660exhibits multi-periodic variability with a prominent period of nearly 1h. These periods need to be investigated and make HD 118660 aparticularly interesting target for further observations. For HD 207561,a star classified as Am, a probable pulsation with a period of 6 min wasfound in the light curves obtained on two consecutive nights. Both HD102480 and HD 98851 exhibit unusual alternating high and low amplitudemaxima, with a period ratio of 2:1. The analysis of the null resultsconfirms the photometric quality of the Nainital site.
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delta Scuti and related stars: Analysis of the R00 Catalogue
We present a comprehensive analysis of the properties of the pulsatingdelta Scuti and related variables based mainly on the content of therecently published catalogue by Rodríguez et al.(\cite{retal00a}, hereafter R00). In particular, the primaryobservational properties such as visual amplitude, period and visualmagnitude and the contributions from the Hipparcos, OGLE and MACHOlong-term monitoring projects are examined. The membership of thesevariables in open clusters and multiple systems is also analyzed, withspecial attention given to the delta Scuti pulsators situated ineclipsing binary systems. The location of the delta Scuti variables inthe H-R diagram is discussed on the basis of HIPPARCOS parallaxes anduvbybeta photometry. New borders of the classical instability arepresented. In particular, the properties of the delta Scuti pulsatorswith nonsolar surface abundances (SX Phe, lambda Boo, rho Pup, delta Deland classical Am stars subgroups) are examined. The Hipparcos parallaxesshow that the available photometric uvbybeta absolute magnitudecalibrations by Crawford can be applied correctly to delta Scutivariables rotating faster than v sin i ~ 100 km s{-1} withnormal spectra. It is shown that systematic deviations exist for thephotometrically determined absolute magnitudes, which correlate with vsin i and delta m1. The photometric calibrations are found tofit the lambda Boo stars, but should not be used for the group ofevolved metallic-line A stars. The related gamma Dor variables and thepre-main-sequence delta Scuti variables are also discussed. Finally, thevariables catalogued with periods longer than 0fd 25 are examined on astar-by-star basis in order to assign them to the proper delta Scuti, RRLyrae or gamma Dor class. A search for massive, long-period delta Scutistars similar to the triple-mode variable AC And is also carried out.
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Absolute proper motions of open clusters. I. Observational data
Mean proper motions and parallaxes of 205 open clusters were determinedfrom their member stars found in the Hipparcos Catalogue. 360 clusterswere searched for possible members, excluding nearby clusters withdistances D < 200 pc. Members were selected using ground basedinformation (photometry, radial velocity, proper motion, distance fromthe cluster centre) and information provided by Hipparcos (propermotion, parallax). Altogether 630 certain and 100 possible members werefound. A comparison of the Hipparcos parallaxes with photometricdistances of open clusters shows good agreement. The Hipparcos dataconfirm or reject the membership of several Cepheids in the studiedclusters. Tables 1 and 2 are only available in electronic form at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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Pulsation behavior of classical Am star 60 Tauri
Five nights photoelectric photometric observations through v and y bandsconfirm the pulsation of classical Am δ Scuti variable 60 Tau.Power spectrum of light curves shows multi-period pulsation behavior of60 Tau and two pulsation modes f1=13.0364 andf2=11.8521 cycles per day are definitely identified.Classical Am star 60 Tau is a complicated pulsation δ Scutivariable. Considering the pulsation constant Q, 60 Tau is identified tobe low overtone f or p1 modes tendentiously.
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A revised catalogue of delta Sct stars
An extensive and up-dated list of delta Sct stars is presented here.More than 500 papers, published during the last few years, have beenrevised and 341 new variables have been added to our last list, sixyears ago. This catalogue is intended to be a comprehensive review onthe observational characteristics of all the delta Sct stars known untilnow, including stars contained in earlier catalogues together with othernew discovered variables, covering information published until January2000. In summary, 636 variables, 1149 references and 182 individualnotes are presented in this new list. Tables 1 and 2 will be accessibleonly in electronic form at the CDS via anonymous ftp tocdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
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Observing roAp Stars with WET: A Primer
We give an extensive primer on roAp stars -- introducing them, puttingthem in context and explaining terminology and jargon, and giving athorough discussion of what is known and not known about them. Thisprovides a good understanding of the kind of science WET could extractfrom these stars. We also discuss the many potential pitfalls andproblems in high-precision photometry. Finally, we suggest a WETcampaign for the roAp star HR 1217.
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Mode identification and asteroseismology of delta Scuti stars
The use of multicolour photometry for mode identification in pulsatingstars is discussed. We present a new, statistically based, algorithm forfinding the best estimate of the spherical harmonic degree, and aconfidence level from which the uniqueness can be ascertained. Themethod is applied to some well-observed delta Sct stars with multicolourphotometry. We also propose an algorithm to deduce the effectivetemperature, luminosity and equatorial velocity from the observedfrequencies. We find that fixing the modes of at least some frequenciesis essential for a unique solution. The method is applied to a subset ofthe delta Sct stars which have a suitable number of frequencies and modeidentifications.
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The nature of some doubtful open clusters as revealed by HIPPARCOS
We discuss the nature of some galactic open clusters by using propermotions and parallaxes from the Hipparcos and ACT catalogues. We showthat the clusters Collinder 399, Upgren 1, NGC 1252 and Melotte 227 donot exist. Collinder 132 is found to be mainly composed out of membersof an OB association, but there may be a star cluster present in thisarea too. Roeser & Bastian (1994) proposed that NGC 2451 consists oftwo star clusters. We show that NGC 2451 A definitively does exist, NGC2451 B may exist. A star cluster may also be present in the area ofRoslund 5. The Hipparcos data finally confirm the reality of Collinder135.
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Metallicism and pulsation: the discovery of large-amplitude delta Scuti pulsation in a high-metallicity rho Puppis star, HD 40765
We have discovered that HD 40765 is a singly periodic delta Scuti starpulsating in the fundamental or first overtone radial mode with a periodof 4.070h. Its light variations are non-sinusoidal and have peak-to-peakamplitudes of DeltaB=0.21 mag and DeltaV=0.15 mag. This star is stronglymetallic-lined. We classify the spectrum Fmp (kA7hF5mF5), where the `p'does not indicate peculiar in the Ap sense, but peculiar in the sensethat the spectrum cannot be fully parametrized. HD 40765 is alarge-amplitude delta Scuti star which is also a rho Puppis, or evolvedAm, star. By comparison with rho Puppis itself, the inferred surfaceradial velocity variations are 14 km s^-1 peak-to-peak. This implieseither (1) that such pulsation can be non-turbulent at the level ofpredicted diffusion velocities of order cm s^-1, or (2) that diffusionshould be reconsidered as the sole explanation for the abundanceanomalies in this star.
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A catalogue of variable stars in the lower instability strip.
Identifications, positions, photometry, spectra, some pulsationalfeatures, other astrophysical parameters and literature for 302pulsating variable stars in the lower instability strip, near the ZAMS,are given. About 185 stars have near homogeneous photometric informationin the Stroemgren's uvby-β photometric system. Thiscatalogue/database covers information published until November 1993.
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Stroemgren photometry of F- and G-type stars brighter than V = 9.6. I. UVBY photometry
Within the framework of a large photometric observing program, designedto investigate the Galaxy's structure and evolution, Hβ photometryis being made for about 9000 stars. As a by-product, supplementary uvbyphotometry has been made. The results are presented in a cataloguecontaining 6924 uvby observations of 6190 stars, all south ofδ=+38deg. The overall internal rms errors of one observation(transformed to the standard system) of a program star in the interval6.5
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δ Scuti stars: a new revised list
An extensive and up to date list of δ Sct stars is presented. Thiscatalogue is intended to be a comprehensive review of observationalcharacteristics of all the δ Sct stars known until now, includingstars contained in earlier catalogues together with other new discoveredvariables, covering information published until November 1993. Globalinformation in the form of histograms and diagrams are also shown.
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Catalogue of CP stars with references to short time scale variability
A catalogue was compiled which contains all references in the literaturesince 1962 related to variations of CP stars on time scales shorter thanthe rotation period. The role of this catalogue lies in the unbiasedlisting of all available references, and not in a critical evaluation.
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Pulsational Activity on Ik-Pegasi
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1994MNRAS.267.1045W&db_key=AST
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Liste des étoiles Ap et Am dans les amas ouverts (édition révisée)
Not Available
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Liste des étoiles Ap et Am dans les amas ouverts (Edition révisée)
Not Available
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Catalog of AP and AM stars in open clusters
The previous results of Raab (1922), Markarian (1951), and Collinder(1931) have been used to catalog Ap and Am stars that are in the fieldof open clusters. Tabular data are presented for the clusterdesignation, the HD or HDE number, the right ascension (1900), thedeclination (1900), and the magnitude. Also listed are the spectraltypes and, for certain stars, the probability of cluster membership.
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Contributing factors to flux changes in nonradial stellar pulsations
The factors contributing to flux changes in nonradial stellar pulsationsare investigated under conditions applicable to a variety of pulsatingstar types by examining a linearized analytic representation of observedflux changes due to nonradial pulsations with mode indices (l,m).Histograms are presented, showing as a function of l, the relativeimportance of local temperature, geometry, pressure, and limb-darkeningvariations in contributing to nonradial flux changes. A procedure forthe comparison of observational light and color data with modelpredictions on an amplitude ratio versus phase difference plane isoutlined. Application of this procedure to data on Beta Cephei, 53Persei, Delta C Scuti, rapidly oscillating Ap, Cepheid, and ZZ Cetivariables stars is shown to agree with published data on these systems.
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Chemically peculiar stars in open clusters. I - The catalog
The largest existing compilation is presented of Ap and Am open clusterstars. The catalog contains information on 381 chemically peculiar (CP)stars of the upper main sequence in 79 open clusters. The catalog iscomposed of the following tables: (1) the main body, which lists CP (orsuspected CP) stars which are kinematical (or suspected kinematical)members of open clusters; (2) the list of CP (or suspected CP) starssometimes numbered among cluster members but which are actuallykinematical nonmembers; (3) the list of stars sometimes designated as'peculiar' but, in fact, probably not CP; (4) references for numberingsystems of cluster stars; (5) references for membership; and (6)references for spectral and/or peculiarity types.
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Classification of intrinsic variables. IX - The Cepheid domain
The present H-beta, RI and intermediate band observations obtained for135 high mass, long- and short-period Cepheids (LPC and SPC) throughoutthe cycle of variation are combined with observations for 100 ultrashortperiod Cepheids in order to delineate the Cepheid domain in the (beta,/C1/) and (M-bol, log Te) planes. The independently derived luminositycalibrations for bright giants and supergiants previously published arefound to closely reproduce the luminosities derived from theSandage-Tammann (1968) PL relation for most variables. The majority ofthe LPC appear to be overabundant in metals by comparison to the sun,and reddening determinations for the LPC suggest a small systematiccorrection to previous results.
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Study of the variability of the Delta Scuti-stars. III - Radial and nonradial pulsations in KW 207
Photoelectric observations of the Delta Scuti star KW 207 (HD 73576) arepresented. Despite low variations, the analysis of the light curve showsat least two significant periodicities, which appear to be related tononradial pulsations. It is pointed out that the high rotationalvelocity of KW 207 weakens the hypothesis that among giants thevariables have considerably lower rotational velocities than constantstars.
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A Spectroscopic Study of the Light Variable Peculiar Star HD188136
Abstract image available at:http://adsabs.harvard.edu/abs/1981ApJ...247..969W
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65th Name-List of Variable Stars
Not Available
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On the stability of observed frequencies in Delta Scuti stars - A reanalysis of Theta TUC
The claim that some Delta Scuti stars change their frequencies on timescales as short as 24 hr is examined. It is suggested that thehypothesis that these Delta Scuti stars have stable frequencies isviable. Stobie and Shobbrook's (1976) data on Theta Tuc is reanalyzedalong with 954 new observations obtained during 70 hr on 21 nights in1979. The frequency of highest amplitude is shown to be present at aconstant amplitude over the 7-yr time span of the entire data set. Apossible set of frequencies is fitted to the Theta Tuc data. Other DeltaScuti stars which have been claimed to have variable frequencies arediscussed. Some of these stars are now known to have stable frequencies.A reanalysis of Stobie, Pickup and Shobbrook's data (1977) and Gupta'sdata (1973) on 21 Mon gives the same result found by Stobie, Pickup, andShobbrook: 21 Mon appears to have changed frequencies in the 2-yrinterval between the data sets. It is pointed out that claims ofchanging frequencies for Delta Scuti stars should only be made withcaution and a large amount of data.
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The frequency analysis of low amplitude delta Scuti stars. V - HD 188520
The paper analyzes HD188520 which is an A7IV/V star shown to be a newdelta Scuti variable. Photometry of this star is consistent with theA7/IV/V spectral classification; a frequency analysis of 502observations of HD188520 in a 60.5 hr period on 10 nights is presented.Two frequencies are present throughout the 66 day time-span of the dataset, although the alias at 3.760/day may be the correct lower frequency.It is suggested that the frequency at 4.762/day may result from g-modepulsation or ellipsoidal variability.
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Radial and non-radial oscillations in the very high metallicity Delta Scuti star HD 188136
The paper analyzes observations which show that HD 188136 is a DeltaScuti star. The metallicity index and the Sr4077 line which is nearly asstrong as H(delta) show that this star has a very high metallicity.Frequency analysis of 173 hr observations obtained on 30 nights in1978-79 was made; three frequencies were present throughout the entiredata set, one of which is due to a nonradial mode. It is suggested thatsince the Delta Scuti star evolves off the main sequence, it passesthrough a stage where radial and nonradial modes of the same k-valuecoincide.
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Uvby-beta photometry of stars in the Michigan Spectral Catalogue. I - The Delta Del stars
uvby-beta photometry of 74 stars classified as Delta Del in Volume 1 ofthe Michigan Spectral Catalogue is presented. The photometry is inagreement with the spectral classification in that it indicates DeltaDel stars are metal-line-enhanced stars with equivalent-temperaturetypes of A9 + or - 2 subtypes. There is a discrepancy between theluminosity implied from the delta c1 index and the spectralclassification. It is argued that c1 is an inadequateluminosity indicator for some late A- to early F-type stars. Several ofthe Delta Del stars are known Delta Scuti pulsators, and some commentson the metallicism-pulsation relation are made.
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Estimation of spectral classifications for bright southern stars with interesting Stromgren indices
This paper investigates the degree of success with which uvby photometrycan be applied to predict spectral classifications for 947 A, F, and Gstars brighter than an apparent magnitude of 8.3 and with four-colorindices indicating some kind of interesting, unusual, or peculiarspectrum. One or several possible spectral classifications are estimatedfor each star from photometry alone, double stars are distinguished, andthe estimates are compared with published classifications. The resultsshow that the framework provided by uvby photometry can be extended toinclude most G and K stars, reddened stars, peculiar stars, and certaintypes of double star.
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Four-color photoelectric photometry of two high-latitude clusters.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1968AJ.....73..556E&db_key=AST
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A survey of stars with composite spectra.
Not Available
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