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Galactic restrictions on iron production by various types of supernovae
We propose a statistical method for decomposition of contributions toiron production from various sources: Type II supernovae and thesubpopulations of Type Ia supernovae, prompt (their progenitors areshort-lived stars with ages lower than ˜100 Myr) and tardy (theirprogenitors are long-lived stars with ages >100 Myr). To do that, wedevelop a theory of oxygen and iron synthesis that takes into accountthe influence of the spiral arms on the amount of the above elementssynthesized by both Type II supernovae and prompt Type Ia supernovae. Inthe framework of the theory, we processed statistically the new, moreprecise, observational data on Cepheid abundances, which, as is wellknown, demonstrate non-trivial radial distributions of oxygen and ironin the Galactic disc with bends in the gradients. In our opinion, suchfine structure in the distribution of elements along the Galactic discenables one to decompose the amount of iron unambiguously into threecomponents produced by the above three sources. In addition, by means ofour statistical methods we solve this task without any preliminarysuppositions about the ratios between the proportions of ironsynthesized by the above sources.The total mass supplied to the Galactic disc during its life by alltypes of supernovae is ˜(4.0 ± 0.4) × 107M&sun;, while the mass of iron occurring in the presentinterstellar medium (ISM) is ˜(1.20 ± 0.05) ×107 M&sun;, i.e. about two thirds of iron iscontained in stars and stellar remnants.The relative proportion of iron synthesized by tardy type Ia supernovaefor the lifetime of the Galaxy is ˜35 per cent (in the present ISMthis portion is ˜50 per cent). Correspondingly, the totalproportion of iron supplied to the disc by Type II supernovae and promptType Ia supernovae is ˜65 per cent (in the present ISM thisproportion is ˜50 per cent). The above result depends slightly onthe adopted mass of oxygen and iron synthesized during one supernovaexplosion and the shape (bimodal or smooth) of the so-called delay-timedistribution function.The proportions of iron mass distributed between short-lived supernovaeare usually as follows: depending on the ejected masses of oxygen oriron during one Type II supernova event, the relative proportion of ironsupplied to the Galactic disc for its age varies in the range 12-32 percent (in the present ISM 9-25 per cent); the proportion supplied byprompt Type Ia supernovae to the Galactic disc is 33-53 per cent (in theISM 26-42 per cent).Our method also confirms that the bend in the observed slope of theoxygen radial distribution and the minimum in [O/Fe] at ˜7 kpcform in the vicinity of the location of the corotation resonance.
| The Distribution of the Elements in the Galactic Disk. II. Azimuthal and Radial Variation in Abundances from Cepheids
This paper reports on the spectroscopic investigation of 101 Cepheids inthe Carina region. These Cepheids extend previous samples by about 35%in number and increase the amount of the Galactic disk coverageespecially in the direction of l ? 270°. The new Cepheids do notadd much information to the radial gradient, but provide a substantialincrease in azimuthal coverage. We find no azimuthal dependence inabundance over an 80° angle from the Galactic center in an annulusof 1 kpc depth centered on the Sun. A simple linear fit to the Cepheiddata yields a gradient d[Fe/H]/dRG = -0.055 ± 0.003dex kpc-1 which is somewhat shallower than found from ourprevious, smaller Cepheid sample.
| Photoelectric observations of Cepheids in UBV(RI)c (Berdnikov, 2008)
This catalog gathers the observation of 894 Cepheids made between 1986to 2004.Observations are listed in alphabetical order of the constellations. Thestandard deviation for every magnitude and color is 0.01mag.This version supersedes the 1997 edition (Cat. )(3 data files).
| Galactic Cepheids. Catalogue of light-curve parameters and distances
We report a new version of the catalogue of distances and light-curveparameters for Galactic classical Cepheids. The catalogue listsamplitudes, magnitudes at maximum light, and intensity means for 455stars in BVRI filters of the Johnson system and (RI)_C filters of theCron-Cousins system. The distances are based on our new multicolour setof PL relations and on our Cepheid-based solution for interstellarextinction law parameters and are referred to an LMC distance modulus of18.25. The catalogue is only available in electronic form at the CDS viaanonymous ftp (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/Abstract.html
| Multi-colour PL-relations of Cepheids in the bt HIPPARCOS catalogue and the distance to the LMC
We analyse a sample of 236 Cepheids from the hipparcos catalog, usingthe method of ``reduced parallaxes'' in V, I, K and the reddening-free``Wesenheit-index''. We compare our sample to those considered by Feast& Catchpole (1997) and Lanoix et al. (1999), and argue that oursample is the most carefully selected one with respect to completeness,the flagging of overtone pulsators, and the removal of Cepheids that mayinfluence the analyses for various reasons (double-mode Cepheids,unreliable hipparcos solutions, possible contaminated photometry due tobinary companions). From numerical simulations, and confirmed by theobserved parallax distribution, we derive a (vertical) scale height ofCepheids of 70 pc, as expected for a population of 3-10 Msunstars. This has consequences for Malmquist- and Lutz-Kelker (Lutz &Kelker 1973, Oudmaijer et al. 1998) type corrections which are smallerfor a disk population than for a spherical population. The V and I datasuggest that the slope of the Galactic PL-relations may be shallowerthan that observed for LMC Cepheids, either for the whole period range,or that there is a break at short periods (near log P_0 ~ 0.7-0.8). Westress the importance of two systematic effects which influence thedistance to the LMC: the slopes of the Galactic PL-relations andmetallicity corrections. In order to assess the influence of thesevarious effects, we present 27 distance moduli (DM) to the LMC. Theseare based on three different colours (V,I,K), three different slopes(the slope observed for Cepheids in the LMC, a shallower slope predictedfrom one set of theoretical models, and a steeper slope as derived forGalactic Cepheids from the surface-brightness technique), and threedifferent metallicity corrections (no correction as predicted by one setof theoretical models, one implying larger DM as predicted by anotherset of theoretical models, and one implying shorter DM based onempirical evidence). We derive DM between 18.45 +/- 0.18 and 18.86 +/-0.12. The DM based on K are shorter than those based on V and I andrange from 18.45 +/- 0.18 to 18.62 +/- 0.19, but the DM in K could besystematically too low by about 0.1 magnitude because of a bias due tothe fact that NIR photometry is available only for a limited number ofstars. From the Wesenheit-index we derive a DM of 18.60 +/- 0.11,assuming the observed slope of LMC Cepheids and no metallicitycorrection, for want of more information. The DM to the LMC based on theparallax data can be summarised as follows. Based on the PL-relation inV and I, and the Wesenheit-index, the DM is 18.60 ± 0.11(± 0.08 slope)(^{+0.08}_{-0.15} ;metallicity), which is ourcurrent best estimate. Based on the PL-relation in K the DM is ;;;;18.52 +/- 0.18 (± 0.03 ;slope) (± 0.06 ;metallicity)(^{+0.10}_{-0} ;sampling ;bias). The random error is mostly due to thegiven accuracy of the hipparcos parallaxes and the number of Cepheids inthe respective samples. The terms between parentheses indicate thepossible systematic uncertainties due to the slope of the GalacticPL-relations, the metallicity corrections, and in the K-band, due to thelimited number of stars. Recent work by Sandage et al. (1999) indicatesthat the effect of metallicity towards shorter distances may be smallerin V and I than indicated here. From this, we point out the importanceof obtaining NIR photometry for more (closeby) Cepheids, as for themoment NIR photometry is only available for 27% of the total sample.This would eliminate the possible bias due to the limited number ofstars, and would reduce the random error estimate from 0.18 to about0.10 mag. Furthermore, the sensitivity of the DM to reddening,metallicity correction and slope are smallest in the K-band. Based ondata from the ESA HP astrometry satellite.
| I- and JHK-band photometry of classical Cepheids in the HIPPARCOS catalog
By correlating the \cite[Fernie et al. (1995)]{F95} electronic databaseon Cepheids with the ``resolved variable catalog'' of the hipparcosmission and the simbad catalog one finds that there are 280 Cepheids inthe hipparcos catalog. By removing W Vir stars (Type ii Cepheids),double-mode Cepheids, Cepheids with an unreliable solution in thehipparcos catalog, and stars without photometry, it turns out that thereare 248 classical Cepheids left, of which 32 are classified asfirst-overtone pulsators. For these stars the literature was searchedfor I-band and near-infrared data. Intensity-mean I-band photometry onthe Cousins system is derived for 189 stars, and intensity-mean JHK dataon the Carter system is presented for 69 stars.
| New method to recognize s-Cepheids
A new method of delineating sinusoidal or s-Cepheids is presented. Themethos uses the values of (V) (the mean intensity), V - Bar (the averagemagnitude), and Vmean (the value of the mean magnitude).Fourier coefficient data from galactic Cepheids is used to derive theseterms in the V band and the differences between the various terms showsystematic trends with increasing period. The Cepheids can be easilygrouped into 3 divisions-short period s-Cepheids, intermediate periodCepheids (P less than 9 days), and long period Cepheids (P greater than9 days). Cepheids previously designated as s-Cepheids by others arecompared to those found using the method outlined here. The method isalso applied to Cepheids in the Small Magellanic Cloud to examine itssuitability as a pulsation mode discriminator.
| The Fourier decomposition as a mode discriminator - New first overtone pulsators among Cepheids with P less than 5.5 D
New very accurate light curves of 12 Cepheids with P less than 5.5 d arepresented. Their Fourier decomposition enabled us to individuate eightother stars which do not follow the Hertzsprung progression. Theproperties of the Fourier parameters of this subclass, now composed by28 objects, are consequently better defined. In the phi(21)-P plane 2stars located on the lower sequence and 2 other stars located on thediscontinuity at 3 d were found. All these 28 stars occupy the sameregion in the R(21)-P plane and the phi(31) values, when available,originate a unique sequence in the phi(31)-P plane. All these loci arewell separated from those of the classical Cepheids, which arefundamental mode pulsators. The hypotheses of a first overtone pulsationand of a resonance between this mode and a higher overtone explain theobservational facts well.
| Physical parameters of pulsating variables with periods between one and three days. II - Fundamental parameters
On the basis of the Walraven VBLUW photometry data reported by Diethelm(1986) on 57 pulsating variables with periods between one and threedays, primary parameters (metallicity, log g, Teff, and the amount ofreddening) were deduced for 11 of these stars, using a semiempiricalapproach based on model atmosphere calculations. Results indicate thatboth the C-delta and the SA-class of the pulsating variables are youngstars of the disc-population pulsating either in the fundamental(C-delta) or in the first overtone mode (SA). The AHB1 stars, whichshowed a marked deficiency in metal abundance, are members of the halopopulaton. The stars of the AHB2 and AHB3 groups, which show anintermediate metallicity, must be considered as members of anintermediate stellar population.
| Quasi-160-minute oscillation period of Delta Scuti stars
The resonance power spectrum (or commensurability spectrum) computed for217 Delta Scuti stars indicates that the dominant (most commensurate)period for the total set of oscillation periods of these stars is 162.2+ or - 2.8 min. Within the error limits, this period coincidesapproximately with the 160-min period of global oscillations of the sun.
| Physical parameters of pulsating variables with periods between one and three days. I - Photometry and metallicities
Based on a new set of observations in the Walraven VBLUW system,obtained at the European Southern Observatory, La Silla, Chile,Fe/H(VBLU) values of 57 pulsating variables, mostly with periods betweenone and three days,. are determined. The distribution of the metalabundances is shown to be essentially bimodal. All the variables withFe/H ratios of less than -0.4 were classified by Diethelm (1983) as RRdstars. They are identified as the galactic field counterpart of theCepheids in the same period range found in globular clusters.
| Light Elements for DK Velorum - A Corrigendum
Abstract image available at:http://adsabs.harvard.edu/abs/1972PASP...84..664J
| The Red RR Lyrae Variable DK Velorum
Abstract image available at:http://adsabs.harvard.edu/abs/1971PASP...83..471J
| Observations of southern RR Lyrae stars
Not Available
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תצפית ומידע אסטרומטרי
| קבוצת-כוכבים: | מפרש |
| התרוממות ימנית: | 09h17m16.72s |
| סירוב: | -53°05'05.5" |
| גודל גלוי: | 10.729 |
| תנועה נכונה: | -3.8 |
| תנועה נכונה: | 7.2 |
| B-T magnitude: | 11.68 |
| V-T magnitude: | 10.808 |
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