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1.
This is the first paper of the series dedicated to the analysis of the magnetism of chemically peculiar (CP) stars of the upper Main Sequence. We use our own measurements and published data to compile a catalog of magnetic CP stars containing a total of 326 objects with confidently detected magnetic fields and 29 stars which are very likely to possess magnetic field. We obtained the data on the magnetism of the overwhelming majority of the stars solely based on the analysis of longitudinal field component B e . The surface magnetic field, B s , has been measured for 49 objects. Our analysis shows that the number of magnetic CP stars decreases with increasing field strength in accordance with exponential law, and stars with B e exceeding 5kG occur rarely (about 3% objects of our list).  相似文献   

2.
Observations with the 6-m telescope revealed eight new magnetic, chemically peculiar stars: HD 29925, HD 40711, HD 115606, HD 168796, HD 178892, HD 196691, HD 209051, and BD+32°2827. Zeeman observations of all these objects have been carried out for the first time. We selected candidates by analyzing the depression profile at a wavelength of λ5200 Å. This technique for selecting candidate magnetic stars was shown to be efficient: we found magnetic fields in 14 of the 15 objects that we selected for our observations with a Zeeman analyzer. A maximum longitudinal field strength B e exceeding 8 kG was found in HD 178892; in HD 209051 and HD196691, B e reaches 3.3 and 2.2 kG, respectively. For the remaining stars, we obtained lower limits of the longitudinal field (more than several hundred G).  相似文献   

3.
Our observations with the 6-m telescope revealed six new magnetic chemically peculiar (CP) stars among objects with large depressions in the continuum: HDE 293764, BD+17°3622, HD 169887, HDE 231054, HDE 338226, and HDE 343872. The presence of a magnetic field is suspected in several other CP stars. The maximum longitudinal field component B e exceeds 1.5 kG for all six stars; in HDE 293764 and HDE 343872, it reaches 3.8 kG. For each object, we present our magnetic-field measurements and published data on previous studies. The method of searching for magnetic stars based on an analysis of spectrophotometry shows its efficiency.  相似文献   

4.
We analyzed the chemical composition of the chemically peculiar (CP) star HD 0221=43 Cas using spectra taken with the NES spectrograph of the 6-m telescope with a spectral resolution of 45 000. The Hβ line profile corresponds most closely to Teff = 11 900 K and log g = 3.9. The rotational velocity is ve sin i = 27 ± 2 km s?1, and the microturbulence is ξt = 1 km s?1. The results of our abundance determination by the method of synthetic spectra show that the star has chemical anomalies typical of SrCrEu stars, although its effective magnetic field is weak, Be < 100 G. For silicon, we obtained an abundance distribution in atmospheric depth with a sharp jump of 1.5 dex at an optical depth of log τ5000 = ?0.3 and with silicon concentration in deep atmospheric layers. Similar distributions were found in the atmospheres of cooler stars with strong and weak magnetic fields. A comparison of the chemical peculiarities in HD 10221 with known CP stars with magnetic fields of various strengths leads us to conclude that a low rotational velocity rather than amagnetic field is the determining factor in the formation mechanism of chemical anomalies in the atmospheres of CP stars.  相似文献   

5.
Based on observations with the 6-m SAO RAS telescope, we have found that chemically peculiar star with a large depression of the continuum at λ5200 Å and strengthened silicon lines in the spectrum has a strong magnetic field. The longitudinal field component Be has a negative polarity and varies from ?300 G to ?2000 G with a period of 1.756 days. Photometric variations of brightness take place with the same period. We determined the variability of the radial velocity at times of about tens of years pointing to a possible binarity of the object. We have built a magnetic model of this star, determined the inclination angles of the rotation axis to the line of sight i = 20° and of the dipole axis to the rotation axis β = 116°, and the field strength at the pole is Bp = 10 kG. We carried out a chemical composition analysis and found a lack of helium for almost an order of magnitude, some overabundance of silicon and metal elements for more than an order of magnitude, particularly, cobalt for three orders of magnitude.  相似文献   

6.
Our spectrophotometric analysis of the atmospheres of HD 37058, HD 212454, and HD 224926 shows these objects to be typical He-w stars with close-to-zero microturbulence velocities, very different magnetic fields, and wide scatter of chemical anomalies. However, one of the main manifestations of separation is that helium moves from the outer layers of the atmosphere into the star’s interior.Our analysis of the stars HD 212454 and 224926 with Be<100 G shows that despite their weak magnetic fields they have the same degree of chemical anomaly as highly magnetized stars. Chemical composition varies over a wide range for stars with the same magnitude of magnetic field. We find the conditions in the temperature interval 13000–16000 K to be the most favorable for the formation of He-w type stars. Helium underabundance is the strongest near the maximum of the distribution and it is observed in stars with weak as well as strong fields. Because of the scatter mentioned above the degree of chemical anomalies is not strictly related to the magnitude of the magnetic field, although the field has an appreciable effect on the formation of chemical inhomogeneities at the star’s surface. Its influence is minimal in stars with very weak magnetic fields and the presence of strong chemical anomalies indicates that microturbulence in these stars is sufficiently weak even without the effect of the magnetic field. It is plausible to assume that the anomalies arise due to slow rotation.The temperature dependences of rotation velocity vsini for stars with weak magnetic fields show no apparent trends associated with the magnitude of magnetic field. The rotation velocities vsini of almost all stars are lower than those of normal stars, except for HD 131120, 142096, 142990, and 143669, which rotate with the same velocity or even faster than normal stars. These objects do not obey the general rule and their example shows that stable atmospheres can also be found among fast rotators and that magnetic field takes no part in the spin-down of CP stars. We believe that CP stars inherited their slow rotation from protostellar clouds.  相似文献   

7.
The dependence of the degree of anomaly of parameter Z of Geneva photometry (Z0 = Z CP ?Z norm.) on the average surface magnetic field Bs is analyzed. The Z0 value is proportional to the degree of anomaly of chemical composition. It was found that Bs → 0 corresponds Z0 → ?0.010÷ ?0.015, i.e., part of CP stars are virtually devoid of magnetic field, but exhibit chemical anomalies. This effect may be due to selection whereby only objects with strong chemical anomalies are classified as CP stars, thereby producing a deficit of stars with relatively weak anomalies. Moreover, CP stars have other sources of stabilization of their atmospheres besides the magnetic field, e.g., slow rotation. Formulas relating Z0 to Bs are derived.  相似文献   

8.
The low rotation velocities of magnetic CP stars are discussed. Arguments against the involvement of the magnetic field in the loss of angular momentum are given: (1) the fields are not strong enough in young stars in the stage of evolution prior to the main sequence; (2) there is no significant statistical correlation between the magnetic field strength and the rotation period of CP stars; (3) stars with short periods have the highest fields; (4) a substantial number of stars with very low magnetic fields (B e < 500 G) have rotation speeds that are typical of other CP stars; (5) simulations of the magnetic fields by Leroy and the author show that the orientation of dipoles inside rotating stars, both slow and fast, is consistent with an arbitrary orientation of the dipoles; and, (6) slow rotators with P>25 days, which form 12% of the total, probably lie at the edge of the velocity distribution for low mass stars. All of these properties conflict with the hypothesis of magnetic braking of CP stars.  相似文献   

9.
We describe the results of our magnetometric monitoring of two white dwarfs: 40 Eri B and WD 0009+501. We found periodic variations in the longitudinal magnetic field of 40 Eri B. The field variability with an amplitude of ～4 kG and a zero mean is discussed in terms of an oblique rotator model. The rotation period is ～5 h 17 min, but there is another period of 2 h 25 min that may be related to nondipolar field components. The published projected rotational velocities of 40 Eri B measured from a narrow non-LTE Hα peak V sin i?8 km s?1 are in good agreement with our measurements of the magnetic field and the rotation period. The combined effect of magnetic and rotational broadening of the central Hα component constrains the rotation period, P? 5.2 h. We discovered the rotation period (1.83 h) of the magnetic white dwarf WD 0009+501. The period was found from the periodically varying magnetic field of the star with a mean 〈Be〉 = ?42.3±5.4 kG and a half-amplitude of 32.0±6.8 kG.  相似文献   

10.
We present the results of magnetic field measurements of four chemically peculiar (CP) stars with helium abundance anomalies which are the members of the Orion stellar association OB1. The stars under study were classified as magnetic by other authors earlier. The present paper contains the results of the extensive study of the stars. Magnetic field measurements allowed us to conclude that HD36540 has a weak field and the longitudinal component B e does not exceed 500 G. The longitudinal field of HD36668 varies with the period P = 2. d 11884 and the amplitude from ?2 to +2 kG. The magnetic field of HD36916 has mainly negative polarity and varies within the range from 0 to ?1 kG with the period P = 1.d 565238. HD37058 is a magnetic star, the longitudinal field of which varies from ?1.2 to +0.8 kG with the period P = 14. d 659. The B e field variability pattern for the stars HD36916 and HD37058 is of a simple harmonic type. The longitudinal field of HD36668 is best described with two combined harmonic functions (“a doublewave”). The variability period of HD36540 is still undetermined. For all the stars from this paper, we measured radial velocities V r, axial rotation rates v e sin i, and determined basic parameters of atmospheres (effective temperatures T eff and gravity acceleration log g). We also estimated masses M, luminosities L, and radii R of the stars.  相似文献   

11.
We report the results of our search for magnetic fields in a sample of 16 field Be stars, the binary emission‐line B‐type star υ Sgr, and in a sample of fourteen members of the open young cluster NGC3766 in the Carina spiral arm. The sample of cluster members includes Be stars, normal B‐type stars and He‐strong/He‐weak stars. Nine Be stars have been studied with magnetic field time series obtained over ∼1 hour to get an insight into the temporal behaviour and the correlation of magnetic field properties with dynamical phenomena taking place in Be star atmospheres. The spectropolarimetric data were obtained at the European Southern Observatory with the multi‐mode instrument FORS1 installed at the 8m Kueyen telescope. We detect weak photospheric magnetic fields in four field Be stars, HD 62367, μ Cen, o Aqr, and ε Tuc. The strongest longitudinal magnetic field, 〈Bz〉 = 117 ± 38 G, was detected in the Be star HD 62367. Among the Be stars studied with time series, one Be star, λ Eri, displays cyclic variability of the magnetic field with a period of 21.12 min. The binary star υ Sgr, in the initial rapid phase of mass exchange between the two components with strong emission lines in the visible spectrum, is a magnetic variable star, probably on a timescale of a few months. The maximum longitudinal magnetic field 〈Bz〉 = –102 ± 10 G at MJD 54333.018 was measured using hydrogen lines. The cluster NGC3766 seems to be extremely interesting, where we find evidence for the presence of a magnetic field in seven early B‐type stars out of the observed fourteen cluster members (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

12.
Based on an analysis of the catalog of magnetic fields, we have investigated the statistical properties of the mean magnetic fields for OB stars. We show that the mean effective magnetic field B of a star can be used as a statistically significant characteristic of its magnetic field. No correlation has been found between the mean magnetic field strength B and projected rotational velocity of OB stars, which is consistent with the hypothesis about a fossil origin of the magnetic field. We have constructed the magnetic field distribution function for B stars, F(B), that has a power-law dependence on B with an exponent of ≈−1.82. We have found a sharp decrease in the function F(B) for B ⩽ 400 G that may be related to rapid dissipation of weak stellar surface magnetic fields.  相似文献   

13.
The spectra taken with the Main Stellar Spectrograph (MSS) of the 6-m telescope with a resolution of R ～ 15000 and a signal-to-noise ratio of 200–300 are used to determine the radial velocities and projected rotational velocities (υ e sin i) for 32 magnetic CP stars. Measured υ e sin i values range from 18 km/s (the lower boundary determined by the instrumental profile) to 65 km/s. Measurements of standard stars demonstrate the absence of systematic differences between our and published data. Eight of the 32 magnetic stars are found or confirmed to be binary and binarity is suspected for another four stars. The components of tangential velocity are determined for 27 stars with known parallaxes.  相似文献   

14.
The paper presents results of measurements of magnetic-field longitudinal components B e , radial velocities V r , and projections of the rotation velocity in the line of sight v e sin i for 74 objects, mainly main-sequence chemically peculiar stars and standard stars. Observations were carried out in 2011 at the 6-m BTA telescope using the Main Stellar Spectrograph (MSS) with a Zeeman analyzer. Seven new magnetic stars were discovered: HD38129, HD47152, HD50341, HD63347, HD188501, HD191287, and HD260858. Three more stars were suspected to have magnetic fields. Observations of magnetic standard stars and non-magnetic stars confirm the absence of any systematic errors capable of introducing distortions into the B e longitudinal-field measurement results. The paper gives comments on the research results for each of the 74 stars.  相似文献   

15.
Our knowledge of the presence and the strength of magnetic fields in intermediate‐mass pre‐main‐sequence stars remains very poor. We present new magnetic field measurements in six Herbig Ae/Be stars observed with HARPS in spectropolarimetric mode. We downloaded from the European Southern Observatory (ESO) archive the publically available HARPS spectra for six Herbig Ae/Be stars. Wavelength shifts between right‐ and left‐hand side circularly polarised spectra were interpreted in terms of a longitudinal magnetic field 〈Bz〉, using the moment technique introduced by Mathys. The application of the moment technique to the HARPS spectra allowed us in addition to study the presence of the crossover effect and quadratic magnetic fields. Our search for longitudinal magnetic fields resulted in first detections of weak magnetic fields in the Herbig Ae/Be stars HD 58647 and HD 98922. Further, we confirm the previous tentative detection of a weak magnetic field in HD 104237 by Donati et al. and confirm the previous detection of a magnetic field in the Herbig Ae star HD 190073. Surprisingly, the measured longitudinal magnetic field of HD 190073, 〈Bz〉 = 91 ± 18 G at a significance level of 5σ is not in agreement with the measurement results of Alecian et al. (2013), 〈Bz〉 = –10 ± 20 G, who applied the LSD method to exactly the same data. No crossover effect was detected for any star in the sample. Only for HD 98922 the crossover effect was found tobe close to 3σ with a measured value of –4228 ± 1443 km s–1 G. A quadratic magnetic field of the order of 10 kG was detected in HD 98922, and of ∼3.5 kG in HD 104237. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)  相似文献   

16.
The paper argues in favor of the assumption that magnetic and non-magnetic protostars, from which CP stars were formed, are the objects that had rotation velocities of the parent cloud V smaller than a critical value V c . At V greater than the critical value, differential rotation emerges in the collapsing protostellar cloud, which twists magnetic lines of force into an’ invisible’ toroidal shape and disturbs the stability of the atmosphere. In magnetic protostars, the loss of angular momentum is due to magnetic braking, while in metallic protostars, the loss of rotation momentum occurs due to tidal interactions with a close component. HgMn stars are most likely not affected by some braking mechanism, but originated from the slowest protostellar rotators. The boundary of V c where the differential rotation occurs is not sharp. The slower the protostar rotates, the greater the probability of suppressing the differential rotation and the more likely the possibility of CP star birth.  相似文献   

17.
We present the results of measuring longitudinal magnetic fields (Be), rotation velocities (ve sin i), and radial velocities (Vr) of 44 stars observed with the Main Stellar Spectrograph (MSS) of the 6-m BTA telescope of the Special Astrophysical Observatory in 2009. For the first time, magnetic fields were detected for the stars HD5441, HD199180, HD225627, and BD+00° 4535. We show that for the same stars, the longitudinal fields Be measured from the Hβ hydrogen line core and from metal lines can differ by 10% and up to a factor of 2–3. Except in rare cases, magnetic fields measured from the metal lines are stronger. We believe that this phenomenon is of a physical nature and depends on the magnetic field topology and the physical conditions inside a specific star. Observations of standard stars without magnetic fields confirm the absence of systematic errors capable of introducing distortions into the longitudinal-field measurement results. In this work we comment on the results for each of the stars.  相似文献   

18.
This paper reviews the current state of the problem of magnetism in massive Main Sequence stars. Chemically peculiar Bp stars with enhanced silicon lines and anomalous helium lines in their spectra are shown to be the most promising targets for the observational verification of various mechanisms of the formation and subsequent evolution of magnetic fields in CP stars. A catalog of magnetic Bp stars, containing 125 objects is prepared. Applying different criteria, we compiled a variety of magnetic star samples, which were then used to analyze magnetic fields in objects of different ages. The results of this analysis show that massive stars generally have stronger fields in all the samples studied, and thus confirm earlier results based on smaller star samples. No tight relation is observed and the parameters of individual objects show a very large scatter about the mean relation. The strongest and most complex fields are found in the youngest Bp stars with ages below 30 Myr. Magnetic Bp stars generally rotate slower than normal B-type stars, except for the hottest objects with enhanced helium lines, which have normal rotation velocities. No systematic differences are found between the angular rotation velocities of Bp stars with anomalous helium and silicon lines. We discuss various criteria, which can be used to observationally test the alternative mechanisms of formation and evolution of magnetic fields in CP stars and, in particular, to quantitatively compare not only the magnitudes, but also the topology of fields in objects of different ages.  相似文献   

19.
New spectral observations of chemically peculiar (CP) magnetic stars were obtained using an NES echelle spectrometer with a BTA telescope in the Special Astrophysical Observatory (Russian Academy of Sciences). Several stars were shown to have anomalous Li abundances. Testing and monitoring the stars with Doppler shifts Vsini > 10 km/s indicated that the lithium 6708 Å line was variable in the spectra of some roaAP-CP stars. To distinguish variable features in the spectra, the dispersogram technique was used. The most peculiar among the stars studied is HD 12098. The strong and variable lithium 6708 Å line was detected in the spectrum of this star. The star has been shown to have greatly different lithium abundances in two rotation phases corresponding to opposite surface areas. As mentioned earlier, a similar behavior of the Li blend was found in the spectra of HD 83368 and HD 60435 which have lithium spots on their surface. Spectral observations of slowly rotating CP stars with the Doppler shifts Vsini < 10 km/s revealed the strong and nonvariable lithium 6708 Å line in the spectra of these stars. Quantitative spectral analysis using the Li I 6708 Å resonance doublet and the Li I 6103 Å line shows the lithium abundance, as determined by the 6103 Å line, to be somewhat greater than that determined by the 6708 Å line. A higher ratio of 6Li/7Li amounting to ～0.3–0.5 was found in these stars. 6Li production is assumed to be due to spallation reactions on the surface of magnetic CP stars; this isotope ratio remained in strong magnetic fields.  相似文献   

20.
We present an analytical survey of key publications concerned with the study of stellar magnetism published in 2015. We considered about 80 publications, the most significant from our point of view, presented brief reviews of them, and made generalizations. The paper considers: instruments, techniques of observations and analysis; large-scale magnetic fields of OBA stars on the Main Sequence (MS) (formation and evolution, field topology, search for new magnetic stars including the projects MiMeS, BOB, and BinaMIcS and observations with the Russian 6-m telescope, rotation and chemical abundance analysis of magnetic CP stars); magnetic fields, chemical abundance and variability of stars related to peculiar, primarily, active cool stars, solar-type stars and white dwarfs; multiple magnetic stars including interferometry data, exoplanets in a system of magnetic stars. We make a conclusion that the accuracy of magnetic field measurements has grown due to universal application of the multilinear method of observations especially with high-resolution spectropolarimeters. Usage of Zeeman-Doppler imaging technique (ZDI) when analyzing the obtained data allows us to confidently search and measure fields of complex topology of the order of 10 Gs. For the first time, a magnetic field has been detected for post-AGB stars and some other types of objects.  相似文献   

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