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New magnetic chemically peculiar stars
Spectropolarimetric observations of 96 chemically peculiar (CP)main-sequence stars have been carried out at the 6-m telescope at theSpecial Astrophysical Observatory of the Russian Academy of Sciences(SAO RAS) with the aim of searching for the presence of stellar magneticfields. The stars selected for investigation were CP stars known to havestrong anomalies in the wavelength region of the continuum fluxdepression around λ 5200Å. This selection was conductedwith the aid of low-resolution spectral observations, made with the SAORAS 1-m telescope, and of published differential photometric data.Magnetic fields have been successfully detected in 72 stars of whichonly three stars were previously known to have magnetic fields. For twostars, the longitudinal component of the magnetic field Beexceeds 5 kG: HD178892 - 7.4 kG, and HD258686 - 6.7 kG. We failed toreliably detect the magnetic field in the other 24 CP stars. These starsare mostly fast rotators, a feature which hampers accurate measurementsof Be. It is demonstrated in this paper that selectingcandidate magnetic stars by considering their photometric indices Z orΔa, or alternatively, by inspecting low-resolution spectra aroundthe λ5200Å flux depression, considerably increases thedetection rate.This paper is based on data obtained at the 6-m telescope of the RussianAcademy of Sciences.E-mail: dkudr@sao.ru
| The discovery of 8.0-min radial velocity variations in the strongly magnetic cool Ap star HD154708, a new roAp star
HD154708 has an extraordinarily strong magnetic field of 24.5kG. Using2.5h of high time resolution Ultraviolet and Visual Echelle Spectrograph(UVES) spectra we have discovered this star to be an roAp star with apulsation period of 8min. The radial velocity amplitudes in the rareearth element lines of NdII, NdIII and PrIII are unusually low -~60ms-1 - for an roAp star. Some evidence suggests that roApstars with stronger magnetic fields have lower pulsation amplitudes.Given the central role that the magnetic field plays in the obliquepulsator model of the roAp stars, an extensive study of the relation ofmagnetic field strength to pulsation amplitude is desirable.Based on observations collected at the European Southern Observatory,Paranal, Chile, as part of programme 075.D-0145.E-mail: dwkurtz@uclan.ac.uk
| HD 178892 - a cool Ap star with extremely strong magnetic field
We report a discovery of the Zeeman resolved spectral lines,corresponding to the extremely large magnetic field modulus < B_s>= 17.5 kG, in the cool Ap star HD 178892. The mean longitudinal field ofthis star reaches 7.5 kG, and its rotational modulation implies thestrength of the dipolar magnetic component B_p≥ 23 kG. We haverevised rotation period of the star using the All Sky Automated Surveyphotometry and determined P = 8.2478 d. Rotation phases of the magneticand photometric maxima of the star coincide with each other. We obtainedGeneva photometric observation of HD 178892 and estimated T_eff =7700±250 K using photometry and the hydrogen Balmer lines.Preliminary abundance analysis reveals abundance pattern typical ofrapidly oscillating Ap stars.
| Eight New Magnetic Stars with Large Continuum Depressions
Observations with the 6-m telescope revealed eight new magnetic,chemically peculiar stars: HD 29925, HD 40711, HD 115606, HD 168796, HD178892, HD 196691, HD 209051, and BD +32o2827. Zeemanobservations of all these objects have been carried out for the firsttime. We selected candidates by analyzing the depression profile at awavelength of lambda 5200 A. This technique for selecting candidatemagnetic stars was shown to be efficient: we found magnetic fields in 14of the 15 objects that we selected for our observations with a Zeemananalyzer. A maximum longitudinal field strength B_e exceeding 8 kG wasfound in HD 178892; in HD 209051 and HD 196691, B_e reaches 3.3 and 2.2kG, respectively. For the remaining stars, we obtained lower limits ofthe longitudinal field (more than several hundred G).
| The HR-diagram from HIPPARCOS data. Absolute magnitudes and kinematics of BP - AP stars
The HR-diagram of about 1000 Bp - Ap stars in the solar neighbourhoodhas been constructed using astrometric data from Hipparcos satellite aswell as photometric and radial velocity data. The LM method\cite{luri95,luri96} allows the use of proper motion and radial velocitydata in addition to the trigonometric parallaxes to obtain luminositycalibrations and improved distances estimates. Six types of Bp - Apstars have been examined: He-rich, He-weak, HgMn, Si, Si+ and SrCrEu.Most Bp - Ap stars lie on the main sequence occupying the whole width ofit (about 2 mag), just like normal stars in the same range of spectraltypes. Their kinematic behaviour is typical of thin disk stars youngerthan about 1 Gyr. A few stars found to be high above the galactic planeor to have a high velocity are briefly discussed. Based on data from theESA Hipparcos astrometry satellite and photometric data collected in theGeneva system at ESO, La Silla (Chile) and at Jungfraujoch andGornergrat Observatories (Switzerland). Tables 3 and 4 are onlyavailable 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
| New Peculiar Stars Noted on Objective-Prism Plates
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Observation and Astrometry data
| Constellation: | Aquila |
| Right ascension: | 19h09m54.75s |
| Declination: | +14°57'58.3" |
| Apparent magnitude: | 8.949 |
| Distance: | 270.27 parsecs |
| Proper motion RA: | -1 |
| Proper motion Dec: | -23.5 |
| B-T magnitude: | 9.334 |
| V-T magnitude: | 8.981 |
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