TRAFICOS – an Échelle Zeeman spectrograph

Abstract

We describe the TRAnsportable FIbre Coupled kchelle Spectrograph (TRAFICOS) equipped with a Zeeman analyzer and manufactured mainly for the observation of stellar magnetic fields. The IntroductionMagnetic fields are observed on stars with quite different temperatures, masses, and states of evolution. In stars with masses of about one solar mass and smaller and the so-called T-Tauri variable stars the magnetic fields are an important indicator for confirmation of the dynamo theory. in stars with higher masses, especially in stars belonging to the chemically peculiar stars, CP stars, the connection between the magnetic field and the distribution of the chemical elements on the stellar surface should provide decisive arguments for the diffusion theory.In the past our investigations of stellar magnetic fields were mainly concentrated on CP stars and based on observations carried out photographically at the coudk focus of the 2 m telescope in Tautenburg. In most C P stars the temporal variations of the magnetic field observed are periodical and most frequently interpreted by the rotation of the star possessing a magnetic field, which has a lack of symmetry with regard to the axis of rotation. The widespread evidence observed of one extremum more prominent than the other requires a field geometry which differs from that of a centred or decentred dipole even with arbitrary obliquity. In order to continue the investigations on magnetic fields with an up-to-date device a fibre-fed kchelle spectrograph, equipped with a Zeeman analyzer for measurement of the circularly polarized light, was designed and constructed and is at the moment installed at the Nasmyth focus of the reflector in Tautenburg, but it can also be used at the focus of other telescopes with f/8 to f/12. For the determination of magnetic fields the observations with the new device at the Nasmyth focus should be more suitable than the previous ones at the coudC focus. The reason is that the number of light reflexions in the telescope is only two (instead of five in the coudk system), so that, on the one hand, the speed at the Nasmyth focus should be higher than at the coudC and, on the other hand, the problems of the instrumental polarization are not so difficult to handle as in the path of rays of the coudk system. Furthermore, the achromatic quarter wave plate of the Zeeman analyzer allows the magnetic field from lines of a wide spectral region to be derived, especially so for spectral lines in the red domain.

A study of polarized spectra of magnetic CP stars: Predicted vs. observed Stokes IQUV profiles forβCrB and 53 Cam

“…This is a particular difficult task in 53 Cam, owing to a strong blend in the blue wing of the line (Mathys et al 1997). Furthermore, it should be noted that in presence of a such a strong field as observed in 53 Cam, the formation Babcock (1958Babcock ( , 1960b; empty triangles: Preston & Stȩpień (1968); filled circles: Borra & Landstreet (1977); empty stars: Hildebrandt et al (1997); empty circles: Hill et al (1998); filled squares: Wade et al (2000c); open squares: this work (from SAO spectra) filled triangles: this work (from Catania spectra). For the mean field modulus B (left bottom panel), the filled square represents the measurement by Preston (1969), filled triangles the observations by Huchra (1972), filled circles those by Mathys et al (1997).…”

“…In the first case, we considered only the photopolarimetric B z determinations of Borra & Landstreet (1977) and of Hill et al (1998). In the second case, we considered only the "photographic" B z values of Preston & Stȩpień (1969), Hildebrandt et al (1997), Wade et al (2000c), and those reported in Table 1 of this work. Finally, in the third case, we considered all of the available B z observations (but those by Babcock, see Sect.…”

“…An additional 33 observations were later obtained by the same author, but are only available in the form of a plot (see, e.g., Babcock 1960b). With a similar technique, eight longitudinal field determinations were performed by Preston & Stȩpień (1968), and another four by Hildebrandt et al (1997). Wade et al (2000c) have added ten more observations.…”

New findings supporting the presence of a thick disc and bipolar jets in the $\mathsf{\beta}$ Lyrae system

“…Since the data at our disposal represent 682 additional RVs and extend the time span covered for 4335 days, it was deemed useful to derive an improved quadratic ephemeris based on all 2214 RVs. In addition to the new RVs measured in all Ondřejov and DAO electronic spectra, we also included the RVs of the donor from the Crimean CCD spectra (Skul'skij 1992(Skul'skij , 1993 and from the Tautenburg CCD spectra (Hildebrandt et al 1997) and, of course, used all 1532 RVs already used by Harmanec & Scholz (1993). In all cases, we used mean RVs for each spectrogram.…”

A statistical analysis of the magnetic structure of CP stars

“…We also considered additional measurements, to be published by Mathys et al (in preparation), most of which were already used by Landstreet & Mathys (2000). Additional mean longitudinal field data were taken from Bagnulo et al (2001), Borra & Landstreet (1977, 1978, Hildebrandt et al (1997), Hill et al (1998), Leone et al (2000), Leone & Catanzaro (2001), Preston & Stȩpień (1968), Wade et al (1996Wade et al ( , 1997Wade et al ( , 2000aWade et al ( , 2000bWade et al ( , 2000c. Further mean field modulus data were taken from Huchra (1972), and Preston (1969).…”