The ruling of diffraction gratings at the Mount Wilson Observatory.

Babcock, Harold D.; Babcock, Horace W.

doi:10.1086/106590

Cited by 17 publications

(17 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The high rotation speed makes this star oblate, in fact the ratio between polar and equatorial radii is ≈ 0.88 (Grunhut et al 2012a). HR 5907's variability has been explained in the framework of the Oblique Rotator Model (ORM), where the star is characterized by a mainly dipolar magnetic field topology, having the magnetic dipole axis tilted with respect to the rotational axis (Babcock 1949;Stibbs 1950).…”

Section: The Magnetic Early B-type Star Hr 5907mentioning

confidence: 99%

A combined multiwavelength VLA/ALMA/Chandra study unveils the complex magnetosphere of the B-type star HR5907

Leto

Trigilio

Oskinova

et al. 2018

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We present new radio/millimeter measurements of the hot magnetic star HR 5907 obtained with the VLA and ALMA interferometers. We find that HR 5907 is the most radio luminous early type star in the cm-mm band among those presently known. Its multi-wavelength radio light curves are strongly variable with an amplitude that increases with radio frequency. The radio emission can be explained by the populations of the non-thermal electrons accelerated in the current sheets on the outer border of the magnetosphere of this fast rotating magnetic star. We classify HR 5907 as another member of the growing class of strongly magnetic fast rotating hot stars where the gyro-synchrotron emission mechanism efficiently operates in their magnetospheres. The new radio observations of HR 5907 are combined with archival X-ray data to study the physical condition of its magnetosphere. The X-ray spectra of HR 5907 show tentative evidence for the presence of non-thermal spectral component. We suggest that non-thermal X-rays originate a stellar X-ray aurora due to streams of non-thermal electrons impacting on the stellar surface. Taking advantage of the relation between the spectral indices of the X-ray power-law spectrum and the non-thermal electron energy distributions, we perform 3-D modeling of the radio emission for HR 5907. The wavelength-dependent radio light-curves probe magnetospheric layers at different heights above the stellar surface. A detailed comparison between simulated and observed radio light-curves leads us to conclude that the stellar magnetic field of HR 5907 is likely non-dipolar, providing further indirect evidence of the complex magnetic field topology of HR 5907.

show abstract

Section: The Magnetic Early B-type Star Hr 5907mentioning

confidence: 99%

A combined multiwavelength VLA/ALMA/Chandra study unveils the complex magnetosphere of the B-type star HR5907

Leto

Trigilio

Oskinova

et al. 2018

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…These gratings are mainly produced by mechanical ruling and ion-beam etching [5]. Until now, because of deep grooves with strict shapes, echelles and infrared-laser gratings are still produced by mechanical ruling [6].…”

Section: Introductionmentioning

confidence: 99%

Real-time monitoring of ruling grating resolution by digital wavefront

Chao

et al. 2015

Appl. Opt.

View full text Add to dashboard Cite

In order to solve the problem that the grating quality cannot be monitored directly in real time, we provided a method based on Rayleigh criterion with our designing optical measurement structure to measure yaw and displacement errors of a grating ruling machine feeding system. Gratings are ruled with or without errors correction by the real-time monitoring system . It shows that the resolution obtained without errors correction is reduced from 99.97% to 87.47% of theoretical value, while the resolution obtained with errors correction is stable, remaining at 99.99%-97.21%. The experimental result is that the grating quality can be guaranteed by monitoring grating resolution in real time.

show abstract

“…For this class of stars, it is commonly accepted that the stellar surface is characterised by the presence of a non-homogeneous distribution of various chemical elements and a magnetic field organised on a large scale. Thus the In memory of Horace Babcock. above-mentioned periodic variations are a consequence of the stellar rotation (Babcock 1949a). Starting with Deutsch (1958), much effort has been devoted to the mapping of the distributions of the elements and it is now evident that these nonhomogeneous distributions can be very different for the various elements (Kuschnig et al 1999) and even for the various ionisation states of an element (Strasser et al 2001).…”

Section: Introductionmentioning

confidence: 99%

The effect of the surface distribution of elements on measuring the magnetic field of chemically peculiar stars

Leone

Catanzaro

2004

A&A

View full text Add to dashboard Cite

Abstract.A non-homogeneous distribution over the stellar surface of the chemical elements and the presence of a large-scale magnetic field are invoked in order to explain the periodic line strength, photometric and magnetic variability of magnetic chemically peculiar stars. In such a framework, the variability period is identical to the rotational period. In magnetic chemically peculiar stars, the so-called effective magnetic field H eff , the average over the visible stellar disk of the longitudinal field component weighted by the local line strength, is routinely measured from Stokes I and V profiles of selected spectral lines. In spite of evidence that the distribution of the various chemical elements over the stellar surface can be inhomogeneous and different from element to element, H eff values obtained from lines of different elements are often statistically combined to improve the accuracy of effective field measurements. Similarly, mean high S/N profiles are obtained from the profiles of lines of different elements. We have established, by means of R = 115 000 circular spectropolarimetry of the magnetic chemically peculiar star HD 24712 in the 4700−7000 Å range, the dependence of the measurements of H eff on the atomic weight of 24 elements (from carbon to erbium, if possible at different ionisation states). At all 3 rotational phases considered, H eff values derived from different elements can differ by up to 800 G. We find an overall increase in H eff with atomic number and a maximum near Z = 60. The behaviour of sodium is quite singular inasmuch as it always exhibits a negative value of the field, peaking at −0.39 kG when the rare earths give H eff = 1.2 kG. Under the assumption of a dipolar field, we conclude that the elements giving the largest values of H eff are concentrated near the positive polar region and that the other elements are more homogeneously distributed over the stellar surface or concentrated in belts around the magnetic equator. Sodium seems to be localised in the negative magnetic hemisphere only. This picture is corroborated by the equivalent width variability of the lines: up to iron, equivalent widths changes out-of-phase with respect to the H eff variability; elements heavier than iron present equivalent widths that are variable in-phase. We do not find any relation between the respective amplitudes of the equivalent width variations and the atomic numbers of the elements. For iron, the observed equivalent width variability does not seem to be simply related to any non-homogeneous distribution over the stellar surface. We conclude that measurements originating from different elements cannot in general be combined to improve the precision of H eff measurements. Indeed, any modelling attempt based on the periodic variations in H eff is subject to the risk that the sampling of the magnetic field over the stellar surface by the lines of a given chemical element is uneven or incomplete.

show abstract

The ruling of diffraction gratings at the Mount Wilson Observatory.

Cited by 17 publications

References 0 publications

A combined multiwavelength VLA/ALMA/Chandra study unveils the complex magnetosphere of the B-type star HR5907

A combined multiwavelength VLA/ALMA/Chandra study unveils the complex magnetosphere of the B-type star HR5907

Real-time monitoring of ruling grating resolution by digital wavefront

The effect of the surface distribution of elements on measuring the magnetic field of chemically peculiar stars

Contact Info

Product

Resources

About