Magnetic properties of three cool CP stars with strong fields

Semenko, E. A.; Kichigina, L.A.; Kuchaeva, E. Yu.

doi:10.1002/asna.201111598

“…From B e measurements and HIPPARCOS photometry, Semenko et al (2011) determined the variability period of HD 178892 equal to 8.2549 days.…”

Section: Hd 178892mentioning

confidence: 99%

Twenty-year monitoring of the surface magnetic field of peculiar stars

Giarrusso¹,

Cecconi²,

Cosentino³

et al. 2021

Preprint

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Magnetic chemically peculiar stars of the main sequence can present rotational periods as long as many decades. Here we report the results of an observational campaign started in 2001 aimed to establish these very long periods from the variability of the surface magnetic field, as measured from the Zeeman split of the FeII 6149.258 Å spectral line. Thirty-six stars have been monitored with several high-resolution spectrographs at different telescopes, for a total of 412 new collected spectra. To extend and fill at the best the time frame, we have also exploited all public archives containing high-resolution spectra, many not yet published. At the start of the campaign, most of the variability periods were unknown and stars selected for the sharpness of their spectral lines only, and thirteen stars were found to present variability periods on the scale of weeks. A final plot of magnetic field strength versus rotational periods is given.

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Twenty-year monitoring of the surface magnetic fields of chemically peculiar stars

Giarrusso

¹

,

Cecconi

²

,

Cosentino

³

et al. 2022

Monthly Notices of the Royal Astronomical Society

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Magnetic chemically peculiar stars of the main sequence can present rotational periods as long as many decades. Here we report the results of an observational campaign started in 2001 aimed at establishing these very long periods from the variability of the integrated magnetic field modulus, the so-called surface magnetic field Bs, as measured from the Zeeman splitting of the Fe ii 6149.258 Å spectral line. Thirty-six stars have been monitored with various high-resolution spectrographs at different telescopes, totalling 412 newly collected spectra. To improve the phase coverage, we have also exploited all public archives containing high-resolution spectra, many not yet published. On the basis of these new Bs variability curves, we 1) confirm or revisit the periods of 24 stars, 2) extend the lower limits to the periods of HD 55719 (P > 38 yr), HD 165474 (P > 27 yr), HD 177765 (P > 37 yr), 3) establish for the first time the periods of HD 29578 (P = 10.95 yr), HD 47103 (P = 17.683 d), HD 150562 (P = 5.7 yr), HD 216018 (P = 34.044 d), and 4) set lower limits to the periods of HD 75445 (P > >14 yr), HD 110066 (P > >29 yr), HD 116114 (P > 48 yr), and HD 137949 (P > 27 yr). As to γ Equ, whose period must exceed 90 years, we point out a clear decrease in the field modulus, the maximum of which coincides within the uncertainties with the minimum of the variation in the integrated longitudinal field.

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Discovery of extraordinary X-ray emission from magnetospheric interaction in the unique binary stellar system ϵ Lupi

Das

¹

,

Petit

²

,

Naze

³

et al. 2023

Monthly Notices of the Royal Astronomical Society

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We report detailed X-ray observations of the unique binary system ε Lupi, the only known short-period binary consisting of two magnetic early-type stars. The components have comparably strong, but anti-aligned magnetic fields. The orbital and magnetic properties of the system imply that the magnetospheres overlap at all orbital phases, suggesting the possibility of variable inter-star magnetospheric interaction due to the non-negligible eccentricity of the orbit. To investigate this effect, we observed the X-ray emission from ε Lupiboth near and away from periastron passage, using the Neutron Star Interior Composition Explorer mission (NICER) X-ray Telescope. We find that the system produces excess X-ray emission at the periastron phase, suggesting the presence of variable inter-star magnetospheric interaction. We also discover that the enhancement at periastron is confined to a very narrow orbital phase range ($\approx 5~{{\%}}$ of the orbital period), but the X-ray properties close to periastron phase are similar to those observed away from periastron. From these observations, we infer that the underlying cause is magnetic reconnection heating the stellar wind plasma, rather than shocks produced by wind-wind collision. Finally, by comparing the behavior of ε Lupiwith that observed for cooler magnetic binary systems, we propose that elevated X-ray flux at periastron phase is likely a general characteristic of interacting magnetospheres irrespective of the spectral types of the constituent stars.

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Magnetic properties of three cool CP stars with strong fields

Cited by 6 publications

References 17 publications

Twenty-year monitoring of the surface magnetic field of peculiar stars

Twenty-year monitoring of the surface magnetic field of peculiar stars

Twenty-year monitoring of the surface magnetic fields of chemically peculiar stars

Discovery of extraordinary X-ray emission from magnetospheric interaction in the unique binary stellar system ϵ Lupi

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