<i>Chandra</i> X-ray study confirms that the magnetic standard Ap star KQ Vel hosts a neutron star companion

Oskinova, L. M.; Ignace, Richard; Leto, Paolo; Постнов, К. А.

doi:10.1051/0004-6361/202038214

Cited by 4 publications

(15 citation statements)

References 39 publications

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“…Independent of the model details, we find a flux value of F X = 1.4 ± 0.1 × 10 −12 erg cm −2 s −1 in the 0.3−10.0 keV band. Overall, our analysis is in agreement, within the error bars, with the one presented by Oskinova et al (2020) from the same data, making an allowance for the solar abundances adopted by these authors.…”

Section: X-ray Emissionsupporting

confidence: 90%

“…HD 94660 has an effective temperature of T eff = 11 300 ± 400 K, a mass of 3.0 ± 0.2 M (Bailey et al 2015), and a rotation period of 2800 ± 200 d (Mathys 2017). A temperature of 11 300 K is indicative of a spectral type B8.5p (e.g., Eker et al 2020), rather than the A0p indicated by Renson & Manfroid (2009). Hensberge (1993) already reported long-term photometric variability with peak-to-peak amplitudes of ∼0.03 mag and determined a period on the order of 2700 d. Bailey et al (2015) estimated that HD 94660 has completed less than half of its main sequence lifetime.…”

Section: Introductionmentioning

confidence: 99%

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The near-infrared companion to HD 94660 (=KQ Vel)

Schöller

Hummel

Hubrig

et al. 2020

A&A

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Context. The Bp star HD 94660 is a single-lined spectroscopic binary. Some authors have suggested that the unseen companion of at least 2 M⊙ may be a compact object. Aims. We intend to study this multiple system in detail, especially to learn more about the thus far unseen companion. Methods. We have collected and analyzed PIONIER (Precision Integrated-Optics Near-infrared Imaging ExpeRiment) H-band data from the Very Large Telescope Interferometer, TESS (Transiting Exoplanet Survey Satellite) visible photometric data, and X-ray observations with Chandra of HD 94660. Results. Using PIONIER, we were able to detect the companion to HD 94660, which is absent from high quality spectra at visible wavelengths, with a magnitude difference of 1.8 in the H band at a separation of 18.72 mas. The TESS light curve shows variations with a period of 2.1 d and also flaring. The Chandra spectrum is well described by emission from hot thermal plasma, yet it might include a nonthermal component. The X-ray properties are compatible with a magnetically active companion, while it is also possible that there might be some magnetospheric contributions from the primary. Conclusions. We can rule out that the companion to HD 94660 is a compact source. It is also very unlikely that this companion is a single star, as the estimated mass of more than 2 M⊙, the magnitude difference of 1.8 in the H band, and its nondetection in visible spectra are difficult to realize in a single object. One alternative could be a pair of late F stars, which would also be responsible for the detected photometric variations. Interferometric observations over the full binary orbit are necessary to determine the real mass of the companion and to add constraints on the overall geometry of the system.

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Section: X-ray Emissionsupporting

confidence: 90%

Section: Introductionmentioning

confidence: 99%

The near-infrared companion to HD 94660 (=KQ Vel)

Schöller

Hummel

Hubrig

et al. 2020

A&A

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“…High-quality visual spectra of KQ Vel did not evidence any clear spectral signatures able to characterize the nature of the companion of the bright magnetic Ap star (Bailey et al 2015). On the other hand, KQ Vel is also a bright X-ray source whose origin cannot be simply related to the visible Ap star (Oskinova et al 2020). To explain how the X-ray emission from KQ Vel originates, different scenarios involving the unknown companion have been proposed.…”

Section: Summary On Kq Velmentioning

confidence: 99%

“…To explain how the X-ray emission from KQ Vel originates, different scenarios involving the unknown companion have been proposed. Oskinova et al (2020) considered various scenarios, including a possibility that the companion is a RS CVn-type binary consisting of late-type stars with high-level of coronal magnetic activity. This possibility was discarded because typical activity signs (e.g.…”

Section: Summary On Kq Velmentioning

confidence: 99%

“…CaII spectral lines) have not been reported in the literature. Finally, Oskinova et al (2020) favored a scenario involving the presence of a hot shell surrounding a massive degenerate unseen companion (a propelling magnetic neutron star) as responsible for the observed Xray emission. However, the detection of a faint infrared source close to the bright Ap star, with short-period (2.1 d) photometric variability, and of flares (Schöller et al 2020) re-opened the possibility that the companion of the Ap star is a binary system composed of a pair of non-degenerate stars, with masses close to the mass of the Sun and characterized by solar-like magnetic activity able to explain the measured X-ray emission level.…”

Section: Summary On Kq Velmentioning

confidence: 99%

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Discovery and origin of the radio emission from the multiple stellar system KQVel

Leto¹,

Oskinova²,

Buemi³

et al. 2022

Preprint

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KQ Vel is a binary system composed of a slowly rotating magnetic Ap star with a companion of unknown nature. In this paper, we report the detection of its radio emission. We conducted a multi-frequency radio campaign using the ATCA interferometer (band-names: 16cm, 4cm, and 15mm). The target was detected in all bands. The most obvious explanation for the radio emission is that it originates in the magnetosphere of the Ap star, but this is shown unfeasible. The known stellar parameters of the Ap star enable us to exploit the scaling relationship for non-thermal gyro-synchrotron emission from early-type magnetic stars. This is a general relation demonstrating how radio emission from stars with centrifugal magnetospheres is supported by rotation. Using KQ Vel's parameters the predicted radio luminosity is more than five orders of magnitudes lower than the measured one. The extremely long rotation period rules out the Ap star as the source of the observed radio emission. Other possible explanations for the radio emission from KQ Vel, involving its unknown companion, have been explored. A scenario that matches the observed features (i.e. radio luminosity and spectrum, correlation to X-rays) is a hierarchical stellar system, where the possible companion of the magnetic star is a close binary (possibly of RS CVn type) with at least one magnetically active late-type star. To be compatible with the total mass of the system, the last scenario places strong constraints on the orbital inclination of the KQ Vel stellar system.

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

Giarrusso

Cecconi

Cosentino

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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Chandra X-ray study confirms that the magnetic standard Ap star KQ Vel hosts a neutron star companion

Cited by 4 publications

References 39 publications

The near-infrared companion to HD 94660 (=KQ Vel)

The near-infrared companion to HD 94660 (=KQ Vel)

Discovery and origin of the radio emission from the multiple stellar system KQVel

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

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