Photometry and spectroscopy of the central star of the Trifid
 nebula

Kohoutek, L.; Mayer, P.; Lorenz, R.

doi:10.1051/aas:1999128

Cited by 21 publications

(31 citation statements)

References 6 publications

(9 reference statements)

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“…The distance is uncertain, with values from 1.7-2.84 kpc discussed in the recent literature (Lynds & Oneil 1985;Rho et al 2008;Cambrésy et al 2011), although even smaller distances (under 1 kpc) have been proposed (Kohoutek et al 1999).…”

Section: Introductionmentioning

confidence: 99%

HD 164492C: a rapidly rotating, Hα-bright, magnetic early B star associated with a 12.5 d spectroscopic binary

Wade

Shultz

Sikora

et al. 2016

Mon. Not. R. Astron. Soc.

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We employ high resolution spectroscopy and spectropolarimetry to derive the physical properties and magnetic characteristics of the multiple system HD 164492C, located in the young open cluster M20. The spectrum reveals evidence of 3 components: a broad-lined early B star (HD 164492C1), a narrow-lined early B star (HD 164492C2), and a late B star (HD 164492C3). Components C2 and C3 exhibit significant (> 100 km/s) bulk radial velocity variations with a period of 12.5351(7) d that we attribute to eccentric binary motion around a common centre-of-mass. Component C1 exhibits no detectable radial velocity variations. Using constraints derived from modeling the orbit of the C2+C3 binary and from synthesis of the combined spectrum, we determine the approximate physical characteristics of the components. We conclude that a coherent evolutionary solution consistent with the published age of M20 implies a distance to M20 of 0.9 ± 0.2 kpc, corresponding to the smallest published values. We confirm the detection of a strong magnetic field in the combined spectrum. The field is clearly associated with the broad-lined C1 component of the system. Repeated measurement of the longitudinal magnetic field allows the derivation of the rotation period of the magnetic star, P rot = 1.36986(6) d. We derive the star's magnetic geometry, finding i = 63±6• , β = 33 ± 6• and a dipole polar strength B d = 7.9 +1.2 −1.0 kG. Strong emission -varying according to the magnetic period -is detected in the Hα profile. This is consistent with the presence of a centrifugal magnetosphere surrounding the rapidly rotating magnetic C1 component.

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Section: Introductionmentioning

confidence: 99%

HD 164492C: a rapidly rotating, Hα-bright, magnetic early B star associated with a 12.5 d spectroscopic binary

Wade

Shultz

Sikora

et al. 2016

Mon. Not. R. Astron. Soc.

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“…The spectacular, well-known optical H ii region provides an ideal place for investigating the onset of star birth and triggered star formation. This large nebula is ionised by the O7.5 Vz star HD 164492A (Sota et al 2014), which is the central object of the multiple system ADS 10991, containing at least seven components (A to G; Kohoutek et al 1999). Due to the faintness of the components HD 164492B and HD 164492E-G (all have visual magnitudes fainter than 10.6), we only searched for a magnetic field for the three most massive components, HD 164492A, C, and D.…”

Section: Introductionmentioning

confidence: 99%

B fields in OB stars (BOB): The discovery of a magnetic field in a multiple system in the Trifid nebula, one of the youngest star forming regions

Hubrig

Fossati

Carroll

et al. 2014

A&A

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Aims. Recent magnetic field surveys in O-and B-type stars revealed that about 10% of the core-hydrogen-burning massive stars host large-scale magnetic fields. The physical origin of these fields is highly debated. To identify and model the physical processes responsible for the generation of magnetic fields in massive stars, it is important to establish whether magnetic massive stars are found in very young star-forming regions or whether they are formed in close interacting binary systems. Methods. In the framework of our ESO Large Program, we carried out low-resolution spectropolarimetric observations with FORS 2 in 2013 April of the three most massive central stars in the Trifid nebula, HD 164492A, HD 164492C, and HD 164492D. These observations indicated a strong longitudinal magnetic field of about 500-600 G in the poorly studied component HD 164492C. To confirm this detection, we used HARPS in spectropolarimetric mode on two consecutive nights in 2013 June. Results. Our HARPS observations confirmed the longitudinal magnetic field in HD 164492C. Furthermore, the HARPS observations revealed that HD 164492C cannot be considered as a single star as it possesses one or two companions. The spectral appearance indicates that the primary is most likely of spectral type B1-B1.5 V. Since in both observing nights most spectral lines appear blended, it is currently unclear which components are magnetic. Long-term monitoring using high-resolution spectropolarimetry is necessary to separate the contribution of each component to the magnetic signal. Given the location of the system HD 164492C in one of the youngest star formation regions, this system can be considered as a Rosetta Stone for our understanding of the origin of magnetic fields in massive stars.

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“…The distance of this young nebula (10 5 years) is still debated. The observation of the central O7 star responsible for the photoionization, HD 164492, yields a distance ranging from 1.67 kpc (Lynds et al 1985) to 2.8 kpc (Kohoutek et al 1999). This active region has its first generation of massive stars interacting with the ISM and is very likely A&A 527, A141 (2011) triggering a second generation of star formation (Cernicharo et al 1998).…”

Section: Introductionmentioning

confidence: 99%

Variation of the extinction law in the Trifid nebula

Cambrésy

Rho

Marshall

et al. 2011

A&A

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Context. In the past few years, the extinction law has been measured in the infrared wavelengths for various molecular clouds and different laws have been obtained. Aims. In this paper we seek variations of the extinction law within the Trifid nebula region. Such variations would demonstrate local dust evolution linked to variation of the environment parameters such as the density or the interstellar radiation field. Methods. The extinction values, A λ /A V , are obtained using the 2MASS, UKIDSS and Spitzer/GLIMPSE surveys. The technique is to inter-calibrate color-excess maps from different wavelengths to derive the extinction law and to map the extinction in the Trifid region. Results. We measured the extinction law at 3.6, 4.5, and 5.8 μm and we found a transition at A V ≈ 20 mag. Below this threshold the extinction law is as expected from models for R V = 5.5 whereas above 20 mag of visual extinction, it is flatter. Using these results the color-excess maps are converted into a composite extinction map of the Trifid nebula at a spatial resolution of 1 arcmin. A tridimensional analysis along the line-of-sight allowed us to estimate a distance of 2.7 ± 0.5 kpc for the Trifid. The comparison of the extinction with the 1.25 mm emission suggests the millimeter emissivity is enhanced in the dense condensations of the cloud. Conclusions. Our results suggest a dust transition at large extinction which has not been reported so far as well as dust emissivity variations.

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Photometry and spectroscopy of the central star of the Trifid nebula

Cited by 21 publications

References 6 publications

HD 164492C: a rapidly rotating, Hα-bright, magnetic early B star associated with a 12.5 d spectroscopic binary

HD 164492C: a rapidly rotating, Hα-bright, magnetic early B star associated with a 12.5 d spectroscopic binary

B fields in OB stars (BOB): The discovery of a magnetic field in a multiple system in the Trifid nebula, one of the youngest star forming regions

Variation of the extinction law in the Trifid nebula

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