Spectroscopy and linear spectropolarimetry of the early Herbig Be stars PDS 27 and PDS 37

Ababakr, K. M.; Fairlamb, J.; Oudmaijer, R. D.; Ancker, M. E. van den

doi:10.1093/mnras/stv1483

Cited by 10 publications

(18 citation statements)

References 53 publications

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“…This argument is supported by the observed line effects across the absorptive component of Hα in PDS 27, PDS 37 and PDS 133, as the line effect is stronger for a weaker absorption component. Ababakr et al (2015) suggested a similar scenario in an in-depth study of PDS 27 and PDS 37, but here we have an extra object that follows the same pattern.…”

Section: Mclean Effectsupporting

confidence: 74%

“…A1) in appendix A). PDS 37 shows a possible line effect in only the first two datasets while the second two datasets do not show such a line effect (Ababakr et al 2015). Therefore, the line effect in PDS 37 is not a conclusive result based on the current data.…”

Section: Ca II Linesmentioning

confidence: 71%

“…The results of PDS 27 and PDS 37 have been published elsewhere in a study dedicated to these two objects, but we keep them in here (Ababakr et al 2015).…”

Section: Source Selectionmentioning

confidence: 98%

“…They are presented in Table 1, alongside their spectral type and V magnitudes. The spectral type is taken from Ababakr et al (2015) and Fairlamb et al (2015) while the V magnitude is taken from Vieira et al (2003) and SIMBAD.…”

Section: Source Selectionmentioning

confidence: 99%

“…They were first identified by Herbig as having a spectral type A or B with emission lines (Herbig 1960). The current view is that HAeBe stars are surrounded Ababakr et al (2015) and Fairlamb et al (2015) while the V magnitude is taken from Vieira et al (2003) and SIMBAD. The integration times (column 8, 9 & 10) denote the total exposures in V (4560 -5860Å), R (5750 -7310Å) and Z (7730 -9480Å) bands.…”

Section: Introductionmentioning

confidence: 99%

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Linear spectropolarimetry across the optical spectrum of Herbig Ae/Be stars

Ababakr¹,

Oudmaijer²

2016

Mon. Not. R. Astron. Soc.

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We present the results of spectropolarimetric observations of 12 Herbig Ae/Be objects. Our data have the largest spectropolarimetric wavelength coverage, 4560Å to 9480Å, published to date. A change in linear polarisation across the Hα line, is detected in all objects. Such a line effect reveals the fact that stellar photons are scattered off free electrons that are not distributed in a spherically symmetric volume, suggesting the presence of small disks around these accreting objects. Thanks to the large wavelength coverage, we can report that Hα is the spectral line in the optical wavelength range that is most sensitive to revealing deviations from spherical symmetry, and the one most likely to show a line effect across the polarisation in such cases. Few other spectral lines display changes in polarisation across the line. In addition, Hα is the only line which shows an effect across its absorption component in some sources. We present a scenario explaining this finding and demonstrate that the detection of the line effect strongly relies on the number of photons scattered into our line of sight. We highlight the special case of R Mon, which is the only object in our sample to show many lines with a polarisation effect, which is much stronger than in all other objects. Given that the object and its nebulosity is spatially resolved, we argue that this is due to scattering of the stellar and emission spectrum off circumstellar dust.

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Section: Mclean Effectsupporting

confidence: 74%

Section: Ca II Linesmentioning

confidence: 71%

“…The results of PDS 27 and PDS 37 have been published elsewhere in a study dedicated to these two objects, but we keep them in here (Ababakr et al 2015).…”

Section: Source Selectionmentioning

confidence: 98%

Section: Source Selectionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Linear spectropolarimetry across the optical spectrum of Herbig Ae/Be stars

Ababakr¹,

Oudmaijer²

2016

Mon. Not. R. Astron. Soc.

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The Polstar high resolution spectropolarimetry MIDEX mission

Scowen

Gayley

Ignace

et al. 2022

Astrophys Space Sci

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Herschel observations of the circumstellar environments of the Herbig Be stars R Mon and PDS 27

Jiménez-Donaire

Meeus

Karska

et al. 2017

A&A

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Context. The circumstellar environment of Herbig Be stars in the far-infrared is poorly characterised, mainly because they are often embedded and rather distant. The analysis of far-infrared spectroscopy allows us to make a major step forward by covering multiple rotational lines of molecules, e.g. CO, that are useful probes of physical conditions of the gas. Aims. To characterise the gas and dust in the disc and environment of Herbig Be stars, and to compare the results with those of their lower-mass counterparts, the Herbig Ae stars. Methods. We report and analyse far-infrared observations of two Herbig Be stars, R Mon and PDS 27, obtained with Herschel's instruments PACS and SPIRE. We construct spectral energy distributions and derive the infrared excess. We extract line fluxes from the PACS and SPIRE spectra and construct rotational diagrams in order to estimate the excitation temperature of the gas. We derive CO, [O I] and [C I] luminosities to determine physical conditions of the gas, as well as the dominant cooling mechanism. Results. We confirm that the Herbig Be stars are surrounded by remnants from their parental clouds, with an IR excess that mainly originates in a disc. In R Mon we detect [O I], [C I], [C II], CO (26 transitions), water and OH, while in PDS 27 we only detect [C I] and CO (8 transitions). We attribute the absence of OH and water in PDS 27 to UV photo-dissociation and photo-evaporation. From the rotational diagrams, we find several components for CO: we derive T rot 949±90 K, 358±20 K & 77±12 K for R Mon, 96±12 K & 31±4 K for PDS 27 and 25±8 K & 27±6 K for their respective compact neighbours. The forsterite feature at 69 µm was not detected in either of the sources, probably due to the lack of (warm) crystalline dust in a flat disc. We find that cooling by molecules is dominant in the Herbig Be stars, while this is not the case in Herbig Ae stars where cooling by [O I] dominates. Moreover, we show that in the Herbig Be star R Mon, outflow shocks are the dominant gas heating mechanism, while in Herbig Ae stars this is stellar. Conclusions. The outflow of R Mon contributes to the observed line emission by heating the gas, both in the central spaxel/beam covering the disc and the immediate surroundings, as well as in those spaxels/beams covering the parabolic shell around it. PDS 27, a B2 star, has dispersed a large part of its gas content and/or destroyed molecules; this is likely given its intense UV field.

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Spectroscopy and linear spectropolarimetry of the early Herbig Be stars PDS 27 and PDS 37

Cited by 10 publications

References 53 publications

Linear spectropolarimetry across the optical spectrum of Herbig Ae/Be stars

Linear spectropolarimetry across the optical spectrum of Herbig Ae/Be stars

The Polstar high resolution spectropolarimetry MIDEX mission

Herschel observations of the circumstellar environments of the Herbig Be stars R Mon and PDS 27

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