A Sensitive Spectral Survey of Interstellar Features in the Near-Uv [3050-3700 Å]

Bhatt, N. H.; Cami, J.

doi:10.1088/0067-0049/216/2/22

Cited by 19 publications

(30 citation statements)

References 62 publications

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“…Moreover, using their unreddened superspectrum in the same figure as a reference, we estimate the central absorption depths of the two features to be ∼0.004-0.005, which is significantly higher than their 3σ detection limit. These values are approximately half of that (0.009 ± 0.003) derived from the averaged spectrum presented here, consistent with the possibility that the large data set of in total 51 diffuse/translucent clouds in Bhatt & Cami (2015) contains some SH-poor objects. This shows that the two features are real and fully coincide with the SH absorption lines we have found in our averaged spectra.…”

Section: Resultssupporting

confidence: 90%

“…Following the work presented above, we found that the two SH features we identified here are also visible in the reddened "superspectrum" recently presented by Bhatt & Cami (2015). This spectrum has a typical S /N ∼ 1500 in the near-UV that is realized by averaging 185 VLT/UVES observations of 51 reddened, early-type (O and B) stars.…”

Section: Resultssupporting

confidence: 83%

“…Special care is needed because the observed positions are very close to the strong Ti II 3242 Å interstellar absorption feature that has been found to exhibit a complex component structure along many lines of sight (see Table A.2 in Bhatt & Cami 2015). To further strengthen the identification of the two features as originating from SH, that is, to exclude that these are not associated with the weak Doppler components of the Ti II 3242 Å feature, we carefully compared the multicomponent spectral profiles of the Ti II 3242 and 3384 Å lines.…”

Section: Resultsmentioning

confidence: 99%

“…near-ultraviolet absorption features of the electronic transitions of SH + in diffuse or translucent interstellar clouds have been searched for in several observational studies, but all attempts were unsuccessful (Millar & Hobbs 1988;Magnani & Salzer 1989, 1991Bhatt & Cami 2015). In contrast, to our knowledge, similar searches for SH in translucent clouds have not been reported.…”

Section: Introductionmentioning

confidence: 99%

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Mercapto radical (SH) in translucent interstellar clouds

Zhao

Галазутдинов

Linnartz

et al. 2015

A&A

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We present the first detection of rotationally resolved electronic transitions of the mercapto radical (SH) in the near-ultraviolet in translucent interstellar clouds. Observational data acquired by the Ultraviolet and Visual Echelle Spectrograph of the Very Large Telescope were used to search for the near-ultraviolet absorption spectra of SH. Two weak absorption features at ∼3242.40 and 3240.66 Å, assigned as the p P 11 (3/2) and the ( q P 21 (3/2) + q Q 11 (3/2)) doublet transitions in the A 2 Σ + -X 2 Π (0, 0) band of SH, respectively, were identified in the averaged spectrum of four selected lines of sight: HD 73882, HD 78344, HD 80077, and HD 154368. These features are weak, but can be identified within a 3σ detection limit, and are found in other published data sets as well. We compiled a set of line positions and oscillator strengths of SH to facilitate the data analysis. We derived an averaged value of the SH column density, ∼1.5 ± 0.3 × 10 13 cm −2 , that is most likely representative for the magnitude of SH column densities in individual SH-rich translucent clouds. This value is also consistent with predictions from models for C-type shocks and turbulent dissipation regions with typical translucent cloud conditions.

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Section: Resultssupporting

confidence: 90%

Section: Resultssupporting

confidence: 83%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Mercapto radical (SH) in translucent interstellar clouds

Zhao

Галазутдинов

Linnartz

et al. 2015

A&A

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“…Galazutdinov et al 2000;Hobbs et al 2009). Most of them are seen in the optical, with some additional DIBs clearly identified in the near infrared (Joblin et al 1990;Foing & Ehrenfreund 1994;Cox et al 2014;Hamano et al 2016) and a few proposed candidates in the near-UV (Bhatt & Cami 2015). Also, DIBs seem omnipresent.…”

Section: Introductionmentioning

confidence: 99%

Measuring diffuse interstellar bands with cool stars

Monreal-Ibero

Lallement

2017

A&A

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Context. Diffuse Stellar Bands (DIBs) are ubiquitous in stellar spectra. Traditionally, they have been studied through their extraction from hot (early-type) stars, because of their smooth continuum. In an era where there are several going-on or planned massive Galactic surveys using multi-object spectrographs, cool (late-type) stars constitute an appealing set of targets. However, from the technical point of view, the extraction of DIBs in their spectra is more challenging due to the complexity of the continuum. Aims. In this contribution we will provide the community with an improved set of stellar lines in the spectral regions associated to the strong DIBs at λ6196.0, λ6269.8, λ6283.8, and λ6379.3. These lines will allow for the creation of better stellar synthetic spectra, reproducing the background emission and a more accurate extraction of the magnitudes associated with a given DIB (e.g. equivalent width, radial velocity). Methods. The Sun and Arcturus were used as representative examples of dwarf and giant stars, respectively. A high quality spectrum for each of them was modeled using TURBOSPECTRUM and the VALD stellar line list. The oscillator strength log(g f ) and/or wavelength of specific lines were modified to create synthetic spectra where the residuals in both the Sun and Arcturus were minimized. Results. The TURBOSPECTRUM synthetic spectra based on the improved line lists reproduce the observed spectra for the Sun and Arcturus in the mentioned spectral ranges with greater accuracy. Residuals between the synthetic and observed spectra are always ∼ < 10%, much better than with previously existing options. The new line list has been tested with some characteristic spectra, from a variety of stars, including both giant and dwarf stars, and under different degrees of extinction. As it happened with the Sun and Arcturus residuals in the fits used to extract the DIB information are smaller when using synthetic spectra made with the updated line lists. Tables with the updated parameters are provided to the community.

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Laboratory spectroscopy and astronomical significance of the fully-benzenoid PAH triphenylene and its cation

Kofman

Sarre

Hibbins

et al. 2017

Molecular Astrophysics

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a b s t r a c tTriphenylene (C 18 H 12 ) is a highly symmetric polycyclic aromatic hydrocarbon (PAH) molecule with a 'fully-benzenoid' electronic structure. This confers a high chemical stability compared with PAHs of similar size. Although numerous infrared and UV-vis experimental spectroscopic and theoretical studies of a wide range PAHs in an astrophysical context have been conducted, triphenylene and its radical cation have received almost no attention. There exists a huge body of spectroscopic evidence for neutral and ionised PAHs in astrophysical sources, obtained principally through detection of infrared emission features that are characteristic of PAHs as a chemical class. However, it has so far not proved possible to identify spectroscopically a single isolated PAH in space, although PAHs including triphenylene have been detected mass spectrometrically in meteorites. In this work we focus on recording laboratory electronic spectra of neutral and ionised triphenylene between 220 and 780 nm, trapped in H 2 O ice and solid argon at 12 K. The studies are motivated by the potential for spectroscopic astronomical detection of electronic absorption spectra of PAHs in ice mantles on interstellar grains as discussed by Linnartz (2014), and were performed also in a cold Ar matrix to provide guidance as to whether triphenylene (particularly in its singly positively ionised form) could be a viable candidate for any of the unidentified diffuse interstellar absorption bands. Based on the argon-matrix experimental results, comparison is made with previously unpublished astronomical spectra near 400 nm which contain broad interstellar absorption features consistent with the predictions from the laboratory matrix spectra, thus providing motivation for the recording of gas-phase electronic spectra of the internally cold triphenylene cation.

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A Sensitive Spectral Survey of Interstellar Features in the Near-Uv [3050-3700 Å]

Cited by 19 publications

References 62 publications

Mercapto radical (SH) in translucent interstellar clouds

Mercapto radical (SH) in translucent interstellar clouds

Measuring diffuse interstellar bands with cool stars

Laboratory spectroscopy and astronomical significance of the fully-benzenoid PAH triphenylene and its cation

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