Unidentified emission features in the R Coronae Borealis star V854 Centauri

Oostrum, L. C.; Ochsendorf, Bram; Kaper, L.; Tielens, A. G. G. M.

doi:10.1051/0004-6361/201731549

Cited by 4 publications

(4 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus, we regard our result as evidence that the RR-features and the nearby DIBs are likely not related. Finally, we note that the sharp band features in the RR are a unique phenomenon, which so far has only been detected in RR and the circumstellar envelope of the R Coronae Borealis star V854 Centauri (Rao et al 1993;Oostrum et al 2018). We note that no ERE was detected in the case of V854 Centauri.…”

Section: Absence Of the Sharp Rr-emission Featuresmentioning

confidence: 54%

“…A second test made possible by the fortuitous alignment of an ERE filament in the reflection nebula IC 63 with a suitable background star is an inquiry into the nature of the unidentified, sharp optical emission features seen in the spectrum of the Red Rectangle nebula (RR-features) and the R Coronae Borealis star V854 Centauri (Rao et al 1993;Oostrum et al 2018) and their possible relation to DIBs (Scarrott et al 1992;Sarre et al 1995;Glinski & Anderson 2002). The close proximity in wavelengths of some of the RR-features to the wavelengths of prominent DIBs has led to the suggestion that the RR-features are DIBs seen in emission (Sarre et al 1995;Van Winckel et al 2002;Adams & Oka 2019), and thus produced by the same carriers.…”

Section: Rr Emission Features and The Probe Of Isrfmentioning

confidence: 99%

See 1 more Smart Citation

Are the carriers of diffuse interstellar bands and extended red emission the same?

Lai

Witt

Álvarez

et al. 2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

We report the first spectroscopic observations of a background star seen through the region between the ionization front and the dissociation front of the nebula IC 63. This photodissociation region (PDR) exhibits intense extended red emission (ERE) attributed to fluorescence by large molecules/ions. We detected strong diffuse interstellar bands (DIB) in the stellar spectrum, including an exceptionally strong and broad DIB at λ4428. The detection of strong DIBs in association with ERE could be consistent with the suggestion that the carriers of DIBs and ERE are identical. The likely ERE process is recurrent fluorescence, enabled by inverse internal conversions from highly excited vibrational levels of the ground state to low-lying electronic states with subsequent transitions to ground. This provides a path to rapid radiative cooling for molecules/molecular ions, greatly enhancing their ability to survive in a strongly irradiated environment. The ratio of the equivalent widths (EW) of DIBs λ5797 and λ5780 in IC 63 is the same as that observed in the low-density interstellar medium with UV interstellar radiation fields (ISRF) weaker by at least two orders of magnitude. This falsifies suggestions that the ratio of these two DIBs can serve as a measure of the UV strength of the ISRF. Observations of the nebular spectrum of the PDR of IC 63 at locations immediately adjacent to where DIBs were detected failed to reveal any presence of sharp emission features seen in the spectrum of the Red Rectangle nebula. This casts doubts upon proposals that the carriers of these features are the same as those of DIBs seen at slightly shorter wavelengths.

show abstract

Section: Absence Of the Sharp Rr-emission Featuresmentioning

confidence: 54%

Section: Rr Emission Features and The Probe Of Isrfmentioning

confidence: 99%

Are the carriers of diffuse interstellar bands and extended red emission the same?

Lai

Witt

Álvarez

et al. 2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…At the low spectral resolutions at which ERE spectra are typically observed, the ERE band does not exhibit any recognizable spectral structure. One possible exception is the RR nebula, where a set of sharp, (Rao et al 1993;Oostrum et al 2018), however with the distinct absence of the broad ERE band. It appears most likely, therefore, that the sharp emission bands seen in the RR nebula and in V 854 Cen are a phenomenon separate from ERE (Lai et al 2020), with a different set of carriers but similar excitation requirements.…”

Section: Spectral Characteristicsmentioning

confidence: 99%

“…These sharp bands are spatially closely correlated with the ERE in the RR nebula (Schmidt and Witt 1991), but they have not been observed in any other well observed ERE spectrum. Furthermore, the only other location where these narrow emission bands have been seen is the circum-stellar dust region of the R Corona Borealis star V854 Cen (Rao et al 1993;Oostrum et al 2018), however with the distinct absence of the broad ERE band. It appears most likely, therefore, that the sharp emission bands seen in the RR nebula and in V 854 Cen are a phenomenon separate from ERE (Lai et al 2020), with a different set of carriers but similar excitation requirements.…”

Section: Spectral Characteristicsmentioning

confidence: 99%

Extended red emission: observational constraints for models

Witt

Lai

2020

Astrophys Space Sci

View full text Add to dashboard Cite

Extended Red Emission (ERE) is a widely observed optical emission process, present in a wide range of circumstellar and interstellar environments in the Milky Way galaxy as well as other galaxies. Definitive identifications of the ERE carriers and the ERE process are still a matter of debate. Numerous models have been proposed in recent decades, often developed without consideration of the growing body of observational constraints, which by now invalidate many of these models. This review focuses on the most wellestablished observational constraints which should help to delineate the way toward a generally accepted explanation of the ERE and an understanding of its place in the radiation physics of the interstellar medium.

show abstract

A plethora of new R Coronae Borealis stars discovered from a dedicated spectroscopic follow-up survey

Tisserand

Clayton

Bessell

et al. 2020

A&A

View full text Add to dashboard Cite

Context. It is increasingly suspected that R Coronae Borealis (RCB) stars -rare hydrogen-deficient and carbon-rich supergiant stars -are the product of mergers of white-dwarfs in the intermediary mass regime (0.6 < M T ot < 1.2M ). They show a wide range of effective temperatures and chemical abundances. Aims. Only 78 RCB stars are currently known in our Galaxy while up to 1000 were expected. It is necessary to find more of these peculiar and diverse stars to understand their origin and evolutionary path. We are undertaking such a dedicated search. We plan to follow up spectroscopically 2356 targets of interest that were carefully selected using the all sky 2MASS and WISE surveys. They have similar brightnesses and shell temperatures to known RCB stars and only a spectrum can reveal their real nature. Methods. We have observed nearly 500 of these targets using optical low-resolution spectrographs. These spectra were compared to synthetic spectra from a new grid of MARCs hydrogen-deficient atmospheric models. Classical RCB stars' photospheric temperatures range mostly from 4000 K to about 8500 K, and therefore their spectra look very different showing the presence of carbon molecules C 2 and CN up to ∼6800 K and solely atomic absorption lines above that. From the study of both observed and synthetic spectra, we have put in place a series of criteria to distinguish RCB stars from other AGB carbon-rich stars, mainly using estimates of the C/N ratio and 13 C strength, intensities of potential Balmer lines, and estimates of T eff using the Ca II triplet lines strength. Results. We found 45 new RCB stars, including 30 Cold (4000 < T e f f < 6800 K), 14 Warm (6800 < T e f f < 8500 K) and one hot RCB (T e f f > 10000 K). Forty of these belong to the Milky Way and five are located in the Magellanic Clouds. We also confirmed with the same spectroscopic method that the long lasting candidate KDM 5651 is indeed a new Magellanic RCB star, increasing the total number of Magellanic Cloud RCB stars to 30. Our method is particularly efficient at detecting Warm RCB stars as we have increased their number by a factor 4. Conclusions. We have increased by ∼50% the total number of RCB stars known, now reaching 147. We also include a list of 14 strong RCB candidates, most certainly observed during a dust obscuration phase. From the detection efficiency and success rate so far, we estimate that there should be no more than 500 RCB stars/HdC stars in the Milky Way.

show abstract

Unidentified emission features in the R Coronae Borealis star V854 Centauri

Cited by 4 publications

References 26 publications

Are the carriers of diffuse interstellar bands and extended red emission the same?

Are the carriers of diffuse interstellar bands and extended red emission the same?

Extended red emission: observational constraints for models

A plethora of new R Coronae Borealis stars discovered from a dedicated spectroscopic follow-up survey

Contact Info

Product

Resources

About