1,721,803 research outputs found
THE CIRCUMSTELLAR ENVIRONMENT OF THE PECULIAR F-HYPERGIANT IRC+10420
No full textIRC +10420 is to date the only object that has been proposed to be in the transition from the Red Supergiant Phase to the Wolf-Rayet phase. In this contribution we report on new high resolution optical spectra of IRC +10420
THE CIRCUMSTELLAR ENVIRONMENT OF THE PECULIAR F-HYPERGIANT IRC+10420
No full textIRC +10420 is to date the only object that has been proposed to be in the transition from the Red Supergiant Phase to the Wolf-Rayet phase. In this contribution we report on new high resolution optical spectra of IRC +10420.</p
The XMM-Newton view of the yellow hypergiant IRC+10420 and its surroundings
Get PDFpeer reviewedAmong evolved massive stars likely in transition to the Wolf-Rayet phase, IRC +10420 is probably one of the most enigmatic. It belongs to the category of yellow hypergiants and it is characterized by quite high mass loss episodes. Even though IRC+10420 benefited of many observations in several wavelength domains, it has never been a target for an X-ray observatory. We report here on the very first dedicated observation of IRC+10420 in X-rays, using the XMM-Newton satellite. Even though the target is not detected, we derive X-ray flux upper limits of the order of 1–3 ×10−14 erg cm−2 s−1 (between 0.3 and 10.0 keV), and we discuss the case of IRC+10420 in the framework of emission models likely to be adequate for such an object. Using the Optical/UV Monitor on board XMM-Newton, we present the very first upper limits of the flux density of IRC +10420 in the UV domain (between 1800 and 2250 Å and between 2050 and 2450 Å). Finally, we also report on the detection in this field of 10 X-ray and 7 UV point sources, and we briefly discuss their properties and potential counterparts at longer wavelengths
High resolution spectroscopy of the post-red supergiant IRC+10420: I. The data
Get PDFA high resolution optical spectrum of the post-red supergiant candidate IRC+10420 is presented. The Utrecht Echelle Spectrograph observations, with a total integration time of more than 9 hours! provide a spectral coverage front 3850 Angstrom to 1 mu m, and a spectral resolution of 9 km s(-1). The spectrum is shown, and an identification list of lines in the spectrum is provided. From a preliminary analysis of the spectrum we find that the spectral type of IRC+10420 has changed from F8I(+) in 1973 to mid- to early A type now, confirming the results of Oudmaijer et al. (1996), who claimed a change in temperature based on photometric changes. It is shown that most of the emission lines in the spectrum of IRC+10420 are blue-shifted with respect to the systemic velocity traced by circumstellar rotational CO emission. while the (few) absorption lines - with the exception of some high excitation lines are red-shifted by 25 km s(-1), which may suggest infall of material onto the star. Finally, it is found that the interstellar extinction towards IRC+10420 as traced by the Diffuse Interstellar Bands is very large, with an inferred E(B-V) of 1.4 +/- 0.5 compared to a total E(B-V) of 2.4
The spectral energy distribution and mass-loss history of IRC+10420
No full textWe present a study of the spectral energy distribution of the peculiar hypergiant IRC + 10420. To this end we have collected published photometry of IRC + 10420 and obtained some new data, in order to construct the spectral energy distribution and fit it with a radiative transfer model. In addition high-quality (CO)-C-12 spectra of the rotational J=1-0, 2-1, 3-2 and 4-3 transitions have been obtained to determine the gas outflow velocity and independently estimate the gas mass-loss rate. The main conclusions from this work are that the photometric changes over the last 20 years indicate that the object has increased in temperature by more than 1000 K and that the spectral energy distribution cannot be fitted with a single-shell model without first including a hot component. This hot component is likely to be a circumstellar disc. Finally, we present evidence that IRC + 10420 is nota post-AGE star
The spectral energy distribution and mass-loss history of IRC+10420
No full textWe present a study of the spectral energy distribution of the peculiar hypergiant IRC + 10420. To this end we have collected published photometry of IRC + 10420 and obtained some new data, in order to construct the spectral energy distribution and fit it with a radiative transfer model. In addition high-quality (CO)-C-12 spectra of the rotational J=1-0, 2-1, 3-2 and 4-3 transitions have been obtained to determine the gas outflow velocity and independently estimate the gas mass-loss rate.The main conclusions from this work are that the photometric changes over the last 20 years indicate that the object has increased in temperature by more than 1000 K and that the spectral energy distribution cannot be fitted with a single-shell model without first including a hot component. This hot component is likely to be a circumstellar disc. Finally, we present evidence that IRC + 10420 is nota post-AGE star.</p
IRAS 18357-0604 – an analogue of the galactic yellow hypergiant IRC +10420?
Get PDFContext. Yellow hypergiants represent a short-lived evolutionary episode experienced by massive stars as they transit to and from a red supergiant phase. As such, their properties provide a critical test of stellar evolutionary theory, while recent observations unexpectedly suggest that a subset may explode as Type II supernovae. Aims. The galactic yellow hypergiant IRC +10420 is a cornerstone system for understanding this phase since it is the strongest post-RSG candidate known, has demonstrated real-time evolution across the Hertzsprung-Russell diagram and been subject to extensive mass loss. In this paper we report on the discovery of a twin of IRC +10420 - IRAS 18357-0604. Methods. Optical and near-IR spectroscopy are used to investigate the physical properties of IRAS 18357-0604 and also provide an estimate of its systemic velocity, while near- to mid-IR photometry probes the nature of its circumstellar environment. Results. These observations reveal pronounced spectral similarities between IRAS 18357-0604 and IRC +10420, suggesting comparable temperatures and wind geometries. IR photometric data reveals a similarly dusty circumstellar environment, although historical mass loss appears to have been heavier in IRC +10420. The systemic velocity implies a distance compatible with the red supergiant-dominated complex at the base of the Scutum Crux arm; the resultant luminosity determination is consistent with a physical association but suggests a lower initial mass than inferred for IRC +10420 (≲20 M⊙ versus ~40 M⊙). Evolutionary predictions for the physical properties of supernova progenitors derived from ~18–20 M⊙ stars – or ~12–15 M⊙ stars that have experienced enhanced mass loss as red supergiants – compare favourably with those of IRAS 18357-0604, which in turn appears to be similar to the the progenitor of SN2011dh; it may therefore provide an important insight into the nature of the apparently H-depleted yellow hypergiant progenitors of some Type IIb SNe.This research is partially supported by the Spanish Ministerio de Economía y Competitividad (Mineco) under grants AYA2010-21697-C05-05 and AYA2012-39364-C02-02. The AAT observations have been supported by the OPTICON project (observing proposal 2012/A015), which is funded by the European Commission under the Seventh Framework Programme (FP7)
Detection of circumstellar nitric oxide. Enhanced nitrogen abundance in IRC +10420
No full textInternational audienceAims: During a full line survey towards IRC +10420 in the 3 and 1 mm bands, we detected the emission of circumstellar nitric oxide for the first time. We aim to study the formation of NO and to confirm the enrichment of nitrogen expected for the most massive, evolved stars predicted by the hot bottom burning process. Methods: We counted on a detailed model of the structure and kinematics of the molecular gas around IRC+˙10420. In addition, we used a chemical model to derive the NO abundance profile. We modified the initial nitrogen abundance in order to fit the observed NO profiles. These synthetic profiles were obtained using an LVG radiative transfer code. Results: We have detected NO in a circumstellar envelope for the first time, along with a variety of N-rich molecules, which in turn shows that IRC +10420 presents a N-rich chemistry. Furthermore, we have found that to reproduce the observed NO line profiles, the initial abundance of nitrogen in the chemical model has to be increased by a factor 20 with respect to the values of the standard O-rich stars. Based on observations carried out with the IRAM 30 m Telescope. IRAM is supported by INSU/CNRS (France), MPG (Germany), and IGN (Spain).Figures 3 and 4 are available in electronic form at http://www.aanda.or
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