Suchergebnisse

17 pags., 16 figs. ; Aims. We investigate the structure, dynamics, and chemistry of the molecule-rich nebula around the stellar symbiotic system R Aqr, which is significantly affected by the presence of a white dwarf (WD) companion. We study the effects of the strong dynamical interaction between the AGB wind and the WD and of photodissociation by the WD UV radiation on the circumstellar shells. Methods. We obtained high-quality ALMA maps of the 12CO J = 2-1, J = 3-2, and J = 6-5 lines and of 13CO J = 3-2. The maps were analyzed by means of a heuristic 3D model that is able to reproduce the observations. In order to interpret this description of the molecule-rich nebula, we performed sophisticated calculations of hydrodynamical interaction and photoinduced chemistry. Results. We find that the CO-emitting gas is distributed within a relatively small region ≲ 1.″5. Its structure consists of a central dense component plus strongly disrupted outer regions, which seem to be parts of spiral arms that are highly focused on the orbital plane. The structure and dynamics of these spiral arms are compatible with our hydrodynamical calculations. We argue that the observed nebula is the result of the dynamical interaction between the wind and the gravitational attraction of the WD. We also find that UV emission from the hot companion efficiently photodissociates molecules except in the densest and best-shielded regions, that is, in the close surroundings of the AGB star and some shreds of the spiral arms from which the detected lines come. We can offer a faithful description of the distribution of nebular gas in this prototypical source, which will be a useful template for studying material around other tight binary systems. ; This work has been supported by the Spanish MICINN, grants AYA2016-78994-P, AYA2016-75066-C2-1-P, PID2019- 105203GB-C2, PID2019-106110GB-I00, and PID2019-107115GB-C21, and by the National Science Centre, Poland, grant OPUS 2017/27/B/ST9/01940. M.A. acknowledges funding support from the Ramón y Cajal programme of Spanish MICIU (grant RyC-2014-16277) and from the European Research Council (ERC Grant 610256: NANOCOSMOS). H.K. acknowledges support by the National Research Foundation of Korea (NRF), grant funded by the Korea government (MIST) (No. 2021R1A2C1008928). This paper makes use of the following ALMA data: ADS/JAO.ALMA#2017.1.00363.S and 2018.1.00638.S. ALMA is a partnership of ESO (representing its member more states), NSF (USA) and NINS (Japan), together with NRC (Canada), MOST and ASIAA (Taiwan), and KASI (Republic of Korea), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ.

10 pags., 8 figs., 1 tab., 1 app. ; We aim to study the properties of a particular type of evolved stars, C-rich evolved stars with high expansion velocities. For this purpose we have focused on the two best studied objects within this group, IRC+10401 and AFGL 2233. We focused on determining their luminosity by studying their spectral energy distribution. Also, we have obtained single-dish line profiles and interferometric maps of the CO J = 1-0 and J = 2-1 emission lines for both objects. We have modeled this emission using a LVG radiative transfer code to determine the kinetic temperature and density profiles of the gas ejected by these stars. We have found that the luminosities obtained for these objects (log(L/L ) = 4.1 and 5.4) locate them in the domain of the massive asymptotic giant branch stars (AGBs) and the red supergiant stars (RSGs). In addition, the mass-loss rates obtained (1.5 × 10-6 ×10 M yr) suggest that while IRC+10401 might be an AGB star, AFGL 2233 could be an RSG star. All these results, together with those from previous works, suggest that both objects are massive objects, IRC+10401 a massive evolved star with M ∼ 5-9 M which could correspond to an AGB or an RSG and AFGL 2233 an RSG with M ∼ 20 M , which would confirm the existence of massive C-rich evolved stars. Two scenarios are proposed to form these types of objects. The first one is capable of producing high-mass AGB stars up to ∼8 M and the second one is capable of forming C-rich RSGs like AFGL 2233. ; The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ ERC grant Agreement n. 610256 (NANOCOSMOS). We would also like to thank the Spanish MINECO for funding support from grants CSD2009-00038, AYA2012-32032, AYA2016- 75066-C2-1-P and AYA2016-78994-P. M.A. also thanks for funding support from the Ramón y Cajal programme of Spanish MINECO (RyC-2014-16277). This work has made use of data from the European Space Agency (ESA) mission Gaia, processed by the Gaia Data Processing and Analysis Consortium (DPAC. Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement ; Peer Reviewed

The Astrophysical Journal 794.2 (2014): 99 reproduced by permission of the AAS ; We present results from the most recent set of observations obtained as part of the Chandra X-ray observatory Planetary Nebula Survey (CHANPLANS), the first comprehensive X-ray survey of planetary nebulae (PNe) in the solar neighborhood (i.e., within∼1.5 kpc of the Sun). The survey is designed to place constraints on the frequency of appearance and range of X-ray spectral characteristics of X-ray-emitting PN central stars and the evolutionary timescales of wind-shock-heated bubbles within PNe. CHANPLANS began with a combined Cycle 12 and archive Chandra survey of 35 PNe. CHANPLANS continued via a Chandra Cycle 14 Large Program which targeted all (24) remaining known compact (R neb ≲ 0.4 pc), young PNe that lie within∼1.5 kpc. Results from these Cycle 14 observations include first-time X-ray detections of hot bubbles within NGC 1501, 3918, 6153, and 6369, and point sources in HbDs 1, NGC 6337, and Sp 1. The addition of the Cycle 14 results brings the overall CHANPLANS diffuse X-ray detection rate to 27% and the point source detection rate to 36%. It has become clearer that diffuse X-ray emission is associated with young (≲ 5 × 103 yr), and likewise compact (R neb ≲ 0.15 pc), PNe with closed structures and high central electron densities (ne ≳ 1000 cm-3), and is rarely associated with PNe that show H2 emission and/or pronounced butterfly structures. Hb 5 is one such exception of a PN with a butterfly structure that hosts diffuse X-ray emission. Additionally, two of the five new diffuse X-ray detections (NGC 1501 and NGC 6369) host [WR]-type central stars, supporting the hypothesis that PNe with central stars of [WR]-type are likely to display diffuse X-ray emission ; We thank the anonymous referee for helpful comments. This research was supported via award No. GO3–14019A to RIT issued by the Chandra X-ray Observatory Center, which is operated by the Smithsonian Astrophysical Observatory for and on behalf of NASA under contract NAS8-03060. Jesus A. Toalá and Martín A. Guerrero are supported by the Spanish MICINN grant AYA 2011-29754-C03-02 co-funded with FEDER funds. The Digitized Sky Surveys were produced at STScI under U.S. Government Grant NAG W-2166. This research has also made use of the SIMBAD database, operated at CDS, Strasbourg, France

22 pags., 27 figs., 6 tabs. ; Context. Yebes 40 m radio telescope is the main and largest observing instrument at Yebes Observatory and is devoted to very long baseline interferometry (VLBI) and single-dish observations since 2010. It has been covering frequency bands between 2 GHz and 90 GHz in discontinuous and narrow windows in most cases in order to match the current needs of the European VLBI Network (EVN) and the Global Millimeter VLBI Array (GMVA). Aims. The Nanocosmos project, a European Union-funded synergy grant, has enabled an increase in the instantaneous frequency coverage of the Yebes 40 m radio telescope, making it possible to observe many molecular transitions with single tunings in single-dish mode. This reduces the observing time and maximises the output from the telescope. Methods. We present technical specifications of the recently installed 31.5-50 GHz (Q band) and 72-90.5 GHz (W band) receivers along with the main characteristics of the telescope at these frequency ranges. We observed IRC+10216, CRL 2688, and CRL 618, which harbour a rich molecular chemistry, to demonstrate the capabilities of the new instrumentation for spectral observations in single-dish mode. Results. Our results show the high sensitivity of the telescope in the Q band. The spectrum of IRC+10126 offers an unprecedented signal-to-noise ratio for this source in this band. On the other hand, the spectrum normalised by the continuum flux towards CRL 618 in the W band demonstrates that the 40 m radio telescope produces comparable results to those from the IRAM 30 m radio telescope, although with a lower sensitivity. The new receivers fulfil one of the main goals of Nanocosmos and open up the possibility to study the spectrum of different astrophysical media with unprecedented sensitivity. ; The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC-SyG-2013 Grant Agreement No. 610256 Nanocosmos. Part of this work was supported by Programa operativo pluriregional de España, YDALGO. The observations mentioned in this article have been done under commissioning time and within projects 19A010 and 20A017. The Yebes 40m radio telescope belongs to Instituto Geográfico Nacional (IGN).

22 pags., 27 figs., 6 tabs. ; Context. Yebes 40 m radio telescope is the main and largest observing instrument at Yebes Observatory and is devoted to very long baseline interferometry (VLBI) and single-dish observations since 2010. It has been covering frequency bands between 2 GHz and 90 GHz in discontinuous and narrow windows in most cases in order to match the current needs of the European VLBI Network (EVN) and the Global Millimeter VLBI Array (GMVA). Aims. The Nanocosmos project, a European Union-funded synergy grant, has enabled an increase in the instantaneous frequency coverage of the Yebes 40 m radio telescope, making it possible to observe many molecular transitions with single tunings in single-dish mode. This reduces the observing time and maximises the output from the telescope. Methods. We present technical specifications of the recently installed 31.5-50 GHz (Q band) and 72-90.5 GHz (W band) receivers along with the main characteristics of the telescope at these frequency ranges. We observed IRC+10216, CRL 2688, and CRL 618, which harbour a rich molecular chemistry, to demonstrate the capabilities of the new instrumentation for spectral observations in single-dish mode. Results. Our results show the high sensitivity of the telescope in the Q band. The spectrum of IRC+10126 offers an unprecedented signal-to-noise ratio for this source in this band. On the other hand, the spectrum normalised by the continuum flux towards CRL 618 in the W band demonstrates that the 40 m radio telescope produces comparable results to those from the IRAM 30 m radio telescope, although with a lower sensitivity. The new receivers fulfil one of the main goals of Nanocosmos and open up the possibility to study the spectrum of different astrophysical media with unprecedented sensitivity. ; The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC-SyG-2013 Grant Agreement No. 610256 Nanocosmos. Part of this work was supported by Programa operativo pluriregional de España, YDALGO. The observations mentioned in this article have been done under commissioning time and within projects 19A010 and 20A017. The Yebes 40m radio telescope belongs to Instituto Geográfico Nacional (IGN).

CONTEXT: Yebes 40m radio telescope is the main and largest observing instrument at Yebes Observatory and it is devoted to Very Long Baseline Interferometry (VLBI) and single dish observations since 2010. It has been covering frequency bands between 2 GHz and 90 GHz in discontinuous and narrow windows in most of the cases, to match the current needs of the European VLBI Network (EVN) and the Global Millimeter VLBI Array (GMVA). AIMS: Nanocosmos project, a European Union funded synergy grant, opened the possibility to increase the instantaneous frequency coverage to observe many molecular transitions with single tunnings in single dish mode. This reduces the observing time and maximises the output from the telescope. METHODS: We present the technical specifications of the recently installed 31.5 – 50GHz (Q band) and 72 – 90.5 GHz (W band) receivers along with the main characteristics of the telescope at these frequency ranges. We have observed IRC+10216, CRL 2688 and CRL 618, which harbour a rich molecular chemistry, to demonstrate the capabilities of the new instrumentation for spectral observations in single dish mode. RESULTS: The results show the high sensitivity of the telescope in the Q band. The spectrum of IRC+10126 offers a signal to noise ratio never seen before for this source in this band. On the other hand, the spectrum normalised by the continuum flux towards CRL 618 in the W band demonstrates that the 40 m radio telescope produces comparable results to those from the IRAM 30 m radio telescope, although with a smaller sensitivity. The new receivers fulfil one of the main goals of Nanocosmos and open the possibility to study the spectrum of different astrophysical media with unprecedented sensitivity.