{"title":"Ammonia in circumstellar environment of V Cyg","authors":"B. Etma'nski, M. Schmidt, R. Szczerba","doi":"10.17721/2227-1481.10.7-11","DOIUrl":"https://doi.org/10.17721/2227-1481.10.7-11","url":null,"abstract":"The HIFI instrument on board of the Herschel Space Observatory (HSO) has been very successful in detecting molecular lines from the circumstellar envelopes around evolved stars, like massive red supergiants, Asymptotic Giant Branch (AGB) and post-AGB stars, as well as the planetary nebulae. Among others, ammonia have been found in the circumstellar envelopes of C-rich AGB stars in amounts that significantly exceeded the theoretical predictions for C-rich stars. Few scenarios have been proposed to resolve this problem: formation of ammonia behind the shock front and photochemical processes in the inner part of the envelope partly transparent to UV background radiation due to the clumpy structure of the gas and formation of ammonia on dust grains. Careful analysis of observations may help to put the constraints on one or another mechanism of ammonia formation. Here, we present results of the non-LTE radiative transfer modeling of ammonia transitions including the crucial process of radiative pumping via the v2=1 vibrational band (at ∼10 μm) for V Cyg. Only the ground-based ammonia transition NH3 J = 10-00 at 572.5 GHz has been observed by HIFI. Therefore, to determine the abundance of ammonia we estimate the photodissociation radius of NH3 using chemical model of the envelope consistent with the dust grain properties concluded from the spectral energy distribution.","PeriodicalId":52077,"journal":{"name":"Advances in Astronomy and Space Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-11-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46538261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Some peculiarities of activity for comets with orbits\u0000on 2–5 AU","authors":"E. Musiichuk, S. Borysenko","doi":"10.17721/2227-1481.9.3-7","DOIUrl":"https://doi.org/10.17721/2227-1481.9.3-7","url":null,"abstract":"Periodic comets of different dynamical groups with orbits at 2–5 AU still occasionally active. The observed dust activity of such objects can be connected with the processes of water ice sublimation (MBCs) or crystallisation of amorphous water ice (QHCs) as well as with external causes. Despite the absence of connections between cometary flares and cyclic variations of solar activity indexes, some individual solar flares can affect the brightness of comets. Cometary objects in the main asteroid belt have lower statistic of flares than comets at orbits similar to quasi-Hilda objects.","PeriodicalId":52077,"journal":{"name":"Advances in Astronomy and Space Physics","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"46142291","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}