Third Coast最新文献

{"title":"A new slowly pulsating subdwarf-B star: HD 4539","authors":"C. Schoenaers, A. Lynas-Gray","doi":"10.1553/CIA151S67","DOIUrl":"https://doi.org/10.1553/CIA151S67","url":null,"abstract":"We report the spectroscopic discovery of slow pulsations in the subdwarf-B (sdB) star HD 4539. It is amongst the brightest sdB stars and, as such, has been well studied. Its temperature and gravity would place it squarely where the so-called “Betsy” stars (long-period sdB pulsators) are found, and this has been confirmed by the discovery of line-profile variations reported in this paper for the first time. As periodogram analyses of radial velocity curves obtained in 2005 and 2006 yield several significant frequencies, line-profile variations are very probably a consequence of pulsation.","PeriodicalId":151133,"journal":{"name":"Third Coast","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122338922","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":"Physical properties of the oEA star IV Cas","authors":"S.-L. Kim, C.‐U. Lee, J. W. Lee, J. Youn","doi":"10.1553/CIA150S69","DOIUrl":"https://doi.org/10.1553/CIA150S69","url":null,"abstract":"We present photometric and spectroscopic observing results of the oEA star IV Cas. Spectral types of the binary system are derived to be A3 (Teff = 8500 K) for the primary component and G9 (Teff = 5370 K) for the secondary. We detected two δ Scuti-type pulsation frequencies of f1 = 32.6894 c/d (cycles per day) and f2 = 36.6714 c/d, for the primary component.","PeriodicalId":151133,"journal":{"name":"Third Coast","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133453549","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":"Observational Asteroseismology of slowly pulsating B stars","authors":"P. Cat","doi":"10.1553/CIA150S167","DOIUrl":"https://doi.org/10.1553/CIA150S167","url":null,"abstract":"We review the status of observational asteroseismology of slowly pulsating B (SPB) stars. Their asteroseismic potential is extremely good because the excited high-order g-modes probe the deep interior of these hot stars. To enable asteroseismic modelling, a sufficient amount of well-identified modes is mandatory. To reach this goal with ground-based observations, dedicated long-term and preferably multi-site campaigns are needed to increase the number and the accuracy of detectable frequencies. The first results for SPB stars based on observations obtained with the asteroseismic space-mission MOST are very promising, guaranteeing the success of missions like CoRoT, launched in December 2006. These results also indicate that high-precision observations are needed to detect and to study low-amplitude SPB stars. Although SPB pulsations are not restricted to slow rotators, there is some observational evidence for an amplitude drop towards high values of the projected rotational velocity. For several SPB stars, close frequency multiplets are observed. In some cases, the observed frequencies might be components of a rotationally split mode, but in other cases an alternative explanation is needed. Magnetic fields of a few hundred Gauss, that recently have been detected for fourteen confirmed members, can cause such frequency shifts. SPB stars can no longer be considered as non-magnetic stars and magnetic fields should be included in the theoretical models. We argue that mode identification of g modes still remains one of the main obstacles, although progress has been made in this field recently. Asteroseismic potential After conducting a systematic study of variability amongst B type stars, Waelkens (1991) introduced the slowly pulsating B (SPB) stars as an independent class of stars pulsating in high-order, low degree gravity modes (g modes) with typical periods of the order of days. These modes are excited by the opacity mechanism acting on the metal-bump. They are trapped deep in the interior of these hot stars, making them very interesting from an asteroseismic point of view. On the other hand, they are very difficult targets for in-depth asteroseismic studies because the theoretical frequency spectra of SPB stars are very dense, the observed amplitudes are low (cf. Fig. 4), and most of the currently known SPBs are multi-periodic, giving rise to beat periods of the order of months or even years. Currently, at least 51 confirmed and 65 candidate galactic SPB stars are known, of which 15 are in open clusters. Thanks to the OGLE-II and MACHO databases, extra-galactic SPBs were recently found: 59 in the LMC and 11 in the SMC (Ko laczkowski et al. 2006). For the SPB stars observed in the Geneva photometric system, the effective temperatures and surface gravities were determined with the code CALIB in the same way as described by De Cat et al. (2007). As shown in Fig. 1, these stars cover the (young) part of the theoretical SPB instability strip. This fig","PeriodicalId":151133,"journal":{"name":"Third Coast","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123226766","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":"Small IRAIT Telescope: photometry and asteroseismology at Dome C","authors":"G. Tosti","doi":"10.1553/CIA150S315","DOIUrl":"https://doi.org/10.1553/CIA150S315","url":null,"abstract":"Small IRAIT is a 25 cm telescope planned to be installed at Dome C during February 2007. It will be equipped with a CCD, a filter wheel, two photomultipliers and a liquid crystal tunable filter. Small IRAIT is intended to: test astronomical measurements from Dome C; provide site qualification and suitability for asteroseismology by taking advantage of the low scintillation level and the possibility for long uninterrupted observations. Small IRAIT will be the forerunner of the IRAIT telescope that will be installed during the Antarctic Summer 2007−2008. Astronomy from Antarctica In the last years attention has been focused towards Antarctica as a possible astronomical site. Extremely low temperatures (-30 C during summer, -80 C during winter), small scintillation and good seeing (at least a factor of two better than at La Silla, Agabi et al. 2006) and the long duration of the polar night are promising ingredients for photometry. Antarctica seems to be an alternative to expensive space missions, with the great advantage of the possibility for logistics and personnel to work on the experiments on the base. Concordia Base, a joint Italian-French cooperation, has been fully operational also in the winter period since 2005. Small IRAIT Telescope Small IRAIT is the little brother of the IRAIT infrared telescope. The task of the small telescope is to perform astronomical experiments before the arrival of IRAIT itself. Small IRAIT is an optical telescope, 25 cm of diameter and with 3 m focal length. The acquisition unit set up on the focal plane is inside a heated, insulated box. It is equipped with an automated temperature controller and is decoupled from the outside by an optical window. The experimental setup has been assembled following two guidelines: redundancy, in order to continue its function even in case of a breakdown, and multipurpose to carry out different astronomical experiments. The focal plane is equipped with a CCD (MaxCam, with KAF-0402E/ME, 768× 512 pixels), photomultipliers, filterwheel and standard UBVRI filters, precision focuser, and liquid crystal interference filters. Electronics include a lock-in amplifier and a modulation and demodulation apparatus. Scientific goal for winter 2007 The Small IRAIT mission will provide a first test of astronomical measurements during the polar night. Similar tests have been performed in the last years by other groups, mainly devoted to site testing and measurements of atmospheric turbulence parameters (Aristidi et 316 Small IRAIT Telescope: photometry and asteroseismology at Dome C al. 2005, Agabi et al. 2006). Small IRAIT, with its multi-purpose focal plane instrumentation, will provide different kinds of tests. Three principal goals are foreseen: • instrumental tests to check operating conditions during the cold polar winter, with emphasis on remote control and communications • site qualification, which includes measurements of multiband extinction coefficients, transparency stability throughou","PeriodicalId":151133,"journal":{"name":"Third Coast","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126651520","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":"Stellar Oscillations Network Group","authors":"F. Grundahl, H. Kjeldsen, J. Christensen-Dalsgaard, T. Arentoft, S. Frandsen","doi":"10.1553/CIA150S300","DOIUrl":"https://doi.org/10.1553/CIA150S300","url":null,"abstract":"Stellar Oscillations Network Group (SONG) is an initiative aimed at designing and building a network of 1m-class telescopes dedicated to asteroseismology and planet hunting. SONG will have 8 identical telescope nodes each equipped with a high-resolution spectrograph and an iodine cell for obtaining precision radial velocities and a CCD camera for guiding and imaging purposes. The main asteroseismology targets for the network are the brightest (V < 6) stars. In order to improve performance and reduce maintenance costs the instrumentation will only have very few modes of operation. In this contribution we describe the motivations for establishing a network, the basic outline of SONG and the expected performance.","PeriodicalId":151133,"journal":{"name":"Third Coast","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127997057","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":"Strömgren photometry of the δ Sct star V402 Cep","authors":"V. Costa, P. Coca, A. Rolland, E. Rodríguez, I. Olivares, S. Martín-Ruiz, J. García-Pelayo","doi":"10.1553/CIA150S65","DOIUrl":"https://doi.org/10.1553/CIA150S65","url":null,"abstract":"A preliminary analysis of photometric observations carried out during the 2003 and 2005 campaigns of the δ Scuti-type variable star V402 Cep is presented. We show the results of","PeriodicalId":151133,"journal":{"name":"Third Coast","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"113974412","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":"Asteroseismology: Lessons From the Past and Prospects for the Future","authors":"S. Kawaler","doi":"10.1553/CIA150S279","DOIUrl":"https://doi.org/10.1553/CIA150S279","url":null,"abstract":"Ground-based, and now space-based, studies of a range of stellar families (all represented at this workshop) have, in large part, moved from study of pulsations for their own sake on to information of real value for stellar physics and its applications. This required a combination of improved observations, and open-minded stellar modelling, that continues today. Pulsating compact stars provide a good example of this progress. A flurry of activity from the mid 1980s to the mid 1990s, both observational and theoretical, began to realize this potential. A new generation of stellar models, coupled with reanalysis of seismological data and discovery of many new faint pulsators, have recently revitalized this field and may soon provide firm answers to some of the outstanding problems of post-AGB evolution. The discovery and analysis of pulsating sdB stars has followed an accelerated trajectory, enjoying mature theoretical model framework largely in place at the same time as the developing observational base.","PeriodicalId":151133,"journal":{"name":"Third Coast","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129756168","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":"One small satellite, so many light curves: Examples of δ Scuti asteroseismology from the MOST space mission 1","authors":"J. Matthews","doi":"10.1553/CIA150S333","DOIUrl":"https://doi.org/10.1553/CIA150S333","url":null,"abstract":"The skies are alive with the sound of music. The symphonies of δ Scuti stars, both postand pre-main sequence, offer more exciting potential for asteroseismology than ever before. Continuous precise light curves of δ Scuti stars obtained by the MOST (Microvariability & Oscillations of STars) space mission offer rich eigenspectra and accurate relative mode amplitudes to test models of stellar structure and nonlinear pulsation dynamics. Many of these δ Scuti pulsators have been discovered among the MOST Guide Star sample. One of them, HD 209775, exhibits more than 80 frequencies, rivalling FG Vir in its richness. The observed amplitude distribution is a test of theoretical mode growth rates and the histogram of frequency spacings places meaningful constraints on the stellar structure and evolutionary phase. MOST has also discovered at least two ”hybrid” pulsators, simultaneously exhibiting both δ Scuti p-modes and γ Doradus g-modes, doubling (or tripling) the number of known hybrids. MOST has also been used to target pre-main sequence pulsators (like those in the cluster NGC 2264), performing ’ultrasound’ of stellar embryos based on the acoustic oscillations.","PeriodicalId":151133,"journal":{"name":"Third Coast","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130914626","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":"Coordinated observational campaigns for non-radially pulsating objects","authors":"K. Pollard, D. Wright, P. Cottrell, R. Woollands, D. Ramm, T. Böhm","doi":"10.1553/CIA150S133","DOIUrl":"https://doi.org/10.1553/CIA150S133","url":null,"abstract":"In recent years we have initiated and contributed to a number of campaigns to study nonradially pulsating objects. Our observing facility is the Mt John University Observatory 1.0 m telescope equipped with a high-efficiency and extremely stable echelle spectrograph, ideal for spectroscopic mode identification. Our current interests include δ Scuti star campaigns and a programme to study the non-radial pulsations in γ Dor stars. We are investigating several different methods of line profile analysis and spectroscopic mode identification of these targets. An overview of the programme, with specific examples, is presented.","PeriodicalId":151133,"journal":{"name":"Third Coast","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116257353","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":"Discussion on solar-like oscillators and γ Doradus stars","authors":"D. Gough","doi":"10.1553/CIA150S155","DOIUrl":"https://doi.org/10.1553/CIA150S155","url":null,"abstract":"","PeriodicalId":151133,"journal":{"name":"Third Coast","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2007-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114252383","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}