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Astrophysical lasers and nonlinear optical effects in space
The present state of the art concerning astrophysical lasers (APL) andnonlinear optical effects under astrophysical conditions is reviewed.The operational conditions of an APL (amplification under non-LTEconditions) and astrophysical predecessors of the laboratory lasers areconsidered in the introduction of the review. The rareness of observedAPL action in the visible range in comparison with astrophysical masers(APM) in the microwave range is explained. Early proposals of APLs withcollisional and optical pumping are discussed. APL/M in the mid-IR andsubmillimeter ranges linking APL and APM are also discussed. APLs in theWeigelt blobs of Eta Carinae operating in FeII and OI with a Bowen typeoptical pumping are considered in detail. General questions (narrowingof APL spectral lines, the possibility of scattering feedback and waysof measuring the true spectral width of an APL) are considered.Nonlinear optical effects in astrophysical conditions andresonance-enhanced two-photon conditions, in particular, are discussedin the conclusion.
| The emission spectrum of the strong Fe II emitter BAL Seyfert 1 galaxy IRAS 07598+6508
The narrow-line Seyfert 1 galaxy IRAS 07598+6508 is known to be a stongFe II emitter. The analysis of several high S/N ratio spectra shows thatits spectrum is dominated by a relatively narrow "broad line" region(1780 km s-1 FWHM) emitting not only Fe II, but also Ti IIand Cr II lines. Although we were unable to find a completelysatisfactory physical model, we got the best agreement with theobservations with collisional rather than radiative models, with a highdensity (n=1015 cm-3), a high column density(NH = 1025 cm-2) and a microturbulenceof 100 km s-1. This BLR is qualitatively similar to the oneobserved in I Zw 1. We have not found traces in IRAS 07598+6508 of thenarrow line regions found in I Zw 1.
| Pulsation of the late-type star in symbiotic systems
Pulsation has been detected spectroscopically in the late-type star inboth D- and S-type symbiotic binaries. Time-series radial velocitiesreveal Mira stellar pulsation in the late-type star in D-typesymbiotics. Orbital motion has too long a period to be detected withcurrent time series. For the S-type systems time series of radialvelocities are typically dominated by orbital motion but in some systems``long-secondary period'' stellar pulsation is present.
| BAV-Beobachtungen von XX Oph.
Not Available
| Lifting the Iron Curtain: Toward an Understanding of the Iron Stars XX Oph and AS 325
We present new optical, near-infrared, and archival ultravioletobservations of XX Ophiuchi and AS 325, two proposed ``iron'' stars.These unusual stars have optical spectra dominated by emission linesarising from hydrogen, as well as ionized metals such as iron, chromium,and titanium. Both stars have been classified as ``iron'' stars, and anumber of exotic models have been presented for their origin. Using 2years of moderately high resolution optical spectroscopy, the first highsignal-to-noise ratio K-band spectroscopy of these sources (whichreveals stellar photospheric absorption lines), and new near-infraredinterferometric observations, we confirm that both systems are composedof two stars, likely binaries, containing a hot Be star with an evolvedlate-type secondary. The hydrogen emission features arise in the hotwind from the Be star, while the corresponding P-Cygni absorption linesare produced from dense material in the expanding, radiation-driven windaround each system. The optical Fe II emission lines are pumped byultraviolet Fe II absorption lines through fluorescence. Contrary tosome claims in the literature, the spectral features of XX Oph and AS325 are quite similar, evidence that they are comparable systems. Weexamine the variability of the spectral morphology and radial velocitymotions of both sources. We also study the variability of XX Oph duringa major photometric event and find that the spectral nature of thesystem varies during the event. A comparison of the velocity of theabsorption-line components in our new spectra with those in theliterature show that the structure of the stellar wind from XX Oph haschanged since the system was observed in 1951.
| The Proto-Planetary Nebula M1-92 and the Symbiotic Star MWC 560: Two Evolutionary Phases of the Same Type of Object?
Important similarities between the objects M1-92, a proto-planetarynebula of bipolar morphology, and MWC 560, a symbiotic star with a jet,have been found. A brief review of the previous studies for both objectsis presented for the purpose of proposing mechanisms that best explainthese similarities, since up to now both objects have been studiedindependently. From the comparison of the spectra of both objects, theexistence of a jet is confirmed for the proto-planetary nebula M1-92, aswell as its binary nature and the existence of a circumnuclear disk.Finally, an evolutionary sequence is proposed for the two objects whereM1-92 is ~900 yr more evolved than MWC 560.
| Aus den IBVS.
Not Available
| Do Iron Stars Really Exist?
Only two stars have been classified as Iron Stars: XX Oph and AS 325.This distinction is bestowed upon them as their optical spectra consistentirely of a forest of emission lines, most of which are due to theionized metals of iron, chromium, and titanium. Over the years, XX Oph(Merrill's iron star) and AS 325 have received various classificationsincluding spectral types from B to M and even thought to be binarystars. Using new optical and near-IR spectroscopy we have finallyobserved the stellar photospheres in these two objects. They appear tobe evolved stars trapped in a dense region of the Rho Oph star formingregion. Taking our multi-wavelength observations plus past work byothers, we have developed a new model for what these two unique objectsreally are.
| XX Ophiuchi in Deep Minimum after 37 Years
XX Ophiuchi is a unique object, which is very difficult to classify.This star only slowly varied around the maximum magnitude (V approx 9mag) during the past 37 years. In March 2004, the brightness started tofade by 0.2 mag per month. I stress the urgent need of the spectroscopicobservations during this minimum.
| The unusual emission line spectrum of I Zw 1
Most Seyfert 1 galaxies show strong Fe II lines in their spectrum havingthe velocity and width of the broad emission lines. To remove the Fe IIcontribution in these objects, an accurate template is necessary. Weused very high signal-to-noise, medium resolution archive opticalspectra of I Zw 1 to build such a template. I Zw 1 is a brightnarrow-line Seyfert 1 galaxy. As such it is well suited for a detailedanalysis of its emission line spectrum. Furthermore it is known to havea very peculiar spectrum with, in addition to the usual broad and narrowline regions, two emission regions emitting broad and blue shifted [OIII] lines making it a peculiarly interesting object. While analysingthe spectra, we found that the narrow-line region is, unlike the NLR ofmost Seyfert 1 galaxies, a very low excitation region dominated by bothpermitted and forbidden Fe II lines. It is very similar to the emissionspectrum of a blob in η Carinae which is a low temperature(Te˜6500 K), relatively high density (Ne=106 cm-3) cloud. The Fe II lines in this cloud aremainly due to pumping via the stellar continuum radiation field (Verneret al. \cite{verner02}). We did not succeed in modelling the spectrum ofthe broad-line region, and we suggest that a non radiative heatingmechanism increases the temperature in the excited H I region, thusproviding the necessary additional excitation of the Fe II lines. Forthe low-excitation narrow-line region, we are able to apply boundariesto the physical conditions accounting for the forbidden and permitted FeII lines (106
| Spectroscopic observations of Hα emission-line stars from Sanduleak & Stephenson's 1973 (SS73) list
We present spectroscopic observations of 33 emission line stars from theSanduleak & Stephenson's (1973) list. This work is part of a programto investigate emission-line objects in the southern hemisphere whosenature is not well established in the literature. The objects wereobserved at two different spectral regions providing full coverage inthe 3100-8700 Å, interval. In this paper we describe the mainspectroscopic features and discuss the nature of the objects. It isproposed that 16 of them are Be stars, 5 are peculiar Be stars, 4 are TTauri stars, 7 are M-type stars with emission-lines and 1 is a Herbigobject.Based on observations made with the 1.52 m telescope at the EuropeanSouthern Observatory (La Silla, Chile) under the agreement with theObservatório Nacional, Brazil.
| The rich 6 to 9 vec mu m spectrum of interstellar PAHs
IR spectroscopy provides a valuable tool for the characterisation andidentification of interstellar molecular species. Here, we present 6-9μm spectra of a sample of reflection nebulae, HII regions, YSOs,evolved stars and galaxies that show strong unidentified infrared bands,obtained with the SWS spectrograph on board ISO. The IR emissionfeatures in this wavelength region show pronounced variations. 1) The6.2 μm feature shifts from 6.22 to 6.3 μm and clearly showsprofile variations. 2) The 7.7 μm complex is comprised of at leasttwo subpeaks peaking at 7.6 and one longwards of 7.7 μm. In somecases the main peak can apparently shift up to 8 μm. Two sources donot exhibit a 7.7 μm complex but instead show a broad emissionfeature at 8.22 μm. 3) The 8.6 μm feature has a symmetric profilein all sources and some sources exhibit this band at slightly longerwavelengths. For the 6.2, 7.7 and 8.6 μm features, the sources havebeen classified independently based on their profile and peak position.The classes derived for these features are directly linked with eachother. Sources with a 6.2 μm feature peaking at ~ 6.22 μm exhibita 7.7 μm complex dominated by the 7.6 μm component. In contrast,sources with a 6.2 μm profile peaking longwards of 6.24 μm show a7.7 μm complex with a dominant peak longwards of 7.7 μm and a 8.6μm feature shifted toward the red. Furthermore, the observed 6-9μm spectrum depends on the type of object. All ISM-like sources and afew PNe and Post-AGB stars belong to the first group while isolatedHerbig AeBe stars, a few Post-AGB stars and most PNe belong to thesecond group. We summarise existing laboratory data and theoreticalquantum chemical calculations of the modes emitting in this wavelengthregion of PAH molecules. We discuss the variations in peak position andprofile in view of the exact nature of the carrier. We attribute theobserved 6.2 μm profile and peak position to the combined effect of aPAH family and anharmonicity with pure PAHs representing the 6.3 μmcomponent and substituted/complexed PAHs representing the 6.2 μmcomponent. The 7.6 μm component is well reproduced by both pure andsubstituted/complexed PAHs but the 7.8 μm component remains anenigma. In addition, the exact identification of the 8.22 μm featureremains unknown. The observed variations in the characteristics of theIR emission bands are linked to the local physical conditions. Possibleformation and evolution processes that may influence the interstellarPAH class are highlighted. Based on observations with ISO, an ESAproject with instruments funded by ESA Member States (especially the PIcountries: France, Germany, the Netherlands and the United Kingdom) andwith the participation of ISAS and NASA.
| The ISO-SWS post-helium atlas of near-infrared stellar spectra
We present an atlas of near-infrared spectra (2.36 mu m-4.1 mu m) of ~300 stars at moderate resolution (lambda /delta lambda ~ 1500-2000). Thespectra were recorded using the Short-Wavelength Spectrometer aboard theInfrared Space Observatory (ISO-SWS). The bulk of the observations wereperformed during a dedicated observation campaign after the liquidhelium depletion of the ISO satellite, the so-called post-heliumprogramme. This programme was aimed at extending the MK-classificationto the near-infrared. Therefore the programme covers a large range ofspectral types and luminosity classes. The 2.36 mu m-4.05 mu m region isa valuable spectral probe for both hot and cool stars. H I lines(Bracket, Pfund and Humphreys series), He I and He II lines, atomiclines and molecular lines (CO, H2O, NH, OH, SiO, HCN,C2H2, ...) are sensitive to temperature, gravityand/or the nature of the outer layers of the stellar atmosphere(outflows, hot circumstellar discs, etc.). Another objective of theprogramme was to construct a homogeneous dataset of near-infraredstellar spectra that can be used for population synthesis studies ofgalaxies. At near-infrared wavelengths these objects emit the integratedlight of all stars in the system. In this paper we present the datasetof post-helium spectra completed with observations obtained during thenominal operations of the ISO-SWS. We discuss the calibration of the SWSdata obtained after the liquid helium boil-off and the data reduction.We also give a first qualitative overview of how the spectral featuresin this wavelength range change with spectral type. The dataset isscrutinised in two papers on the quantitative classification ofnear-infrared spectra of early-type stars ({Lenorzer} et al.\cite{lenorzer:2002a}) and late-type stars (Vandenbussche et al., inprep). Based on observations with ISO, an ESA project with instrumentsfunded by ESA Members States (especially the PI countries France,Germany, the Netherlands and the United Kingdom) and with theparticipation of ISAS and NASA. The full atlas is available inelectronic form at www.edpsciences.org Table 1 is only available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?/A+A/390/1033
| Searching for the Physical Drivers of Eigenvector 1: From Quasars to Nanoquasars
We point out an analogy between two accreting white dwarfs (CH Cyg andMWC 560) with jets and powerful quasars. In spite of the enormousdifference in the mass of the central object (a factor ~107),the emission lines are strikingly similar to those of I Zw 1 (theprototype ``narrow-line Seyfert 1'' nucleus whose spectrum is widelyused as an Fe II template for almost all quasars). The spectralsimilarities give us the unique possibility to consider the opticalEigenvector 1 diagram using objects less massive by a factor ofmillions. Our results reinforce the interpretation of the ``Eigenvector1 correlations'' found for low-redshift quasars as driven mainly by thesource luminosity-to-central compact object mass ratio. The accretingwhite dwarfs CH Cyg and MWC 560, their jets and emission lines, may wellrepresent the low-energy, nonrelativistic end of the accretionphenomena, which encompass the most powerful quasars and microquasars.The remarkable similarities suggest that they may be legitimatelyconsidered ``nanoquasars.''
| A multi-epoch spectrophotometric atlas of symbiotic stars
A multi-epoch, absolute-fluxed spectral atlas extending from about 3200to 9000 Å is presented for 130 symbiotic stars, including membersof the LMC, SMC and Draco dwarf galaxies. The fluxes are accurate tobetter than 5% as shown by comparison with Tycho and ground-basedphotometric data. The spectra of 40 reference objects (MKK cool giantstandards, Mira and Carbon stars, planetary nebulae, white dwarfs, hotsub-dwarfs, Wolf-Rayet stars, classical novae, VV Cep and Herbig Ae/Beobjects) are provided to assist the interpretation of symbiotic starspectra. Astrometric positions and counterparts in astrometriccatalogues are derived for all program symbiotic stars. The spectra areavailable in electronic form from the authors. Based on observationscollected with the telescopes of the European Southern Observatory (ESO,Chile) and of the Padova & Asiago Astronomical Observatories(Italy). Tables 2 and 3 are only available in electronic form (a) at theCDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or viahttp://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/383/188, and (b) from thepersonal home page http://ulisse.pd.astro.it/symbio_atlas/ Figures 4-256are only available in electronic form (a) at http://www.edpsciences.organd (b) from the personal home pagehttp://ulisse.pd.astro.it/symbio_atlas/
| A photometric catalogue of southern emission-line stars
We present a catalogue of previously unpublished optical and infraredphotometry for a sample of 162 emission-line objects and shell starsvisible from the southern hemisphere. The data were obtained between1978 and 1997 in the Walraven (WULBV), Johnson/Cousins(UBV(RI)c) and ESO and SAAO near-infrared (JHKLM) photometricsystems. Most of the observed objects are Herbig Ae/Be (HAeBe) stars orHAeBe candidates appearing in the list of HAeBe candidates of Théet al. (1994), although several B[e] stars, LBVs and T Tauri stars arealso included in our sample. For many of the stars the data presentedhere are the first photo-electric measurements in the literature. Theresulting catalogue consists of 1809 photometric measurements. Opticalvariability was detected in 66 out of the 116 sources that were observedmore than once. 15 out of the 50 stars observed multiple times in theinfrared showed variability at 2.2 mu m (K band). Based on observationscollected at the European Southern Observatory, La Silla, Chile and onobservations collected at the South African Astronomical Observatory.Tables 2-4 are only available in electronic form at the CDS viaanonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/380/609
| Spectroscopic monitoring of the jet in the symbiotic star MWC 560. I. Spectroscopic properties, general outflow structure and system parameters
We present the results of an intensive monitoring program of the jetabsorptions in the symbiotic system MWC 560, obtained with the FEROSechelle spectrograph at the ESO 1.5 m Telescope. MWC 560 is a unique jetsource because the line of sight lies practically parallel to the jetaxis so that the outflowing gas is seen as absorption in the continuumof the accreting object, in the emission line spectrum of the accretiondisk and temporary also in the spectrum of the red giant companion.Highly variable, blue-shifted jet absorption components, due to H i, Hei, Na i, Ca ii and Fe ii are observed, which are detached from theundisplaced, narrow emission line components. The allowed emission linesfrom neutral and singly ionized heavy elements vary simultaneously withthe strongly variable continuum emission. Therefore they can beattributed to the irradiated (chromospheric) layers of the neutral partof the accretion disk. The fluxes of forbidden emission lines arepractically constant because they originate in a much larger volume. Thestructure and variability of the jet absorptions indicate the presenceof three distinct outflow regions along the jet axis: i. An initialacceleration region above the disk with low velocities <600 kms-1 which covers only partly the central continuum source;ii. A highly variable outflow region covering the continuum source andup to about half of the line emission from the disk. This region showsrepeatedly high velocity components ~1800-2500 km s-1 whichare decelerated to <1500 km s-1 within one to a few days.The appearance of high velocity components is anti-correlated andtherefore closely related to the low velocity absorptions of region i.The life time of the high velocity components suggests that region iiextends to about one to a few AU from the jet source; iii. A steady flowat an intermediate velocity of ~900-1300 km s-1 at a distanceof the order ~ 10 AU from the jet source. This component covers the hotcontinuum source and the entire narrow line region of the accretiondisk. At the beginning of our campaign region iii covers also theextended red giant companion with two absorption components at 1250 kms-1 and 1140 km s-1, which can be considered asterminal velocities vinfty of the jet outflow. The componentsdisappear during the following several weeks as expected for the end ofan occultation phase of the red giant by the collimated jet occuringprobably regularly once per binary orbit. Several fast moving (1300-1700km s-1), narrow absorptions are present in the Ca iiresonance lines. The high speed, low column density, and the long lifetime ( ~ months) suggest that these are radiative bow shocks in the jetcocoon generated by the collision of the transient high velocitycomponents with slower moving jet material. A geometric model for thejet outflow in MWC 560 is presented. System parameters are derived basedon our spectroscopic data and previous studies. Beside other parametersa binary separation of the order 4 AU, a jet inclination of<16o, a mass accretion rate of 5x 10-7Msun yr-1 and a jet outflow rate larger than 7x10-9 Msun yr-1 are derived. Based onobservations obtained with FEROS at the ESO 1.5 m Telescope at La Silla,Chile (ESO program 62.H-0319).}
| A high resolution spectroscopic study of XX Ophiuchi
The star XX Oph has been known to exhibit peculiar spectralvariabilities since the work of Merrill in 1924. A high resolutionspectroscopic study of the XX Oph spectra taken in July 1996 and laterin June 1997 also exhibit distinctly different line profiles in severalspectral regions, the most pronounced variations being in the sodium Dand H? profiles. We have estimated the displacement velocities of thestrong emission line profiles and their absorption components wheneverpossible and made an attempt to examine possible physical scenarios thatcan account for its peculiar variability.
| Emission-line spectra of XX Ophiuchi in 1996 and 1997
Not Available
| Aufsuchkarten fur intrinsic Variable Stars in Brno.
Not Available
| Low resolution spectroscopy of hot post-AGB candidates
Spectral types are determined from low resolution optical spectra of 40IRAS sources with far-infrared colours similar to planetary nebulae. Thepresence of circumstellar dust, high galactic latitude, and earlysupergiant or giant spectral type, sometimes with emission in the Balmerlines, indicate that some of these stars are low mass stars in thepost-AGB stage of evolution. Based on observations obtained at the CerroTololo Inter-American Observatory (CTIO), Chile.
| The Milton Bureau Revisited
Under the direction of Cecilia Payne-Gaposchkin and Sergei Gaposchkin, aprogram was subsidized by the Milton Fund of Harvard Observatory in 1937for the study of all variable stars then known to be brighter than tenthphotographic magnitude at maximum. This included some 1512 stars forwhich a grand total of 1,263,562 estimates of magnitude were made,ranging from a low of 16 (except for a few novae) to 4084 observationsper star. The sky had been divided into 54 fields, and the results ofthe measurements presented field by field in two volumes of the Annalsof Harvard Observatory. Then, in another volume, the results werediscussed in four sections, each dealing with a particular class ofvariable: 1, those of RV Tauri type; 2, the eclipsing variables; 3,Cepheids and RR Lyrae variables, and 4, the red variables, especiallyMira-type and semiregular variables.For the present paper, many of these results have been compared withmodern determinations in the 1985-87 version of the "General Catalogueof Variable Stars (GCVS)". In particular, there are numerous instancesof disagreement as to whether a star should be classified RV or SR.Although there are many instances where the Milton Bureau determinationsof types of variability differ from the types given in moderncatalogues, the reasons for the differences are generallyunderstandable.For 17 RV Tauri type stars in this survey multiple periods have now beendetermined. Many of these still deserve continued observations in orderto ascertain the constance of the periods and improve the accuracy oftheir longest reported periods.
| Five-colour photometry of OB-stars in the Southern Hemisphere
Observations of OB-stars, made in 1959 and 1960 at the Leiden SouthernStation near Hartebeespoortdam, South Africa, with the VBLUW photometerattached to the 90 cm light-collector, are given in this paper. They arecompared with photometry obtained by \cite[Graham (1968),]{gra68}\cite[Walraven & Walraven (1977),]{wal77} \cite[Lub & Pel(1977)]{lub77} and \cite[Van Genderen et al. (1984).]{gen84} Formulaefor the transformation of the present observations to those of\cite[Walraven & Walraven (1977)]{wal77} and \cite[Lub & Pel(1977)]{lub77} are given. Table 4 is only available in electronic format the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) orvia http://cdsweb.u-strasbg.fr/Abstract.html
| V380 Ori--A Herbig Ae/Be star at an early stage of envelope formation: Hydrogen-line profiles
We continue to analyze the spectrum of the Herbig Ae/Be star V380 Ori.The hydrogen-line profiles in the spectra of V380 Ori, BF Ori, and gammaCas shell stars (XX Oph and Pleione) are compared. We analyze thethree-component model that consists of optically thick and opticallythin (in continuum) envelopes around an A0 star with a luminosity closeto the ZAMS luminosity. The star manifests itself only in thehydrogen-line wings. The emission shell changes its luminosity andshape, which shows up in highly variable bright emission lines of gasesand metals. The optically thick envelope is more stable. The origin,luminosity, and instability of the envelopes are related tononstationary accretion from a cold protoplanetary disk. The chemicalcomposition of the envelopes lends support to this version.
| JHK photometry of symbiotic stars
We present the results of multi-epoch JHK photometry of a sample of 30known or suspected symbiotics and related objects. These are the firstresults of an ongoing programme of near-IR monitoring of symbiotic starsfrom the Mt. Abu IR Observatory of Physical Research Laboratory (PRL).
| UBV beta Database for Case-Hamburg Northern and Southern Luminous Stars
A database of photoelectric UBV beta photometry for stars listed in theCase-Hamburg northern and southern Milky Way luminous stars surveys hasbeen compiled from the original research literature. Consisting of over16,000 observations of some 7300 stars from over 500 sources, thisdatabase constitutes the most complete compilation of such photometryavailable for intrinsically luminous stars around the Galactic plane.Over 5000 stars listed in the Case-Hamburg surveys still lackfundamental photometric data.
| IRAS06562-0337, the Iron-clad Nebula: a young star embedded in a molecular cloud
We present millimeter and sub-millimeter observations of IRAS06562-0337,the so-called Iron-clad Nebula. It had been suggested previously thatthis object could be an evolved star in the transitional phase betweenthe AGB and a planetary nebula. However, our observations show that thisIRAS source lies at the center of a dense massive molecular cloud whichexhibits strong lines of CO, {(13) CO}, CS, and CI. The closeassociation of the source with this molecular cloud, the proximity toother molecular complexes, the infrared spectral energy distribution,and the main characteristics of the previously observed optical spectra,imply that IRAS06562-0337 is a young stellar object (or a small cluster)still associated to its parent molecular cloud. IRAS06562 is placed at7+/-3 kpc from the Sun, in the anticenter direction. Its location in theGalaxy, at about 15 kpc from the galactic center, makes the objectparticularly interesting for studies of galactic structure.
| Classification and Identification of IRAS Sources with Low-Resolution Spectra
IRAS low-resolution spectra were extracted for 11,224 IRAS sources.These spectra were classified into astrophysical classes, based on thepresence of emission and absorption features and on the shape of thecontinuum. Counterparts of these IRAS sources in existing optical andinfrared catalogs are identified, and their optical spectral types arelisted if they are known. The correlations between thephotospheric/optical and circumstellar/infrared classification arediscussed.
| Spectral atlas of the symbiotic star MWC 560 for the region between H-beta and H-alpha.
Not Available
| IRAS06562-0337: the Iron-clad Nebula
In this paper we report on spectroscopic observations that shed newlight on the nature of the peculiar IRAS source 06562-0337. Thehigh-excitation forbidden lines reported earlier have not been observedagain, but the high signal-to-noise ratio of the new spectra led to thediscovery of a multitude of faint emission lines almost exclusively fromFeII, permitted and forbidden. In addition to making this a very rareobject in its own right, this also opens a new perspective concerningthe importance of this source in the context of late stellar evolution.With its history of variability in the spectrum, this object might be inthe transitional phase between the AGB and a planetary nebula. Inparticular, its closest relatives can be found in the peculiar young PNeTh2-B and He2-25 and the post-AGB star IRAS17423-1755.
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