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Kinematical structure of the circumstellar environments of galactic B[e]-type stars

Kinematical structure of the circumstellar environments of galactic B[e]-type stars
Kinematical structure of the circumstellar environments of galactic B[e]-type stars

a r X i v :a s t r o -p h /0308087v 1 6 A u g 2003

Astronomy &Astrophysics manuscript no.zickgraf February 2,2008

(DOI:will be inserted by hand later)

Kinematical structure of the circumstellar environments of

galactic B[e]-type stars ?

F.-J.Zickgraf

Hamburger Sternwarte,Gojenbergsweg 112,21029Hamburg,Germany

Received date;accepted date

Abstract.High resolution line pro?les are presented for selected forbidden and permitted emission lines of a sample of galactic B[e]-type stars.The spectral resolution corresponds to 5-7km s ?1with the exception of some line pro?les which were observed with a resolution of 9-13km s ?1.All H αpro?les are characterized by a narrow split or single emission component with a width of ~150?250km s ?1(FWHM)and broad wings with a full width of ~1000?2000km s ?1.The H αpro?les can be classi?ed into three groups:double-peaked pro?les representing the majority,single-peaked emission-line pro?les,and normal P Cygni-type pro?les.Likewise,the forbidden lines exhibit in most cases double-peaked pro?les.In particular,the majority of stars

shows split [O I ]λ6300?A.

Double-peaked pro?les are also found in several stars for [N II ]λ6583?A and [Fe II ]λ7155?A although these lines in many stars exhibit single-peaked emission pro?les.The split forbidden line pro?les have peak separations of as little as ~10km s ?1,and were therefore only discernible for the ?rst time in the high-resolution spectra.The ratio of violet to red emission peak intensities,V /R ,is predominantly smaller or equal to 1.Theoretical pro?les were calculated for the optically thin case.A latitude-dependent stellar wind with a radial expansion and a velocity decreasing from the pole to the equator was adopted.This con?guration can produce split line pro?les if viewed under some angle with respect to the line of sight.In addition an equatorial dust ring with various optical depths was assumed.It can explain line asymmetries observed in some stars.Moreover,the V /R ratios can be understood in terms of this model.The comparison of the observed line pro?les with the models thus con?rms the assumption of disk-like line-formation regions as commonly adopted for B[e]-type stars.Key words.Stars:circumstellar matter –Stars:early-type –Stars:emission-line,Be –Stars:mass-loss

1.Introduction

The class of B[e]-type stars is characterized by the B[e]phe-nomenon (Lamers et al.1998).This term summarizes the pres-ence of strong Balmer emission lines,narrow permitted and forbidden low-excitation emission lines of Fe II ,[Fe II ]and [O I ],and in particular a strong near to mid-IR excess.It is attributed to hot circumstellar dust (T dust ~1000K)and is a distinguishing characteristic with respect to other classes of peculiar emission-line stars.The presence of dust requires re-gions of high density and a temperature low enough to allow dust condensation.A recent review of the properties of this still enigmatic class of emission-line stars was given by Zickgraf (1998)during the ?rst workshop dedicated entirely to this type of stars (Hubert &Jaschek 1998).It was shown that although B[e]-type stars share the mentioned properties,indicating very similar physical conditions in their circumstellar environments with regard to temperature,density,and velocity,they form by

2 F.-J.Zickgraf:Circumstellar environments of galactic B[e]-type stars

in the Magellanic Clouds(MCs).These observations strongly suggested that the stellar winds can be described by a two-component model.In this picture a cool and dense equatorial wind emerging from a single star is responsible for the for-mation of the narrow low-excitation emission lines.It is also supposed to be the site of dust formation.The polar region is dominated by a hot and fast expanding OB star wind with the high wind velocities observed normally for stars of this type.

A similar model had been proposed earlier by Swings(1973a) for the galactic B[e]-type star HD45677also based on spectro-scopic observations.In contrast to the post-main sequence MC sgB[e]s it seems to be a(near)main-sequence object.Likewise, the pre-main sequence Herbig Ae/Be stars are supposed to pos-sess circumstellar disks.

Disk-like circumstellar environments could also be caused by binarity.Apart from objects belonging to the subclass of symB[e]several B[e]stars have in fact been shown to be com-ponents of a binary system.In the SMC two B[e]supergiants, Hen S18and R4,were found to possess lower mass com-panions(Zickgraf et al.1989,1996).Likewise,in the Milky Way a couple of B[e]stars were found to be binaries,e.g. MWC623(Zickgraf&Stahl1989),AS381(Miroshnichenko et al.2002a),and CI Cam(=MWC84).Further instances are possibly MWC349A(Hofmann et al.2002)and MWC342 (Miroshnichenko&Corporon1999).It is,however,not clear whether in these objects the B[e]phenomenon itself is actually caused by their binary nature.For some objects this seems not to be the case.In Hen S18,R4,and MWC623the B[e]phe-nomenon can be ascribed to the B star component in the binary systems.These B[e]stars behave like single stars(Zickgraf et al.1989,1996,Zickgraf2001).AS381on the other hand shows signs of mass transfer suggesting that interaction could play a role in the occurence of the B[e]phenomenon in this object(Miroshnichenko et al.2002a).At this time the role of binarity is thus controversial.

Spectroscopic studies showed that the low-excitation lines attributed to the disks are narrow and thus indicative for low wind velocities in the line forming region.Typically, line widths(FWHM)of the order of less than~100km s?1 to300km s?1are observed(e.g.Swings&Andrillat1981, Zickgraf et al.1986).Given the early spectral types of the un-derlying stars such small wind velocities are unusual.

In the case of stars viewed edge-on the direct investiga-tion of the velocity structure of the disk winds is possible by studying absorption lines formed in the disk.This method was used by Zickgraf et al.(1996)to study three B[e]supergiants in the MCs using satellite UV spectroscopy.The observations of UV resonance lines showed that the disk winds are in fact very slow,at least in the case of massive supergiants.The expansion velocities measured were of the order of70-100km s?1,i.e. typically a factor of10less than usually observed for stars of similar spectral type.This may also hold for members of other B[e]star classes.

For viewing angles deviating from edge-on one can make use of the low-excitation emission lines to study the kinematics of the disk winds.Of particular interest are lines from forbidden transitions because they are optically thin.Therefore radiation transfer does not complicate the interpretation of the line in-Table1.Observed sample of B[e]-type stars.References for

spectral types are:WS85=Wolf&Stahl(1985),McG88= McGregor et al.(1988),WW89=Winkler&Wolf(1989), LeB89=Le Bertre et al.(1989),Th′e94=Th′e et al.(1994), Sw73=Swings(1973a),C99=Clark et al.(1999),Lei77= Leibowitz1977),L98=Lamers et al.(1998),Isr96=Israelian et al.(1996),Drew97=Drew et al.(1997).

star spec.class.references tensities and pro?les.Furthermore,the forbidden lines should form at a large distance from the central star.Hence,in the case of a radially accelerated out?ow(as e.g.the usually adopted β-type velocity law)the radial velocity component in the line forming region should have reached the terminal wind speed. Because of the small velocities involved the investigation of the emission-line pro?les requires high spectral resolution.If one aims at a resolution of about1/10of the terminal velocity a spectral resolution of about~5?10km s?1is necessary for the wind velocities measured e.g.by Zickgraf et al.(1996)for

B[e]supergiants.

In order to study the disk winds using emission-line pro-?les a sample of galactic B[e]-type stars listed in Table1was observed with high spectral resolution.In Sect.2the observa-tions are described.The observed line pro?les are described in Sect.3.The density conditions in the line formation region of the forbidden lines are discussed in Sect.4.The role of rotation and expansion is investigated in Sect.5.In Sect.6model cal-culations of optically thin line pro?les are presented and com-pared with the observed lines.Finally,conclusions are given in Sect.7.The Appendix contains the observational data in Sects.

A and B,and remarks on individual stars in Sect.C.An atlas of the high-resolution spectra is presented in Sect.D1.

F.-J.Zickgraf:Circumstellar environments of galactic B[e]-type stars3 Table3.Lines observed with CES in1986(+)and in1988(×).

star Hα+[N II][O I][Fe II][Fe II]Fe II Fe II He I+Na I D

λ6300?Aλ7155?Aλ4287?Aλ6456?Aλ4549/56?Aλ5876?A

Table4.Lines observed at Calar Alto Observatory.Coud′e observations with a resolution of45000are indicated by the letter”h”, coud′e observations obtained with the lower resolution of23000are indicated by”m”.Supplementary observations with FOCES are denoted by the letter“F”.

star Hα+[N II][N II][O I][Fe II]He I+Na I D He I

λ6583?Aλ6300?Aλ7155?Aλ5876?A&λ6678?A

2.Observations and data reduction

The spectroscopic observations were carried out in1986and

1988with the Coud′e Echelle Spectrometer(CES)at the1.4m

CAT at ESO,La Silla,and in1987with the coud′e spec-

trograph at the2.2m telescope at the Centro Astronomico

Hispano Aleman(CAHA)on Calar Alto,Spain.For a few

stars with incomplete coud′e data the observations were sup-

plemented by echelle spectra obtained with FOCES at Calar

Alto Observatory in June2000and February2002.The journal

of observations is given in Table2.

Due to the small spectral coverage of about?30?60?A

provided by the coud′e spectrographs strong emission lines

characteristic for B[e]-type stars were selected and the ob-

served wavelength ranges adjusted around these lines.In Tabs.

3and4the observed lines are listed for each studied object.

During the1987observing run on Calar Alto the northern B[e]-

type star MWC623was included in the sample.The results

on this star have been presented already by Zickgraf&Stahl

(1989)and Zickgraf(2001)and are therefore omitted here.

The CES spectra were collected during two campaigns in

November1986and March1988.The short camera of the

spectrograph was equipped with a RCA CCD(ESO CCD#8,

4 F.-J.Zickgraf:Circumstellar environments of galactic B[e]-type stars

Table2.Journal of observations.

date wavel.range spectral res.instrument

[?A]R=λ/?λ

chip with24μm pixel size.With a diaphragm diameter of 200μm and an entrance slit width of180μm a spectral resolu-tion of34000was achieved,i.e.9km s?1.A full discussion of the FOCES spectra will be given elsewhere(Zickgraf2003,in preparation).Here only the lines observed also with the coud′e spectrographs will be considered.

During all observing campaigns wavelength calibration was obtained with Th-Ar lamps.For?at?elding built-in lamps were used.The coud′e spectra were reduced by application of standard procedures(bias subtraction,?at-?elding,wavelength calibration,normalization)of the ESO-MIDAS image process-ing software package,context longslit.For the FOCES data the ESO-MIDAS context echelle was used.All spectra were?nally rebinned to heliocentric wavelengths.

The spectra in the red spectral region are strongly affected by narrow telluric absorption features.To correct for these lines,the normalized spectra were divided by the normalized spectrum of a hot comparison star with a line free continuum or with possible photospheric lines removed during the normal-ization procedure.For the Hαlines the correction spectrum was created from the object spectra themselves.First each spec-trum was smoothed.Then the original spectrum was divided by the smoothed spectrum.The?nal correction spectrum was then created by averaging several of these individual spectra observed during the same night as the spectrum to be corrected.

The observed spectral sections are displayed in the Appendix in Figs.D.1to D.8together with remarks on the in-dividual objects in Sect.C.For Hαsee Fig.1.3.Observed line pro?les

In the following the observed characteristics of the line pro?les are summarized.Table A.1in the Appendix lists relevant line parameters.Measurements of heliocentric radial velocities are also listed in the Appendix in Table B.1.The pro?les of Hα, of He I emission lines,and of the forbidden lines rebinned on a velocity scale are displayed in Figs.13and2a,b.

The line pro?les can be categorized into four groups:

–group1:normal P Cygni-type line pro?les with an absorp-tion component reaching below the continuum on the violet side of the pro?le and an emission component on the red side,

–group2:single-peaked pure emission lines without absorp-tion components,

–group3:double-peaked emission lines with a central or al-most central absorption component,or at least an intensity dip on one of the line?anks,

–group4:absorption lines.

These pro?le groups correspond to Beals types I,V,III,and VII-VIII,respectively,de?ned by Beals(1955).The pro?le types of the observed lines are summarized in Table5.

3.1.Hαpro?les

A general characteristic of all Hαpro?les displayed in Fig.1is that they exhibit a narrow single or split emission component with a full width at half maximum(FWHM)of about3-5?A, i.e.~150?250km s?1,and broad wings on both sides of the emission component extending up to typically~20?25?A,i.e.~1000km s?1.These wings are generally ascribed to electron scattering(e.g.Zickgraf et al.1986).

Only one star,CPD?52?9243,shows a P Cygni pro?le which resembles the“normal”(group1)pro?le type.Hen485 in1988and MWC1055may also be classed with group1,al-though the absorption components do not reach below the con-tinuum level.

The Hαpro?les of four stars,MWC84,MWC137, MWC297,and Hen230,fall into group2,which exhibits pure emission line pro?les.The FWHM is of the order of3-5?A. Note,however,that the lines are not symmetric.The asymme-try is particularly pronounced in the case of MWC84.

Most of the investigated stars belong to group3exhibiting double-peaked Hαemission lines.In all of the eleven cases of this group the blue emission peak is weaker than the red peak. In no case the central absorption components reaches below the continuum level.For the peculiar line pro?les of HD45677and MWC645see Sect.C.

For several stars Hαwas observed more than once.The pro?les are plotted in Fig.1:MWC137in1987(solid line) and in2002(dashed line);MWC342in1987(solid line)and in2000(dashed line);MWC939in1987(solid line)and1988 (dashed line),the pro?le observed in2000is indistinguish-able that of1988;MWC1055in1987(solid line)and2000 (dashed line);HD87643in1986(solid line)and1988(dashed line);Hen485in1986(solid line)and1988(dashed line).For

Hen485(see text).

malized to the peak?ux.From bottom to top the pro?les of[O I]λ6300A,[Fe II]λ7155A,[N II]λ6583A,and[S III]λ6312A are plotted with shifts in relative intensity of0,0.75,1.5,and2.25,respectively.

the line observed in2002is shown.

3.2.2.[N II]lines

The wavelength region around[N II]λ6583?A is displayed in Fig.D.2.In two stars,CPD?52?9243and HD87643,the [N II]line is absent.The lines visible in the spectra of these stars aroundλ6585?A are probably due to Fe IIλ6586.69?A. Heliocentric radial velocities are v rad=?72km s?1for CPD?52?9243and v rad=?18km s?1for HD87643.In MWC1055[N II]is only weakly discernible.The majority of stars,however,exhibits clearly visible,in many cases strong, [N II]λ6583?A emission.Eight stars show double-peak pro?les. Hen1191shows a sloping line top inclined towards the red side similar to the[O I]line of Hen230,however with a weak peak on the blue edge.Due to this feature the line was classi?ed type 3.Eight stars exhibit single-peaked emission lines.However,in two of these cases,respectively,the pro?les were observed with the lower resolution of23000and34000.They are labelled “e”and”f”in Table5.Note that each of these stars shows a double-peaked(type3)[O I]pro?le.

3.2.3.[Fe II]

The spectral section with[Fe II]λ7155?A is shown in Fig.D.3. Note for that CD?24?5721the forbiddden lines[Fe II]λλ4287, 4276?A were observed instead of the red line(Fig.D.4).In ?ve cases the[Fe II]pro?les are double-peaked similar to[O I]. However,contrary to[O I]the majority of objects,i.e.10,ex-hibits single-peaked pro?les,2of them on a resolution level of 9km s?1.3.2.4.[S III]lines

The[S III]λ6312?A lines are displayed in Fig.D.1.Only four stars exhibit this higher-excitation emission line,i.e.MWC17, MWC84,MWC137,and MWC349A.In MWC137it is very weak and not much can be said about its pro?le.The[S III] line of MWC84is also weak.The strongest[S III]was found in MWC349A.

3.2.5.Fe II lines

For only half of the sample permitted Fe II lines were observed, mostly Fe IIλ6456?A,but also Fe II lines around4550?A for a few stars instead.The wavelength region around Fe IIλ6456?A is displayed in Fig.D.5.Three of the observed stars exhibit single-peak emission lines.Four stars show double-peaked pro-?les.For Hen485the double-peak structure is only weakly in-dicated.CPD?52?9243is the only star showing a P Cygni pro-?le of group1.CD?24?5721is exceptional.This star shows narrow absorption lines(Fig.D.6).The lines identi?ed in the observed spectral sections of this star are listed in Table C.1.

3.2.6.Na I D lines

The lines of the Na I D doublet are shown in Fig.D.7.The spectral section shown in this?gure also contains the line of He Iλ5876?A(see below).Most stars clearly show circumstel-lar Na I emission.Only4of the14observed stars do not show an emission component of the doublet.In most cases the ab-sorption components are blends of multiple narrow absorption

F.-J.Zickgraf:Circumstellar environments of galactic B[e]-type stars9 Table5.Classi?cation of the line pro?le types of the programme stars into groups1to4:1=normal P Cygni pro?le,2=single-peaked emission line,3=double-peaked emission line,4=absorption line.Additional classi?cation codes are:?=weak line, no further classi?cation possible,0=no line visible,–=not observed.For class3a minus or plus sign denotes objects with V/R≤1.0or V/R>1.0,respectively.For Na I D no group is listed because of the confusion due to interstellar absorption components.For this doublet only the presence of emission(“em”)or pure absorption(“abs”)is indicated.

star Hα[O I][Fe II][N II][S III]Fe II He I Na I D

a:Fe IIλ6586c:He Iλ6678in emission

d:He Iλ6678possible blue shifted absorption component

e:observed with R=23000f:observed with FOCES

lines which are very likely mainly due to interstellar absorp-tion.This makes it dif?cult to detect circumstellar absorption features.Because of this problem only the overall appearance of emission or absorption is listed in Table5.Exceptions are CPD?52?9243and possibly Hen485,cf.Sect.C.18and C.14. Heliocentric radial velocities of the absorption components are listed in Table B.2.

3.3.He I lines

The He Iλ5876?A lines are displayed in Fig.D.7.They appear in all four varieties of pro?le types.However,only one star exhibits a clear P Cyg pro?le of type1,namely MWC300.In CPD?57?2874an emission component seems to partly?ll in the absorption component.Two stars show split type3pro?les and?ve stars single-peaked emission pro?les.Six stars show an absorption line.For four stars no observation of He Iλ5876?A were obtained.In MWC137strong variability was found be-tween1987and2002.The He I line changed from absorption to emission(cf.Sect.C.3).

3.4.Summary

An important result of the observations presented here is the detection of one or more double-peaked emission lines in many objects(cf.Table5).Actually,15,possibly16,of the18objects show at least one line with a double-peaked pro?le.This pro?le type is found for both,permitted and forbidden lines,but not necessarily for each line of a particular star.Eleven of the18 objects have split Hαpro?les.Split forbidden lines are found in13objects.Twelve stars exhibit split[O I]lines.The frac-tion of split lines of[N II]and[Fe II]is smaller.Only8of18 stars exhibit split[N II]lines,and5of17stars have split[Fe II] lines.There are only2cases where Hαis double-peaked, but all forbidden lines are single-peaked emission lines.These are HD87643and MWC300.According to Oudmaijer et al. (1998),and Wolf&Stahl(1985and Winkler&Wolf(1989), respectively,they belong to the B[e]supergiants and are most likely viewed under intermediate to pole-on inclination angles. Note,however,that the nature of these stars still is controver-sially discussed(see also Sect.C.5).

A remarkable feature of the double-peaked pro?les is that most,i.e.,~85%,of the observed lines have an intensity ratio of the violet to red component of V/R≤1.Of the43detected type3lines only8show a V/R ratio larger than1.These are 6of26forbidden,and2of16permitted lines(cf.Table A.1). The latter are all Fe II lines.

4.Density conditions in the forbidden-line

forming zone

The interpretation of the observed line pro?les might be com-plicated by the fact that the sample of B[e]-type stars is not ho-mogeneous with respect to the intrinsic object characteristics. The discussion by Lamers et al.(1998)showed that the con-nection between the different classes of B[e]-type stars is the

10 F.-J.Zickgraf:Circumstellar environments of galactic B[e]-type stars

uniformity of the B[e]phenomenon which calls for invoking a common cause for its occurence in different environments.In the following we will therefore take the view of looking primar-ily at the B[e]phenomenon itself rather than at speci?c object classes.

The forbidden-lines in the spectra of B[e]-type stars are dominated by lines of low-excitation ions of neutral or singly ionized metals.Higher excitation lines like [S III ]are rare.This indicates that the temperature

in the

line

emitting

region is about 104K (Lamers et al.1998).The forbidden lines probe the outer low-density zone of the line formation region.A measure for the maximum density in this region is the critical density,N cr ,for which downward collisional and radiative rates are equal.In the approximation of a 2-level ion with upper level u and lower level l it is given by N cr =

A ul

?(u,l )

T

2

(2)

with the collision strength ?(u,l ),the statistical weight g u and

the electron temperature T .According to Viotti (1976)?(u,l )is given by

?(u,l )≈0.2λ4g u A ul

(3)

with the wavelength λin microns.For [Fe II ](14F)λ7155?A

this leads to N cr ?2.2108cm ?3for T e =104K.The critical den-sities are summarized in Table 6.

Table 6.Critical densities,N cr ,of the observed forbidden lines for an electron temperature of T e =104K,and total ion-ization energies,χ,for the production of the respective ion (Cox 2000).The last line gives D 0=N 0/N cr for a density N 0=1011cm ?3at r =1R ?.

ion [O I ]

[Fe II ]

[N II ]

[S III ]

line

λ6300?A

λ7155?A

λ6583?A

λ6312?A

The forbidden lines not only differ with respect to the crit-ical density but also have different ionisation potentials.The

ionisation energy necessary to form Fe II is 7.9eV .For N II an energy of 14.53eV is required.With χ=33.70eV S III has the highest ionisation energy of the observed forbidden lines.Hence,the forbidden lines probe a density interval of about three orders of magnitude,~105-108cm ?3,and a range of ionisation from neutral,[O I ],to [S III ]with an ionisation po-tential of ~34eV .

5.Disk wind:radial expansion vs.rotation

A spherically symmetric and radially expanding wind is ex-pected to form ?at-topped pro?les if the lines are optically thin.This has already been shown by Beals (1931).The forbidden lines in particular form at large distances from the central star where the wind has reached the terminal velocity (see below).A constant velocity wind is expected to form box-shaped lines if the emissivity is constant throughout the emitting volume.

In the observed sample of B[e]-type stars there is just one case,CPD ?57?2874,where a line pro?le comes close to ?at-topped,however not box-shaped.This is the line [O I ]λ6300of this object.The vast majority of the observed pro?les are clearly different from ?at-topped and therefore are inconsis-tent with a spherically symmetric and optically thin line for-mation region.Deviations from ?at-topped pro?les could be produced in the case of spherical symmetry by additional ex-tinction due to dust distributed evenly throughout the line for-mation region.This has been discussed e.g by Appenzeller et al.(1984)for T Tauri stars.However,the pro?le shape expected for this con?guration is not observed in any of the B[e]-type stars of the sample presented here.The polarimetric observa-tions and the forbidden line pro?les therefore strongly indicate that the B[e]phenomenon is correlated with an anisotropic dis-tribution of the circumstellar matter.

Split pro?les of H αsimilar to those shown in Fig.1are fre-quently found in classical Be stars,although the H αequivalent widths in these stars are usually much smaller than in B[e]-type stars and the underlying photospheric absorption component is often discernible.The double-peaked Be star pro?les are gener-ally assigned to a disk-like geometry of the line forming region in connection with rotation.

Mihalas &Conti (1980)discussed the formation of Beals type III,i.e.type 3,line pro?les in the context of the combi-nation of rotation and expansion in a disk-like circumstellar environment.Adding expansion could in particular explain the blueshifted absorption components of H αand the V/R ratios smaller than 1.It would introduce an asymmetry of the line pro?les by shifting the central reversals towards shorter wave-lengths as observed for most B[e]-type stars.For the forbidden lines,however,this mechanism would not work because the lines are optically thin and therefore absorption does not con-tribute.Nevertheless,the combination of expansion and rota-tion could at least explain the observed double-peaked pro?les of H α.

The double-peaked pro?les of the optically thin lines could quite naturally be produced in rotating disks as shown e.g.by P¨o llitsch (1981).Keplerian disks could for example ex-ist around binary B[e]stars (see Sect.1).The pro?les calcu-lated by P¨o llitsch display,however,two emission peaks with

F.-J.Zickgraf:Circumstellar

V/R=1due to the axial symmetry.Pro?les of this type found only in a few cases,e.g.[S III]of MWC349A,[N II] CPD?57?2874,[N II]and[Fe II]of MWC939,and[O I] CD?24?5721and CPD?57?2874.However,the majority double-peak lines has V/R<1including other lines of mentioned stars.It is therefore not obvious that rotation is likely explanation for the double-peaked pro?les.Rather, line pro?les seem to be determined by radial out?ow.

Let us assume as an example a disk-like con?guration

a rotational velocity v0at1R?of v0=300km s?1and constant radial expansion velocity of v exp.Angular

tum conservation requires v rot(r)=v0R?/r.Hence at distance of10R?the rotation velocity would have dropped

ures the solid line designates a ratio of line widths of1.

The observed line widths may help to better understand the possible role of expansion and rotation.In a disk-like circum-stellar environment in which rotation dominates over expansion the forbidden lines are expected to be narrower than the permit-ted lines because the rotational velocity decreases outwards.If rotation is negligible compared to the expansion velocity of a wind accelerated outwards the forbidden lines should have a larger width than the permitted lines.The latter are formed in the accelerating inner wind zone.The forbidden lines originate at large distance from the star where the wind has reached the terminal velocity.

In Figs.5and6the FWHM of[O I]λ6300?A is plotted ver-sus the FWHM of Hαand He I,respectively.They clearly show

The comparison of the line widths of the forbidden lines shown in Fig.7reveals a correlation which is consistent with the assumption that the velocity in the line forming region is constant,and hence that rotation is not important far from the central star.With few exceptions the[O I]line is approx-imately as broad as the[Fe II]line.For[N II]the result is similar,however,with larger scatter.The comparison of[N II] and[Fe II]displayed in the lower left panel of Fig.7shows four stars with broader[Fe II]than[N II].Note that in two of these cases,MWC137and MWC1055,the lines are very weak and the line widths are uncertain.Only Hen485and CPD?57?2874show signi?cantly broader[Fe II]than[N II]. The general trend is towards equal widths or smaller widths for[Fe II].The comparison with[S III]is not meaningful and therefore not shown because only three stars exhibit this line, i.e.MWC17,MWC137,and MWC349A.Inspecting the line

Fig.9.Line splitting of[O I]vs.[N II](left panel)and of[O I] vs.[Fe II](right panel).Upper limits are plotted as arrows. Equal peak separation is represented by the diagonal lines in each panel.

widths listed in Table A.1for[S III]no clear trend emerges for the few lines.

The line splitting is depicted in Figs.8and9.For single lines the velocity corresponding to the spectral resolution was adopted as upper limit of the line splitting.For the line splitting no clear correlation between different lines exists.However, Hαexhibits a much larger splitting than the forbidden metal lines,which is again indicative of a higher velocity in the Hαforming region.A few stars with both,split[Fe II]and[N II] are found close to the diagonal line of equal splitting shown in Fig.9.For[O I]and[N II]the scatter is large.Most upper limits of the line splitting of[N II]λ6583?A are close to the line of equal peak separation.

The line widths are thus consistent with the assumption that in the inner wind zone rotation could play a role.In the outer regions where the forbidden lines are formed a constant veloc-ity wind seems to prevail.

Alternative to rotation,split optically thin emission-line pro?les can result from a radial out?ow with a hollow-cone geometry as discussed e.g.by Appenzeller et al.(1984).Such a con?guration may be considered an approximation of the ra-dially out?owing equatorial disk wind adopted by Zickgraf et al.(1985,1986)for the B[e]supergiants.However,as before the axial symmetry of this con?guration entails the problem of understanding the V/R ratios.In the case of T Tauri stars asymmetric line pro?les were explained e.g by Appenzeller et

(1987)by assuming an opaque

phenomenon is characterized by

dust,a dust disk is also a possible

in B[e]-type stars.As will be

that this disk is opaque.The

a constant velocity law leads

what is observed for the majority

≤1.However,modifying the

pro?les similar to the observed

will be shown in the following

of optically thin lines

wind

thin emission-line pro?les

(1987)(E87hereafter)for the case

stars.They calculated line pro?les

expanding winds with an

forbidden lines of the B[e]-

thin lines were calculated follow-

is shortly summarized here.The

in Fig.5of E87.The requirement

by allowing arbitrary optical depths for an equatorial dust ring(see below).The inclination angle i is measured with respect to the polar axis.Polar coordi-nates r,θ,φof the vector r are de?ned in the stellar reference frame with r being the distance from the star,θthe angle of the vector r with the polar axis andφthe rotation angle around the polar axis.

For the velocity law the latitude-dependent model of E87 was chosen for two reasons.Firstly,it represents a disk-like structure resembling the two-component wind model for B[e] supergiants suggested by Zickgraf et al.(1985)with a fast po-lar and a slow equatorial wind.Secondly,the pro?les for the latitude-independent wind shown in E87do not resemble the observed line pro?les of the B[e]-type stars neither for opti-cally thick nor optically thin dust absorption.

In the latitude-dependent model the wind was chosen to have a constant velocity v(θ)in radial direction depending on the latitudeθaccording to

v(θ)=v max f(θ)(4) with v max being the velocity in polar direction.The latitude-dependent factor f(θ)describes the variation of the wind ve-locity from the pole towards the equator.Assuming e.g.a B supergiant wind in the direction towards the pole with a max-imum expansion velocity of~500?1000km s?1an equa-torial wind velocity of~50?200km s?1would correspond to f(π/2)~0.05?0.25.This assumption is consistent with the equatorial velocities of~100km s?1measured for B[e] supergiants by Zickgraf et al.(1996).

For the model calculations presented below in Figs.10to 14a linear decrease of f(θ)from1to0.2betweenθ=0 andπ/2was adopted.Note that the minimum value of f(π/2)

depths,τ=1000(solid line),τ=1(short dashed line),andτ=0.1(long dashed line).D0and R d were set to1.0and1R?, respectively.The ordinate is the?ux normalized to the maximum.The abscissa is the radial velocity normalized to the maximum wind speed.

speci?es the line width at FWHM.The pro?le shape,however, is independent of this value.The wind velocity was normal-ized to1relative to the velocity in the direction of the polar axis.Other functional dependencies of f(θ)are possible.For example,in the bi-stable wind model suggested by Lamers and Pauldrach(1991)for out?owing disk winds of early-type stars f(θ)could be described by a step or ramp-like function which takes constant values within certain ranges around the equator and the pole with some transition region in between.However, the general characteristics of the pro?les remain similar unless the constant velocity part of the wind prevails.Then the models approach the latitude-independent case.

The electron density N e at point r normalized to the critical density N cr is given by

D e(r,θ,φ)=N e(r,θ,φ)/N cr=D0(R?/r)2v(θ)?1,(5) where D0is the density ratio at r=R?andθ=0.For a given density distribution N e(r)the parameter D0thus depends on the critical density of the line considered.Lower critical density lines correspond to larger D0values.A line with D0=1,1000, or10000has reached the critical density at r=1R?,33R?, or100R?,respectively,in the polar direction.Note that due to the v(θ)dependence the density distribution is disk-like with the density increasing towards the equatorial plane.According to E87the emissivity j(r,θ,φ)for a2-level atom is

j(r,θ,φ)∝D2e[1+D e(δ+1)]?1(6) whereδis the ratio of the collisional rate coef?cients of the lower and upper level.The line pro?les turned out to be insen-sitive toδwhich could therefore be set toδ=0.The emissivity was set to zero for rN cr.For each volume element?V the radial velocity along the direc-tion of the line of sight was calculated from

v(r,θ,φ)=?v(θ)cosβ(7) with

cosβ=cosθcos i+sinθsin i sinφ,(8)βbeing the angle between r and the line of sight.Finally,the ?ux contributions j(r)?V of all volume elements within r≤r max were summed up in the suitable velocity intervals evenly distributed between?1and+1.

14 F.-J.Zickgraf:Circumstellar

Edwards et al.assumed the presence of an opaque blocking entirely the receding part of the wind.For the stars an equatorial ring structure was adopted instead with inner ring radius R d≥R?and an optical depth ofτd≥The case R d=R?andτd=∞corresponds to the

?guration of E87.The ring structure with R d>R?into account that the inner rim of the dust disk should pend on the dust condensation radius.According to

&Cassinelli(1998)the equilibrium temperature of the varies as T d?T e?(2R d/R?)?2/5.For the B[e]-type stars can therefore be estimated to be~102R?to~2103R?T e?between104K and2.5104K and T d~103K.V elements below the equatorial plane,i.e.atθ>π/2, tribute F d=j(r)?V exp(?τd)to the observed?ux

the line of sight passes through the central hole.In this

F d=F=j(r)?V.Hence,for R d>R?lines with critical densities can be affected differently by the dust

tion because the inner radius of the line-emitting volume,r depends on N cr.

In Figs.10to12the results of the model calculations displayed for the linear f(θ)law and various parameter nations.Figure10shows line pro?les calculated for D0=1. R d=1R?different inclination angles i,and three

of the optical depthτd of0.1,1,and1000.Note that R d=1R?the pro?le shape does not depend on D0.The

?les forτd=1000are identical to those shown by E87. smallerτd leads to a more symmetrical pro?le.For large nation angles double-peaked pro?les are produced.The ratio of the peak?uxes is always≤1and depends onτd. smallτd leads to V/R≈1for all inclination angles.Forτd>~the V/R ratio deviates signi?cantly from1except for large The peak separation is determined by f(θ=π/2)and

also on the inclination i.Decreasing f(θ=π/2)and/or i

a smaller velocity difference of the line peaks.There is some weak dependence of the peak separation onτd.

In Figs.11and12the in?uence of D0as a function of clination is shown for models with a dust ring.The inner

of the ring is assumed to be R d=1000R?.Two sets of

are shown for which the optical depth of the dust isτd=1 1000,respectively.Different D0values were adopted for a lar density at the base of the wind of N0=1011cm?3and critical densities given in Table6for[Fe II],[O I],and[N II This N0corresponds to an equatorial density of~1012cm?For smallτd the pro?les remain nearly symmetric with

ing D0.Only a small decrease of the?ux on the red wing be seen.For intermediate inclination angles the split show a trend of decreasing V/R with increasing D0.For

τd the lines become more asymmetric for increasing D0be-cause the emission for lines with a low critical density starts at a larger distance from the star.Therefore less emission can be seen through the central hole of the dust ring.The con?gura-tion thus approaches that of Fig.10.The receding part of the wind produces a weak bump on the red side of the pro?le if the inclination angles is not too large.For high inclination the V/R ratio decreases with increasing D0,passes through a minimum and then increases again.The models thus show that one line may show V/R≈1and at the same time another line with a different N cr can have V/R<1.dashed line),and1106(long dashed line).For the dust ring an optical depth ofτd=1and an inner radius of R d=1000R?was adopted.

Up to now a disk-like wind model with a latitude-independent ionization structure has been considered. However,lines with different ionization potentials may originate in different zones of the wind.For example,the two-component stellar wind model by Zickgraf et al.(1985) suggests that the cool equatorial zone should give rise to

15

dashed line),and1106(long dashed line).For the dust ring an optical depth ofτd=1000and an inner radius of R d= 1000R?was adopted.

neutral or low-ionisation lines of ions like[O I]and[Fe II]. Lines with higher ionization potential like[N II]and[S III] would originate in hotter yet tenuous regions at higher latitude towards the polar zone.A scenario like this is therefore char-acterized by a latitude-dependent ionization structure.It can be sketched by the hollow and?lled cone model,respectively,

hollow cone geometry

within a certain angle

the?lled cone is

from the polar axis.In the

and“polar cone”will

and?lled cone geometry,

for the case of an opening

plane)for the equa-

(measured from the polar

depth of the dust(τd=1)

are complex.The equa-

to the latitude-independent

(opening angle90?).The

with a decreasing

D0or decreasing

becomes weaker.

in Fig.2and of the

that the general char-

qualitatively be repro-

split or asymmetric

wind model

optical depths.The single

peaks observed for a cou-

inclination angles and

or disk.Furthermore,for a

different critical densities

line pro?les.Likewise,

1to>1are expected if the

e.g.in the equatorial disk

MWC297,MWC349A,

and CPD?52?9243quali-

in Fig.10to12for inter-

In most cases the wings ap-

as expected for a small

are MWC645and

pro?les resemble those for

intermediate inclination.

asymmetry with pro-

In Hen485the[O I]line

also show an asymmetric

645.Line splitting is

of splitting expected for an intermediate inclination could be due to turbulent broaden-ing as discussed below.

The lines of MWC300and HD87643are similar to the pro?les for a small inclination angle and small optical depth of the dust.A near pole-on viewing angle was suggested by Winkler&Wolf(1989)for MWC300and by Oudmaijer et al. (1998)for HD87643.

In Hen1191and CPD?57?2874the[N II]lines are charac-terized by a broad pedestal on top of which a narrow peak is sit-ting.This bears some resemblance with the pro?les calculated

16 F.-J.Zickgraf:Circumstellar environments of galactic B[e]-type stars

for small optical depth of the dust and small to intermediate inclination.

An interesting feature of the polar cone lines shown in Fig. 13and14is that they can have V/R>1if seen under in-termediate to large inclination angle.Neither the models with opening angles of90?displayed in Figs.10to12nor the equatorial disk lines in Figs.13and14show this behaviour. This could explain the[O I]lines in MWC137,MWC342, and CD?24?5721,and the[N II]lines of MWC349A and CPD?57?2874.Likewise,the equatorial disk and polar cone model produces lines with different width,both FWHM and FWZI,which is not the case in the latitude-independent ioniza-tion model.

The complex pro?les obtained for a equatorial disk and polar cone model with optically thin dust were not observed in the sample discussed here.However,the forbidden lines of MWC17and MWC349A show a strong resemblance with the pro?les displayed in Fig.14for optically thick dust and incli-nation i=80?.In both stars the lines of[N II]and[S III]are broader than[O I]and[Fe II].This is expected for the equa-torial disk and polar cone model if the higher ionization lines originate in the polar zone(?lled cone)and the lower ioniza-tion lines in the equatorial region(hollow cone).The pro?les displayed in Fig.11for optically thin dust also exhibit the double peak structure if the inclination is high.However,in these models the line forming regions are not separate for lines with different ionization potential.Contrary to the observa-tions the lines should thus show the same widths.Note that for MWC349A there is observational evidence for the existence of a dust disk seen edge-on(White&Becker1985,Leinert1986, Hofmann et al.2002).The observations are thus in favour of the equatorial disk and polar cone model with optically thick dust.

An interesting feature of this model in the case of large op-tical depth of the dust disk is the behaviour of the V/R ratio. The polar cone line can have a?ux ratio V/R>1and at the same time the corresponding equatorial disk line has V/R<1. This could explain qualitatively the different appearance of the lines in MWC349A which shows simultaneously[O I],[Fe II], and[S III]lines with V/R<1and[N II]with V/R>1.

The equatorial disk and polar cone model also seems promising for MWC137,MWC342,and CD?24?5721.In these objects the[O I]exhibits a V/R ratio>1.In MWC137 the line widths and the V/R ratio suggest that[O I]is a polar cone line,whereas[S III]and[N II]are equatorial disk lines.

In Hen230and MWC1055the[N II]line shows a red wing indicating that this line originates in a polar cone seen under an intermediate aspect angle.In Hen230the wing is also indicated in[Fe II].

Though many line characteristics can thus be understood in terms of the latitude-dependent wind model there seems to be a problem in explaining simultaneously split and single-peaked forbidden lines as observed in several stars.In many of these cases insuf?cient spectral resolution or too low an S/N ratio might be an explanation for the apparent differ-ences of the pro?les,e.g.in MWC297,and MWC1055.In MWC17,MWC342,HD45677,and CD?24?5721,however, the differences seem to be real.A possible explanation could be the existence of macroscopic turbulent motion of the order of~10?30km s?1.It would broaden the local line pro?le and therefore smear out line splitting if the expansion veloc-ities are small enough.As an example a hollow cone model with an opening angle of30?and an inclination angle of45?is shown in Fig.15.For the wind a polar velocity of v max= 300km s?1,and an equatorial velocity of v eq=25km s?1, i.e.f(π/2)=0.08,was adopted.The line broadening due to macro turbulence was assumed to have a Gaussian shape with a FWHM given by the turbulent velocity v t.Four values were as-sumed for v t,i.e.15,20,30,and35km s?1.The optical depth of the dust disk wasτd=1.The?gure shows that the split pro?le disappears for high v t.If the lines originate in differ-ent regions,e.g.due to ionization effects,a location-dependent turbulence velocity could therefore lead to the observed differ-ences in the pro?les.A high v t could also be responsible for the sloping tops of the lines of CPD?52?9243.V/R<1and [N II]with V/R<1(cf.Fig.2).

Alternatively,the simultaneous appearance of split and single-peaked lines of the different ions can be explained with the equatorial disk and polar cone model.MWC342and HD45677show split[O I],but single-peaked[Fe II]and[N II]. Surprisingly,such a combination of pro?les can be produced in a nearly pole-on geometry.This is illustrated in Fig.16for a model with an inclination angle of i=10?.Here it is assumed that the split line originates in the polar cone with a large open-ing angle of about~70?to~80?.The line has a V/R ratio of>1.The single-peaked line is produced with an opening an-gle of90?,which means latitude-independent ionization.This confguration thus can lead to split lines with V/R>1and simultaneously to single-peaked lines.

7.Conclusions

High-resolution line pro?les of selected permitted and forbid-den lines of B[e]-type stars were discussed.A main result was the detection of double-peaked forbidden lines in a large frac-tion of the observed sample.This strongly indicates that the line formation environment has a non-spherical distribution, most likely in a disk-like con?guration.Lines formed close to the star like Hαand He I were compared with forbidden lines formed in the tenuous outskirts.The comparison suggests that rotation could dominate in the inner zones but is overtaken by a radially expanding disk wind in the outer regions.

Line pro?les were calculated for the optically thin case. Pro?les similar to the observed forbidden lines are expected for a radially expanding latitude-dependent wind.This wind con-?guration can be considered a parametrization of the generally accepted two-component wind model for B[e]-type stars.

For many objects in the sample the observed line pro?les are consistent with models assuming a latitude-independent ionization structure of the wind.There are,however,two other groups of objects for which the models suggest(partly)sepa-rated line forming regions for the different ions.In one group the low ionization lines seem to originate in an equatorial disk. In the second group the neutral line of[O I]appears to originate in a polar cone instead.

F.-J.Zickgraf:Circumstellar environments of galactic B[e]-type stars17

It is clear,though,that due to simplifying assumptions of the model it cannot be expected to explain all details of the observed pro?les.Rather,the discrepancies might suggest that the environments,although in general having a disk-like struc-ture,are apparently more complicated than assumed here.In particular,the ionization structure is taken into account only simplistically with the hollow and?lled cone model because of the lack of information on this parameter.For example,charge tranfer reactions can have a strong in?uence on the ioniza-tion balance of oxygen and nitrogen(e.g.Chamberlain1956, Butler&Dalgarno1979).This has not been investigated for B[e]star disks so far.Binarity could add further complexity. However,as long as an expanding wind dominates the circum-stellar environment at large distances from the central object the latitude-dependent wind model could also be applicable to such a subclass of B[e]-type stars.Thus even with the simpli-fying assumptions the results obtained here support the com-monly adopted point of view that the forbidden emission lines of B[e]-type stars are formed in disk-like circumstellar envi-ronments.

Acknowledgements.I would like to thank the Deutsche Forschungs-gemeinschaft for granting travel funds(Zi420/7-1)and for?nancial support under grants Wo269/2-1and Wo269/2-2.I would also like to thank the referee,Dr.A.S.Miroshnichenko,for his critical comments which helped to improve the paper.This research has made use of the SIMBAD database,operated at CDS,Strasbourg,France. References

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Appendix A:Emission line parameters

In Table A.1the line parameters of the observed emission lines listed.Line peak intensities I line=F line/F cont(for the stronger

in case of split pro?les)and the ratio of blue and red peak ties,V/R=(F blue?F cont)/(F red?F cont),are given in the two columns.W is the equivalent width in?A,?v(in km s?1)is peak separation for lines of type3.FWZI and FWHM(in km s?are the full width at zero intensity and full width at half respectively.Errors of FWZI and FWHM were found to be about 15%.The meaning of“FWHM”is taken literally by measuring line widths at the50%?ux level of the maximum peak?ux

dent of the line pro?le shape.For type3pro?les with V/R<0.5 type1P Cygni pro?les this only measures the width of the red sion peak which is then used as a rough estimate for the FWHM. Hαonly a lower limit for FWZI can be given due to the small length intervals covered by the spectra.

Appendix B:Heliocentric radial velocities

In Table B.1heliocentric radial velocities of the different lines listed.For double-peaked emission lines“e b”and“e r”denote the locities of the blue and red emission components,respectively. single-peaked emission lines“c”denotes the velocities of the center emission.In the case of double-peaked lines“c”is the velocity of central absorption or of the central dip between the emission

For pure absorption lines it is the central velocity of the feature.Velocities of absorption components are additionally

by the letter“a”.For type1pro?les absorption velocities are

in the column“e b/a”.The laboratory wavelengths used for the bidden lines are6300.31?A for[O I],7155.14?A for[Fe II],6583.37

for[N II],and6312.10?A for[S III].Table B.2lists the heliocentric dial velocities of the absorption components of the Na I D doublet.In some cases not all components were detectable in each of the doublet components.This is often due to saturation effects in the strong line cores.ometry withτd=1,D0=3105and R d=500R?.For the equatorial disk(solid line)an opening angle of30?measured from the equatorial plane was adopted.The polar cone(dashed line)is the complementary volume with an opening angle of 60?measured from the polar axis.

20 F.-J.Zickgraf:Circumstellar environments of galactic B[e]-type stars Table A.1.Line parameters.

MWC17

Hα180.10.72?680>~205017890 He Iλ5876?A 5.70.68?7.22009754 [O I]λ6300?A25.40.91?27.11035120 [N II]λ6583?A 3.40.92?3.51567016 [Fe II]λ7155?A 3.6–?2.510145–[S III]λ6312?A 3.10.76?3.51397545 line I line V/R W FWZI FWHM?v

MWC137

Hα(1987)86.9–?395>~1400197–Hα(2002)105.3–?464~1600196–He Iλ5876?A(87)––+1.3–––He Iλ5876?A(02) 1.9–?4.1796270–[O I]λ6300?A 1.6 1.20?0.781415829 [Fe II]λ7155?A 1.05–?0.09132:77:–[N II]λ6583?A 1.450.96?0.39953411: [S III]λ6312?A 1.14–?0.106932–line I line V/R W FWZI FWHM?v

MWC300

Hα89.00.38?150>~11406578 He Iλ5876?A 2.10–?1.4120159–[O I]λ6300?A24.5–?10.77521–[N II]λ6583?A 3.1–?1.338825–[Fe II]λ7155?A 1.90–?0.616529–line I line V/R W FWZI FWHM?v line I line V/R W FWZI FWHM?v

MWC645

Hα4780.38?195>~133070188 [O I]λ6300?A10.10.83?14.02797419 [N II]λ6583?A 1.24–?0.3010569–[Fe II]λ7155?A 5.550.82?8.32607026 line I line V/R W FWZI FWHM?v

MWC1055

Hα(1987)680.04?181>~1740101(206) Hα(2000)620.03?1133300113(330) [O I]λ6300?A 2.540.86?0.9054287: [N II]λ6583?A 1.07–?0.0326:13:–[Fe II]λ7155?A 1.11–?0.074726–

Fe IIλ6456?A 1.12–?0.2721899–line I line V/R W FWZI FWHM?v

Hen485

Hα198645.6–?170>~1800159–

Hα198844.70.04:?156>~1830133–

He Iλ5876?A 1.32–?0.92374127–[O I]λ6300?A 1.34–?0.3411641–[N II]λ6583?A(86) 1.67–?0.315322–[N II]λ6583?A(88) 2.86–?0.926222–[Fe II]λ7155?A 1.21–?0.3215345–

Fe IIλ4549?A 2.44–?2.1219885–

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聚合诸侯捍卫中原,匡正天下功业千秋。号令诸侯以匡周室,主要靠的不是 武力。 行为磊落不欺诈,美德流传于身后。孔子赞美齐桓公,也称赞管仲。 百姓深受恩惠,天子赐肉与桓公,命其无拜来接受。桓公称小白不敢,天子 威严就在咫尺前。 晋文公继承来称霸,亲身尊奉周天王。周天子赏赐丰厚,仪式隆重。 接受玉器和美酒,弓矢武士三百名。晋文公声望镇诸侯,从其风者受尊重。 威名八方全传遍,名声仅次于齐桓公。佯称周王巡狩,招其天子到河阳,因 此大众议论纷纷。 赏析 《短歌行》 (“周西伯昌”)主要是曹操向内外臣僚及天下表明心 迹,当他翦灭群凶之际,功高震主之时,正所谓“君子终日乾乾,夕惕若 厉”者,但东吴孙权却瞅准时机竟上表大说天命而称臣,意在促曹操代汉 而使其失去“挟天子以令诸侯”之号召, 故曹操机敏地认识到“ 是儿欲据吾著炉上郁!”故曹操运筹谋略而赋此《短歌行 ·周西伯 昌》。 西伯姬昌在纣朝三分天下有其二的大好形势下, 犹能奉事殷纣, 故孔子盛称 “周之德, 其可谓至德也已矣。 ”但纣王亲信崇侯虎仍不免在纣王前 还要谗毁文王,并拘系于羑里。曹操举此史实,意在表明自己正在克心效法先圣 西伯姬昌,并肯定他的所作所为,谨慎惕惧,向来无愧于献帝之所赏。 并大谈西伯姬昌、齐桓公、晋文公皆曾受命“专使征伐”。而当 今天下时势与当年的西伯、齐桓、晋文之际颇相类似,天子如命他“专使 征伐”以讨不臣,乃英明之举。但他亦效西伯之德,重齐桓之功,戒晋文 之诈。然故作谦恭之辞耳,又谁知岂无更讨封赏之意乎 ?不然建安十八年(公元 213 年)五月献帝下诏曰《册魏公九锡文》,其文曰“朕闻先王并建明德, 胙之以土,分之以民,崇其宠章,备其礼物,所以藩卫王室、左右厥世也。其在 周成,管、蔡不静,惩难念功,乃使邵康公赐齐太公履,东至于海,西至于河, 南至于穆陵,北至于无棣,五侯九伯,实得征之。 世祚太师,以表东海。爰及襄王,亦有楚人不供王职,又命晋文登为侯伯, 锡以二辂、虎贲、斧钺、禾巨 鬯、弓矢,大启南阳,世作盟主。故周室之不坏, 系二国是赖。”又“今以冀州之河东、河内、魏郡、赵国、中山、常 山,巨鹿、安平、甘陵、平原凡十郡,封君为魏公。锡君玄土,苴以白茅,爰契 尔龟。”又“加君九锡,其敬听朕命。” 观汉献帝下诏《册魏公九锡文》全篇,尽叙其功,以为其功高于伊、周,而 其奖却低于齐、晋,故赐爵赐土,又加九锡,奖励空前。但曹操被奖愈高,心内 愈忧。故曹操在曾早在五十六岁写的《让县自明本志令》中谓“或者人见 孤强盛, 又性不信天命之事, 恐私心相评, 言有不逊之志, 妄相忖度, 每用耿耿。

2008年浙师大《外国文学名著鉴赏》期末考试答案

(一)文学常识 一、古希腊罗马 1.(1)宙斯(罗马神话称为朱庇特),希腊神话中最高的天神,掌管雷电云雨,是人和神的主宰。 (2)阿波罗,希腊神话中宙斯的儿子,主管光明、青春、音乐、诗歌等,常以手持弓箭的少年形象出现。 (3)雅典那,希腊神话中的智慧女神,雅典城邦的保护神。 (4)潘多拉,希腊神话中的第一个女人,貌美性诈。私自打开了宙斯送她的一只盒子,里面装的疾病、疯狂、罪恶、嫉妒等祸患,一齐飞出,只有希望留在盒底,人间因此充满灾难。“潘多拉的盒子”成为“祸灾的来源”的同义语。 (5)普罗米修斯,希腊神话中造福人间的神。盗取天火带到人间,并传授给人类多种手艺,触怒宙斯,被锁在高加索山崖,受神鹰啄食,是一个反抗强暴、不惜为人类牺牲一切的英雄。 (6)斯芬克司,希腊神话中的狮身女怪。常叫过路行人猜谜,猜不出即将行人杀害;后因谜底被俄底浦斯道破,即自杀。后常喻“谜”一样的人物。与埃及狮身人面像同名。 2.荷马,古希腊盲诗人。主要作品有《伊利亚特》和《奥德赛》,被称为荷马史诗。《伊利亚特》叙述十年特洛伊战争。《奥德赛》写特洛伊战争结束后,希腊英雄奥德赛历险回乡的故事。马克思称赞它“显示出永久的魅力”。 3.埃斯库罗斯,古希腊悲剧之父,代表作《被缚的普罗米修斯》。6.阿里斯托芬,古希腊“喜剧之父”代表作《阿卡奈人》。 4.索福克勒斯,古希腊重要悲剧作家,代表作《俄狄浦斯王》。5.欧里庇得斯,古希腊重要悲剧作家,代表作《美狄亚》。 二、中世纪文学 但丁,意大利人,伟大诗人,文艺复兴的先驱。恩格斯称他是“中世纪的最后一位诗人,同时又是新时代的最初一位诗人”。主要作品有叙事长诗《神曲》,由地狱、炼狱、天堂三部分组成。《神曲》以幻想形式,写但丁迷路,被人导引神游三界。在地狱中见到贪官污吏等受着惩罚,在净界中见到贪色贪财等较轻罪人,在天堂里见到殉道者等高贵的灵魂。 三、文艺复兴时期 1.薄迦丘意大利人短篇小说家,著有《十日谈》拉伯雷,法国人,著《巨人传》塞万提斯,西班牙人,著《堂?吉诃德》。 2.莎士比亚,16-17世纪文艺复兴时期英国伟大的剧作家和诗人,主要作品有四大悲剧——《哈姆雷特》、《奥赛罗》《麦克白》、《李尔王》,另有悲剧《罗密欧与朱丽叶》等,喜剧有《威尼斯商人》《第十二夜》《皆大欢喜》等,历史剧有《理查二世》、《亨利四世》等。马克思称之为“人类最伟大的戏剧天才”。 四、17世纪古典主义 9.笛福,17-18世纪英国著名小说家,被誉为“英国和欧洲小说之父”,主要作品《鲁滨逊漂流记》,是英国第一部现实主义长篇小说。10.弥尔顿,17世纪英国诗人,代表作:长诗《失乐园》,《失乐园》,表现了资产阶级清教徒的革命理想和英雄气概。 25.拉伯雷,16世纪法国作家,代表作:长篇小说《巨人传》。 26.莫里哀,法国17世纪古典主义文学最重要的作家,法国古典主义喜剧的创建者,主要作品为《伪君子》《悭吝人》(主人公叫阿巴公)等喜剧。 五、18世纪启蒙运动 1)歌德,德国文学最高成就的代表者。主要作品有书信体小说《少年维特之烦恼》,诗剧《浮士德》。 11.斯威夫特,18世纪英国作家,代表作:《格列佛游记》,以荒诞的情节讽刺了英国现实。 12.亨利·菲尔丁,18世纪英国作家,代表作:《汤姆·琼斯》。 六、19世纪浪漫主义 (1拜伦, 19世纪初期英国伟大的浪漫主义诗人,代表作为诗体小说《唐璜》通过青年贵族唐璜的种种经历,抨击欧洲反动的封建势力。《恰尔德。哈洛尔游记》 (2雨果,伟大作家,欧洲19世纪浪漫主义文学最卓越的代表。主要作品有长篇小说《巴黎圣母院》、《悲惨世界》、《笑面人》、《九三年》等。《悲惨世界》写的是失业短工冉阿让因偷吃一片面包被抓进监狱,后改名换姓,当上企业主和市长,但终不能摆脱迫害的故事。《巴黎圣母院》 弃儿伽西莫多,在一个偶然的场合被副主教克洛德.孚罗洛收养为义子,长大后有让他当上了巴黎圣母院的敲钟人。他虽然十分丑陋而且有多种残疾,心灵却异常高尚纯洁。 长年流浪街头的波希米亚姑娘拉.爱斯梅拉达,能歌善舞,天真貌美而心地淳厚。青年贫诗人尔比埃尔.甘果瓦偶然同她相遇,并在一个更偶然的场合成了她名义上的丈夫。很有名望的副教主本来一向专心于"圣职",忽然有一天欣赏到波希米亚姑娘的歌舞,忧千方百计要把她据为己有,对她进行了种种威胁甚至陷害,同时还为此不惜玩弄卑鄙手段,去欺骗利用他的义子伽西莫多和学生甘果瓦。眼看无论如何也实现不了占有爱斯梅拉达的罪恶企图,最后竟亲手把那可爱的少女送上了绞刑架。 另一方面,伽西莫多私下也爱慕着波希米亚姑娘。她遭到陷害,被伽西莫多巧计救出,在圣母院一间密室里避难,敲钟人用十分纯朴和真诚的感情去安慰她,保护她。当她再次处于危急中时,敲钟人为了援助她,表现出非凡的英勇和机智。而当他无意中发现自己的"义父"和"恩人"远望着高挂在绞刑架上的波希米亚姑娘而发出恶魔般的狞笑时,伽西莫多立即对那个伪善者下了最后的判决,亲手把克洛德.孚罗洛从高耸入云的钟塔上推下,使他摔的粉身碎骨。 (3司汤达,批判现实主义作家。代表作《红与黑》,写的是不满封建制度的平民青年于连,千方百计向上爬,最终被送上断头台的故事。“红”是将军服色,指“入军界”的道路;“黑”是主教服色,指当神父、主教的道路。 14.雪莱,19世纪积极浪漫主义诗人,欧洲文学史上最早歌颂空想社会主义的诗人之一,主要作品为诗剧《解放了的普罗米修斯》,抒情诗《西风颂》等。 15.托马斯·哈代,19世纪英国作家,代表作:长篇小说《德伯家的苔丝》。 16.萨克雷,19世纪英国作家,代表作:《名利场》 17.盖斯凯尔夫人,19世纪英国作家,代表作:《玛丽·巴顿》。 18.夏洛蒂?勃朗特,19世纪英国女作家,代表作:长篇小说《简?爱》19艾米丽?勃朗特,19世纪英国女作家,夏洛蒂?勃朗特之妹,代表作:长篇小说《呼啸山庄》。 20.狄更斯,19世纪英国批判现实主义文学的重要代表,主要作品为长篇小说《大卫?科波菲尔》、《艰难时世》《双城记》《雾都孤儿》。21.柯南道尔,19世纪英国著名侦探小说家,代表作品侦探小说集《福尔摩斯探案》是世界上最著名的侦探小说。 七、19世纪现实主义 1、巴尔扎克,19世纪上半叶法国和欧洲批判现实主义文学的杰出代表。主要作品有《人间喜剧》,包括《高老头》、《欧也妮·葛朗台》、《贝姨》、《邦斯舅舅》等。《人间喜剧》是世界文学中规模最宏伟的创作之一,也是人类思维劳动最辉煌的成果之一。马克思称其“提供了一部法国社会特别是巴黎上流社会的卓越的现实主义历史”。

(完整版)the的用法

定冠词the的用法: 定冠词the与指示代词this ,that同源,有“那(这)个”的意思,但较弱,可以和一个名词连用,来表示某个或某些特定的人或东西. (1)特指双方都明白的人或物 Take the medicine.把药吃了. (2)上文提到过的人或事 He bought a house.他买了幢房子. I've been to the house.我去过那幢房子. (3)指世界上独一无二的事物 the sun ,the sky ,the moon, the earth (4)单数名词连用表示一类事物 the dollar 美元 the fox 狐狸 或与形容词或分词连用,表示一类人 the rich 富人 the living 生者 (5)用在序数词和形容词最高级,及形容词等前面 Where do you live?你住在哪? I live on the second floor.我住在二楼. That's the very thing I've been looking for.那正是我要找的东西. (6)与复数名词连用,指整个群体 They are the teachers of this school.(指全体教师) They are teachers of this school.(指部分教师) (7)表示所有,相当于物主代词,用在表示身体部位的名词前 She caught me by the arm.她抓住了我的手臂. (8)用在某些有普通名词构成的国家名称,机关团体,阶级等专有名词前 the People's Republic of China 中华人民共和国 the United States 美国 (9)用在表示乐器的名词前 She plays the piano.她会弹钢琴. (10)用在姓氏的复数名词之前,表示一家人 the Greens 格林一家人(或格林夫妇) (11)用在惯用语中 in the day, in the morning... the day before yesterday, the next morning... in the sky... in the dark... in the end... on the whole, by the way...

外国名著赏析论文

题目:浅析从简爱到女性的尊严和爱 学院工商学院 专业新闻学3 学号 姓名闫万里 学科外国文学名着赏析 [摘要] 十九世纪中期,英国伟大的女性存在主义先驱,着名作家夏洛蒂勃朗特创作出了她的代表作--《简爱》,当时轰动了整个文坛,它是一部具有浓厚浪漫主义色彩的现实主义小说,被认为是作者"诗意的生平"的写照。它在问世后的一百多年里,它始终保持着历史不败的艺术感染力。直到现在它的影响还继续存在。在作品的序幕、发展、高潮和结尾中,女主人公的叛逆、自由、平等、自尊、纯洁的个性都是各个重点章节的主旨,而这些主旨则在女主人公的爱情观中被展露的淋漓尽致,它们如同乌云上方的星汉,灼灼闪耀着光芒,照亮着后来的女性者们追求爱情的道路。? [关键词] 自尊个性独特新女性主义自由独立平等 《简爱》是一部带有自转色彩的长篇小说,它阐释了这样一个主题:人的价值=尊严+爱。从小就成长在一个充满暴力的环境中的简爱,经历了同龄人没有的遭遇。她要面对的是舅妈的毫无人性的虐待,表兄的凶暴专横和表姐的傲慢冷漠,尽管她尽力想“竭力赢得别人的好感”,但是事实告诉她这都是白费力气的,因此她发出了“不公平啊!--不公平!”的近乎绝望的呼喊。不公平的生长环境,使得简爱从小就向往平等、自由和爱,这些愿望在她后来的成长过程中表现无疑,

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