The effect of stellar activity on the LiI 6708, NaI 5896 and KI 7699 AA lines A comparison
a r X i v :a s t r o -p h /0103419v 1 26 M a r 2001
A&A manuscript no.
(will be inserted by hand later)
Send o?print requests to :D.Barrado y Navascu′e s
?Based on observations collected with the Gregory-Coud′e telescope,operated on the island
of Tenerife by the Universit¨a ts-Sternwarte G¨o ttingen in the Spanish Observatorio del Teide of
the Instituto de Astrof ′?sica de Canarias.
2 D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines activity.However,under realistic values for the?lling factors,only a small portion of the observed spread could be explained by these e?ects.
Key words:Sun:activity–Sun:faculae,plages–sunspots–Stars:abundances–Stars: activity–Stars:late type
D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines3 slow rotators.Balachandran et al.(1998)discuss di?erent aspects of the lithium-rotation connection and mixing in late-type stars.Note,however,that slightly older clusters do not clearly show this connection,as in the case of M35(Barrado y Navascu′e s et al. 2001b).Alternatively,it has also been suggested that chromospheric activity could a?ect the formation of the Li line,partially accounting for the observed dispersion(Houdebine &Doyle1995;Barrado y Navascu′e s1996;Russel1996;Je?ries1999;King et al.2000). In this case the Li-rotation connection would be a Li-activity-rotation relation(higher rotation means higher activity)and the observed dispersion in Li equivalent widths(Ws) would not(or only in part)correspond to a real dispersion in Li abundances.
Soderblom et al.(1993)found that the K i7699?A equivalent widths of K-type stars in the Pleiades exhibited a similar trend to that of Li i6708?A but with a lower spread. They concluded in their study that activity could only partially in?uence the observed Li spread.Stuik et al.(1997)compared observed and synthetic Li i and K i spectra(a?ected by the presence of spot and plages)for late-type Pleiades stars.They found that these lines are not sensitive to the presence of a chromosphere,and that they respond to the e?ects of activity on the strati?cation in the deep photosphere.However,they could not establish whether or not magnetic activity is the major contributor to the observed K i (and Li i)scatter.More recently,King et al.(2000)addressed this problem by using di?erential Li abundances(with respect to?tted values vs.e?ective temperature)and di?erential K i equivalent widths.They invoked an incomplete treatment of line formation (in particular,the role of ionization in reducing the the Li i line optical depth;Houdebine &Doyle1995)to explain the correlations found between di?erential Li and K values and di?erences in stellar activity(measured using the Ca ii IR triplet).
None of these previous works has clearly established the quantitative e?ects of stellar activity on the K i and Li i lines.In this paper,we have adopted an empirical approach to this study and included the Na i5896?A line as a complementary indicator.An analytical model has been developed to evaluate the simultaneous e?ect of surface inhomogeneities on the observed line equivalent widths and stellar photometric colors.The inputs to this model come from high-quality,high-resolution observations carried out on di?erent regions of the solar disk.Section2brie?y describes the observational material,while Section3provides the details of the model.A comparison between model predictions and photometric data for the Pleiades is shown in Section4.Section5discusses the e?ect of stellar spots and faculae on the alkali and compares these results with K i and Li i measurements in late-type Pleiades stars.Finally,Section6summarizes our main conclusions.
4 D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines
(a)012
340
1
2
3
4
Fspot+constant 3700 K 4000 K
4575 K
4870 K
3700 K
4000 K 4575 K
4870 K
3700 K
4000 K 4575 K 3700 K 4000 K Tquiet=6344 K Tquiet=5655 K Tquiet=4988 K Tquiet=4500 K (b)
01234
00.20.4
Fspot+constant Tquiet=6344 K Tquiet=5655 K Tquiet=4988 K Tquiet=4500 K Fig.1.Results of our model for a star with T quiet =6344,5655,4988and 4500K.The
solid line shows the computation for a spot at 4870K,the dotted line represents the
values for a spot at 4575K,the short dashed line corresponds to 4000K.Finally,the long
dashed line represents the computation for a spot at 3700K.(a).Variation of the visual
magnitude,?M V ,against the ?lling factor of the spots,F spot .For clarity,we have added
one,two and three units to the models having T quiet equal to 5655,4988and 4500K,
respectively.(b).Dependence of variation of the observed color index (B–V)on the spot
?lling factor.
Table 1.Alkali equivalent widths measured on di?erent solar regions.
Quiet
Faculae Average Umbra Central Umbra Spot 2
(?A )(1)From Brynildsen et al.(private comm.),after Tripicchio et al.(1997,1999).
2.Observational material
The observations used in this work were carried out in September 1994,using the echelle
spectrograph of the Gregory-Coud′e telescope located at the Teide Observatory,Tenerife
(Spain).This instrument provides a great stability together with very high spectral reso-
lution.Spectra with a resolving power of λ/?λ～3.5×105were recorded in each spectral
D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines 5
0.60.8
1 1.2
8
6
4
(B-V)o Fig.2.Visual absolute magnitude against the color index (B–V)for four cases presented
in this study (thin-solid,dotted,short dashed and long dashed lines for spots with 4870,
4575,4000and 3700K,respectively).We have computed the observed photometry for
stars with T quiet =6344,5655,4988and 4500K,corresponding to (B–V)=0.50,0.68,0.90
and 1.10,respectively.The MS appears as a thick solid line,whereas the MS for twin stars
is represented as a short dashed line (MS–0.75mag ).Pleiades data are displayed as open
circles and the size increases with increasing stellar activity.Star without known activity
appear as plus symbols.Solid diamonds represent our calculations for F spot =0.50.All
calculations are displayed up to F spot =0.80.
range using a 1024×1024pixel Thomson CCD (19μm pixel ?1).Long slit observations
were performed in order to obtain a spatial coverage of 160′′in a given measurement.
Each ?nal spectrum is typically the average of 20independent images (50in the case of
Li),which were reduced using MIDAS following the usual procedure for solar observa-
tions carried out with this instrumentation.Final signal-to-noise ratios are in the range
1000?4000.Additional details on the observations and data reduction can be found in
Barrado y Navascu′e s et al.(1995)and Barrado y Navascu′e s (1996).Table 1shows the
equivalent widths measured for di?erent locations of the observed active region and its
surroundings.Since our original spectra have very high resolution,we were able to remove
either the nearby TiO and CN bands –which appear at low temperatures–in the case of
Li i ,or the weak lines in the case of K i and Na i .These equivalent widths will be used
as the input data for the model proposed in the next section.Additional measurements
(for Na and K)were selected from Tripicchio et al.(1997,1999)for a sunspot at 3700K.
6 D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines
3.The model
We estimate in this section the behavior of the equivalent widths of Na i5896,Li i6708 and K i7699?A lines associated with the presence of active regions in late-type stars. Stellar spots(and other surface inhomogeneities)a?ect the observed photometry due to the lower luminosity of the spot in comparison with that of a quiet region of equivalent size.On the other hand,it is known that the equivalent widths(Ws)of the alkali show di?erent values in di?erent solar regions(as can be seen in Table1)associated with the di?erent temperatures of the line forming regions.A simple mathematical model is used here to compute an“observed”(predicted)color index–in our case,(B-V)–and the corresponding e?ective temperature,as well as the“observed”(predicted)equivalent widths of the alkali lines for a given set of parameters.This model is intended to reproduce what happens in late-type stars from our knowledge of the solar surface.
The computation starts from a?ctitious star free of active regions and having a given e?ective temperature.Then,di?erent active regions(spots and faculae)are added to its photosphere in a similar fashion to that followed by Pallavicini et al.(1993).
https://www.wendangku.net/doc/a16226106.html,puting the photometry
Estimating the observed photometry for a stellar disk which contains spots requires the previous computation of the contribution of the region covered by them,i.e.its ?lling factor,F spot.In a similar way,we should consider the fraction covered by faculae, F faculae,and the fraction?lled with quiet regions.For simplicity,we have supposed that the photometric properties of these two last regions are identical.Therefore,it is only necessary to take into account F spot and{1–F spot}.We have not considered the e?ect of limb darkening either.
The absolute magnitude of the region covered by spots can be expressed by:
M V,spot=M(B?V)spot
V,star ?2.5log{F spot×[R(B?V)
quiet
/R(B?V)
spot
]2},(1)
where M(B?V)spot
V,star
is the magnitude of a star with color index(B–V)equal to that one
of the spot,R(B?V)
quiet
is the radius of a star of color equal to the quite region(the real
radius of the considered star),and R(B?V)
spot
is the radius of a star which would have the same color of the spot.
In the case of the region covered by faculae and the quiet photosphere:
M V,faculae=M(B?V)faculae
V,star
?2.5log F faculae,(2) and
M V,quiet=M(B?V)quiet
V,star
?2.5log{1?F spot?F faculae},(3)
D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines7
where we have assumed that M(B?V)faculae
V,star is equal to M(B?V)quiet
V,star
.In a similar way it is
possible to obtain the absolute magnitude in the B band–M B–for the regions covered by spots,faculae and quiet region,and derive the color indices for each region.
Finally,the observed magnitudes can be predicted using the expression:
M obs
V
=?2.5log{10?0.4×M V,spot+10?0.4×M V,faculae+10?0.4×M V,quiet}.(4)
An equivalent expression gives M obs
B
,allowing the computation of the color index (B–V)obs.The Appendix A contains a detailed justi?cation of these expressions.Some results are shown in Figure1.
https://www.wendangku.net/doc/a16226106.html,puting the equivalent widths
There are several factors which a?ect the observed equivalent widths.They depend, among other parameters,on the?lling factors of spots and faculae.Moreover,the Ws depend on the local continuum level.Therefore,it is necessary to compute the ratios αline,between the?uxes from the region covered by spots and the quiet region(and faculae)at the studied wavelengths–αline=Flux(spot)/Flux(quiet):
αline=
e(K(λ)/T quiet)?1
αline×F spot+F faculae+[1?F spot?F faculae]
,(6)
where W line
obs is the predicted equivalent width for a certain line and W line
spot
,W line
faculae
and
W line
quiet
are the actual equivalent widths of the spot,faculae and quiet region,respectively.
3.3.E?ective temperatures,radii,colors,and magnitudes
Tripicchio et al.(1999)have shown that the potassium equivalent width at7699?A is
an excellent temperature indicator(in a very well de?ned spectral range).Therefore,we
have computed the e?ective temperatures from their expression:
Log(W(K)/7699)=?2.85+3.29×10?5×Te??1.43×10?7×Te?2+1.11×10?11×Te?,(7) Color indices(B–V)were derived from the Thorburn et al.(1993)scale temperature, namely:
Te?=
5040
8 D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines
(a)00.20.40.60.810
123Tspot=3700 K Tspot=4000 K
Tspot=4575 K
Tspot=4870 K
Tquiet=5655 K 00.020.04
-0.0100.010.02
0.60.81 1.2 1.4 1.6
200
300
400600
700
800
900
500
1000
0.60.81 1.2 1.4 1.6
200
300
400600
700
800
900
500
1000
Fig.3.The e?ect on potassium.(a)Relative variation of the observed potassium
equivalent width against the ?lling factor of the spot.The set displayed with solid lines
were computed with T spot =4870K,whereas the set plotted with dotted,short dashed
and long dashed lines corresponds to T spot =4575K,T spot =4000K,and T spot =3700K
For a given set,we computed our results using di?erent faculae ?lling factors.From top to
bottom,F faculae =0.00,0.25,0.50and 0.75.(b)Comparison with Pleiades data.Symbols
as in Figure 2.Values measured/estimated for di?erent sunspots appear with the solar
symbol (dot+circle).(c)Comparison with ?eld stars (from Tripicchio et al.1999).These
main sequence stars are represented as crosses.
Absolutes magnitudes were derived using a Pleiades empirical main sequence (MS,see
Figure 2),with a color excess of E(B-V)=0.04and a distance modulus of (m-M)=5.728.
Other examples of empirical main sequences for the Pleiades,Alpha Persei cluster,M35
and ?eld stars can be found in Bouvier et al.(1998),Stau?er et al.(1999),Barrado y
Navascu′e s et al.(2001b)and Barrado y Navascu′e s et al.(1999),respectively.
D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines9 Table2.Input model parameters for Pleiades and?eld stars.Columns#4and#6 provide the(B-V)and radius of a star with the temperature of the spot.
Quiet Quiet Spot Quiet Spot Quiet Spot
(1)(2)(3)(4)(5)(6)(7)(8)
4.The photometry of active solar-type stars
We have performed a series of simulations under di?erent conditions and obtained?nal values of“observed”(predicted)photometry for a main sequence star.This star has an e?ective temperature corresponding to that of the quiet region,and we have assumed di?erent?lling factors for the spots(in principle,the photometry is not a?ected by the presence of faculae).We have used di?erent spots:one of them corresponds to the average of the actual sunspot.The other one is the central part of it–the nucleus of the umbra–,with lower temperature(4870and4575K,respectively).We have also carried out the computations for spots at4000and3700K.The model was applied to stars with the following initial temperatures:6344,5655,4988and4500K,corresponding to(B–V)=0.500,0.679,0.900and1.100,respectively.Table2lists the initial model parameters (magnitudes,colors,radii,e?ective temperatures).The initial values of potassium and sodium equivalent widths adopted for them are shown in Table3.Lithium equivalent widths and abundances are listed in Table4a and Table4b,in the case of the solar-like case and the Pleiades,respectively.
Figure1a shows the variation of the visual magnitude(?M V,de?ned as the di?er-ence between the magnitude of a star only covered by quiet regions and the observed magnitude;always positive)against the?lling factor of the spots,F spot.The solid line
10 D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines
Table3.Sodium and potassium equivalent widths for Pleiades and?eld stars,in m?A.
Quiet Spot Quiet Spot Quiet Spot
(1)(2)(3)(4)(5)(6)(7)
(1)From W(Na I5896)=0.473×10(?0.788+1.311(B?V)),adapted from Tripicchio et al.(1997).
(2)Measured.See Table1.
(3)From?eld stars.See Figure3c.
(4)From direct measurement.See Tripicchio et al.(1999).
(5)From W(K I7699)=1.042×10(1.719+0.762(B?V)),adapted from Tripicchio et al.(1999).
shows the results for a spot at4870K,the dotted line represents the calculation for a spot at4575K,whereas the short and long dashed lines represent the values for spots with4000and3700K,respectively.Although the luminosity can decrease by a factor 10in the most extreme case,a more realistic situation can be considered in the range 0.0≤F spot≤0.5,which,depending on these particular four spots,corresponds to maxi-mum variations of?V～0.70–0.60mag.These values have been observed in several active binary systems such as CF Tuc,BD+25?161,AY Cet,CC Eri,UX Ari,etc(e.g., Strassmeier et al.1993;Strassmeier1995,and references therein).
Figure1b displays the dependence of the observed color index(B–V)on the spot ?lling factor.It is seen that the color can change considerably,a phenomenon which could have important consequences when comparing stars having a high level of activity with inactive stars(i.e.,rapid versus slow rotators)at the same observed color,because the color of the quiet photosphere is bluer than the observed color.Note the di?erent
D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines11 Table4.a Lithium equivalent widths and abundances for a solar-like case.
Quiet Spot Quiet Quiet Spot Spot
(1)(2)(3)(4)(5)(6)(7)
(1)From Soderblom et al.(1993)curves of growth,using A(Li)=1.00.
(2)Measured.See Table1.
(3)From Pavlenko et al.(1996)curves of growth,using A(Li)=1.00.
behavior for di?erent T quiet,due to the fact that the V?lter is centered around～5500?A,which corresponds to a black-body temperature between the spots at4870and4575 K,whereas the B?lter is centered at～4300?A.Therefore,the relative contributions at the?lters B and V are very di?erent depending on the spot and quiet photosphere temperatures.Under realistic conditions,this change can be up to?(B–V)～0.1.Since there is a relationship between the color indices and the stellar mass,the mass estimated for the more active star would be lower than its actual value in the case of MS https://www.wendangku.net/doc/a16226106.html,ing the presence of photometric variations due to the modulation with phase,as the star rotates,can help to avoid this bias,although the lack of modulation does not guarantee the absence of this bias,since the spots can be distributed in a homogeneus way on the stellar disk,producing null or very small photometric variations.In fact,studies made with tomographic spectroscopy or Doppler imaging(Strassmeier1995;Vogt&Hatzes 1995)and theoretical works(Sch¨u ssler1995),show that the spots in very active systems tend to be concentrated in the poles,staying there for a long period of time(time scale of years),and producing minimum photometric variations.
12 D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines
Table4.b Lithium equivalent widths and abundances for Pleiades stars.
Quiet Spot Quiet Quiet Spot
(1)(2)(3)(4)(5)(6)
(1)From Soderblom et al.(1993)curves of growth,using W(Li)–quiet–from Figure6a.
(2)From Pavlenko et al.(1996)curves of growth,using W(Li)–quiet–from Figure6a.
We have performed several comparisons between the observed data and the predic-tions of this model on the e?ect of the presence of surface inhomogeneities on the pho-tometry and the equivalent widths.A?rst check is provided by the Pleiades open cluster by looking at the location of the active stars in the Color-Magnitude diagram(CMD), where the photometric properties of the late-type stars change due to the presence of surface features with di?erent temperatures.Figure2shows the visual absolute magni-tude against the dereddened color index(B–V)for the four cases presented in this study. The behavior of the observed photometry was computed using a quiet photosphere with four di?erent color indices(0.500,0.679,0.900and1.100)corresponding to the e?ective temperatures listed in Table2.The main sequence appears as a thin solid line,whereas the locus for twin stars(MS–0.75mag)is represented as a dotted line parallel to it.Real data for stars belonging to the Pleiades(Soderblom et al.1993)are included as open circles and the size increases with increasing stellar activity,measured using the Ca ii IR triplet at8542?A(Rλ=8542).Those Pleiades stars without measured calcium appear as plus symbols.Solid diamonds in the?gure represent model predictions for F spot=0.50. Our model shows that the presence of spots shifts the location of these stars almost in
D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines13 parallel with the MS,except when the di?erence between the quiet atmosphere and the stellar spot becomes very large.In this last case,when the spots are at temperatures much lower than the photospheric value,large increments of the observed magnitude with respect to the MS at the same observed color could appear,with almost no change in the color.However,the lack of stars in this region suggests that either such di?erences are not possible(i.e.,T quiet=6344K and T spot=3700K)or the?lling factor must be very small in this case.Therefore,for a given observed color index,the active stars would tend to be located in the lower part of the MS(the less luminous region),even below the MS of single and inactive stars.In the most extreme case,they could be found below the Zero Age Main Sequence(ZAMS).However,the comparison with the Pleiades shows that this phenomenon is not observed.Several factors can explain this situation:?rst, the physical size of the cluster can introduce a scatter in the CMD equivalent to several tenths of magnitude,which can hide the e?ect of the activity on the photometry(i.e. Barrado y Navascu′e s&Stau?er1996).On the other hand,an important fraction of the stars are in fact binaries and each component can have a di?erent degree of activity,a case not included in the assumptions made in our simple model.However,the e?ect of stellar spot on the observed photometry of star suggests that it might be in?uencing on the Hipparcos problem(i.e.,the fact that the locus of very well known,nearby open clusters whose distance have been measured by the Hipparcos satellite.See Pinsonneault et al.2000;Robichon et al.2000,and references therein),in the sense that two open clusters of similar ages but very di?erent rotational velocity distributions might have a shift in the locus of their main sequence when compared with each other.In summary, Figure2shows that the photometry obtained using our model is compatible with the observational data and their uncertainties for situations showing not large di?erences between T quiet and T spot and realistic values of F spot.
5.The e?ect of stellar spots and faculae on the alkali
5.1.Potassium(K i7699?A)
The direct comparison between the W(K i7699?A)corresponding to di?erent regions of the solar photosphere indicates that the variations due to the presence of spots have to be small,except for large values of the spot?lling factor.Figure3a shows the relative variation of the observed W(K)against F spot for the solar-like case.In the most extreme cases,when F spot～1,changes close to a300%can be reached.However,the more realistic values shown in the?gure indicate changes between0%and50%.In any case, this kind of variation due to spots should be easily observed,as we show below.
Figure3a includes several sets of curves:the dotted lines represent the results obtained using a spot at4575K and di?erent values of the faculae?lling factor.From top to
14 D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines
(a)
00.20.40.60.810
0.5
11.522.53
3.54
4.5Tquiet=5655 K Tspot=4870 K Tspot=4575 K Tspot=4000 K Tspot=3700 K
00.020.04
-0.1-0.05
0.50.751 1.25 1.5200300400
500
600
700
800
900
1000
2000
3000400050006000
Fig.4.(a)Variations of the sodium equivalent width against the spot ?lling factor.
Symbols as in Figure 3a.(b)Variations of the sodium equivalent width against (B–V)
color index.Field dwarfs from Tripicchio et al.(1997)are displayed as crosses.
bottom,F faculae =0.00,0.25,0.50and 0.75.The solid lines correspond to the computations
for T spot =4870K.Other sets,computed with T spot =4000K and T spot =3700K,are
shown as short and long dashed lines,respectively.A detail of the graph appears in
the box (we only display the ?rst two cases).Essentially,the values of F faculae do not
a?ect the observed value of W(K),as a consequence of the small di?erence between the
measured equivalent widths in the quiet region and the faculae.
In an analogous way to the previous ?gure,it is possible to compare the variations
of the W(K)with (B–V)–the values that would be observed,in both cases.There is a
quasi-linear relation between both quantities.However,a more interesting comparison
is made in Figure 3b,where we have included real data corresponding to the Pleiades
cluster (Soderblom et al.1993).The size of the symbols,as in Figure 2,increases with
increasing stellar activity (measured using R λ=8542).As noted by Soderblom et al.(1993),
in the range 0.50≤(B–V)≤0.80there is a clear trend between activity and the potassium
equivalent width for a given value of (B–V):the larger the activity,the larger W(K).The
reproduction of this behavior has been attempted previously by Stuik et al.(1997),using
a purely theoretical model under NLTE conditions.However,their models were not able
to match the Pleiades observations (see their Figure 8).
In order to verify if our empirical approximation would be able to match the behavior
observed in the Pleiades,we proceeded as described in Section 3.We computed the
D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines15 results using four di?erent situations:a star having a color(B–V)=0.500,another star having a color corresponding to that one of the quiet region surrounding the sunspot –(B–V)=0.679–,a third star with(B–V)=0.900,and another with(B–V)=1.100,the same values used for the simulations shown in Figure2.We used spots at four di?erent temperatures(4870,4575,4000and3700K),indicated with solid,dotted,short dashed and long dashed lines.The solar symbols(dots plus circles)indicate the location of the quiet sun and the data for the solar spots.A comparison with?eld dwarfs,from Tripicchio et al.(1999)are displayed in Figure3c.In this case,?eld stars are shown as crosses.Unfortunately,information regarding the activity of these stars is available for only a handful of them.
As can be concluded from Figure3b and Figure3c,the behavior of W(K)is well reproduced despite the simplicity of the procedure.It explains why active stars tend to have larger equivalent widths.The model also explains why there is not a sharp distinction between the location of inactive and active stars:it is predicted that there are locations where it is possible to?nd stars having high and intermediate activity,or intermediate and low activity.This is because stars having di?erent masses are compared:since the activity of the more massive stars modi?es the observed photometry to a greater extent,both stars(the very active and the less active)have similar apparent colors.Note,however, that realistic values of the spot?lling factor(F spot≤0.50;indicated by solid diamonds in Fig.3b)cannot reproduce those stars having the largest values of the W(K i7699)for a given color.On the other hand,the?gures should be interpreted with some caution,since the model is rather sensitive to the initial conditions(i.e.,the initial e?ective temperature of the spot and the quiet photosphere and the potassium equivalent width of the spot).
5.2.Sodium(Na i5896?A)
As it is shown in Table1,the W(Na)is much larger in a sunspot than in the quiet region. Therefore,the observed value of the equivalent width changes in a much larger amount than in the case of potassium for the same?lling factor of the spot,although the relative variation is similar for both K i and Na i(with respect to their respective equivalent widths).Figures3a and4a illustrate this fact.In addition,the model predicts that the observed value for Na i could be smaller than the equivalent width corresponding to the star when it is inactive.This unlikely situation would appear if an important fraction of the surface were covered by active regions(faculae)but having very small spot coverage. In any case,the important result coming from this?gure is that it is possible to have a situation in which a high degree of activity corresponds with no variations of the W(Na). This would happen if the active regions were distributed homogeneously,or for certain combinations of the values of F spot and F faculae.
16
D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines
(a)
00.20.40.60.81051015202530354045
Tquiet=5655 K Tspot=3700 K Tspot=4000 K
Tspot=4575 K
Tspot=4870 K 00.050.100.25
0.650.70.750.80.850.90.951 1.05 1.1 1.15 1.2
4
567891020
30
40
50
60
70
80
9025
100200
00.51 1.52 2.5
10
203040Fig.5.(a)Variations of the lithium doublet equivalent width against the spot ?lling
factor.(b)Lithium equivalent width versus (B–V)color index.(c)Variations of the
lithium doublet equivalent width against photometric variations.A detail of these graphs
are displayed in the small boxes.Symbols as in Figure 3a.
Figure 4b plots predicted W(Na)against (B–V).We have included in the ?gure,as
crosses,data corresponding to ?eld dwarfs (Tripicchio et al.1997).Note that the ?eld
stars could have di?erent abundances of sodium.However,assuming a similar abundance,
our model is able,in principle,to explain the scatter of the observed W(Na).Although,
to our knowledge,there are no studies about the behavior of this doublet in late-type
stars for young clusters,we would expect in principle a similar behavior to the case
of K i 7699?A (i.e.,for a given color,the larger the activity,the larger the equivalent
width).However,there is a signi?cant di?erence between Na i 5896and K i 7699?A lines:
the signi?cant di?erence of equivalent widths between faculae and quiet regions for Na i ,
which is not observed for K i .So,the scatter displayed in Figure 3b (potassium equivalent
D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines 17
0.40.60.8
1 1.
2 1.420
3040
60
70
80
90
50
100200300400
500
(B-V)o
7000600050004000
1
23
4Teff (K)https://www.wendangku.net/doc/a16226106.html,parison with Pleiades data:(a)Lithium equivalent width against color.(b)
Lithium abundance against e?ective temperature.Symbols as in Figure 2.We have also
included the case for the Sun.
width against color index)might be di?erent in a similar plot for sodium.Therefore,a
sample of coeval stars of di?erent colors might not show a clear relationship between
activity and W(Na),since a star can have a large activity and,simultaneously,change
minimally the equivalent width of Na i 5896?A (if a large fraction of the stellar surface is
covered with active regions).This is a very interesting tool to verify the e?ect of spots
and faculae on the equivalent widths of alkali.
5.3.Lithium (Li i 6708?A )
5.3.1.The behavior of the W(Li)
The study of the variation of the lithium equivalent width due to the presence of surface
inhomogeneities (spots and faculae)can provide essential hints to understand the abun-
dances derived for stars with a high level of activity,such as chromospherically active
binary systems and rapid rotators belonging to young clusters.
Our model predicts a large variation in W(Li),even close to 3500%,due to the
presence of spots.This can be clearly seen in Figure 5a.This kind of variation has
already been predicted by Giampapa (1984).The behavior of the lithium line is very
sensitive to the temperature of the spot.
As for Na i 5896?A ,the presence of faculae is an important factor that can alter
the observed equivalent widths to a signi?cant degree,even reducing it when comparing
18 D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines
Fig.7.Behavior of the di?erences of lithium abundances(A(Li)model–A(Li)initial)against spot?lling factor(a),(B–V)index(b),photometric variations(c),and e?ective temper-ature(d).Symbols as in Figure3a.In all cases A(Li)initial=1.00dex.
with the characteristic value of a quiet region.Figure5a shows that a solar-like star could have null variations of W(Li)under a wide variety of situations,all of them realistic.This occurs when the?lling factor of the spots is small and a signi?cant part of the photosphere is covered with faculae.
D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines19
Figure5b shows the extraordinary change of the W(Li)as the observed(B–V)color increases in the solar-like case,as a consequence of the presence of active regions.The dependence on the spot temperature is evident:the smaller the temperature,the larger the observed W(Li)and color.
Pallavicini et al.(1993),in a quasi-simultaneous study involving photometry and spectroscopy(measuring Li i6708and Ca i6718?A)of4active stars,did not observe any change in the equivalent width of the Li line,even when these objects presented important photometric variations(up to0.10mag).Our model provides an explanation for this apparent puzzle.Although the values of F spot which correspond to?V=0.10 mag could produce important increments in W(Li),taking into account the faculae in the simulation changes the scenario completely.The region covered by faculae has a very reduced value of the W(Li)and tends to dilute the line produced by the quiet region and by the spot.Moreover,the presence of faculae is not detected in the photometric modulation.It is reasonable to assume that the fraction of the stellar disk covered by faculae has to be at least as large as the fraction covered by spots.The?nal consequence is that a star having high or moderate activity can experience important photometric variations together with reduced variations in the Li equivalent width(either positive or negative),as Figure5c demonstrates,where we represent the relative variation of the equivalent width of lithium against the photometric variation.
5.3.2.A second comparison with the Pleiades
An additional check to our model can be performed by comparing it,again,with Pleiades data.Figure6shows actual Li data(Soderblom et al.1993),where the size of the symbols increases with increasing activity.Simulations with di?erent photospheric temperatures are displayed,computed with spots with four temperatures(4870,4575,4000and3700 K;solid,and dotted,short and long dashed lines,respectively).As with potassium,the spread on the observed lithium equivalent widths in the Pleiades can be reproduced (Figure6a).However,in the lithium case,only part of the spread could be due to the e?ect of the stellar inhomogeneities,since our curves,even for very large?lling factors,do not cover the whole area where the Pleiades stars are located.However,the simulations can explain the trend with stellar activity(for a given color):active stars have a larger value of W(Li).Therefore,part of the spread in the equivalent widths could be due to the simultaneous e?ect of the surface inhomogeneities on the observed equivalent width and color.Some of the cases would require,however,a(non–realistic)very large?lling factor or a large di?erence between the temperature of the quiet photosphere and the spot.
20 D.Barrado y Navascu′e s et al.:The e?ect of stellar activity on alkali lines
2040608050200200300400
500
2004006008001000200040006000200
300
400600
700800
900
500
1000
Fig.8.a Comparison between the relative variations of potassium and lithium for the
Pleiades.Symbols as in Figure 3b.b Comparison between the relative variations of potas-
sium and sodium for ?eld stars.Symbols as in Figure 3c.The last point in our calculations
corresponds to F spot =0.80.
The A(Li)-T e?plane (Figure 6b,where A(Li)=log(Li /H)+12)provides complemen-
tary information.Predicted equivalent widths were translated into Li abundances using
the curves of growth by Soderblom et al.(1993).In the case of temperatures below 4000K
(the lowest temperature of these curves of growth),we used those published by Pavlenko
et al.(1996).Predicted abundances tend to move the observed values to lower e?ective
temperatures for the most active stars,therefore reducing the spread in the abundance
and the rotation-activity relation.The lithium abundances for active stars appear then
to be correct but their location should be shifted toward higher temperatures in the
A(Li)-T e?plane due to the e?ect of the spots on the colors.We must note,however,
that only very large activity levels would change the morphology of the T e?-A(Li)plane.
Even spot ?lling factors close to F spot =0.50move the location of a star in this diagram
by ～180K only towards cooler temperatures.On the other hand,as discussed before,
our simulations do not explain the high lithium abundances in the range 5200–4600K.
Therefore,it seems that these abundances are real and that an important fraction the
lithium spread which is present in the ?gure is real,and that the rotation is a key factor
in the evolution of the lithium abundance in the late spectral type stars.
on the contrary的解析
On the contrary Onthecontrary, I have not yet begun. 正好相反，我还没有开始。 https://www.wendangku.net/doc/a16226106.html, Onthecontrary, the instructions have been damaged. 反之，则说明已经损坏。 https://www.wendangku.net/doc/a16226106.html, Onthecontrary, I understand all too well. 恰恰相反，我很清楚 https://www.wendangku.net/doc/a16226106.html, Onthecontrary, I think this is good. ⑴我反而觉得这是好事。 https://www.wendangku.net/doc/a16226106.html, Onthecontrary, I have tons of things to do 正相反，我有一大堆事要做 Provided by jukuu Is likely onthecontrary I in works for you 反倒像是我在为你们工作 https://www.wendangku.net/doc/a16226106.html, Onthecontrary, or to buy the first good. 反之还是先买的好。 https://www.wendangku.net/doc/a16226106.html, Onthecontrary, it is typically american. 相反，这正是典型的美国风格。 222.35.143.196 Onthecontrary, very exciting.
恰恰相反，非常刺激。 https://www.wendangku.net/doc/a16226106.html, But onthecontrary, lazy. 却恰恰相反，懒洋洋的。 https://www.wendangku.net/doc/a16226106.html, Onthecontrary, I hate it! 恰恰相反，我不喜欢！ https://www.wendangku.net/doc/a16226106.html, Onthecontrary, the club gathers every month. 相反，俱乐部每个月都聚会。 https://www.wendangku.net/doc/a16226106.html, Onthecontrary, I'm going to work harder. 我反而将更努力工作。 https://www.wendangku.net/doc/a16226106.html, Onthecontrary, his demeanor is easy and nonchalant. 相反，他的举止轻松而无动于衷。 https://www.wendangku.net/doc/a16226106.html, Too much nutrition onthecontrary can not be absorbed through skin. 太过营养了反而皮肤吸收不了. https://www.wendangku.net/doc/a16226106.html, Onthecontrary, I would wish for it no other way. 正相反，我正希望这样 Provided by jukuu Onthecontrary most likely pathological. 反之很有可能是病理性的。 https://www.wendangku.net/doc/a16226106.html, Onthecontrary, it will appear clumsy. 反之，就会显得粗笨。 https://www.wendangku.net/doc/a16226106.html,
英语造句
一般过去式 时间状语：yesterday just now (刚刚) the day before three days ag0 a week ago in 1880 last month last year 1. I was in the classroom yesterday. I was not in the classroom yesterday. Were you in the classroom yesterday. 2. They went to see the film the day before. Did they go to see the film the day before. They did go to see the film the day before. 3. The man beat his wife yesterday. The man didn’t beat his wife yesterday. 4. I was a high student three years ago. 5. She became a teacher in 2009. 6. They began to study english a week ago 7. My mother brought a book from Canada last year. 8.My parents build a house to me four years ago . 9.He was husband ago. She was a cooker last mouth. My father was in the Xinjiang half a year ago. 10.My grandfather was a famer six years ago. 11.He burned in 1991
学生造句--Unit 1
●I wonder if it’s because I have been at school for so long that I’ve grown so crazy about going home. ●It is because she wasn’t well that she fell far behind her classmates this semester. ●I can well remember that there was a time when I took it for granted that friends should do everything for me. ●In order to make a difference to society, they spent almost all of their spare time in raising money for the charity. ●It’s no pleasure eating at school any longer because the food is not so tasty as that at home. ●He happened to be hit by a new idea when he was walking along the riverbank. ●I wonder if I can cope with stressful situations in life independently. ●It is because I take things for granted that I make so many mistakes. ●The treasure is so rare that a growing number of people are looking for it. ●He picks on the weak mn in order that we may pay attention to him. ●It’s no pleasure being disturbed whena I settle down to my work. ●I can well remember that when I was a child, I always made mistakes on purpose for fun. ●It’s no pleasure accompany her hanging out on the street on such a rainy day. ●I can well remember that there was a time when I threw my whole self into study in order to live up to my parents’ expectation and enter my dream university. ●I can well remember that she stuck with me all the time and helped me regain my confidence during my tough time five years ago. ●It is because he makes it a priority to study that he always gets good grades. ●I wonder if we should abandon this idea because there is no point in doing so. ●I wonder if it was because I ate ice-cream that I had an upset student this morning. ●It is because she refused to die that she became incredibly successful. ●She is so considerate that many of us turn to her for comfort. ●I can well remember that once I underestimated the power of words and hurt my friend. ●He works extremely hard in order to live up to his expectations. ●I happened to see a butterfly settle on the beautiful flower. ●It’s no pleasure making fun of others. ●It was the first time in the new semester that I had burned the midnight oil to study. ●It’s no pleasure taking everything into account when you long to have the relaxing life. ●I wonder if it was because he abandoned himself to despair that he was killed in a car accident when he was driving. ●Jack is always picking on younger children in order to show off his power. ●It is because he always burns the midnight oil that he oversleeps sometimes. ●I happened to find some pictures to do with my grandfather when I was going through the drawer. ●It was because I didn’t dare look at the failure face to face that I failed again. ●I tell my friend that failure is not scary in order that she can rebound from failure. ●I throw my whole self to study in order to pass the final exam. ●It was the first time that I had made a speech in public and enjoyed the thunder of applause. ●Alice happened to be on the street when a UFO landed right in front of her. ●It was the first time that I had kept myself open and talked sincerely with my parents. ●It was a beautiful sunny day. The weather was so comfortable that I settled myself into the
英语句子结构和造句
高中英语~词性~句子成分~语法构成 第一章节：英语句子中的词性 1.名词：n. 名词是指事物的名称，在句子中主要作主语.宾语.表语.同位语。 2.形容词;adj. 形容词是指对名词进行修饰~限定~描述~的成份，主要作定语.表语.。形容词在汉语中是（的）.其标志是: ous. Al .ful .ive。. 3.动词：vt. 动词是指主语发出的一个动作，一般用来作谓语。 4.副词：adv. 副词是指表示动作发生的地点. 时间. 条件. 方式. 原因. 目的. 结果.伴随让步. 一般用来修饰动词. 形容词。副词在汉语中是（地）.其标志是：ly。 5.代词：pron. 代词是指用来代替名词的词，名词所能担任的作用，代词也同样.代词主要用来作主语. 宾语. 表语. 同位语。 6.介词：prep.介词是指表示动词和名次关系的词，例如：in on at of about with for to。其特征：
介词后的动词要用—ing形式。介词加代词时，代词要用宾格。例如：give up her（him）这种形式是正确的，而give up she（he）这种形式是错误的。 7.冠词：冠词是指修饰名词，表名词泛指或特指。冠词有a an the 。 8.叹词：叹词表示一种语气。例如：OH. Ya 等 9.连词：连词是指连接两个并列的成分，这两个并列的成分可以是两个词也可以是两个句子。例如：and but or so 。 10.数词：数词是指表示数量关系词，一般分为基数词和序数词 第二章节：英语句子成分 主语：动作的发出者，一般放在动词前或句首。由名词. 代词. 数词. 不定时. 动名词. 或从句充当。 谓语：指主语发出来的动作，只能由动词充当，一般紧跟在主语后面。 宾语：指动作的承受着，一般由代词. 名词. 数词. 不定时. 动名词. 或从句充当. 介词后面的成分也叫介词宾语。 定语：只对名词起限定修饰的成分，一般由形容
六级单词解析造句记忆MNO
M A: Has the case been closed yet? B: No, the magistrate still needs to decide the outcome. magistrate n.地方行政官，地方法官，治安官 A: I am unable to read the small print in the book. B: It seems you need to magnify it. magnify vt.１．放大，扩大；２．夸大，夸张 A: That was a terrible storm. B: Indeed, but it is too early to determine the magnitude of the damage. magnitude n.１．重要性，重大；２．巨大，广大 A: A young fair maiden like you shouldn’t be single. B: That is because I am a young fair independent maiden. maiden n.少女，年轻姑娘，未婚女子 a.首次的，初次的 A: You look majestic sitting on that high chair. B: Yes, I am pretending to be the king! majestic a.雄伟的，壮丽的，庄严的，高贵的 A: Please cook me dinner now. B: Yes, your majesty, I’m at your service. majesty n.１．［Ｍ－］陛下（对帝王，王后的尊称）；２．雄伟，壮丽，庄严 A: Doctor, I traveled to Africa and I think I caught malaria. B: Did you take any medicine as a precaution? malaria n.疟疾 A: I hate you! B: Why are you so full of malice? malice n.恶意，怨恨 A: I’m afraid that the test results have come back and your lump is malignant. B: That means it’s serious, doesn’t it, doctor? malignant a.１．恶性的，致命的；２．恶意的，恶毒的 A: I’m going shopping in the mall this afternoon, want to join me? B: No, thanks, I have plans already. mall n.（由许多商店组成的）购物中心 A: That child looks very unhealthy. B: Yes, he does not have enough to eat. He is suffering from malnutrition.
base on的例句
意见应以事实为根据. 3 来自辞典例句 192. The bombers swooped ( down ) onthe air base. 轰炸机 突袭 空军基地. 来自辞典例句 193. He mounted their engines on a rubber base. 他把他们的发动机装在一个橡胶垫座上. 14 来自辞典例句 194. The column stands on a narrow base. 柱子竖立在狭窄的地基上. 14 来自辞典例句 195. When one stretched it, it looked like grey flakes on the carvas base. 你要是把它摊直, 看上去就象好一些灰色的粉片落在帆布底子上. 18 来自辞典例句 196. Economic growth and human well - being depend on the natural resource base that supports all living systems. 经济增长和人类的福利依赖于支持所有生命系统的自然资源. 12 1 来自辞典例句 197. The base was just a smudge onthe untouched hundred - mile coast of Manila Bay. 那基地只是马尼拉湾一百英里长安然无恙的海岸线上一个硝烟滚滚的污点. 6 来自辞典例句 198. You can't base an operation on the presumption that miracles are going to happen. 你不能把行动计划建筑在可能出现奇迹的假想基础上.
英语造句大全
英语造句大全English sentence 在句子中，更好的记忆单词！ 1、(1)、able adj. 能 句子：We are able to live under the sea in the future. (2)、ability n. 能力 句子：Most school care for children of different abilities. (3)、enable v. 使。。。能句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的句子：We must have the accurate calculation. (2)、accurately adv. 精确地 句子：His calculation is accurately. 3、(1)、act v. 扮演 句子：He act the interesting character. （2）、actor n. 演员 句子：He was a famous actor. (3)、actress n. 女演员 句子：She was a famous actress. (4)、active adj. 积极的 句子：He is an active boy. 4、add v. 加 句子：He adds a little sugar in the milk. 5、advantage n. 优势 句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n.
(完整版)主谓造句
主语+谓语 1. 理解主谓结构 1) The students arrived. The students arrived at the park. 2) They are listening. They are listening to the music. 3) The disaster happened. 2．体会状语的位置 1) Tom always works hard. 2) Sometimes I go to the park at weekends.. 3) The girl cries very often. 4) We seldom come here. The disaster happened to the poor family. 3. 多个状语的排列次序 1) He works. 2) He works hard. 3) He always works hard. 4) He always works hard in the company. 5) He always works hard in the company recently. 6) He always works hard in the company recently because he wants to get promoted. 4. 写作常用不及物动词 1. ache My head aches. I’m aching all over. 2. agree agree with sb. about sth. agree to do sth. 3. apologize to sb. for sth. 4. appear (at the meeting, on the screen) 5. arrive at / in 6. belong to 7. chat with sb. about sth. 8. come (to …) 9. cry 10. dance 11. depend on /upon 12. die 13. fall 14. go to … 15. graduate from 16. … happen 17. laugh 18. listen to... 19. live 20. rise 21. sit 22. smile 23. swim 24. stay (at home / in a hotel) 25. work 26. wait for 汉译英： 1.昨天我去了电影院。 2.我能用英语跟外国人自由交谈。 3.晚上7点我们到达了机场。 4.暑假就要到了。 5.现在很多老人独自居住。 6.老师同意了。 7.刚才发生了一场车祸。 8.课上我们应该认真听讲。9. 我们的态度很重要。 10. 能否成功取决于你的态度。 11. 能取得多大进步取决于你付出多少努力。 12. 这个木桶能盛多少水取决于最短的一块板子的长度。
初中英语造句
【it's time to和it's time for】 ——————这其实是一个句型,只不过后面要跟不同的东西. ——————It's time to跟的是不定式（to do）.也就是说,要跟一个动词,意思是“到做某事的时候了”.如： It's time to go home. It's time to tell him the truth. ——————It's time for 跟的是名词.也就是说,不能跟动词.如： It's time for lunch.(没必要说It's time to have lunch) It's time for class.(没必要说It's time to begin the class.) They can't wait to see you Please ask liming to study tonight. Please ask liming not to play computer games tonight. Don’t make/let me to smoke I can hear/see you dance at the stage You had better go to bed early. You had better not watch tv It’s better to go to bed early It’s best to run in the morning I am enjoy running with music. With 表伴随听音乐 I already finish studying You should keep working. You should keep on studying English Keep calm and carry on 保持冷静继续前行二战开始前英国皇家政府制造的海报名字 I have to go on studying I feel like I am flying I have to stop playing computer games and stop to go home now I forget/remember to finish my homework. I forget/remember cleaning the classroom We keep/percent/stop him from eating more chips I prefer orange to apple I prefer to walk rather than run I used to sing when I was young What’s wrong with you There have nothing to do with you I am so busy studying You are too young to na?ve I am so tired that I have to go to bed early
The Kite Runner-美句摘抄及造句
《The Kite Runner》追风筝的人--------------------------------美句摘抄 1.I can still see Hassan up on that tree, sunlight flickering through the leaves on his almost perfectly round face, a face like a Chinese doll chiseled from hardwood: his flat, broad nose and slanting, narrow eyes like bamboo leaves, eyes that looked, depending on the light, gold, green even sapphire 翻译：我依然能记得哈桑坐在树上的样子，阳光穿过叶子，照着他那浑圆的脸庞。他的脸很像木头刻成的中国娃娃，鼻子大而扁平，双眼眯斜如同竹叶，在不同光线下会显现出金色、绿色，甚至是宝石蓝。 E.g.: A shadow of disquiet flickering over his face. 2.Never told that the mirror, like shooting walnuts at the neighbor's dog, was always my idea. 翻译：从来不提镜子、用胡桃射狗其实都是我的鬼主意。E.g.:His secret died with him, for he never told anyone. 3.We would sit across from each other on a pair of high
翻译加造句
一、翻译 1. The idea of consciously seeking out a special title was new to me., but not without appeal. 让我自己挑选自己最喜欢的书籍这个有意思的想法真的对我具有吸引力。 2.I was plunged into the aching tragedy of the Holocaust, the extraordinary clash of good, represented by the one decent man, and evil. 我陷入到大屠杀悲剧的痛苦之中，一个体面的人所代表的善与恶的猛烈冲击之中。 3.I was astonished by the the great power a novel could contain. I lacked the vocabulary to translate my feelings into words. 我被这部小说所包含的巨大能量感到震惊。我无法用语言来表达我的感情（心情）。 4，make sth. long to short长话短说 5.I learned that summer that reading was not the innocent(简单的) pastime(消遣) I have assumed it to be., not a breezy, instantly forgettable escape in the hammock(吊床)，( though I’ ve enjoyed many of those too ). I discovered that a book, if it arrives at the right moment, in the proper season, will change the course of all that follows. 那年夏天，我懂得了读书不是我认为的简单的娱乐消遣，也不只是躺在吊床上，一阵风吹过就忘记的消遣。我发现如果在适宜的时间、合适的季节读一本书的话，他将能改变一个人以后的人生道路。 二、词组造句 1. on purpose 特意，故意 This is especially true here, and it was ~. (这一点在这里尤其准确，并且他是故意的) 2.think up 虚构，编造，想出 She has thought up a good idea. 她想出了一个好的主意。 His story was thought up. 他的故事是编出来的。 3. in the meantime 与此同时 助记：in advance 事前in the meantime 与此同时in place 适当地... In the meantime, what can you do? 在这期间您能做什么呢？ In the meantime, we may not know how it works, but we know that it works. 在此期间，我们不知道它是如何工作的，但我们知道，它的确在发挥作用。 4.as though 好像，仿佛 It sounds as though you enjoyed Great wall. 这听起来好像你喜欢长城。 5. plunge into 使陷入 He plunged the room into darkness by switching off the light. 他把灯一关，房
改写句子练习2标准答案
The effective sentences:(improve the sentences!) 1.She hopes to spend this holiday either in Shanghai or in Suzhou. 2.Showing/to show sincerity and to keep/keeping promises are the basic requirements of a real friend. 3.I want to know the space of this house and when it was built. I want to know how big this house is and when it was built. I want to know the space of this house and the building time of the house. 4.In the past ten years,Mr.Smith has been a waiter,a tour guide,and taught English. In the past ten years,Mr.Smith has been a waiter,a tour guide,and an English teacher. 5.They are sweeping the floor wearing masks. They are sweeping the floor by wearing masks. wearing masks,They are sweeping the floor. 6.the drivers are told to drive carefully on the radio. the drivers are told on the radio to drive carefully 7.I almost spent two hours on this exercises. I spent almost two hours on this exercises. 8.Checking carefully,a serious mistake was found in the design. Checking carefully,I found a serious mistake in the design.
用以下短语造句
M1 U1 一. 把下列短语填入每个句子的空白处（注意所填短语的形式变化）： add up (to) be concerned about go through set down a series of on purpose in order to according to get along with fall in love (with) join in have got to hide away face to face 1 We’ve chatted online for some time but we have never met ___________. 2 It is nearly 11 o’clock yet he is not back. His mother ____________ him. 3 The Lius ___________ hard times before liberation. 4 ____________ get a good mark I worked very hard before the exam. 5 I think the window was broken ___________ by someone. 6 You should ___________ the language points on the blackboard. They are useful. 7 They met at Tom’s party and later on ____________ with each other. 8 You can find ____________ English reading materials in the school library. 9 I am easy to be with and _____________my classmates pretty well. 10 They __________ in a small village so that they might not be found. 11 Which of the following statements is not right ____________ the above passage? 12 It’s getting dark. I ___________ be off now. 13 More than 1,000 workers ___________ the general strike last week. 14 All her earnings _____________ about 3,000 yuan per month. 二.用以下短语造句： 1.go through 2. no longer/ not… any longer 3. on purpose 4. calm… down 5. happen to 6. set down 7. wonder if 三. 翻译： 1.曾经有段时间，我对学习丧失了兴趣。（there was a time when…） 2. 这是我第一次和她交流。（It is/was the first time that …注意时态） 3.他昨天公园里遇到的是他的一个老朋友。（强调句） 4. 他是在知道真相之后才意识到错怪女儿了。（强调句） M 1 U 2 一. 把下列短语填入每个句子的空白处（注意所填短语的形式变化）： play a …role (in) because of come up such as even if play a …part (in) 1 Dujiangyan(都江堰) is still ___________in irrigation(灌溉) today. 2 That question ___________ at yesterday’s meeting. 3 Karl Marx could speak a few foreign languages, _________Russian and English. 4 You must ask for leave first __________ you have something very important. 5 The media _________ major ________ in influencing people’s opinion s. 6 _________ years of hard work she looked like a woman in her fifties. 二.用以下短语造句： 1.make (good/full) use of 2. play a(n) important role in 3. even if 4. believe it or not 5. such as 6. because of
英语造句
English sentence 1、(1)、able adj. 能 句子：We are able to live under the sea in the future. (2)、ability n. 能力 句子：Most school care for children of different abilities. (3)、enable v. 使。。。能 句子：This pass enables me to travel half-price on trains. 2、(1)、accurate adj. 精确的 句子：We must have the accurate calculation. (2)、accurately adv. 精确地 句子：His calculation is accurately. 3、(1)、act v. 扮演 句子：He act the interesting character.（2）、actor n. 演员 句子：He was a famous actor. (3)、actress n. 女演员 句子：She was a famous actress. (4)、active adj. 积极的 句子：He is an active boy. 4、add v. 加 句子：He adds a little sugar in the milk. 5、advantage n. 优势 句子：His advantage is fight. 6、age 年龄n. 句子：His age is 15. 7、amusing 娱人的adj. 句子：This story is amusing. 8、angry 生气的adj. 句子：He is angry. 9、America 美国n. 句子：He is in America. 10、appear 出现v. He appears in this place. 11. artist 艺术家n. He is an artist. 12. attract 吸引 He attracts the dog. 13. Australia 澳大利亚 He is in Australia. 14.base 基地 She is in the base now. 15.basket 篮子 His basket is nice. 16.beautiful 美丽的 She is very beautiful. 17.begin 开始 He begins writing. 18.black 黑色的 He is black. 19.bright 明亮的 His eyes are bright. 20.good 好的 He is good at basketball. 21.British 英国人 He is British. 22.building 建造物 The building is highest in this city 23.busy 忙的 He is busy now. 24.calculate 计算 He calculates this test well. 25.Canada 加拿大 He borns in Canada. 26.care 照顾 He cared she yesterday. 27.certain 无疑的 They are certain to succeed. 28.change 改变 He changes the system. 29.chemical 化学药品