Photometric searches for transiting planets results and challenges

a r X i v :a s t r o -p h /0510846v 1 31 O c t 2005

Tenth anniversary of 51Peg-b :Status of and prospects for hot Jupiter studies Proceedings of Haute Provence Observatory Colloquium (22-25august 2005)Edited by L.Arnold,F.Bouchy,&C.Moutou

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2m)on smaller ?elds and fainter stars (14-20mag),and from space with the HST.On paper,these surveys could be expected to detect dozens or even hundreds of hot Jupiters (e.g.Horne 2001).Even the most modest of the surveys were expected to ?nd one or two transiting hot Jupiters each season.

The results up to now,however,have been meager in compari-son with initial expectations.Most surveys have failed to con?rm any transiting exoplanet candidate.Indeed only two surveys,the TrES net-work (Alonso et al.2004)and the OGLE survey (Konacki et al.2003,Bouchy et al.2004,Pont et al.2004,Konacki et al.2005)have yielded any detection at all.The OGLE survey alone can be credited with 5of the 6transiting planets found by ground-based transit surveys.In this review,I will concentrate on the OGLE survey,considering how the conclusions from the analysis and follow-up of the OGLE data are also relevant to other surveys generally,in particular to the issue of why the yield of most surveys has been

modest.

Figure 1.:Mass-radius relation for the known transiting exoplanets.

2.The OGLE planetary transit candidates

Using the 1.3-m Warsaw University Telescope at Las Campanas Obser-vatory (Chile)with an 8k ×8k CCD mosaic covering a 0.34deg 2?eld-of-view,the OGLE-III survey (Udalski et al.2002a-c,2004)has realised an extensive photometric search for planetary and low-luminosity ob-ject transits.In four observing seasons,about 3square degrees near the Galactic plane were monitored for periodic eclipse signals with depth from a few per cent down to slightly below one per cent.Altogether

Title of contribution3 177shallow periodic transit signals were detected and announced.The radii of the transiting low-luminosity objects,estimated from the shape of the transit signal,range from0.5Jupiter radius to0.5solar radius, and their orbital periods from0.8to8days.The smallest objects could be suspected to be extrasolar giant planets,but the radius estimated from the photometric signal is not su?cient to conclude on the plan-etary nature of the objects.They could as well be brown dwarfs or low-mass stars,since in the low mass regime(M<0.1M⊙)the radius becomes practically independent of the mass.Some con?gurations of grazing binary eclipses and of eclipsing binaries in multiple systems can also mimic a planetary transit signal.

Some indications on the nature of the OGLE transiting companion can be gathered from the light curve(e.g.Sirko&Paczyincki2003)and with low-resolution spectroscopy(e.g.Dreizler et al.2003,Gallardo et al.2005).However,high-accuracy radial velocity follow-up is the only way to con?rm the exact nature of the systems by measuring the true mass of the companions.The spectroscopy of the central star,which is a by-product of the radial velocity measurement,allows to constrain the radius of the star and hence the real size of the transiting companion. The measurement of the true mass of the companion by the radial velocity orbit,coupled with the measurement of its radius,also leads to a direct measurement of its mean density.

The di?culty of Doppler follow-up of OGLE candidates comes from the faintness of the stars(with V magnitudes in the range15-18)located in very crowded?elds.To characterize a hot Jupiter,one needs radial velocity precision better than100m s?1and the capability to distinguish whether the system is blended by a third star.Radial velocity of such accuracy had never been measured before for such faint stars.

3.Follow-up of OGLE candidates with VLT/FLAMES

Sixty of the most promising OGLE candidates from the?rst two seasons (OGLE-TR-1to TR-137)were observed with the FLAMES facility on the VLT(Bouchy et al.2005,Pont et al.2005a).FLAMES is a multi-?ber link which feeds the UVES echelle spectrograph with up to7targets in a?eld-of-view of25arcmin diameter,in addition to a simultaneous Thorium calibration.The?ber link allows a stable illumination at the entrance of the spectrograph,and the simultaneous Thorium calibration is used to track instrumental drift.As a result the systematics in the radial velocity measurements are reduced to less than35m s?1.A45-minute exposure on a V=17magnitude target gives in a photon-noise limit of30m s?1on the radial velocity for late-type,slow-rotating https://www.wendangku.net/doc/8617347800.html,bining photon noise and systematics,

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typical precisions of40-60m s?1are reached on each individual Doppler measurements for the OGLE planet-host targets.

Radial velocity orbits of planetary amplitudes were detected with FLAMES for?ve of the targets(see Table1),one of them(OGLE-TR-56)already known from similar measurements by Konacki et al. (2003).

Period Transit Depth Planet Planet

[days][%]mass[R J]radius[M J] Table1.:Data for the OGLE transiting planets.The uncertainties are ～10%on the masses and～5%on the radii.

The characteristics of the?ve OGLE transiting planets have al-ready lead to a series of interesting conclusions on hot Jupiters,the most prominent being the existence of the so-called“very hot Jupiters”(Bouchy et al.2004),gas giants on very short orbits(shorter than2 days)and heavier on average(Mazeh et al.2004)than the more com-mon P>3-days hot Jupiters.

4.Sorting out planetary transits from impostors

Along with the?ve transiting hot Jupiters,the spectroscopic follow-up programmes has led to the characterisation of more than50cases of “planetary transit impostors”,i.e.con?gurations that could mimic the photometric signal of a planetary transit within the level of photometric noise of a ground-based transit survey.These systems fall into four categories.Let us review these four types of impostors in terms of implications for the follow-up of transit surveys:

(1)Grazing eclipsing binaries

Two large stars,when eclipsing at an inclined angle,can produce shal-low transit-like dips in the light curve.These cases produce,on average, rather deep signals in the light curve and are the easiest to discriminate. Several hints are usually present in the light curve itself,such as a V-shaped transit curve,ellipsoidal modulations due to tidal e?ects,or a mismatch between the transit duration and the transit depth assuming a planet-sized transiting body.Nevertheless,at low signal-to-noise such systems can also be mistaken for planetary transits.They are easy to

Title of contribution5 resolve with spectroscopic observations,thanks to the presence of two

sets of lines in the spectra with large velocity variations.

(2)M-dwarf transiting companions

A small M-dwarf transiting a larger star can produce a photometric sig-nal closely similar to a planetary transit.If the companion is not larger than a hot Jupiter,and the orbital distance is too large for tidal and re-?ection e?ects to be detectable in the light curve,then the photometric signal is strictly identical to that of a planetary transit.In both cases, an opaque,Jupiter-size object transits the target star.These cases can only be resolved by Doppler observations,the amplitude of the re?ex motion of the star revealing the mass of the transiting companion.Two nice examples of planet-size transiting stellar companions were found in our FLAMES follow-up among the OGLE candidates,OGLE-TR-122 (Pont et al.2005b)and OGLE-TR-123(Pont et al.2005c).In partic-ular,OGLE-TR-122,with a period of7.2days and a companion size smaller than that of HD209458b,produces a light curve that is strictly identical to that of a planetary transit down to a very high level of detail.

(3)Multiple systems

An eclipsing binary can produce shallow transit-like signals if the eclipse is diluted by the light of a third star.There are many possible con?g-urations for such systems,and as a result they can be very di?cult to disentangle,even with Doppler information.In most cases,multi-ple systems are readily discriminated with high-resolution spectroscopy from the presence of several systems of lines in the spectra(see Figure2, lower left panel).However,in some cases,the parameters can conspire not only to mimic the light curve of a planetary transit,but also to induce planet-like variations of the inferred radial velocity,produced by the blending of several sets of lines in the spectra.OGLE-TR-33 (Torres et al.2004)is such a case.Another similar case was found in the TrES survey(Mandushev et al.2005).

(4)False positives

Stellar variability and systematic trends in the photometry can produce ?uctuations in the light curve interpreted as a possible transit signal, especially as one tries to detect shallower signals near the detection threshold.OGLE-TR-58,for instance,was found to exhibit an intrisic level of variability that could explain the transit-like signal detected by OGLE without invoking a transiting companion(Bouchy et al.2005). Further photometric observations at the epoch of the detected signal are needed in these cases to distinguish bona?de transits from false positives.

The FLAMES/VLT Doppler follow-up,by illustrating the ubiquity of the“impostors”and the ability of certain con?gurations to mimic sev-

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Figure2.:Example of radial velocity data for the four types of planetary transit“impostors”:grazing binary(top left),low-mass companion(top right),multiple system(bottom left)and false positive(bottom right, the dotted line indicates a Jupiter-mass orbit).Figure from Pont et al. (2005a).

eral aspects of the signal of bona?de transiting planets,showed that the detection of a planetary radial velocity orbit was mandatory to establish the planetary nature of a transit candidate.Moreover,the spectroscopic data must be of high-enough resolution and signal-to-noise to be able to study the evolution of the line shape(bisector analysis)over the course of the transit phase,to eliminate scenarios of multiple systems.The present practical limit for such observations is around V=17mag with FLAMES on the VLT.This has an important implication for transit surveys:deep transit surveys using large telescopes and the HST will produce candidates that are to faint to be con?rmed spectroscopically with present-day telescopes(V>17),and therefore will not lead to any con?rmed transiting planet detection!This is in contrast to their very good detection rates“on paper”and represents a large drawback for such programmes.

Title of contribution7 5.Detection threshold and expected yield of transit surveys Three transiting exoplanets have been found by radial velocity searches,out of a few thousand target stars.This is roughly in line with prior expectations:the rate of occurence of hot Jupiter transits is about one in a thousand.On the other hand,photo-metric transit surveys have found1transiting planet around a rel-atively bright star(TrES-1),and5around fainter stars(OGLE). This is much lower than initial expectations,with hundreds of thou-sands of?eld stars having been sampled by several dozen surveys (STARE/WASP/VULCAN/EXPLORE/RAPTOR/PSST/SLEUTH/PISCES/ OGLEIII/STEPS/BEST/UNSW etc...).

The case of the most successful transit search so far,the OGLE sur-vey,gives some precious hint as to the basic reason behind this meager results.Table1gives the period and transit depth of the?ve planets detected by the OGLE survey.A remarkable conclusion stems from this table:the detected planets all have exceptionally favourable parameters for transit detection.A typical hot Jupiter hosted by a typical?eld star will have a period above3days and a transit depth of the order of1%. By contrast,each of the detected planets has a combination of at least two of these three factors favouring detection:

-A very short periods(P<2days)–thus providing many more transit signals in a given survey duration;

-A period resonant with the1-day peak of the observation window function,like OGLE-TR-111at almost exactly4days or OGLE-TR-132near5/3days–which allows the transit signal to be oversampled; -A host star much smaller than the average in the?eld–which causes a large transit depth.

The implication of this is that no“normal”transiting hot Jupiter was detected by the OGLE survey.Thus the OGLE survey–again, the most successful ground-based survey to date–had to rely on the very large number of targets observed to pick up a few exceptional transiting hot Jupiters.Its detection threshold was actually too high to detect normal hot Jupiters!TrES-1also produces an exceptionally deep transit,and it is likely that our considerations apply to other ground-based transit survey as well.

In theory,estimating the detection thresold and expected yield of a given transit survey is rather straightforward.The transit detection procedure is akin to?nding a periodic square-shaped decrease in the ?ux from the target.The signal-to-noise ratio of the detection is the signi?cance of the di?erence between the signal during the putative transit and the signal outside the transit.If most data points are outside the transit,the uncertainty on the continuum level is negligible,and

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the detection signal-to-noise is simply the transit depth divided by its uncertainty:

SNR=depth

n

(1)

whereσis the photometric uncertainty on individual points and n is the number of data points during the transit.

To compute the expected yield of a given survey,one can simulate the population of target stars,assume a frequency of planet,then com-pute the expected number of detections given two conditions:(1)that at least2or3transits are observed(to establish the periodicity of the signal);(2)that the detection SNR is above some threshold,SNR min. The SNR min threshold is usually assumed between7and10according to the number of false detections deemed acceptable.

Such simulations have been done for many existing and planned surveys.If the survey duration is su?cient for at least3transits to be observed for most hot Jupiters,then these simulations invariably predict good SNR detectability for normal hot Jupiters,at least for the brightest targets,hence resulting in signi?cant predicted yields.

However,there is an important hidden assumption in Eq.1above: it is based on the assumption of white,independent noise.If the noise is not independent and has some covariance structure,then the equivalent formula is

SNR=

depth

σ2/n+1/n2 i=j cov[i;j](2)

where the cov[i;j]are the elements of the covariance matrix.Therefore, the estimated yields based on the assumption of white noise are correct

only ifσ2/n>>1/n2 i=j cov[i;j].However,in real ground-based data in the relevant regime for hot Jupiters,the opposite is true!Plugging

representative numbers shows that generally1/n2 i=j cov[i;j]>σ2/n. For instance in the OGLE survey,σ=3?10mmag,n=20?50,so that σ2/n?0.2?5mmag2,whereas the covariance of the residuals sampled on constant lightcurves gives a covariance term1/n2 i=j cov[i;j]?9?11mmag2.

In the jargon of signal analysis,the noise in photometric data has

a white component(mainly photon noise)and a red component.The

noise on ground-based millimagnitude photometry is”pink”.The red component comes from the systematics caused by the variations in at-mospheric conditions,telescope tracking and detector characteristics. Figure3(left panel)displays an example of these three kinds of noise, white,red and pink.Ground-based photometric data at the millimag-

Title of contribution9 nitude level look like the bottom curve,with some white noise super-imposed on some systematics trends on longer timescale.

Figure3.:Left:A photometric time series with white,red or pink noise.The global dispersion is the same for the three curves.Right: the same series averaged over a transit duration(the transit duration is shown by the bar at the bottom right).

It is clear that the systematic trends will limit the detectability of transit signals,especially the trends operating on hour timescale–the timescale of transits.What Eq.2expresses is that the detection threshold of transit surveys will depend on the average of the photon noise over a transit-length duration and the average of the covariance over this duration.The right panel of Fig.3shows the average of the curves in the left panel over a transit duration.It shows graphically what was found algebraically from Eq.2:for transit detections,the ef-fect of the red components dominates over that of the white component (because the white component averages out to very small values over the duration of transits,whereas the red component does not).

6.Revised yield estimates for ground-based surveys

The implications of the presence of red noise(”systematics”)in the pho-tometric data on the expected yields of transit surveys are fundamental. In fact,in many cases a good approximation is to ignore the white noise entirely,and to base the detection threshold on the red noise only.

This profoundly modi?es the predictions for the sensitivity of ground-based transit surveys.Not only the resulting detection thresh-old is higher than with the white-noise assumption,it also has a di?erent

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dependence on period and magnitude.For instance,the presence of red noise favours the detection of very short-period transiting planets(”very hot Jupiters”)compared to longer periods.

Figure4.:Detection threshold in transit depth vs.magnitude,for a 3.5-day period planet in the OGLE survey.Dotted line:with the as-sumption of white noise,solid line:taking the red component of the noise into account.

Figure4gives,for the OGLE survey,the detection threshold of transit signals as a function of magnitude,assuming white noise only (dotted curve)and assuming pink noise(solid curve),for planets at P=3.5days.The di?erence between the two thresholds has a large e?ect on the expected rate of detection of hot Jupiter transits,since those are expected to produce typical transit near1%,exactly in the region where the prediction of white noise and pink noise diverge.

White-noise calculations predict the detectability of transit signals around the brightest stars in the survey down to very small transit depths–thanks to the averaging of the independent noise.But taking into account the red noise leads to a much higher e?ective threshold, and to a?oor value that is higher than the typical depth of hot Jupiter transits.The bottom line is that the presence of systematics in the photometry drastically reduces the detectability of planetary transits in ground-based surveys.

We have devised a simpli?ed model of the covariance matrix to be able to estimate the yields of transit surveys in the presence of red noise (Pont&Zucker2006,in prep.).This model uses a simpli?ed descrip-tion of the matrix based on a single parameter,calledσr,describing the amplitude of the red noise in the relevant regime.This model was

Title of contribution11 applied to some ongoing transit surveys1estimatingσr from published data,to predict the yield of these surveys per season in terms of tran-siting hot Jupiter detections(we did not include”very hot Jupiters”). Table2shows the results compared to the predictions assuming white noise only.

HJ/season

0.9 1.10.20.60.01

HJ/season

71418162

1STARE(Brown&Charbonneau2000),OGLE(Udalski et al.2002a),HAT(Bakos et al.2004),Vulcan(Borucki et al.2001),UNSW(Hidas et al.2005)

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to与for的用法和区别

to与for的用法和区别 一般情况下, to后面常接对象; for后面表示原因与目的为多。 Thank you for helping me. Thanks to all of you. to sb.表示对某人有直接影响比如，食物对某人好或者不好就用to; for表示从意义、价值等间接角度来说，例如对某人而言是重要的，就用for. for和to这两个介词，意义丰富，用法复杂。这里仅就它们主要用法进行比较。 1. 表示各种“目的” 1. What do you study English for? 你为什么要学英语？ 2. She went to france for holiday. 她到法国度假去了。 3. These books are written for pupils. 这些书是为学生些的。 4. hope for the best, prepare for the worst. 作最好的打算，作最坏的准备。 2．对于 1．She has a liking for painting. 她爱好绘画。 2．She had a natural gift for teaching. 她对教学有天赋/ 3．表示赞成同情，用for不用to. 1. Are you for the idea or against it? 你是支持还是反对这个想法？ 2. He expresses sympathy for the common people.. 他表现了对普通老百姓的同情。 3. I felt deeply sorry for my friend who was very ill. 4 for表示因为，由于（常有较活译法） 1 Thank you for coming. 谢谢你来。 2. France is famous for its wines. 法国因酒而出名。 5．当事人对某事的主观看法，对于（某人），对…来说（多和形容词连用）用介词to，不用for.. He said that money was not important to him. 他说钱对他并不重要。 To her it was rather unusual. 对她来说这是相当不寻常的。 They are cruel to animals. 他们对动物很残忍。 6．for和fit, good, bad, useful, suitable 等形容词连用，表示适宜，适合。 Some training will make them fit for the job. 经过一段训练，他们会胜任这项工作的。 Exercises are good for health. 锻炼有益于健康。 Smoking and drinking are bad for health. 抽烟喝酒对健康有害。 You are not suited for the kind of work you are doing. 7. for表示不定式逻辑上的主语，可以用在主语、表语、状语、定语中。 1．It would be best for you to write to him. 2．The simple thing is for him to resign at once. 3．There was nowhere else for me to go. 4．He opened a door and stood aside for her to pass.

of与for的用法以及区别

of与for的用法以及区别 for 表原因、目的 of 表从属关系 介词of的用法 （1）所有关系 this is a picture of a classroom （2）部分关系 a piece of paper a cup of tea a glass of water a bottle of milk what kind of football，American of soccer？ （3）描写关系 a man of thirty 三十岁的人 a man of shanghai 上海人 （4）承受动作 the exploitation of man by man．人对人的剥削。 （5）同位关系 It was a cold spring morning in the city of London in England． （6）关于，对于 What do you think of Chinese food？ 你觉得中国食品怎么样？ 介词 for 的用法小结 1. 表示“当作、作为”。如: I like some bread and milk for breakfast. 我喜欢把面包和牛奶作为早餐。What will we have for supper? 我们晚餐吃什么?

2. 表示理由或原因,意为“因为、由于”。如: Thank you for helping me with my English. 谢谢你帮我学习英语。 Thank you for your last letter. 谢谢你上次的来信。 Thank you for teaching us so well. 感谢你如此尽心地教我们。 3. 表示动作的对象或接受者,意为“给……”、“对…… (而言)”。如: Let me pick it up for you. 让我为你捡起来。 Watching TV too much is bad for your health. 看电视太多有害于你的健康。 4. 表示时间、距离,意为“计、达”。如: I usually do the running for an hour in the morning. 我早晨通常跑步一小时。We will stay there for two days. 我们将在那里逗留两天。 5. 表示去向、目的,意为“向、往、取、买”等。如: let’s go for a walk. 我们出去散步吧。 I came here for my schoolbag.我来这儿取书包。 I paid twenty yuan for the dictionary. 我花了20元买这本词典。 6. 表示所属关系或用途,意为“为、适于……的”。如: It’s time for school. 到上学的时间了。 Here is a letter for you. 这儿有你的一封信。 7. 表示“支持、赞成”。如: Are you for this plan or against it? 你是支持还是反对这个计划? 8. 用于一些固定搭配中。如: Who are you waiting for? 你在等谁? For example, Mr Green is a kind teacher. 比如,格林先生是一位心地善良的老师。

常用介词用法(for to with of)

For的用法 1. 表示“当作、作为”。如: I like some bread and milk for breakfast. 我喜欢把面包和牛奶作为早餐。 What will we have for supper? 我们晚餐吃什么? 2. 表示理由或原因,意为“因为、由于”。如: Thank you for helping me with my English. 谢谢你帮我学习英语。 3. 表示动作的对象或接受者,意为“给……”、“对…… (而言)”。如: Let me pick it up for you. 让我为你捡起来。 Watching TV too much is bad for your health. 看电视太多有害于你的健康。 4. 表示时间、距离,意为“计、达”。如: I usually do the running for an hour in the morning. 我早晨通常跑步一小时。 We will stay there for two days. 我们将在那里逗留两天。 5. 表示去向、目的,意为“向、往、取、买”等。如: Let’s go for a walk. 我们出去散步吧。 I came here for my schoolbag.我来这儿取书包。 I paid twenty yuan for the dictionary. 我花了20元买这本词典。 6. 表示所属关系或用途,意为“为、适于……的”。如: It’s time for school. 到上学的时间了。 Here is a letter for you. 这儿有你的一封信。 7. 表示“支持、赞成”。如: Are you for this plan or against it? 你是支持还是反对这个计划? 8. 用于一些固定搭配中。如: Who are you waiting for? 你在等谁? For example, Mr Green is a kind teacher. 比如,格林先生是一位心地善良的老师。 尽管for 的用法较多，但记住常用的几个就可以了。 to的用法: 一：表示相对，针对 be strange (common, new, familiar, peculiar) to This injection will make you immune to infection. 二：表示对比，比较 1：以-ior结尾的形容词，后接介词to表示比较，如：superior ,inferior,prior,senior,junior 2: 一些本身就含有比较或比拟意思的形容词，如equal，similar，equivalent，analogous A is similar to B in many ways.

(完整版)介词for用法归纳

介词for用法归纳 用法1：(表目的)为了。如： They went out for a walk. 他们出去散步了。 What did you do that for? 你干吗这样做？ That’s what we’re here for. 这正是我们来的目的。 What’s she gone for this time? 她这次去干什么去了？ He was waiting for the bus. 他在等公共汽车。 【用法说明】在通常情况下，英语不用for doing sth 来表示目的。如： 他去那儿看他叔叔。 误：He went there for seeing his uncle. 正：He went there to see his uncle. 但是，若一个动名词已名词化，则可与for 连用表目的。如： He went there for swimming. 他去那儿游泳。(swimming 已名词化) 注意：若不是表目的，而是表原因、用途等，则其后可接动名词。(见下面的有关用法) 用法2：(表利益)为，为了。如： What can I do for you? 你想要我什么？ We study hard for our motherland. 我们为祖国努力学习。 Would you please carry this for me? 请你替我提这个东西好吗？ Do more exercise for the good of your health. 为了健康你要多运动。 【用法说明】(1) 有些后接双宾语的动词(如buy, choose, cook, fetch, find, get, order, prepare, sing, spare 等)，当双宾语易位时，通常用for 来引出间接宾语，表示间接宾语为受益者。如： She made her daughter a dress. / She made a dress for her daughter. 她为她女儿做了件连衣裙。 He cooked us some potatoes. / He cooked some potatoes for us. 他为我们煮了些土豆。 注意，类似下面这样的句子必须用for： He bought a new chair for the office. 他为办公室买了张新办公椅。 (2) 注意不要按汉语字面意思，在一些及物动词后误加介词for： 他们决定在电视上为他们的新产品打广告。 误：They decided to advertise for their new product on TV. 正：They decided to advertise their new product on TV. 注：advertise 可用作及物或不及物动词，但含义不同：advertise sth＝为卖出某物而打广告；advertise for sth＝为寻找某物而打广告。如：advertise for a job=登广告求职。由于受汉语“为”的影响，而此处误加了介词for。类似地，汉语中的“为人民服务”，说成英语是serve the people，而不是serve for the people，“为某人的死报仇”，说成英语是avenge sb’s death，而不是avenge for sb’s death，等等。用法3：(表用途)用于，用来。如： Knives are used for cutting things. 小刀是用来切东西的。 This knife is for cutting bread. 这把小刀是用于切面包的。 It’s a machine for slicing bread. 这是切面包的机器。 The doctor gave her some medicine for her cold. 医生给了她一些感冒药。 用法4：为得到，为拿到，为取得。如： He went home for his book. 他回家拿书。 He went to his friend for advice. 他去向朋友请教。 She often asked her parents for money. 她经常向父母要钱。

of和for的用法

of 1....的,属于 One of the legs of the table is broken. 桌子的一条腿坏了。 Mr.Brown is a friend of mine. 布朗先生是我的朋友。 2.用...做成的;由...制成 The house is of stone. 这房子是石建的。 3.含有...的;装有...的 4....之中的;...的成员 Of all the students in this class,Tom is the best. 在这个班级中,汤姆是最优秀的。 5.(表示同位) He came to New York at the age of ten. 他在十岁时来到纽约。 6.(表示宾格关系) He gave a lecture on the use of solar energy. 他就太阳能的利用作了一场讲演。 7.(表示主格关系) We waited for the arrival of the next bus. 我们等待下一班汽车的到来。

I have the complete works of Shakespeare. 我有莎士比亚全集。 8.来自...的;出自 He was a graduate of the University of Hawaii. 他是夏威夷大学的毕业生。 9.因为 Her son died of hepatitis. 她儿子因患肝炎而死。 10.在...方面 My aunt is hard of hearing. 我姑妈耳朵有点聋。 11.【美】(时间)在...之前 12.(表示具有某种性质) It is a matter of importance. 这是一件重要的事。 For 1.为,为了 They fought for national independence. 他们为民族独立而战。 This letter is for you. 这是你的信。

for和to区别

1.表示各种“目的”，用for （1）What do you study English for 你为什么要学英语？ （2）went to france for holiday. 她到法国度假去了。 （3）These books are written for pupils. 这些书是为学生些的。 （4）hope for the best, prepare for the worst. 作最好的打算，作最坏的准备。 2．“对于”用for （1）She has a liking for painting. 她爱好绘画。 （2）She had a natural gift for teaching. 她对教学有天赋/ 3．表示“赞成、同情”，用for （1）Are you for the idea or against it 你是支持还是反对这个想法？ （2）He expresses sympathy for the common people.. 他表现了对普通老百姓的同情。 （3）I felt deeply sorry for my friend who was very ill. 4. 表示“因为，由于”（常有较活译法），用for （1）Thank you for coming. 谢谢你来。

（2）France is famous for its wines. 法国因酒而出名。 5．当事人对某事的主观看法，“对于（某人），对…来说”，（多和形容词连用），用介词to，不用for. （1）He said that money was not important to him. 他说钱对他并不重要。 （2）To her it was rather unusual. 对她来说这是相当不寻常的。 （3）They are cruel to animals. 他们对动物很残忍。 6．和fit, good, bad, useful, suitable 等形容词连用，表示“适宜，适合”，用for。（1）Some training will make them fit for the job. 经过一段训练，他们会胜任这项工作的。 （2）Exercises are good for health. 锻炼有益于健康。 （3）Smoking and drinking are bad for health. 抽烟喝酒对健康有害。 （4）You are not suited for the kind of work you are doing. 7. 表示不定式逻辑上的主语，可以用在主语、表语、状语、定语中。 （1）It would be best for you to write to him. （2） The simple thing is for him to resign at once.

双宾语 to for的用法

1.两者都可以引出间接宾语，但要根据不同的动词分别选用介词to 或for：(1) 在give, pass, hand, lend, send, tell, bring, show, pay, read, return, write, offer, teach, throw 等之后接介词to。 如： 请把那本字典递给我。 正：Please hand me that dictionary. 正：Please hand that dictionary to me. 她去年教我们的音乐。 正：She taught us music last year. 正：She taught music to us last year. (2) 在buy, make, get, order, cook, sing, fetch, play, find, paint, choose,prepare, spare 等之后用介词for 。如： 他为我们唱了首英语歌。 正：He sang us an English song. 正：He sang an English song for us. 请帮我把钥匙找到。 正：Please find me the keys. 正：Please find the keys for me. 能耽搁你几分钟吗(即你能为我抽出几分钟吗)? 正：Can you spare me a few minutes? 正：Can you spare a few minutes for me? 注：有的动词由于搭配和含义的不同，用介词to 或for 都是可能的。如：do sb a favour＝do a favour for sb 帮某人的忙 do sb harm＝do harm to sb 对某人有害

双宾语tofor的用法

1. 两者都可以引出间接宾语，但要根据不同的动词分别选用介词to 或for： (1) 在give, pass, hand, lend, send, tell, bring, show, pay, read, return, write, offer, teach, throw 等之后接介词to。 如： 请把那本字典递给我。 正：Please hand me that dictionary. 正：Please hand that dictionary to me. 她去年教我们的音乐。 正：She taught us music last year. 正：She taught music to us last year. (2) 在buy, make, get, order, cook, sing, fetch, play, find, paint, choose,prepare, spare 等之后用介词for 。如： 他为我们唱了首英语歌。 正：He sang us an English song. 正：He sang an English song for us. 请帮我把钥匙找到。 正：Please find me the keys. 正：Please find the keys for me. 能耽搁你几分钟吗(即你能为我抽出几分钟吗)? 正：Can you spare me a few minutes? 正：Can you spare a few minutes for me? 注：有的动词由于搭配和含义的不同，用介词to 或for 都是可能的。如： do sb a favou r do a favour for sb 帮某人的忙 do sb harnn= do harm to sb 对某人有害

for和of的用法

for的用法： 1. 表示“当作、作为”。如: I like some bread and milk for breakfast. 我喜欢把面包和牛奶作为早餐。 What will we have for supper? 我们晚餐吃什么? 2. 表示理由或原因,意为“因为、由于”。如: Thank you for helping me with my English. 谢谢你帮我学习英语。 Thank you for your last letter. 谢谢你上次的来信。 Thank you for teaching us so well. 感谢你如此尽心地教我们。 3. 表示动作的对象或接受者,意为“给……”、“对…… (而言)”。如: Let me pick it up for you. 让我为你捡起来。 Watching TV too much is bad for your health. 看电视太多有害于你的健康。 4. 表示时间、距离,意为“计、达”。如:

I usually do the running for an hour in the morning. 我早晨通常跑步一小时。 We will stay there for two days. 我们将在那里逗留两天。 5. 表示去向、目的,意为“向、往、取、买”等。如: Let’s go for a walk. 我们出去散步吧。 I came here for my schoolbag.我来这儿取书包。 I paid twenty yuan for the dictionary. 我花了20元买这本词典。 6. 表示所属关系或用途,意为“为、适于……的”。如: It’s time for school. 到上学的时间了。 Here is a letter for you. 这儿有你的一封信。 7. 表示“支持、赞成”。如: Are you for this plan or against it? 你是支持还是反对这个计划? 8. 用于一些固定搭配中。如:

英语形容词和of for 的用法

加入收藏夹 主题： 介词试题It’s + 形容词 + of sb. to do sth.和It’s + 形容词 + for sb. to do sth.的用法区别。 内容： It's very nice___pictures for me. A.of you to draw B.for you to draw C.for you drawing C.of you drawing 提交人：杨天若时间：1/23/2008 20:5:54 主题：for 与of 的辨别 内容：It's very nice___pictures for me. A.of you to draw B.for you to draw C.for you drawing C.of you drawing 答：选A 解析：该题考查的句型It’s + 形容词+ of sb. to do sth.和It’s +形容词+ for sb. to do sth.的用法区别。 “It’s + 形容词+ to do sth.”中常用of或for引出不定式的行为者，究竟用of sb.还是用for sb.，取决于前面的形容词。 1) 若形容词是描述不定式行为者的性格、品质的，如kind，good，nice，right，wrong，clever，careless，polite，foolish等，用of sb. 例： It’s very kind of you to help me. 你能帮我，真好。 It’s clever of you to work out the maths problem. 你真聪明，解出了这道数学题。 2) 若形容词仅仅是描述事物，不是对不定式行为者的品格进行评价，用for sb.，这类形容词有difficult，easy，hard，important，dangerous，（im）possible等。例： It’s very dangerous for children to cross the busy street. 对孩子们来说，穿过繁忙的街道很危险。 It’s difficult for u s to finish the work. 对我们来说，完成这项工作很困难。 for 与of 的辨别方法： 用介词后面的代词作主语，用介词前边的形容词作表语，造个句子。如果道理上通顺用of，不通则用for. 如： You are nice.(通顺，所以应用of)。 He is hard.(人是困难的，不通，因此应用for.) 由此可知，该题的正确答案应该为A项。 提交人：f7_liyf 时间：1/24/2008 11:18:42

to和for的用法有什么不同(一)

to和for的用法有什么不同（一） 一、引出间接宾语时的区别 两者都可以引出间接宾语，但要根据不同的动词分别选用介词to 或for，具体应注意以下三种情况： 1. 在give, pass, hand, lend, send, tell, bring, show, pay, read, return, write, offer, teach, throw 等之后接介词to。如： 请把那本字典递给我。 正：Please hand me that dictionary. 正：Please hand that dictionary to me. 她去年教我们的音乐。 正：She taught us music last year. 正：She taught music to us last year. 2. 在buy, make, get, order, cook, sing, fetch, play, find, paint, choose, prepare, spare 等之后用介词for 。如： 他为我们唱了首英语歌。 正：He sang us an English song. 正：He sang an English song for us. 请帮我把钥匙找到。 正：Please find me the keys. 正：Please find the keys for me. 能耽搁你几分钟吗(即你能为我抽出几分钟吗)? 正：Can you spare me a few minutes?

正：Can you spare a few minutes for me? 3. 有的动词由于用法和含义不同，用介词to 或for 都是可能的。如： do sb a favor＝do a favor for sb 帮某人的忙 do sb harm＝do harm to sb 对某人有害 在有的情况下，可能既不用for 也不用to，而用其他的介词。如： play sb a trick＝play a trick on sb 作弄某人 请比较： play sb some folk songs＝play some folk songs for sb 给某人演奏民歌 有时同一个动词，由于用法不同，所搭配的介词也可能不同，如leave sbsth 这一结构，若表示一般意义的为某人留下某物，则用介词for 引出间接宾语，即说leave sth for sb；若表示某人死后遗留下某物，则用介词to 引出间接宾语，即说leave sth to sb。如： Would you like to leave him a message? / Would you like to leave a message for him? 你要不要给他留个话？ Her father left her a large fortune. / Her father left a large fortune to her. 她父亲死后给她留下了一大笔财产。 二、表示目标或方向的区别 两者均可表示目标、目的地、方向等，此时也要根据不同动词分别对待。如： 1. 在come, go, walk, move, fly, ride, drive, march, return 等动词之后通常用介词to 表示目标或目的地。如： He has gone to Shanghai. 他到上海去了。 They walked to a river. 他们走到一条河边。

202X中考英语：to和for的区别与用法.doc

202X中考英语：to和for的区别与用法中考栏目我为考生们整理了“202X中考英语：to和for的区别与用法”，希望能帮到大家，想了解更多考试资讯，本网站的及时更新哦。 202X中考英语：to和for的区别与用法 to和for的区别与用法是什么 一般情况下, to后面常接对象; for后面表示原因与目的为多。 Thank you for helping me. Thanks to all of you. to sb. 表示对某人有直接影响比如，食物对某人好或者不好就用to; for 表示从意义、价值等间接角度来说，例如对某人而言是重要的，就用for. for和to这两个介词，意义丰富，用法复杂。这里仅就它们主要用法进行比较。 1. 表示各种“目的” 1. What do you study English for? 你为什么要学英语? 2. She went to france for holiday. 她到法国度假去了。 3. These books are written for pupils. 这些书是为学生些的。 4. hope for the best, prepare for the worst. 作最好的打算，作最坏的准备。

2.对于 1.She has a liking for painting. 她爱好绘画。 2.She had a natural gift for teaching. 她对教学有天赋。 3.表示赞成同情，用for不用to. 1. Are you for the idea or against it? 你是支持还是反对这个想法? 2. He expresses sympathy for the common people.. 他表现了对普通老百姓的同情。 3. I felt deeply sorry for my friend who was very ill. 4 for表示因为，由于(常有较活译法) 1.Thank you for coming. 谢谢你来。 2. France is famous for its wines. 法国因酒而出名。 5.当事人对某事的主观看法，对于(某人)，对?来说(多和形容词连用)用介词to，不用for.. He said that money was not important to him. 他说钱对他并不重要。 To her it was rather unusual. 对她来说这是相当不寻常的。 They are cruel to animals. 他们对动物很残忍。

keep的用法及of 、for sb.句型区别

keep的用法 1. 用作及物动词 ①意为"保存；保留；保持；保守"。如： Could you keep these letters for me, please? 你能替我保存这些信吗？ ②意为"遵守；维护"。如： Everyone must keep the rules. 人人必须遵守规章制度。 The teacher is keeping order in class.老师正在课堂上维持秩序。 ③意为"使……保持某种(状态、位置或动作等)"。这时要在keep的宾语后接补足语，构 成复合宾语。其中宾语补足语通常由形容词、副词、介词短语、现在分词和过去分词等充当。如： 例：We should keep our classroom clean and tidy.(形容词) 我们应保持教室整洁干净。 You'd better keep the child away from the fire.(副词)你最好让孩子离火远一点。 The bad weather keeps us inside the house.(介词短语)坏天气使我们不能出门。 Don't keep me waiting for long.(现在分词)别让我等太久。 The other students in the class keep their eyes closed.(过去分词) 班上其他同学都闭着眼睛。 2. 用作连系动词 构成系表结构：keep＋表语，意为"保持，继续(处于某种状态)"。其中表语可用形容词、副词、介词短语等充当。如： 例：You must look after yourself and keep healthy.(形容词) 你必须照顾好自己，保持身体健康。 Keep off the grass.(副词)请勿践踏草地。 Traffic in Britain keeps to the left.(介词短语)英国的交通是靠左边行驶的。 注意：一般情况下，keep后接形容词较为多见。再如： She knew she must keep calm.她知道她必须保持镇静。 Please keep silent in class.课堂上请保持安静。 3. ①keep doing sth. 意为"继续干某事"，表示不间断地持续干某事，keep后不 能接不定式或表示静止状态的v-ing形式，而必须接延续性的动词。 例：He kept working all day, because he wanted to finish the work on time. 他整天都在不停地工作，因为他想准时完成工作。 Keep passing the ball to each other, and you'll be OK.坚持互相传球，你们就

to of和for的区别

to , of 和for的区别 1.to有到的意思，常常和go，come，get连用引出地点。Go to school , go to the shop , go to the cinema. 常见的短语：the way to 去---的路 On one’s way to 在某人去---的路上 以上的用法中，当地点是副词home，here，there等是to 要去掉。如：get home，the way here To后跟动词原形，是不定式的标志 It is +形容词+(for/of +人+)to do sth.(括号内部分可以省略) It is easy for me to learn English. It is very kind of you to lend me your money. 当形容词表示人的行为特征时用of表示to do的性质时用for Want, hope ,decide, plan , try , fail等词后跟to do I want to join the swimming club. Would like to do I’d like to play basketball with them. It is time to have a break. Next to , close to , from ---to--- 2.for 为，表示目的。 Thank you for Buy sth for sb =buy sb sth It is time for bed. Here is a letter for you.

I will study for our country. 3.of表示所属关系意思是：---的 a map of the world a friend of mine

for和of引导的不定式结构的区别

for和of引导的不定式结构的区别 不定式是一种非谓语动词，不能单独作谓语，因此没有语法上的主语。但由于不定式表示的是动作，在意义上可以有它的主体。我们称之为逻辑主语。 提起不定式逻辑主语，人们首先想到的会是“for+名词（宾格代词）+不定式”的复合结构。如：It is important for us to study English well．然而，有时不定式的逻辑主语须要用“of+名词（代词宾格）”才行。例如：It is kind of you to help me．而不能说：It is kind for you to help me．在选择介词“for”还是“of”时，人们往往总是凭感觉而定。有时受习惯影响，多选介词“for”。于是常出现这样的错误：It was careless for him to lose his way．It is cruel for you to do so．由于众多语法书对这种结构中使用“for”与“of”的区别介绍甚少，一些人对其概念认识尚不完全清楚，笔者认为有必要就这一问题作些探讨与介绍。 一、在句中的语法作用不同 a．不定式for结构在句中可以作主、宾、表、定、状、同位语： 1．It is easy for Tom to do this work．（主语）汤姆做此工作是容易的。 2．I'd like for him to come here．（宾语）我喜欢他来这里。 3．His idea is for us to travel in two different groups．（表语）他的想法是：我们分成两组旅行。 4．Have you heard about the plan for you to go abroad．（定语）你听到让你出国的计划吗？ 5．The word is too difficult for him to pronounce well．（状语）这单词太难，他念不准。 6．In the most schools，it is the custom for the headmaster to declare the newterm start．在大部分学校，校长宣布新学期开始是一个习惯。 b．不定式of结构只能在句中作主语。 1．It was careless of him to leave his umbrella in the train．他把伞丢在火车上真是太粗心了。 2．It is awfully good of you to come to see me off at the station．谢谢你来车站送我。 二、逻辑主语的名词有所不同

of和for的用法

for 表原因、目的 of 表从属关系 介词of的用法 （1）所有关系 this is a picture of a classroom （2）部分关系 a piece of paper a cup of tea a glass of water a bottle of milk what kind of football，american of soccer？ （3）描写关系 a man of thirty 三十岁的人 a man of shanghai 上海人 （4）承受动作 the exploitation of man by man．人对人的剥削。 （5）同位关系 it was a cold spring morning in the city of london in england． （6）关于，对于 what do you think of chinese food？ 你觉得中国食品怎么样？ 介词for 的用法小结 1. 表示“当作、作为”。如: i like some bread and milk for breakfast. 我喜欢把面包和牛奶作为早餐。what will we have for supper? 我们晚餐吃什么? 2. 表示理由或原因,意为“因为、由于”。如: thank you for helping me with my english. 谢谢你帮我学习英语。 thank you for your last letter. 谢谢你上次的来信。 thank you for teaching us so well. 感谢你如此尽心地教我们。 3. 表示动作的对象或接受者,意为“给……”、“对…… (而言)”。如:

介词for和to用法完全归纳

介词for用法完全归纳 ？ 本站特约作者陈根花 ？ 用法1：(表目的)为了。如： They went out for a walk. 他们出去散步了。 What did you do that for 你干吗这样做？ That’s what we’re here for. 这正是我们来的目的。 What’s she gone for this time 她这次去干什么去了？ He was waiting for the bus. 他在等公共汽车。 【用法说明】在通常情况下，英语不用 for doing sth 来表示目的。如： 他去那儿看他叔叔。 误：He went there for seeing his uncle. 正：He went there to see his uncle. 但是，若一个动名词已名词化，则可与 for 连用表目的。如： He went there for swimming. 他去那儿游泳。(swimming 已名词化) 注意：若不是表目的，而是表原因、用途等，则其后可接动名词。(见下面的有关用法) 用法2：(表利益)为，为了。如： What can I do for you 你想要我什么？ We study hard for our motherland. 我们为祖国努力学习。 Would you please carry this for me 请你替我提这个东西好吗？ Do more exercise for the good of your health. 为了健康你要多运动。【用法说明】(1) 有些后接双宾语的动词(如 buy, choose, cook, fetch, find, get, order, prepare, sing, spare 等)，当双宾语易位时，通常用 for 来引出间接宾语，表示间接宾语为受益者。如： She made her daughter a dress. / She made a dress for her daughter. 她为她女儿做了件连衣裙。 He cooked us some potatoes. / He cooked some potatoes for us. 他为我们煮了些土豆。 注意，类似下面这样的句子必须用 for： He bought a new chair for the office. 他为办公室买了张新办公椅。 (2) 注意不要按汉语字面意思，在一些及物动词后误加介词 for： 他们决定在电视上为他们的新产品打广告。 误：They decided toadvertise for their new product on TV. 正：They decided to advertise their new product on TV. 注：advertise 可用作及物或不及物动词，但含义不同：advertise sth＝为卖出某物而打广告；advertise for sth＝为寻找某物而打广告。如：advertise for a job=登广告求职。由于受汉语“为”的影响，而此处误加了介词 for。类似地，汉语中的“为人民服务”，说成英语是 serve the people，而不是 serve for the people，“为某人的死报仇”，说成英语是avenge sb’s death，而不是 avenge for sb’s death，等等。