You are an expert at summarizing long articles. Proceed to summarize the following text: 
since the successful launch of the _ fermi _ gamma - ray space telescope in 2008 june , we now have a new opportunity to study gamma - ray emission from different types of high energy sources with much improved sensitivity and localization capabilities than with the egret instrument onboard the _ compton gamma - ray observatory _ ( cgro ) . with the field of view covering 20% of the sky at every moment ( five times larger than egret ) , and its improved sensitivity ( by more than an order of magnitude with respect to egret ) , the large area telescope ( lat ; * ? ? ? * ) aboard _ fermi _ surveys the entire sky each day down to photon flux levels of @xmath0 @xmath1 few @xmath2 . the number of detected gamma - ray sources has increased , with the 2nd catalog ( 2fgl ; * ? ? ? * ) containing 1873 gamma - ray sources in the 100 mev to 100 gev range , while 271 objects were previously listed in the 3rd egret catalog ( 3eg ; * ? ? ? more than 1,000 gamma - ray sources included in the 2fgl are proposed to be associated with active galactic nuclei ( agns ) and 87 sources with pulsars ( psrs ; * ? ? ? * ) , including 21 millisecond pulsars ( msps ) . other associations included supernova remnants ( snrs ; * ? ? ? * ) , low - mass / high - mass x - ray binaries @xcite , pulsar wind nebulae @xcite , normal and starburst galaxies @xcite , and the giant lobes of a radio galaxy @xcite .    however , no obvious counterparts at longer wavelength have been found for as much as 31% of the 2fgl objects so that several hundreds of gev sources currently remain unassociated with any known astrophysical systems . in other words the nature of unassociated gamma - ray sources are still one of the major puzzles , and the mystery has never been solved yet . fortunately , an improved localization capabilities of the ( typical 95% confidence radii @xmath3 , and even 0@xmath4.005 - 0@xmath4.01 for the brightest sources ; @xcite ) , when compared to that of egret ( typical @xmath5 ) , enables more effective follow - up studies at radio , optical , and x - ray frequencies , which can help to unravel the nature of the unid gamma - ray emitters . indeed for example , a lot of _ fermi _ sources were identified using wise ir data @xcite .    in this context , we started a new project to investigate the nature of unid objects through x - ray follow - up observations with the xis sensor onboard the x - ray satellite ( see section 2 ) . for example , the results of the first - year campaign conducted in ao-4 ( 2009 ) were presented in @xcite . in this campaign , the x - ray counterpart for one of the brightest unassociated objects , 1fglj1231.1 - 1410 ( also detected by egret as 3egj1234 - 1318 and egrj1231 - 1412 ) , was discovered for the first time . the x - ray spectrum was well fitted by a blackbody with an additional power - law component , supporting the recent identification of this source with a msp . in the second - year campaign ( ao-5 ) , another seven unid sources were subsequently observed with @xcite . in particular , this paper presented a convenient method to classify the objects into `` agn - like '' and `` psr - like '' by comparing their multiwavelength properties with those of known agns and pulsars . in the third - year ( ao-6 ) , 1fglj2339.7 - 0531 ( yatsu et al . 2013 in prep ; also romani & shaw 2011 ) and 1fglj1311.7 - 3429 @xcite were intensively monitored with a total exposure time of 200 ksec . both sources are now suggested to be `` black widow '' msp systems and newly categorized as `` radio - quiet '' msps . as these projects show , the x - ray follow - up observations especially using provided various fruitful results to clarify the nature of unassociated gamma - ray sources , and was able to find a new type of gamma - ray emitter .    to complete a series of x - ray follow - up programs described above , we further carried out the analysis of all the archival x - ray data of 134 unid gamma - ray sources in the 1fgl catalog of point sources ( 1fgl ; * ? ? ? _ swift_/xrt . note that , all these 134 sources have been detected in the 2fgl catalog , hence the updated data on there lat position and spectra were available from the 2nd @xmath6/lat catalog so are used throughout this work . this allowed us to construct the seds ( seds ) of each objects from radio to gamma - rays ( see section2 and appendix ) for the first time . note that we target all the 1fgl unid sources that satisfy our selections ( see section2 ) , using updated / improved information from the 2fgl catalog on their lat positions and spectra in this paper . moreover , three sources that displayed potentially interesting seds , 1fglj0022.2 - 1850 ( or 2fgl j0022.2 - 1853 ) , 1fglj0038.0 + 1236 ( or 2fgl j0037.8 + 1238 ) and 1fglj0157.0 - 5259 ( or 2fgl j0157.2 - 5259 ) , were deeply observed with as a part of ao7 campaign in 2012 . in the 2fgl catalog , both 1fglj0022.2 - 1850 and 1fglj0157.0 - 5259 are categorized as active galaxies of uncertain type ( agu ) , while 1fglj0038.0 + 1236 was classified as a bl lac type of blazar ( bzb ) based on the positional coincidences to sources observed at another wavelength . but as we see below , the unique seds of these three objects are not well understood as conventional blazars . in section2 we first describe the analysis of the 134 1fgl unid sources with _ swift_. subsequently in section3 , deep follow - up observations of the selected three sources , 1fglj0022.2 - 1850 , 1fglj0038.0 + 1236 and 1fglj0157.0 - 5259 are shown . the results of the analysis are given in section4 . the discussion and summary are presented in section5 and 6 , respectively . @xcite is a gamma - ray observatory launched on 2004 november 20 . the primary goal of this mission is to explore and follow - up the gamma - ray burst , but high mobility and sensitivity to localize sources especially using the xrt @xcite and uvot @xcite , makes it also viable to follow - up unid gamma - ray objects discovered by . in fact , _ swift _ follow - up observations helped study many unid sources @xcite . here we tried to perform a systematic and uniform analysis of unid gamma - ray sources observed thus far with _ swift _ using the archival data . the selection criteria is given as follows ; ( 1 ) categorized as unid sources in 1fgl catalog , ( 2 ) localized at high galactic latitude @xmath7 @xmath8 10@xmath9 , ( 3 ) observational data are in public at the time of october 2011 , ( 4 ) the positional center of _ swift _ field - of - view is within 12 arcmin from the 1fgl sources . among 630 unid sources listed in the 1fgl catalog , this selection yields 134 sources which we analyzed here . in the reduction and the analysis of the _ swift_/xrt and uvot data , headas software version 6.11 and the most recent calibration databases ( caldb ) as of 2011 october 20 were used . we did not use bat data because most sources are not bright enough to be detected within short exposure of typically 10 ksec or less . in the xrt analysis , we only use the pc mode data , while only image data taken from photometry observation is used in the uvot analysis . two types of xrt archival data can be obtained from the _ swift _ data center , level 1 and 2 . level 2 cleaned data have gone through the standard pipeline process ; however , we calibrated the level 1 data ourselves in a way recommended by _ swift _ team . particularly , we selected the good time interval ( gti ) from the level 1 data using ` xrtpipeline ` . in this process , we only changed the default ` xrtpipeline ` selection in the temperature of ccds from `` @xmath10 '' to `` @xmath11 '' , where the former is the default value . in the xrt image analysis , we tried to detect the x - ray counterparts of 1fgl unid sources , and localize each source . first , we extracted x - ray images in the energy range of @xmath12 kev using ` xselect ` . next by using ` ximage ` , we searched for `` possible '' x - ray sources which were @xmath8 3 @xmath13 confidence level in photon statistics against background . the position of these sources are determined with a typical accuracy of @xmath14 using ` xrtcentroid ` . the results of x - ray source detection is listed in table 6 ( see , appendix ) . in the appendix , we also show the xrt images corresponding to each of the 134 1fgl unid gamma - ray sources indicating also the 2fgl error ellipses ( figure11 ) . in these images , bright radio sources and x - ray sources listed in the rosat all - sky survey bright source catalogue ( 1rxs ; * ) corresponding to the xrt sources are also plotted as magenta crosses . finally , if the x - ray sources were detected were within the 2fgl 95@xmath15 position error ellipse , we performed x - ray spectral analysis for those sources . we note that very bright x - ray sources with more than 0.6 c / s should cause serious pile - up effects in the xrt ccd , however , there were no such bright sources in our analyzed sample .    in the xrt spectral analysis , pha files were extracted from event files with ` xselect ` and exposure maps were made using ` xrtexpomap ` . we made auxiliary response files ( arfs ) using ` xrtmkarf ` , while we used the current redistribution matrix files ( rmfs ) in caldb . we extracted photons from circles with 30 arcsec radii around the source positions as the source regions , and we set the concentric rings centered at the source positions with radius 30 - 180 arcsec as the background regions . in the case when some background sources appear in the field , or overall regions can not be fitted in the ccd , we simply remove the region surrounding these background sources , or the region outside the ccd chip . if there is no source detected above @xmath16 inside the 2fgl error ellipse , we derived the upper limit assuming the 2fgl error ellipses as the source region of corresponding x - ray flux . the results of spectral analysis are included in the seds given in the appendix . we note that x - ray spectral data were binned at two different ways according to the source brightness ; ( a)binned with ` grppha ` so that at least 20 photons are included in each bin , ( b)divide x - ray spectral data ( 0.5 - 10.0 kev ) logarithmically into 5 bin . when the source have more than 40 counts , we used ( a ) , but otherwise we used ( b ) . we performed the analysis of uvot data only when the x - ray counterpart of 1fgl source was found in the _ swift_/xrt field of view . _ swift_/uvot archival data has six types of filters ( @xmath17 , @xmath18 , @xmath19 , @xmath20 , @xmath21 and @xmath22 ) , with each filter providing different wavelength data . when each filter included more than one observation , the images and exposure maps were summed using ` uvotimsum ` . using ` uvotdetect ` , we detected the sources which have high signal - to - noise ratio ( @xmath23 ) . we set the circles around those sources with radius  5 arcsec as the sources regions if any source was found in the 90% error ellipse of the _ swift_/xrt source . then , circles with radius 30  as the background regions were taken from the area where no sources are found . finally , we obtained the magnitude of each filter using ` uvotsource ` . the correction of galactic extinction were performed following the way described in cardelli et al . ( 1998 ) .      to construct seds of each 1fgl sources , we used not only the _ swift_/xrt and _ swift_/uvot flux data analyzed in this paper , but gamma - ray fluxes listed in the 2fgl catalog , and radio fluxes mostly from the ned database and w3browse based on a variety of catalogs . we searched for radio counterparts associated with the xrt or uvot objects which were mentioned above in the heasarc / master radio catalog , ( includes the nrao vla sky survey ( nvss ; * ? ? ? * ghz ) , the first survey catalog of 1.4-ghz radio sources ( first ; * ? ? ? * ghz ) , sydney university molonglo sky survey source catalog ( sumss ; * ? ? ? * mhz ) , vla low - frequency sky survey discrete source catalog ( vlss ; * ? ? ? * mhz ) , the westerbork in the southern hemisphere survey ( wish ; * ? ? ? * ) , australia telescope 20-ghz survey catalog ( at20 g ; * ? ? ? * ) , the green bank 6-cm catalog of radio sources ( gb6 ; * ? ? ? * ) , and parkes - mit - nrao southern , tropical , equatorial and zenith survey ( pmn ; * ? ? ? * ) ) and those radio fluxes are added in the seds . note that if no corresponding radio sources were found in the 2fgl 95% error ellipses , we obtained the upper limit from the most bright radio source in the error ellipse . likewise , if no source was found in the error ellipse but some sources were found outside of the region , we used the sensitivity limits of those sources as an upper limit . finally resultant seds and flux values of each wavelength are given in the appendix ( figure 12 , table 5 and 6 ) . we observed three objects that exhibited potentially interesting or anomalous seds ( which is difficult to be explained by standard emission models of blazars , i.e. , ssc or external compton models as explained in @xcite ) with the x - ray astronomy satellite @xcite . these were denoted in the 1fgl catalog as 1fglj0022.2 - 1850 , 1fglj0038.0 + 1236 , and 1fglj0157.0 - 5259 , and in the 2fgl catalog as 2fglj0022.2 - 1853 , 2fglj0037.8 + 1238 , and 2fglj0157.2 - 5259 , respectively . the observation logs are summarized in table1 . the observations were performed with xis which consists of four ccd cameras each placed in the focal plane of the x - ray telescope ( xrt ; * ? ? ? * ) , and with the hard x - ray detector ( hxd ) which consists of si pin photo - diodes ( hxd - pin ) and gso scintillation counters ( hxd - gso ) ( hxd ; * ? ? ? * ; * ? ? ? one of the xis sensors ( xis 1 ) has a back - illuminated ( bi ) ccd , while the other three ( xiss 0 , 2 , and 3 ) utilize front - illuminated ( fi ) ccds . however , because of an anomaly in 2006 november , the operation of xis2 was terminated . hence , here we use only the three remaining ccds . the xis was operated in the normal full - frame clocking mode with the @xmath24 or @xmath25 editing mode . we analyzed the screened xis data , reduced using the software version 1.2 . the screening was based on the following criteria : ( 1 ) only _ asca_-grade 0 , 2 , 3 , 4 , 6 events were accumulated , while hot and flickering pixels were removed from the xis image using the ` sisclean ` script @xcite , ( 2 ) the time interval after the passage of south atlantic anomaly was greater than 60s , ( 3 ) the object was at least @xmath26 and @xmath27 above the rim of the earth ( elv ) during night and day , respectively . in addition , we also selected the data with a cutoff rigidity ( cor ) larger than 6gv . in the reduction and the analysis of the xis data , headas software version 6.12 and a calibration databases ( caldb ) released on 2009 september 25 were used . the xis cleaned event data - set was obtained in the combined @xmath24 and @xmath25 edit modes using ` xselect ` . the hxd data were also processed in a standard way as follows . first , we obtained the appropriate version 2.0 `` tuned '' non - x - ray background file ( nxb ) for this observation . because the hxd background file has a time variation , we made a new gti file to match the good time interval ( gti ) between observation data and nxb data using ` mgtime ` . next , using this new gti file , we generated time - averaged hxd spectra with ` xselect ` . these were then dead time corrected using ` hxddtcor ` script . epoch appropriate response files for xis - nominal pointing were downloaded from the caldb website . the contribution from the cosmic x - ray background ( cxb ) was simulated following a recipe provided by the hxd team . we extracted the xis images within the photon energy range of @xmath28kev from only the two fi ccds ( xis 0 , xis 3 ) . in the image analysis , we excluded calibration sources at the corner of the ccd chips . the images of the nxb were obtained from the night earth data using ` xisnxbgen ` @xcite . since the exposure times for the original data were different from that of nxb , we calculated the appropriate exposure - corrected original and nxb maps using ` xisexpmapgen ` @xcite . the corrected nxb images were next subtracted from the corrected original images . in addition , we simulated flat sky images using ` xissim ` @xcite , and applied a vignetting correction . all the images obtained with xis0 and xis3 were combined and re - binned by a factor of 4 ( ccd pixel size @xmath29@xmath30m@xmath31@xmath30 m , so that @xmath32 pixels cover an @xmath33 region on the sky ; * ? ? ? * ) . throughout these processes , we performed vignetting correction for all the images . finally , the images were smoothed with a gaussian function with @xmath34 . note that the apparent features at the edge of these exposure corrected images are undoubtedly spurious due to low exposure in those regions .      in the spectral analysis of xis , we analyzed the three target sources as point sources , based on the result of our image analysis(see section 5 ) . source regions for spectral analysis indicated by inner green circles were selected around each detected x - ray sources within the error ellipse of a gamma - ray emitters . the corresponding background regions were indicated by outer green ellipse after the removal of source regions . moreover , if the x - ray sources other than target source was found , we excluded the region around those sources from the region for spectral analysis . we extracted the spectra from each source regions with ` xselect ` for each ccd ( xis 0 , xis 1 , xis 3 ) . next , we made redistribution matrix files ( rmfs ) and auxiliary response files ( arfs ) using ` xisrmfgen ` and ` xissimarfgen ` @xcite , respectively . in addition , we used the new contamination files ae_xi0_contami_20120711.fits , ae_xi1_contami_20120711.fits and ae_xi3_contami_20120711.fits , because response function of xis0 is imperfect for recent observations . using these rmfs and arfs , the corrected spectrum about energy response and the effective area of xis were obtained . finally , spectral analysis and model fitting were performed with ` xspec ` version 12.7.0 . in the spectral analysis of hxd , we also subtracted the nxb and cxb to obtain the hxd - pin spectrum , then we performed model fitting together with xis spectrum . we show in this section the results of x - ray image and spectral analysis for each object observed with . since we did nt detect any time - variability for each source in exposures , the results of timing analysis are not shown in this paper . we detected successfully significant signals from the x - ray counterpart of 1fglj0157.0 - 5259 with hxd / pin , but below the sensitivity limit of the hxd / gso , while other two sources were too faint to be detected either with hxd / pin or gso . therefore , as for hxd analysis about 1fglj0157.0 - 5259 in this paper , we only use the data from hxd / pin .      in our observations , we detected one x - ray point source ( ra , dec)=(5@xmath4.540 , -18@xmath4.894 ) within the updated 2fgl error ellipse corresponding to 1fglj0022.2 - 1850 . figure 1 shows the corresponding x - ray image of 1fglj0022.2 - 1850 , as described in section 4.1 . the radio source nvssj003750 + 123818 appears to be the counterpart of 1fglj0022.2 - 1850 , as indicated by the magenta cross at the center of this x - ray source ( see section 5 ) . moreover , one unknown point source is detected within the background region for spectral analysis ( because the central source is very bright , it is difficult to see this source in fig 1 ) .    in figure 4 , the x - ray spectrum of the source , which we argue is the most likely counterpart of 1fglj0022.2 - 1850 , is shown . the xis spectra is given for the energy range @xmath35kev . in the spectral analysis , the target x - ray source is so bright that we selected a source region assuming radii 3@xmath36 ( a typical half - power diameter of the xrt is 2@xmath36:@xcite ) . meanwhile , we excluded one contaminating field x - ray point source detected by , assuming the source region radii 2@xmath36 from the source and background regions for spectral analysis described in section 4.2 . the spectrum is well fitted by a single power - law continuum with a photon index , @xmath37 , moderated by the galactic absorption only . the galactic hydrogen column density was fixed as @xmath38@xmath39 @xcite . the value of @xmath40/d.o.f@xmath41 indicated that this is a satisfactory model for 1fglj0022.2 - 1850 . the details of the fitting results are summarized in table2 . one x - ray point source ( ra , dec)=(9@xmath4.472 , 12@xmath4.639 ) was found with _ suzaku _ within the improved 2fgl error ellipse corresponding to 1fglj0038.0 + 1236 . the corresponding x - ray image made through the way described in section 4.1 is shown in figure2 . moreover , one unknown point source is detected within the background region for spectral analysis . the radio source , nvssj00209 - 185332 ( shown by magenta cross ; see section 6 ) , is coincident with the x - ray position and we propose this to be the most likely counterpart of 1fglj0038.0 + 1236 . figure2 shows the x - ray spectrum of the point source detected by near the center of the 2fgl error ellipse of 1fglj0038.0 + 1236 ( @xmath35kev ) . the source region was selected with radii 3@xmath36 , because the target source is too bright not to cover entire region of the emission from target source with radii 2@xmath36 . when we selected the background region , the region from x - ray contaminant source was excluded with radii 2@xmath36 in order to not subtract too much as background . the spectrum could be well fitted by a single power - law continuum with @xmath42 , moderated by the galactic absorption only . the galactic hydrogen column density was fixed as @xmath43@xmath39 @xcite . the value of @xmath40/d.o.f@xmath44 indicates that this is a satisfactory model for 1fglj0038.0 + 1236 . the details of the fitting results are summarized in table3 . we succeeded in detecting a bright x - ray point source with _ suzaku _ within the 2fgl error ellispe corresponding to 1fglj0157.0 - 5259 . figure 3 shows the corresponding x - ray image ( see section 4.1 ) . the x - ray source is located at ( ra , dec)= ( 29@xmath4.253 , -53@xmath4.035 ) , as shown in figure3 . the position of the radio source , sumssj015657 - 530157 , is shown by a magenta cross ( see section 5 ) . in this observation , we did not find any other contamination source like in the above two observations . the x - ray spectrum ( xis + hxd ) of the source , which we propose to be the most likely counterpart of 1fglj0157.0 - 5259 , is shown in figure 6 within the energy range @xmath45kev ( xis @xmath46kev , hxd @xmath47kev ) . in this spectral analysis , we set the extraction region to be a radius of 4@xmath36 to encircle this bright source . on the other hand , we set the background region with the more larger radius , and the location of the center of background region displaced from the center of target source not to be over the region covering by ccd . the spectrum could be well fitted by a single power - law continuum with @xmath48 , moderated by the galactic absorption only . the galactic hydrogen column density was fixed as @xmath49@xmath39 @xcite . the value of @xmath40/d.o.f@xmath50 indicates that this is a satisfactory model for 1fglj0157.0 - 5259 . the details of the fitting results are summarized in table4 . in the uniform analysis of archival _ swift _ data , we found several objects which seemed to display anomalous seds that are not typical of agns or psrs . then we performed x - ray follow - up observations of three such sources to more accurately determine the seds of each object ( figures 7 , 8 , and 9 ) . different fluxes between _ swift_/xrt and /_xis _ seen in these seds indicate that these objects should have temporal variability that was not seen within the individual shorter exposures . moreover , thanks to the good sensitivity and long exposure of the data , we have additional hints to reveal the nature of each source as discussed below . an x - ray source found within the updated 2fgl error ellipse of 1fglj0022.2 - 1850 is positionally consistent with the radio source nvssj00209 - 185332 found in the nvss catalog @xcite ( see table2 ) . moreover , infrared counterpart source wisej002209.25 - 185334.7 located at ( ra , dec)=(5@xmath4.5385563 , -18@xmath4.8929772 ) was found in the wide field infrared survey explorer ( wise ) all - sky release @xcite . the sed of 1fglj0022.2 - 1850/wisej002209.25 - 185334.7/nvssj00209 - 185332 , including our _ suzaku_/xis data and derived xrt and uvot fluxes from _ swift _ , are shown in figure7 . from the relatively high radio flux and flat x - ray spectrum obtained with _ swift_/xrt , this object is likely to be a low - frequency peaked bl lac ( lbl ) . however , during our observation , the x - ray spectrum was observed to be substantially steeper , more typical of a high - frequency peaked bl lac ( hbl ) . moreover , the flat gev gamma - ray spectrum is typical of hbls like mrk 421 and mrk 501 , rather than a lbl . considering the cherenkov telescope array ( cta ) which is an initiative to built a next generation observatory for very - high energy gamma - rays will have an improved sensitivity by an order of magnitude with respect to current instruments ( @xmath51 above a few tev ) , the upward shape of the spectrum suggests the source could be detected also in tev energy in the near future .    in the case of 1fglj0038.0 + 1236 , the location of a x - ray counterpart discovered in our observations is consistent with nvssj003750 + 123818 described in table2 , and each optical counterpart sdssj003750.88 + 123819.9 ( classified as galaxy ) located at ( ra , dec)=(9@xmath4.462 , 12@xmath4.638875 ) and infrared counterpart wisej003750.87 + 123819.9 located at ( ra , dec)=(9@xmath4.4619958 , 12@xmath4.6388878 ) , were also found in the sloan digital sky survey ( sdss ) catalog @xcite and wise catalog respectively . the constructed radio to x - ray sed together with the _ swift _ xrt / uvot and the lat spectrum is shown in figure8 . since the x - ray spectrum appears very steep , this source seems to be associated with a hbl , while the steep gamma - ray spectrum observed with favors a fsrq origin of this source . while optical and ultraviolet fluxes are extremely bright , this could be due to a contribution of soft photons from the host galaxy as seen in some blazar spectra ( see e.g. , the sed of mrk 501 ; @xcite ) . these results show that this source is difficult to be explained by conventional leptonic models of blazars ( i.e. , ssc or external compton models ) .    in the case of 1fglj0157.0 - 5259 , our _ suzaku_/xis observations revealed the presence of a quite bright x - ray counterpart in the lat error circle , and since the hard x - ray fluxes of this source are very high , we could also obtain data from _ suzaku_/hxd . at the position of this x - ray source , the radio counterpart sumss j015657 - 530157 was found in the sumss catalog @xcite(table2 ) . the broad - band sed of 1fglj0157.0 - 5259/sumssj015657 - 530157 with our _ suzaku_/xis , hxd and derived _ swift_/xrt , uvot data is presented in figure9 . since the x - ray fluxes are connected by a straight line with the radio fluxes , these fluxes are seemed to be explained by synchrotron radiation . the peak frequency of the synchrotron spectrum is very high ( @xmath810 kev ) suggesting that the source could be one a rare type of `` extreme '' blazar like mrk 501 in the historical high state @xcite . if this source is an `` extreme '' blazar , observations at tev energies or more deep observations with may detect significant signal in the future . finally , we made the similar figure described in takahashi et al . ( 2012 ) for the 1fgl 134 unid objects in which we performed follow - up observations with _ swift_/xrt ( figure10 ) . this figure presents a comparison of the agns ( aqua ) , psrs ( green ) , and unassociated sources ( red ) which classified in the 2fgl catalog in the x - ray to gamma - ray flux ratios versus radio to gamma - ray ratios plane . the three sources we observed with in this paper are shown in black stars . apparently , that these sources are situated in the typical agn region of this diagnostic plane . it is noteworthy that , 1fglj0157.0 - 5259 is at the right edge of this typical agn region , and this means the x - ray and gamma - ray flux ratios of this source is quite high , such that @xmath52 2 , which is consistent with our speculation that the source is an extreme hbl - type blazar . in this paper we reported on the results of x - ray follow - up observations of three unid gamma - ray sources detected by instrument which indicate anomalous seds . we have successfully detected x - ray counterparts of 1fglj0022.2 - 1850 , 1fglj0038.0 + 1236 and 1fglj0157.0 - 5259 using . the characteristics of each object are summarized below . we also note that these objects display temporal variability in x - rays , as indicated by the different x - ray fluxes measured by _ suzaku_/xis and _ swift_/xrt ( see , figure7 , 8 , 9 ) . the x - ray spectrum of the discovered counterpart of 1fglj0022.2 - 1850 is well fitted by single power - law model with @xmath37 . the spectral shape obtained with ( in x - ray ) and ( in gamma ray ) suggest the source is typical of a hbl - type blazar , but previous @xmath53 observations rather show it was similar to the lbl - type blazar . the source is potentially a tev emitter that could be detected in the near future . in the case of 1fglj0038.0 + 1236 , the x - ray spectrum is well fitted by single power - law model with a photon index , @xmath54 . at first glance , this source also seems to be classified as a hbl because the x - ray spectrum seen in figure8 appear very steep . however , its steep gamma - ray spectrum observed with favors a fsrq origin for this source . these results show that this source is difficult to be explained by standard emission models of blazars , i.e. , ssc or external compton models . in the case of 1fglj0157.0 - 5259 , the x - ray spectrum obtained from xis and hxd are well fitted by single power - law model with a photon index , @xmath55 . from the multiwavelength analysis shown in figure9 , the peak frequency of synchrotron spectrum is very high ( @xmath5210 kev ) suggesting that source could be one of `` extreme '' blazar like mrk 501 in the historical high state . we would like to thank c. c. cheung for useful comments that helped to improve the organization of the manuscript . abdo , a. a. , ackermann , m. , ajello , m. , et al . 2009 , apj , 701 , 123    abdo , a. a. , ackermann , m. , ajello , m. , et al . 2010a , apjs , 187 , 460    abdo , a.  a. , ackermann , m. , ajello , m. , et al . 2010b , , 188 , 405    abdo , a. a. , ackermann , m. , ajello , m. , et al . 2010c , apj , 709 , 152    abdo , a. a. , ackermann , m. , ajello , m. , et al . 2010d , apj , 710 , 92    abdo , a. a. , ackermann , m. , ajello , m. , et al . 2010e , apj , 714 , 927    abdo , a. a. , ackermann , m. , ajello , m. , et al . 2010f , apj , 720 , 912    ahn , c. p. , alexandroff , r. , et al . 2012 , apjs , 203 , 21    atwood , w. b. , abdo , a. a. , ackermann , m. , et al . 2009 , apj , 697 , 1071    burrows , d. n. , hill , j. e. , nousek , j. a. , 2005 , space sci . , 120 , 165    cardelli , j. a. , et al . 1998 , apj , 345 , 245    cheung , c. c. , donato , d. , et al . 2012 , apj , 756 , 33    cougnard , i. , guillemot , l. , et al . 2011 , apj , 732 , 47    cohen , a. s. , lane , w. m. , et al . 2007 , aj , 134 , 1245    condon , j. j. , cotton , w. d. , greisen , e. w. , et al . 1998 , aj , 115 , 1693    dabrusco , r. , massaro , f. , paggi , a. , apjs , 206 , 12    day , c. , et al . , 1998 , the asca data reduction guide , tech . , ( greenbelt : nasa gsfc ) , v.2.0    de breuck , c. , tang , y. , et al . 2002 , a&a , 394 , 59    dickey , j. m. , & lockman , f. j. , 1990 , ara&a , 28 , 215    fossati , g. , maraschi , l. , celotti , a. , comastri , a. , & ghisellini , g. 1998 , mnras , 299 , 433    gehrels , n. , et al . 2004 , apj , 611 , 1005    ghisellini , g. 2004 , new astronomy review , 48 , 375    gregory , p. c. , scott , w. k. , douglas , k. , condon , j. j. , et al . 1996 , apjs , 103 , 427    hartman , r. c. , bertsch , d. l. , bloom , s. d. , et al . 1999 , apjs , 123 , 79    ishisaki , y. , maeda , y. , fujimoto , r. , et al . 2007 , , 59 , 113    kataoka , j. , mattox , j.  r. , quinn , j. , et al .  1999 , , 514 , 138    kataoka , j. , yatsu , y. , kawai , n. , et al . 2012 , apj , 757 , 176    keith , m. j. , johnston , s. , et al . 2011 , mnras , 414 , 1292    kokubun , m. , makishima , k. , takahashi , t. , et al . 2007 , , 59 , 53    kong , a. k. h. , huang , r. h. h. , et al . 2012 , apj , 747 , 3    koyama , k. , tsunemi , h. , dotani , t. , et al . 2007 , , 59 , 23    maeda , k. , kataoka , j. , nakamori , t. , et al . 2011 , apj , 729 , 103    massaro , f. , dabrusco , r. , paggi , a. , et al . 2013 , apjs , 206 , 13    mauch , t. , et al . 2003 , mnras , 342 , 1117    mitsuda , k. , bautz , m. , inoue , h. , et al . 2007 , pasj , 59 , 1    murphy , t. , sadler , e. m. , et al . 2010 , mnras , 402 , 2403    nolan , p. , abdo , a. a. , ackermann , m. , et al . 2011 , apjs , 199 , 31    ransom , s. m. , ray , p. s. , et al . 2011 , apj , 727 , 16    romani , r. w. , & shaw , m. s. 2011 , , 743 , 26    romani , r. w.  2012 , , 754 , 25    roming , p. w. a. , kennedy , t. e. , mason , k. o. , et al . 2005 , space sci . , 120 , 95    serlemitsos , p.  j. , soong , y. , chan , k .- w . , et al .  2007 , , 59 , 9    takahashi , t. , abe , k. , endo , m. , et al .  2007 , , 59 , 35    takahashi , y. , kataoka , j. , nakamori , t. , et al . 2012 , apj , 747 , 64    tawa , n. , hayashida , k. , nagai , m. , et al .  2008 , , 60 , 11    theureau , g. , parent , d. , et al . 2011 , a&a , 525 , 94    voges , w. , aschenbach , b. , et al . 1999 , a&a , 349 , 389    white , r. l. , becker , r. h. , helfand , d. j. , & gregg , m. d. 1997 , apj , 475 , 479    wright , a. e. , griffith , m. r. , et al . 1994 , apj , 422 , 642    wright , e. l. , et al . 2010 , aj , 140 , 1868    ccccc target name & r.a . [ deg ] & dec . [ deg ] & exposure [ ks ] & obs . start ( ut ) + 1fglj0022.2 - 1850 & 5.5540 & -18.9060 & 34.2 & 2012-may.30 12:57:00 + 1fglj0038.0 + 1236 & 9.4627 & 12.6391 & 18.8 & 2012-jun.29 23:56:00 + 1fglj0157.0 - 5259 & 29.3640 & -53.0280 & 12.1 & 2012-may.28 16:19:00 +    ccccc target name & r.a . [ deg ] & dec . [ deg ] & @xmath56 [ mjy ] & @xmath57 [ mjy ] + nvss j00209 - 185332 & 5.5381667 & -18.892444 & @xmath58 & - + nvss j003750 + 123818 & 9.461875 & 12.638556 & @xmath59 & - + sumss j015657 - 530157 & 29.240833 & -53.032778 & - & @xmath60 +    kev energy band . the magenta cross denote the position of radio counterpart source nvssj00209 - 185332 , the yellow dotted ellipse denotes the 95@xmath15 position error of 2fglj0022.2 - 1853 , and the inner green ellipse denote the source extraction region , the outer green ellipse without inner source region denote the background extraction region.,title="fig:",width=566 ] +     +     +     +     +     +    , 4.6@xmath61 , 12@xmath61 and 22@xmath61 ) are taken from the wise catalog . the optical / uv fluxes were derived from the _ swift_/uvot observations ( this work ) . the x - ray are fluxes taken from the _ suzaku_/xis and _ swift_/xrt observations ( this work ) . finally , the gamma - ray data points are taken from the 2fgl catalog @xcite.,title="fig : " ] +    , 4.6@xmath61 , 12@xmath61 and 22@xmath61 ) are taken from the wise catalog . the optical / uv fluxes were derived from the _ swift_/uvot observations ( this work ) and the sdss catalog . the x - ray fluxes are taken from the _ suzaku_/xis and _ swift_/xrt observations ( this work ) . finally , the gamma - ray data points are taken from the 2fgl catalog @xcite.,title="fig : " ] +     +     + \(1 ) 1fglj0001.94158 +                                                                                                                                                                                                                                                                           \(133 ) 1fglj2350.13005 +   fov . one or more sources are detected within the _ swift_/xrt fov . unfortunately , 2fgl error regions of some sources run off the edge of _ swift_/xrt fov . the signal - to - noise acceptance threshold is set to @xmath63 . the yellow ellipses show @xmath64 error regions of 2fgl catalog gamma - ray sources , and red ellipses show that of 1fgl catalog sources . if there are the radio and bright x - ray sources associated with gamma - ray source , we show those sources as magenta crosses.,title="fig:",width=196 ]    \(134 ) 1fglj2352.1@xmath621752 +   fov . one or more sources are detected within the _ swift_/xrt fov . unfortunately , 2fgl error regions of some sources run off the edge of _ swift_/xrt fov . the signal - to - noise acceptance threshold is set to @xmath63 . the yellow ellipses show @xmath64 error regions of 2fgl catalog gamma - ray sources , and red ellipses show that of 1fgl catalog sources . if there are the radio and bright x - ray sources associated with gamma - ray source , we show those sources as magenta crosses.,title="fig:",width=196 ]
we have analyzed all the archival x - ray data of 134 unidentified ( unid ) gamma - ray sources listed in the first _ 
 fermi / lat _ ( 1fgl ) catalog and subsequently followed up by _ swift / xrt_. we constructed the spectral energy distributions ( seds ) from radio to gamma - rays for each x - ray source detected , and tried to pick up unique objects that display anomalous spectral signatures . 
 in these analysis , we target all the 1fgl unid sources , using updated data from the second _ fermi / lat _ ( 2fgl ) catalog on their lat position and spectra . 
 we found several potentially interesting objects , particularly three sources , 1fglj0022.2 - 1850 , 1fglj0038.0 + 1236 and 1fglj0157.0 - 5259 , which were then more deeply observed with as a part of an ao7 program in 2012 . 
 we successfully detected an x - ray counterpart for each source whose x - ray spectra were well fitted by a single power - law function . 
 the positional coincidence with a bright radio counterpart ( currently identified as agn ) in the 2fgl error circles suggests these are definitely the x - ray emission from the same agn , but their seds show a wide variety of behavior . in particular , the sed of 1fglj0038.0 + 1236 is difficult to be explained by conventional emission models of blazars . the source 1fglj0022.2 - 1850 may be in a transition state between a low - frequency peaked bl lac and a high - frequency peaked bl lac object , and 1fglj0157.0 - 5259 could be a rare kind of extreme blazar . 
 we discuss the possible nature of these three sources observed with , together with the x - ray identification results and seds of all 134 sources observed with _ swift_/xrt .