SIMPLE = T / file does conform to FITS standard BITPIX = 16 / number of bits per data pixel NAXIS = 0 / number of data axes EXTEND = T / FITS dataset may contain extensions COMMENT FITS (Flexible Image Transport System) format is defined in 'AstronomyCOMMENT and Astrophysics', volume 376, page 359; bibcode: 2001A&A...376..359H HDUNAME = 'PRIMARY ' / ASCDM block name LONGSTRN= 'OGIP 1.0' / The HEASARC Long String Convention may be used.COMMENT This FITS file may contain long string keyword values that are COMMENT continued over multiple keywords. The HEASARC convention uses the & COMMENT character at the end of each substring which is then continued COMMENT on the next keyword which has the name CONTINUE. ORIGIN = 'ASC ' / Source of FITS file CREATOR = 'mkarf v0.6.2-0' / Program creating this file MJD_OBS = 5.5293918413902E+04 / Modified Julian date of observation DS_IDENT= 'ADS/Sa.CXO#obs/10986' / dataset identifier CHECKSUM= 'hAK0k6I0hAI0h5I0' / HDU checksum updated 2011-10-15T06:54:36 DATASUM = ' ' / data unit checksum updated 2011-05-12T03:59:48 DATE = '2011-10-15T06:54:36' / Date and time of file creation DATE-OBS= '2010-04-07T22:02:30' / Observation start date DATE-END= '2010-04-08T08:17:14' / Observation end date TIMESYS = 'TT ' / Time system MJDREF = 5.0814000000000E+04 / MJD zero point for times TIMEZERO= 0.0000000000000E+00 / Clock correction TIMEUNIT= 's ' / Time unit CLOCKAPP= T / default DETNAM = 'ACIS-1 ' / ACIS-I1 FILTER = ' ' GRATING = 'NONE ' CYCLE = 'P ' / events from which exps? Prim/Second/Both SIM_X = -7.8090834371673E-01 / [mm] SIM offset SIM_Y = 0.0000000000000E+00 / [mm] SIM offset SIM_Z = -2.3358743446083E+02 / [mm] SIM offset TSTART = 3.8706495096117E+08 / Observation start time TSTOP = 3.8710183456304E+08 / Observation end time MISSION = 'AXAF ' / Mission TELESCOP= 'CHANDRA ' / Telescope Used INSTRUME= 'ACIS ' / Instrument OBS_ID = '10986 ' / Observation id OBI_NUM = 0 / Obi number SEQ_NUM = '200617 ' / Sequence number END XTENSION= 'BINTABLE' / binary table extension BITPIX = 8 / 8-bit bytes NAXIS = 2 / 2-dimensional binary table NAXIS1 = 12 / width of table in bytes NAXIS2 = 1070 / number of rows in table PCOUNT = 0 / size of special data area GCOUNT = 1 / one data group (required keyword) TFIELDS = 3 / number of fields in each row EXTNAME = 'SPECRESP' / Imaging ARF HDUNAME = 'SPECRESP' / ASCDM block name CONTENT = 'SPECRESP' HDUVERS = '1.1.0 ' HDUCLASS= 'OGIP ' HDUCLAS1= 'RESPONSE' HDUCLAS2= 'SPECRESP' HDUVERS1= '1.0.0 ' / Obsolete Keyword HDUVERS2= '1.1.0 ' / Obsolete Keyword ARFVERSN= '1992a ' / Obsolete Keyword TTYPE1 = 'ENERG_LO' / Energy TFORM1 = '1E ' / format of field TUNIT1 = 'keV ' TLMIN1 = 0.0000000E+00 TLMAX1 = 2.0000000E+01 TTYPE2 = 'ENERG_HI' / Effective Area TFORM2 = '1E ' / format of field TUNIT2 = 'keV ' TLMIN2 = 0.0000000E+00 TLMAX2 = 2.0000000E+01 TTYPE3 = 'SPECRESP' / Effective Area TFORM3 = '1E ' / format of field TUNIT3 = 'cm**2 ' LONGSTRN= 'OGIP 1.0' / The HEASARC Long String Convention may be used.COMMENT This FITS file may contain long string keyword values that are COMMENT continued over multiple keywords. The HEASARC convention uses the & COMMENT character at the end of each substring which is then continued COMMENT on the next keyword which has the name CONTINUE. ORIGIN = 'ASC ' / Source of FITS file CREATOR = 'mkarf v0.6.2-0' / Program creating this file ASCDSVER= 'CIAO 4.3' / ASCDS version number MJD_OBS = 5.5293918413902E+04 / Modified Julian date of observation DS_IDENT= 'ADS/Sa.CXO#obs/10986' / dataset identifier REVISION= 1 / Processing version of data CHECKSUM= '7kgD7jdA7jdA7jdA' / HDU checksum updated 2011-10-15T06:54:36 DATASUM = '627527949' / data unit checksum updated 2011-10-15T06:54:36 RAND_SKY= 5.0000000000000E-01 RAND_PI = 0.0000000000000E+00 EQUINOX = 2.0000000000000E+03 / default DATE = '2011-10-15T06:54:36' / Date and time of file creation DATE-OBS= '2010-04-07T22:02:30' / Observation start date OBS_MODE= 'POINTING' / Observation mode DATE-END= '2010-04-08T08:17:14' / Observation end date TIMESYS = 'TT ' / Time system MJDREF = 5.0814000000000E+04 / MJD zero point for times TIMEZERO= 0.0000000000000E+00 / Clock correction TIMEUNIT= 's ' / Time unit BTIMNULL= 3.8221123490213E+08 / Basic Time offset (s) DATACLAS= 'OBSERVED' / default BTIMRATE= 2.5625001301465E-01 / Basic Time clock rate (s / VCDUcount) BTIMDRFT= 1.3002398907991E-19 / Basic Time clock drift (s / VCDUcount^2) FILTER = 'NONE ' / QE includes all filters RESPFILE= '0.3:11.0:0.01' / RMF File ASPFILE = '../../acisf10986/products/aux/asphist_1.fits.gz' / Aspect Histogram FBTIMCORR= 0.0000000000000E+00 / Correction applied to Basic Time rate (s) TIMEREF = 'LOCAL ' / Time reference (barycenter/local) TASSIGN = 'SATELLITE' / Time assigned by clock CLOCKAPP= T / default SIM_X = -7.8090834371673E-01 / [mm] SIM offset SIM_Y = 0.0000000000000E+00 / [mm] SIM offset SIM_Z = -2.3358743446083E+02 / [mm] SIM offset FOC_LEN = 1.0070000000000E+04 / HRMA focal length (mm) TIERRELA= 1.0000000000000E-09 / default TIERABSO= 5.0000000000000E-05 / default TIMVERSN= 'ASC-FITS-2' / Timing system definition TSTART = 3.8706495096117E+08 / Observation start time GRATING = 'NONE ' / Grating DETNAM = 'ACIS-1 ' / ACIS-I1 RA_PNT = 2.2275269500872E+01 / Pointing RA DEC_PNT = -7.3536888181509E+01 / Pointing Dec ROLL_PNT= 1.8518336759269E+02 / Pointing Roll RA_TARG = 2.2301667000000E+01 / Observer's specified target RA DEC_TARG= -7.3533806000000E+01 / Observer's specified target Dec DEFOCUS = 1.4398718632593E-03 / SIM defocus (mm) RA_NOM = 2.2275269500872E+01 / Nominal RA DEC_NOM = -7.3536888181509E+01 / Nominal Dec ROLL_NOM= 1.8518336759269E+02 / Nominal Roll TSTOP = 3.8710183456304E+08 / Observation end time STARTMJF= 16928 / Major frame ctr value at start of data STARTMNF= 58 / Start minor frame ctr at start of data STARTOBT= 0.0000000000000E+00 / On-Board MET close to STARTMJF and STARTMNF STOPMJF = 18010 / Major frame ctr value at stop of data STOPMNF = 89 / Stop minor frame ctr at end of data TIMEPIXR= 5.0000000000000E-01 / default TIMEDEL = 3.2410400000000E+00 / timedel Lev1 (in seconds) CTI_CORR= T CTI_APP = 'PPPPPBPBPP' MISSION = 'AXAF ' / Mission TELESCOP= 'CHANDRA ' / Telescope Used INSTRUME= 'ACIS ' / Instrument READMODE= 'TIMED ' / Read mode FRACEXPO= 9.2853475855677E-01 / Effective fractional exposure DATAMODE= 'FAINT ' / Data mode FLSHTIME= 0.0000000000000E+00 / Inferred duration of each flush. (s) CYCLE = 'P ' / events from which exps? Prim/Second/Both TITLE = 'Cosmic archaeology with Chandra: from a supergiant shell to young s&'CONTINUE 'tellar objects in NGC 602' / Proposal title OBSERVER= 'Dr. Lidia Oskinova' / Principal investigator OBJECT = 'NGC 602 ' / Source name OBS_ID = '10986 ' / Observation id OBI_NUM = 0 / Obi number SEQ_NUM = '200617 ' / Sequence number ONTIME = 3.4051161035240E+04 / [s] Sum of GTIs ONTIME1 = 3.4051161035240E+04 / [s] Sum of GTIs LIVETIME= 3.3619984731064E+04 / [s] Livetime LIVTIME1= 3.3619984731064E+04 / [s] Livetime EXPOSURE= 3.3619925604552E+04 / [secs] Total exposure time EXPOSUR1= 3.3619984731064E+04 / [s] Exposure time DTCOR = 9.8733739787229E-01 / Dead time correction ASPTYPE = 'KALMAN ' FP_TEMP = 1.5344601440000E+02 / [K] Focal Plane Temperature RADESYS = 'ICRS ' / default HISTORY ----------------------------------------------------------------- HISTORY MKARF Processing History HISTORY ----------------------------------------------------------------- HISTORY Startup Directory: /xassist/data/pipeline4/chandra/10986/acisf10986/prodHISTORY ucts HISTORY Cmd Line: mkarf @@/tmp/tmpO5gV8K.par mode=hl HISTORY Parameter file used: /tmp/tmpO5gV8K.par HISTORY Detector Mask File: ../../acisf10986/data/aux/acisf10986_000N001_msk1.fiHISTORY ts.gz HISTORY Source SKY position: (3960.79,4656.85) HISTORY ---------------------------------------------------------------------- HISTORY ARDLIB History Records HISTORY ---------------------------------------------------------------------- HISTORY ARDLIB Version: 0.8.5 HISTORY File used for CALDB info: ../../acisf10986/products/events/fullrun_ccd1_HISTORY acisf10986_pi14-548_pass1_cl_src3_src.evt.gz HISTORY Parameter file: /opt/ciao-4.3/param/ardlib.par HISTORY ACIS QE File: /opt/ciao-4.3/CALDB/data/chandra/acis/qe/acisD1997-04-17qeHISTORY N0006.fits[2] HISTORY ACIS Uniformity File: /opt/ciao-4.3/CALDB/data/chandra/acis/qeu/acisD200HISTORY 0-01-29qeuN0006.fits[2] HISTORY ACIS Contamination File: /opt/ciao-4.3/CALDB/data/chandra/acis/contam/acHISTORY isD1999-08-13contamN0006.fits[2] HISTORY ACIS 1 Badpix File: /opt/ciao-4.3/CALDB/data/chandra/acis/badpix/acisD20HISTORY 00-11-28badpixN0003.fits[2] HISTORY Vignetting File: /opt/ciao-4.3/CALDB/data/chandra/default/vignet/hrmaD19HISTNUM = 22 HISTORY 96-12-20vignetN0003.fits[1] HISTORY Onaxis Area File: /opt/ciao-4.3/CALDB/data/chandra/default/axeffa/hrmaD1HISTORY 996-12-20axeffaN0008.fits[1] HISTORY ---------------------------------------------------------------------- HISTORY ---------------------------------------------------------------------- HISTORY PIXLIB History Records HISTORY ---------------------------------------------------------------------- HISTORY PIXLIB Version: 4.0.0 HISTORY ****** PIXLIB Parameter File ***** HISTORY /opt/ciao-4.3/param/geom.par: HISTORY instruments = /opt/ciao-4.3/CALDB/data/chandra/default/geom/telD1999-07HISTORY -23geomN0006.fits(CALDB) HISTORY aimpoints = /opt/ciao-4.3/CALDB/data/chandra/default/aimpts/telD1999-HISTORY 07-23aimptsN0002.fits(CALDB) HISTORY tdet = /opt/ciao-4.3/CALDB/data/chandra/default/tdet/telD1999-07HISTORY -23tdetN0001.fits(CALDB) HISTORY sky = /opt/ciao-4.3/CALDB/data/chandra/default/sky/telD1999-07-HISTORY 23skyN0002.fits(CALDB) HISTORY shell = /opt/ciao-4.3/CALDB/data/chandra/default/sgeom/telD1999-0HISTORY 7-23sgeomN0001.fits(CALDB) HISTORY obsfile = nowT00:00:00() HISTORY ****** PIXLIB System Configuration ****** HISTORY Telescope = AXAF HISTORY Focal Length (mm) = 10070.000 HISTORY Detector = ACIS HISTORY Focal Plane Sys. = FP-1.1 HISTORY Tiled Detector Plane Sys. = ACIS-2.2 HISTORY SIM Offset (mm) = (0.684 0.75 236.552) HISTORY Aim Point(NONE) (mm) = (-0.780908 0 -233.587) HISTORY Grating Arm = HEG HISTORY Grating Order = 1 HISTORY Dispersion Plane Sys. = ASC-GDP-1.1 HISTORY Rowland Circle (mm) = 8632.48 HISTORY ---------------------------------------------------------------------- HISTORY TOOL :mkarf 2011-10-15T06:54:36 ASC00001HISTORY PARM :asphistfile=../../acisf10986/products/aux/asphist_1.fitsASC00002HISTORY CONT :.gz ASC00003HISTORY PARM :outfile=../../acisf10986/products/spectra/fullrun_ccd1_aASC00004HISTORY CONT :cisf10986_pi14-548_pass1_cl_src3.arf ASC00005HISTORY PARM :sourcepixelx=3960.79409 ASC00006HISTORY PARM :sourcepixely=4656.85409 ASC00007HISTORY PARM :engrid=0.3:11.0:0.01 ASC00008HISTORY PARM :obsfile=../../acisf10986/products/events/fullrun_ccd1_acASC00009HISTORY CONT :isf10986_pi14-548_pass1_cl_src3_src.evt.gz ASC00010HISTORY PARM :pbkfile=../../acisf10986/data/aux/acisf387067076N001_pbkASC00011HISTORY CONT :0.fits.gz ASC00012HISTORY PARM :dafile=CALDB ASC00013HISTORY PARM :mirror=HRMA ASC00014HISTORY PARM :detsubsys=ACIS-I1 ASC00015HISTORY PARM :grating=NONE ASC00016HISTORY PARM :maskfile=../../acisf10986/data/aux/acisf10986_000N001_msASC00017HISTORY CONT :k1.fits.gz ASC00018HISTORY PARM :ardlibparfile=ardlib.par ASC00019HISTORY PARM :geompar=geom ASC00020HISTORY PARM :verbose=0 ASC00021HISTORY PARM :clobber=yes ASC00022END >>R< >R> ={> >>'>>{>>{>33>>33>Q?)5>Q>p?g9>p>\?E>\>Ǯ?߳>Ǯ>@>>@>> =@Sm> =>(@o>(>G@˓>G>ff@DW>ff>A>>A3>>AWL>>HA>H?A/C??\A:?\?A??AT?? =qA? =q? A? ?\)A`_?\)?AbJ??zA?z? =A,? =?A2O??(A?(?RB\?R?!GB!?!G?# B)f?# ?&ffB< ?&ff?(BQ5?(?+Bh?+?.{BX?.{?0B ?0?333Bs?333?5Brr?5?8QB?8Q?:HBM?:H?=pB?=p?@Bc?@?B\Bh?B\?EBݔ?E?GB5p?G?J=qBUj?J=q?LCo[?L?O\)C )?O\)?QC,?Q?TzC?Tz?W =C$?W =?YC,?Y?\(C4aA?\(?^RC@(@Cx@@pCA@p@{C;@{@RCa@R@\)Ct`@\)@ CU@ @ Cc;@ @!GC{@!G@!C@!@"\C@"\@#33CE@#33@# C1@# @$zC"@$z@%C0*@%@%Ch@%@&ffC&'@&ff@' =C@' =@'Cv@'@(QC@(Q@(CО@(@)Cb@)@*=qCܩ@*=q@*HC{@*H@+C@+@,(C@,(@,C@,@-pCb$@-p@.{C޼@.{@.RCL@.R@/\)C1l@/\)@0C}@0@0Cm@0@1GC#/@1G@1C@1@2\CL@2\@333CG@333@3 C @3 @4zCd@4z@5CA@5@5Ck@5@6ffCvp@6ff@7 =Cb@7 =@7C9@7@8QC.@8Q@8CX@8@9C@9@:=qCB@:=q@:HC@:H@;C!@;@<(Cs@<(@{C@>{@>RC@>R@?\)C9@?\)@@C@@@@CeI@@@AGC;@AG@ACb@A@B\C;@B\@C33C%@C33@C C;@C @DzC@Dz@EC)o@E@ECuo@E@FffC;@Fff@G =C)@G =@GCF@G@HQCj@HQ@HC@H@IC@I@J=qC*@J=q@JHC 9@JH@KCs@K@L(C#@L(@LC@L@MpC@Mp@N{CR@N{@NRC;L@NR@O\)C@O\)@PC @P@PC{@P@QGC@QG@QCmy@Q@R\Ci@R\@S33C3u@S33@S C7@S @TzC@Tz@UC@U@UCT@U@VffC@Vff@W =C0@W =@WC@W@XQC@XQ@XCH@X@YCw@Y@Z=qC@Z=q@ZHC P@ZH@[CZ@[@\(CvU@\(@\C@\@]pCs@]p@^{C@^{@^RC/@^R@_\)Cl[@_\)@`C9@`@`C@`@aGC@aG@aCZ9@a@b\C@b\@c33C@c33@c C@@c @dzC 9@dz@eC=8@e@eC^@e@fffC@fff@g =CF@g =@gC(@g@hQC@hQ@hC/@h@iCQK@i@j=qCp@j=q@jHC@jH@kC@k@l(CƇ@l(@lC_@l@mpC@mp@n{C,@n{@nRC:m@nR@o\)CD4@o\)@pCM@p@pC[@p@qGCk@qG@qC|@q@r\C@r\@s33C~@s33@s C~@s @tzC@tz@uCy@u@uC7@u@vffC@vff@w =C@w =@wC @w@xQC @xQ@xCb@x@yC#@y@z=qC+@z=q@zHC0l@zH@{C4@{@|(CT@|(@|Ct@|@}pC@}p@~{C@~{@~RC@~R@\)C@\)@C }@@QC%@Q@CC@@Cb @@GCGe@G@C,@@C@@=qC@=q@\C @\@HC@H@33C@33@Ch@@ C @ @(C@(@zC @z@C@@Cx@@pCeP@p@CR@@{C<@{@ffC'y@ff@RC@R@ =C@ =@\)C@\)@C:@@CO@@QC@Q@Ck@@CPV@@GC*U@G@CK@@C@@=qC#@=q@\C@\@HCq@H@33CO@33@C J@@ C@ @(C@(@zC@z@C[@@C+ @@pC@p@C@@{C<@{@ffCW@ff@RC@R@ =C@ =@\)C*@\)@Ci@@C7@@QC@Q@CQ@@C@@GCI9@G@C @@C@@=qCr@=q@\C.@\@HC8@H@33CH@33@C=@@ C@ @(CG@(@zCK@z@C>@@C^@@pCD@p@C޳@@{C@{@ffCH@ff@RC @R@ =CR@ =@\)C6@\)@C}@@Cc@@QC)@Q@C`@@Cg'@@GC 7@G@CW@@CIO@@=qC$@=q@\Ci@\@HC@H@33C@33@CU@@ C@ @(Cq@(@zC~@z@C_@@CD@@pCʻ@p@CL2@@{CԒ@{@ffC]@ff@RCM@R@ =Cm^@ =@\)C@\)@Cv@@C@@QCv@Q@C @@Co@@GC@G@Cn@@C@@=qCg@=q@\Cr@\@HCY@H@33C^@33@CK@@ C?@ @(CL@(@zCq@z@CHC@@C@@pC1@p@C@@{C@{@ffC@ff@RCz@R@ =C|@ =@\)C@\)@C[@@CŽ@@QC2@Q@C@@C@@GC})@G@C@@CU#@@=qCy@=q@\C3@\@HC@H@33C )@33@CxZ@@ C@ @(CP@(@zC!@z@C@@Cy@@pC;@p@CZ@@{Co@{@ffCDJ@ff@RC@R@ =C@ =@\)C~h@\)@C@@C~@@QC}>@Q@C|p@@C{6<@@GCz0{@G@Cy+ @@Cx@@=qCv%@=q@\Cu!@\@HCt@H@33Csn@33@Crz@@ Cqb(@ @(CpJ,@(@zCo8@z@Cn'}@@Cm@@pCl@p@Ck@@{Cj @{@ffCi@ff@RCh@R@ =Cg@ =@\)Cf t@\)@Cei@@Cd@@QCc@Q@Cb @@Ca@@GC_@G@C^@@C]+@@=qC\\@=q@\C[@\@HCZy@H@33CYr@33@CX@@ CW{@ @(CVa@(@zCU̦@z@CT@@CS@@pCS@p@CRNX@@{CQ'6@{@ffCP@ff@RCN@R@ =CM@ =@\)CL@\)@CK@@CJ@@QCI'@Q@CH@@CGT@@GCF@G@CEg@@CDy@@=qCC5@=q@\CB@\@HCA@H@33C@@33@ÅC?@Å@ C>r@ @(C=@(@zC@ @(B=A@(@zB;`@z@B:l@@B8h@@pB7@p@B6 q@@{B4@{@ffB33@ff@RB1ء@R@ =B0@ =@\)B/7@\)@B-<@AB,gsAA(B+cA(AQB)PAQAzB(AzAB'EAAB&AAB$ӥAAB#AAGB"AGApB!mfApAB 8AABAAB۠AA{B%A{A=qBA=qAffBAffA\BuA\ARBt\ARAHBsxAHA =Bu0A =A33BwA33A\)BnA\)AB[AABI=AA BOCA ABV"AA(B\zA(AQBbAQAzB iAzAB AAB yAAB ?AAB AAGBAGApBvApAB 9AAB!lAABAAA{BcCA{A=qBGA=qAffB1AffA\BA\ARBԞARAHAAHA =A@A =A33A@A33A\)AA\)AAZwAAAAA A)A AAsAA(AA(AQA{AQAzAAzAAdAAAAAA]AA AA A GA\A GA pAA pA AoA A AA A A<;A A {AA {A =qA*A =qA ffAݾA ffA \AI{A \A RAA RA HAQA HA =AA =A 33ASA 33A \)A7A \)A A>A A AѲA A A8 A A Aο=A A (ABA (A QAA QA zAA=A zA AA A AJA A A A A ARbA A GAטA GA pASXA pA AA A AVhA A AA A{AA{A=qAA=qAffAVAffA\A>A\ARA&ARAHAAHA =AA =A33A?A33A\)AA\)AAUMAAAAA A:]A AAbAA(ACA(AQAnAQAzA&AzAAyIAAAcAAAAAAiAAGAAGApAApAA'AAA AAAOAA{AA{A=qAaLA=qAffAAffA\AQA\ARAXARAHAAHA =A`A =A33A?'A33A\)AA\)AAAAAVAA A8A AAn3AA(AA(AQAAQAzAAzAA^AAAAAA}xAAA{ AAGAxAGApAvC4ApAAsLAAAq;AAAoAA{AlA{A=qAjbfA=qAffAhAffA\Ae A\ARAcC4ARAHA`ٝAHA =A^yA =A33A\A33A\)AYA\)AAWUAAAT*AA ARA AAPc2AA(ANA(AQAKAQAzAIAzAAGD?AAADAAABiAAA@yAAGA>FAGApA; ApAA9AAA7hAAA5>AA{A3A{A=qA1 A=qAffA/eAffA\A,A\ARA*ARAHA(AHA =A&tA =A33A$[yA33A\)A">gA\)AA AAA,AA A]A AA4AA(A[A(AQA$AQAzAAzAAAAAlcAAA gxAAA s:AAGA AGApARApAAAAA?AAAAA{@A{A=q@HA=qAff@AffA\@?A\AR@4ARAH@)AHA =@A =A33@ioA33A\)@A\)A@pAA@GAA @ؓA A @&A,A-?91A-A-G?4JA-GA-p?/kA-pA-?*A-A-?%A-A-?!1UA-A.{?kA.{A.=q?FA.=qA.ff?|A.ffA.\??A.\A.R? vA.RA.H?A.HA/ =?A/ =A/33?0A/33A/\)>@A/\)A/>A/A/>J0A/A/ >ḷA/ A0>/C