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1. Analyzing Brightness Variation of an SX Phoenicis Star (XX Cyg)Department of Physics & Astronomy Minnesota State University Moorhead(MSUM) Shouvik Bhattacharya04.05.20134/5/2013 1 2. Outline Background Senior Thesis Theory Methods Results Conclusions4/5/20132 3. Background A star can be defined as a self-gravitatingcelestial object in which there is, or there was(in the case of dead stars), sustainedthermonuclear fusion of hydrogen in their core(LeBlanc 2010). Variable stars vary their brightness. SX Phoenicis is categorized as a HighAmplitude Delta Scuti star.4/5/2013 3 4. Motivation Took Introduction to Research in fall 2010 andread about pulsation theory. Observed SZ Lyn a Delta Scuti star back in spring2011. Found out that there exists a research groupnamed (Delta Scuti Network) in summer of 2011. Scientific Observations of XX Cyg began in fall2011. Found that XX Cygs period has been reported in8 decimal places in spring 2012.4/5/20134 5. Senior Thesis Brightness variation of XX Cyg in differentoptical filters The period of XX Cyg (using the informationon brightness variation in V and R filters) andcompare it with the accepted value4/5/20135 6. Theory SX Phoenicis star has both radial andnonradial modes of pulsation. Researchers predicted that the period ofpulsation is slowly increasing for XX Cyg. Reported period .134865117 days, increasingper year at 1.3 10-8 and theoreticallyincreasing per year at 6.2 10-8 (Conidis et al. 2011)4/5/20136 7. Methods Data Acquisitions (a DFM engineered 16Cassegrain telescope, an Apogee Alta U-seriesCCD Camera, an Optec Intelligent FilterWheel). Getting brightness information Calibration Aperture photometry and Differential photometry Getting period from brightness4/5/20137 8. Data AcquisitionsTable 1.-XX Cyg was observed in the following nights using the B,I,R,V filters at the Paul PFeder Observatory. DateB,I,R,V Other 08.28.2011All 09.05.2011- R 09.06.2011- B,R 09.07.2011- B, R 09.08.2011All - 09.10.2011All - 09.14.2011All - 09.27.2011All - 10.02.2011All - 10.16.2011All - 03.21.2012- R,V 04.03.2012- R4/5/2013 8 9. Bias A list of unwanted signals: Cosmic rays, sky light, instruments, CCD chips, time lag on the computers.A bias frame is exposed at 0 second with the camera shutter closed. Bias frames give an idea of the read-out noise and how the computer interfere in the imaging process. A bias frame sets the pixel scales and the CCD output to the same value, which helps to produce a more accurate image. We subtract bias from the science images. We used the MaxIM DL 5 imaging software at the Paul P Feder Observatory. The software allows us to use an inbuilt feature to take a bias frame with a zero second exposure. A master bias frame actually takes care of the incidence of the cosmic rays, as it applies the mean or minmax function to the bias frames.4/5/20139 10. Bias SIMPLE = T BITPIX= -32 /8 unsigned int, 16 & 32 int, -32 & -64 real NAXIS = 2 /number of axes NAXIS1 = 3073 /fastest changing axis NAXIS2 = 2048 /next to fastest changing axis BSCALE = 1.0000000000000000 /physical = BZERO + BSCALE*array_value BZERO = 0.00000000000000000 /physical = BZERO + BSCALE*array_value EXPTIME = 0.00000000000000000 /Exposure time in seconds EXPOSURE = 0.00000000000000000 /Exposure time in seconds HISTORY Cal Master Bias, 20 inputs XBINNING = 1 /Binning factor in width YBINNING = 1 /Binning factor in height XPIXSZ= 9.0000000000000000 /Pixel Width in microns (after binning) YPIXSZ= 9.0000000000000000 /Pixel Height in microns (after binning) SET-TEMP = -18.899999618530273 /CCD temperature setpoint in C IMAGETYP = BIAS/ Type of image CALSTAT = M SWMODIFY= MaxIm DL Version 5.15 /Name of software that modified the image PEDESTAL = -100 /Correction to add for zero-based ADU A calibrated Master Bias Frame SWOWNER = MNState Physics-9 / Licensed owner of software INPUTFMT= FITS/ Format of file from which image was read4/5/2013 10 11. Dark A dark frame is an exposure taken with the camera shutter open but usually one needs toblocking light from entering the camera chip.At the Paul P. Feder Observatory, we used the MaxIM DL 5 software to take dark frames. Wedo not have to block light, as the camera is already attached in the system.Hot pixels are defect on the CCD chip, which make them to glow without direct contact to thelight.A rule of thumb says one should take as many dark frames as the five times of the exposedscience images.Dark frames are not scalable.The dark frame should adjust automatically. But I like the idea of dark frames during themiddle of the observations or taking dark frames in three intervals during the observingsession.Dark current is an additive effect.4/5/201311 12. Dark SIMPLE = T BITPIX= -32 /8 unsigned int, 16 & 32 int, -32 & -64 real NAXIS = 2 /number of axes NAXIS1 = 3073 /fastest changing axis NAXIS2 = 2048 /next to fastest changing axis BSCALE = 1.0000000000000000 /physical = BZERO +BSCALE*array_value BZERO = 0.00000000000000000 /physical = BZERO +BSCALE*array_value EXPTIME = 10.000000000000000 /Exposure time in seconds EXPOSURE = 10.000000000000000 /Exposure time in seconds HISTORY Cal Master Dark, 10 inputs SWMODIFY= MaxIm DL Version 5.15 /Name ofsoftware that modified the image HISTORY Bias Subtraction (Bias 1, 3073 x 2048, Bin1 x 1, Temp-22C, HISTORY Exp Time 0ms) CALSTAT = BM XBINNING = 1 /Binning factor in width YBINNING = 1 /Binning factor in height XPIXSZ= 9.0000000000000000 /Pixel Width in microns (afterbinning) YPIXSZ= 9.0000000000000000 /Pixel Height in microns (afterbinning) SET-TEMP = -22.000000000000000 /CCD temperature setpoint inC A calibrated Master Dark Frame IMAGETYP = DARK/Type of imagePEDESTAL = -100 /Correction to add for zero-based ADU SWOWNER = MNState Physics-9 / Licensedowner of software4/5/201312 13. Flat A flat field is an exposure taken with the shutter open, which basically gives us informationabout the light path obstructed by the dust particles and other deformities containing inside aCCD chip.Three popular types of flat frames are: 1) Dome Flats, 2) Twilight and 3) Light Box flats.Flat-dark frames are separate from the dark frames which are separately taken to calibrate thescience images.One should expose long enough to increase the signal to noise ratio in a flat frame.You subtract bias and dark frames from the science images. Then you divide the scienceimage by the master flat frames to complete the calibration.Star images (taken during twilight) can be eliminated using the median rejecting process.4/5/201313 14. FlatSIMPLE=TBITPIX= -32 /8 unsigned int, 16 & 32 int, -32 & -64 realNAXIS = 2 /number of axesNAXIS1= 3073 /fastest changing axisNAXIS2= 2048 /next to fastest changing axisBSCALE= 1.0000000000000000 /physical = BZERO +BSCALE*array_valueBZERO = 0.00000000000000000 /physical = BZERO +BSCALE*array_valueEXPTIME = 4.0000000000000000 /Exposure time in secondsEXPOSURE= 4.0000000000000000 /Exposure time in secondsHISTORY Cal Master Flat(R), 10 inputsSWMODIFY= MaxIm DL Version 5.15 /Name of software thatmodified the imageHISTORY Bias Subtraction (Bias 1, 3073 x 2048, Bin1 x 1, Temp -22C,HISTORY Exp Time 0ms)CALSTAT = BDM HISTORY Dark Subtraction (Dark 4, 3073 x 2048, Bin1 x 1, Temp -22C,HISTORY Exp Time 4s)HISTORY Dark-Bias(Bias 1,3073 x 2048,Bin1 x 1,Temp -22C,ExpTime 0ms)XBINNING= 1 /Binning factor in widthYBINNING= 1 /Binning factor in heightXPIXSZ= 9.0000000000000000 /Pixel Width in microns (afterbinning) A calibrated Master Dark Frame YPIXSZ= 9.0000000000000000 /Pixel Height in microns (afterbinning)SET-TEMP= -22.000000000000000 /CCD temperature setpoint in CIMAGETYP= FLAT/ Type of imageFILTER= R/ Filter used when taking imagePEDESTAL= -100 /Correction to add for zero-based ADUSWOWNER = MNState Physics-9 / Licensed owner of software4/5/2013INPUTFMT= FITS/Format of file from which image was read 14 15. Final Calibrated ImageSIMPLE=TBITPIX= 16 /8 unsigned int, 16 & 32 int, -32 & -64 realNAXIS = 2 /number of axesNAXIS1= 3073 /fastest changing axisNAXIS2= 2048 /next to fastest changing axisBSCALE= 1.0000000000000000 /physical = BZERO + BSCALE*array_valueBZERO = 32768.000000000000 /physical = BZERO + BSCALE*array_valueINSTRUME= Apogee Alta /instrument or camera usedDATE-OBS= 2011-09-15T03:38:23 /YYYY-MM-DDThh:mm:ss observationstart, UTEXPTIME = 30.000000000000000 /Exposure time in secondsEXPOSURE= 30.000000000000000 /Exposure time in secondsSET-TEMP= -22.000000000000000 /CCD temperature setpoint in CCCD-TEMP= -22.103825250000007 /CCD temperature at start of exposure inCXPIXSZ= 9.0000000000000000 /Pixel Width in microns (after binning)YPIXSZ= 9.0000000000000000 /Pixel Height in microns (after binning)XBINNING= 1 /Binning factor in widthYBINNING= 1 /Binning factor in heightXORGSUBF= 0 /Subframe X position in binned pixelsYORGSUBF= 0 /Subframe Y position in binned pixelsFILTER= R / Filter used when taking imageIMAGETYP= Light Frame / Type of imageSITELAT = 46 52 00 /Latitude of the imaging locationSITELONG= 96 27 12 /Longitude of the imaging locationFOCALLEN= 0.00000000000000000 /Focal length of telescope in mmAPTDIA= 0.00000000000000000 /Aperture diameter of telescope in mmAPTAREA = 0.00000000000000000 /Aperture area of telescope in mm^2SWCREATE= MaxIm DL Version 4.10 /Name of software that created theimageSBSTDVER= SBFITSEXT Version 1.0 /Version of SBFITSEXT standard ineffectSWOWNER = MNState Physics-9INPUTFMT= FITS/Format of file from which image was readSWMODIFY= MaxIm DL Version 5.15 /Name of software that modified theimageHISTORY Bias Subtraction (Bias 1, 3073 x 2048, Bin1 x 1, Temp -30C,HISTORY Exp Time 0ms)CALSTAT = BDF HISTORY Dark Subtraction (Dark 1, 3073 x 2048, Bin1 x 1, Temp -30C,HISTORY Exp Time 30s)HISTORY Flat Field (Flat R 1, R, 3073 x 2048, Bin1 x 1, Temp -30C,HISTORY Exp Time 8s)PEDESTAL= -100 /Correction to add for zero-based ADUCSTRETCH= Medium/ Initial display stretch modeCBLACK= 94 /Initial display black level in ADUsCWHITE= 187 /Initial display white level in ADUs4/5/201315 16. Aperture Photometry Consists of threeconcentric circles. The innermost circle hasthe largest area. The outer two circlesform an annulus, whichgives information aboutthe sky glow and thebackground.4/5/2013 16 17. Differential Photometry4/5/2013 17 18. Results Light Curve of XX Cyg Obtained in B FilterMaximum 11.51Minimum 12.604/5/201318 19. Results Light Curve of XX Cyg Obtained in I FilterMaximum 11.184/5/2013Minimum 11.70 19 20. Results Light Curve of XX Cyg Obtained in R FilterMaximum 11.304/5/2013Minimum 12.05 20 21. Results Light Curve of XX Cyg Obtained in V Filter4/5/2013Maximum 11.38 21Minimum 12. 16 22. Period Analysis Discrete Fourier Transform Peiod04 Software Time and magnitude Difference4/5/201322 23. ResultsAmplitude versus Frequency Plot (Only Applying the first harmoniccorrection)Frequency is measured in c/d4/5/201323 24. Results Estimated period .1348605856 days 11651.9546 seconds Accepted value .134865117 days 11652.3461 seconds Account theoretical prediction for theincreasing factor 11652.3463 seconds Account reported increasing factor 11652.3462seconds4/5/201324 25. Results Light Curve of XX Cyg in R filter (with my estimated Period)4/5/201325 26. Conclusions Period discrepancy is .6917 seconds. B,I,R,V light curves have different shapes. Would like to be consistent with aperturephotometry to improve brightness variationestimation. Would like to convert JD into HJD to improveperiod computation. Use the Period04 to find actual maxima, minimaand epoch to improve phase estimation.4/5/2013 26 27. Acknowledgements I would like to thank Dr. Arne Henden (AAVSO) for providing valuable advicefor analyzing the data set of XX Cyg. I would also like to thank Drs. JuanCabanela, Matthew Craig, Linda Winkler (MSUM) for helping me with dataacquisition, download and analysis. Deans Research Grant: College of Social & Natural Sciences, Fall 2010,MSUM. I would also like to thank Dr. Steve Lindaas, Dr. Ananda Shastri and JoyLindell (MSUM).This research work cannot be completed without active support that I receivedfrom my peers: Gregory Larson, Aaron Peterson, Nathan Heidt, MatthewZimney, Tyler Lane, Hollee Johnson, LeAnn Washenberger, Nicholas Weir,Uchenna Ogbonnaya. The FM area astronomy enthusiast Doyle Heden.Find more information on my observatory log http://astronomicalobserving.wordpress.com/4/5/2013 27

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