Practical Observational Astronomy Photometry

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Practical Observational Astronomy Photometry

Practical Observational Astronomy Lecture 5 Photometry Wojtek Pych Warszawa, October 2019 History ● Hipparchos 190 – 120 B.C. visible stars divided into 6 magnitudes ● John Hershel 1792- 1871 → Norman Robert Pogson A.D. 1829 - 1891 I m I 1 =100 m1−m2=−2.5 log( ) I m+5 I 2 Visual Observations ●Argelander method ●Cuneiform photometer ●Polarimetric photometer Visual Observations Copyright AAVSO The American Association of Variable Star Observers Photographic Plates Blink comparator Scanning Micro-Photodensitometer Photographic plates Liller, Martha H.; 1978IBVS.1527....1L Photoelectric Photometer ● Photomultiplier tubes – Single star measurement – Individual photons Photoelectric Photometer ● 1953 - Harold Lester Johnson - UBV system – telescope with aluminium covered mirrors, – detector is photomultiplier 1P21, – for V Corning 3384 filter is used, – for B Corning 5030 + Schott CG13 filters are used, – for U Corning 9863 filter is used. – Telescope at altitude of >2000 meters to allow the detection of sufficent amount of UV light. UBV System Extensions: R,I ● William Wilson Morgan ● Kron-Cousins CCD Types of photometry ● Aperture ● Profile ● Image subtraction Aperture Photometry Aperture Photometry Profile Photometry Profile Photometry DAOphot ● Find stars ● Aperture photometry ● Point Spread Function ● Profile photometry Image Subtraction Image Subtraction ● Construct a template image – Select a number of best quality images – Register all images into a selected astrometric position ● Find common stars ● Calculate astrometric transformation ● Calculate photometric scale transformation – Stack images ● Subtract template from the science image(s) Image Subtraction ● Subtract template image from a science image – Find common stars – Calculate astrometric transformation – Calculate photometric scale transformation – Find PSF transformation kernel – Convolve template image with PSF transformation kernel – Subtract template Image Subtraction Image Subtraction ● Detect variable stars ● Aperture or profile photometry on subtracted image ● Profile photometry with aperture corrections on the template image ● Photometric calibration of the light curves Image subtraction.

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High Precision Photometry of Transiting Exoplanets
McNair Scholars Research Journal Volume 3 Article 3 2016 High Precision Photometry of Transiting Exoplanets Maurice Wilson Embry-Riddle Aeronautical University and Harvard-Smithsonian Center for Astrophysics Jason Eastman Harvard-Smithsonian Center for Astrophysics John Johnson Harvard-Smithsonian Center for Astrophysics Follow this and additional works at: https://commons.erau.edu/mcnair Recommended Citation Wilson, Maurice; Eastman, Jason; and Johnson, John (2016) "High Precision Photometry of Transiting Exoplanets," McNair Scholars Research Journal: Vol. 3 , Article 3. Available at: https://commons.erau.edu/mcnair/vol3/iss1/3 This Article is brought to you for free and open access by the Journals at Scholarly Commons. It has been accepted for inclusion in McNair Scholars Research Journal by an authorized administrator of Scholarly Commons. For more information, please contact [email protected]. Wilson et al.: High Precision Photometry of Transiting Exoplanets High Precision Photometry of Transiting Exoplanets Maurice Wilson1,2, Jason Eastman2, and John Johnson2 1Embry-Riddle Aeronautical University 2Harvard-Smithsonian Center for Astrophysics In order to increase the rate of finding, confirming, and characterizing Earth-like exoplanets, the MINiature Exoplanet Radial Velocity Array (MINERVA) was recently built with the purpose of obtaining the spectroscopic and photometric precision necessary for these tasks. Achieving the satisfactory photometric precision is the primary focus of this work. This is done with the four telescopes of MINERVA and the defocusing technique. The satisfactory photometric precision derives from the defocusing technique. The use of MINERVA’s four telescopes benefits the relative photometry that must be conducted. Typically, it is difficult to find satisfactory comparison stars within a telescope’s field of view when the primary target is very bright.
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