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NOT Summer School 2006 La Palma Group A Magnetic star EY Dra Karsten Brogaard, Karianne Holhjem, Sofia Ramstedt, Jari Rantala, Christina Thöne Heidi Korhonen 0 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Outline • Introduction: magnetic activity in stars • Photometry Alfosc-observations Reductions Results • High resolution optical spectroscopy Alfosc spectroscopy with Grism 17 Reductions H line analysis Interpretations • NIR spectroscopy Paschen line Stellar atmosphere model restrictions • Summary and future plans 1 Magnetic activity in stars 2 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Magnetic fields on the Sun • Magnetic fields are produced by flows of hot ionized gas in the solar interior. • The fields are sustained by the combination of a turbulent outer convective zone and differential rotation. 3 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Magnetic activity in stars What do we need? • Early-type stars have rapid rotation, but a radiative outer layer. • Late-type stars have a convective outer layer, but slow rotation. ZAMS Late-type star EY Dra! 4 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen The solar atmosphere • PhotosphereG-band continuum (430.5 nm) • ChromosphereH, Pa CaII H & K • Corona UV and X-rays Yohkoh satellite 5 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Magnetic features SOHO-prominences in the chromosphere QuickTime™ and a YUV420 codec decompressor are needed to see this picture. SST-sunspots on the photosphere and spicules in the chromosphere. SOHO-flare in the lower corona 6 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Stellar light curves Photometric observations at different rotational phase can be used to produce a light curve of the object. From the lightcurve the spotfilling factor can be calculated. 7 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Spectral lines • By doing high resolution spectroscopy of chomospheric lines at different phases, magnetic features can be traced as they rotate the star. • This requires a rapid rotating star with broad lines. • EY Dra vsin(i)=69 km/s 8 Photometry 9 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Photometry • Starspots in the photosphere causing light curve variations • Rotation period of EY Dra is 0.459 days • We needed a good phase coverage • Sets of 3 exposures in V and R band with ALFOSC • Differential photometry 10 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Observations • EYDra, a comparison star and a check star • Windowing decreased read out time to ~35s – Rotation of the field was also needed EYDra Comparison star Check star 11 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Reductions • Basic IRAF tasks: – Zerocombine, flatcombine and ccdproc for different windows • Other tasks from apphot package – Daofind to find the coordinates – Phot for calculating the magnitudes 12 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Results • 4 sets during 1st night, 5 during 2nd night (dots), and their average (stars) – A few points with large variation, reason unknown 13 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Results • W shape already seen in 1995: Might be real! 14 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Results • Inversion using Heidi´s invert-program – Two active regions can be seen 15 Optical spectroscopy 16 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Spectroscopy • Data: EYDra – grism #17 (R=10 000, =6200-6750) – 1. night: 6 epochs, 2. night: 9 epochs remove fringing – distribution over one rotation • Calibration – spectroscopic flats: Halogen lamp (in baffle) – wavelength calibration: Neon lamp beginning/end of each epoch – atmospheric standard: B(E)-star – radial velocity standard star 17 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Reduction of spectra • Bias subtraction • Flat fielding 18 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Reduction of spectra • Spectrum extraction 19 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Reduction of spectra • Spectrum extraction 20 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Reduction of spectra • Spectrum extraction 21 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Reduction of spectra • Identifying lamp spectra 22 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Reduction of spectra • Identifying lamp spectra 23 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Reduction of spectra • Identifying lamp spectra 24 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Reduction of spectra • Assigning the solution to the source spectra 25 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Reduction of spectra • Normalising the continuum 26 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Reduction of spectra • Normalising the continuum 27 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Reduction of spectra • Resulting spectra 28 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Mistakes... • Star to slit...star not to slit...wrong star to slit... • Neon lamp spectrum in absorption! Zur Anzeige wird der QuickTime™ Dekompressor „TIFF (LZW)“ benötigt. Zur Anzeige wird der QuickTime™ Dekompressor „TIFF (LZW)“ benötigt. Zur Anzeige wird der QuickTime™ Dekompressor „TIFF (LZW)“ benötigt. 29 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen EY Dra spectrum H Fe TiO Ca H 30 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Atmospheric standard star H Zur Anzeige wird der QuickTime™ Dekompressor „TIFF (LZW)“ benötigt. H ...turned out to be a BE-star 31 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Radial velocity determination 32 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Radial velocity determination ... fits perfectly, but gives wrong value :-( 33 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen H line analysis • H line fitting (splot) Zur Anzeige wird der QuickTime™ Dekompressor „TIFF (LZW)“ benötigt. 34 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen H line analysis • Equivalent width variations Zur Anzeige wird der QuickTime™ Dekompressor „TIFF (LZW)“ benötigt. 35 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen H line analysis • Line profile/strength changes FWHM 95 - 125 km/s (v*sin(i) = 62 km/s) 36 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Comparison to lightcurve Starspots correspond to increase in H emission similar to the Sun Zur Anzeige wird der QuickTime™ Dekompressor „TIFF (LZW)“ benötigt. 37 IR spectroscopy 38 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Near IR Spectrosopy • • Why NIR? Why study the Paschen β line? 1) correlation with the Hα 2) restricting the model of the stellar atmosphere C.I. Short and J.G. Doyle Astron. Astrophys. 326, 287-299 (1997) Astron. Astrophys. 331, L5–L8 (1998) 39 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen The Paschen β line • λ=12818 A=1,2μm 40 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Observations • NOTCam, high-res camera, J-band, grism #1, 44 μm slit • Frame 50 9 • Dithering ABBA for skysubtraction (or ABBC, or BAAB) • (Target – standard star – target) for removal of lines from the earth´s atmosphere • Spectra of lamps for flatfielding and wavelength callibration 41 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Data reduction procedure • • • • • • Bad pixel mask Flat field Skysubtraction Shift and combine ABBA sequence Extract spectra like for the optical case Divide target by standard star 42 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Prelimary results • The Paschen β is not seen in emission or absorption 43 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Comparison to theory • The pa-β line profile depends on the pressure in the chromosphere • Pressure is messured as log mTR where mTR is the coloumn mass above the bottom of the transition region (g cm-2) 44 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Comparison to theory • We can restrict the model to log mTR < -4 -4 -4,2 -4 -4,2 45 Summary and outlook 46 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Scientific conclusions • Two active regions on EY Dra: separation 180˚ common in active stars • Correlation with H line strength • Restriction of stellar atmosphere models: Pressure: log mTR < -4 47 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Future work • reduce NIR spectra • redo wavelength calibration: radial velocity standard • write the report • write an article ... And drink more wine :-) 48 NOT Summer School 2006 8.7.2006 Karsten Brogaard, Karianne Holhjem, Jari Rantala, Sofia Ramstedt, Christina Thöne, Heidi Korhonen Thanks for your attention! From the 5 most stupid observers of the summer school ;-) 49