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SPECTROSCOPY One Concept for 3 Instruments

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  1. SPECTROSCOPY One Concept for 3 Instruments A comparison of 3 Echelle spectrographs with a similar design but different aims: UV-Visual Echelle Spectrograph (UVES) at the VLT (8m.) (‘99) Fiber Extended Range Optical Spectrograph (FEROS) at ESO 1.52m (‘98) High Accuracy Radial velocity Planet Searcher (HARPS) at ESO 3.6m (‘03) L. Pasquini July 2002

  2. SPECTROSCOPY UVES Science Objectives • Structure, physical conditions and abundances of interstellar and intergalactic gas at early epochs from absorption spectra of high redshift QSO’s • Kinematics of stars and gas in galactic nuclei • Kinematics and mass distribution of stars clusters • Composition, kinematics and physical conditions of the interstellar medium in the • Galaxy and in nearby systems • Chemical composition and atmospheric models of galactic and extragalactic stars • Substellar companions of nearby stars (high precision RV over long time-scales) • Stellar oscillations • DEFINITELY A GENERAL PURPOSE FACILITY! ! L. Pasquini July 2002

  3. SPECTROSCOPY FEROS Science Objectives • Accurate RV surveys (not planet search) • Chemical composition of stars • Line profiles of different types and their variability (Stellar Activity, Doppler imagining, Pulsations) • Search for Diffuse Interstellar Bands (DIBS) • Highly Variable Objects (e.g Novae, SNe) • Regular Monitoring of objects General Purpose, but focalized … emphasis on the time availability of small telescope L. Pasquini July 2002

  4. SPECTROSCOPY HARPS Science Objectives • Detection of Extra Solar Planets • Radial Velocity Survey with long term accuracy of 1 m/sec DEDICATED INSTRUMENT ! L. Pasquini July 2002

  5. SPECTROSCOPY UVES Tec. Specs (abridged) • Working Wavelength range: 300-1100 nm. Whole range with less than 6 exposures • Maximum Optical Efficiency over the whole Range, > 20% • Limiting magnitudes: S/N = 10 in 2 Hours U=18.7, V=19.4 with slit losses 30%. • Spatially Resolved spectroscopy, Derotator, Guiding, pre-slit optical quality • Sampling: better than 4 pixels/arcsecond • R as function of slit width 1” -> 41000; 0.25”--->107000 • Order Separation: Minimum 15 arcseconds, slight height continuously variable • Stray Light: source stray less than 5% , ghost less than 10**-3, diffuse light < 1 e/pix/h • Velocity stability: better than 150 m/sec/hour • Parallel Blue and Red observations L. Pasquini July 2002

  6. SPECTROSCOPY FEROS Tech. Specs (abridged) • Fibre fed spectrograph, Permanently mounted, capability of switching with B&Ch in 5 minutes • Large Spectral Coverage (370-860 nm), without gaps in one frame • Large Throughput (18%@370, 27%@400nm,40% @ larger wavelengths ) • Two fibres: second for SKY or Simultaneous Calibration (or polarimetry..) • RV accuracy: 50 Meters / sec long term • Resolving Power: > 25.000 • ADDITIONAL • No Movable parts (minimal maintenance) • Thermally stable environment, automatic compensation of Camera Focus .. • Data Reduction Software, On-Line pipeline L. Pasquini July 2002

  7. SPECTROSCOPY HARPS Technical Specs (abridged) • Use of the Simultaneous Th-A Calibration Technique (Geneve, Corelie, Elodie) (developed after CORAVEL, Mayor & Queloz 1995, Queloz et al. 1998) • R> 80.000 (e.g. with pixel=1 km/sec 1m/sec=1/1000 of 1 pixel!) • Coverage: 380-680 nm. • Mechanical Stability, vacuum • Efficiency: V=9 star S/N ratio = 100 in 2.5 minutes, • Operations: minimise overheads • Suitable calibration AND procedures to establish short and long term accuracy • Data Reduction and operations is PART of the instrument, to produce Radial Velocities as PRODUCT for the user. L. Pasquini July 2002

  8. SPECTROSCOPY Radial Velocity accuracy: some aspects σ(RV) ~ (S/N)^-1 * Range^(-0.5) * R^(-1) (Hatzes and Cochran 1992 ) Resolving Power, Signal to noise and Spectral range (more correct probably is Q factor, Bouchy et al. 2001). If Systematic effects are relevant, higher Resolving power becomes more important.. Two Main Techniques used: Self Calibrating Cell (Iodine Cell) : + same optical path, Many lines - Loss of light, Limited Spectral Range, Complex DRS. Simultaneous Calibration (Geneve): + Very Efficient, Simple DRS - Not same light path; where are the limits ? L. Pasquini July 2002

  9. Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  10. Doppler-shifted spectral lines m*sin(i) Period Distance Eccentricity +v -v Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  11. s=10 ms-1 RV of Jupiter s=1 ms-1 Why do we need HARPS ? Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  12. Why do we need HARPS ? s=10 ms-1 s=1 ms-1 Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  13. Why do we need HARPS ? Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  14. 0 RV RV 0 Object spectrum ThAr spectrum Wavelength calibration Object fiber ThAr reference Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  15. RV (object) = - RV (measured) RV(drift) 0 RV (measured) RV RV 0 RV(drift) Object spectrum ThAr spectrum Measurement Object fiber ThAr reference Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  16. Simultaneous ThAr reference • Attained long-term accuracy: 2-3 m/s • Spectral range: 380 - 690 nm • Efficiency: 100% • Entire spectral information available • Iodine absorption cell • Attained long-term accuracy : 2-3 m/s • Spectral range: 500 -600 nm • Efficiency: 50% • Not suitable for spectroscopy Simultaneous ThAr is 5 times more efficient than Iodine cell ! Ex.: HARPS on 3.6m telescope is equivalent to UVES on VLT Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  17. G8V star Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  18. Halo stars G dwarfs K dwarfs M dwarfs Tint = 15 Minutes Volume limited sample 50 pc Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  19. Radial Velocities • Does not provide sini • Provides m2sini, a, P, e • Sensitive to short periods • Accuracy does not depend on distance to the star • Microarcsecond Astrometry • Provides sini • Provides m2, a, P, e • Sensitive to long periods • Accuracy does depend on distance to the star • Accuracy does not depend on spectral type  f(m2,sini,a,P,e,Fe/H) • HARPS (sim. Reference) • UVES (iodine cell, Flames) • FEROS • PRIMA (available soon, long-term) • SIM, GAIA (2009 +) Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  20. Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  21. Stellar oscillations, Bouchy & Carrier 2001 Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  22. COROT • KEPLER • EDDINGTON Thousands of short-period planets detected and P determined Transits: Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  23. Transit on HD 209458 HST Brown et al., 2001 Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  24. COROT • KEPLER • EDDINGTON Thousands of short-period planets detected and P determined Transits: However: NO MASS! Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  25. The only way to get the mass … … by RV measurements! Example: 5 M around M0 star at 0.1 AU  K = 2.0 m/s with sRV = 1 m/s and Nobs = 50  mass accuracy 10%  Mass and mean density Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  26. SPECTROSCOPY Light Injection (pre-spectro) FEROS: 2.7” Aperture, MICROLENSES, FIBRES, IMAGE SLICER (2*resolution), PROJECTOR UVES: Variable aperture (0.2-5”), Variable Height SLIT(S), De-ROTATOR, Atmospheric Dispersion Compensator, FILTERS, DICHROIC, Blue and Red Slits, Iodine Cell, Image Slicer … … HARPS: ADC, MICROLENSES, FIBRES, IMAGE SCRAMBLER L. Pasquini July 2002

  27. SPECTROSCOPY The basic Design White Pupil Spectrograph Two Collimators (double pass!) COATINGS!! Echelle Folding Mirror COATINGS!! Crossdisperser Camera L. Pasquini July 2002

  28. SPECTROSCOPY The basic Design White Pupil Spectrograph Two Collimators (double pass!) COATINGS!! Echelle Folding Mirror COATINGS!! Crossdisperser Camera L. Pasquini July 2002

  29. SPECTROSCOPY Otical Train White Pupil (Baranne 1988): Exit Pupil as Entrance Pupil is set at the entrance of the Camera ; big advantage is the small camera, no vignetting. L. Pasquini July 2002

  30. SPECTROSCOPY UVES Optomechanics Double arm (Red-Blue)to optimize efficiency, simultaneous observations with dichroic, image slicer for (R=10^5), iodine cell in pre-slit. 26 movable functions! Within the Red arm the 2 Detectors are optimized L. Pasquini July 2002

  31. SPECTROSCOPY UVES optomechanics UVES opened in the integration hall in Garching: the RED camera and the RED X-disperser are mounted. Note also the crowded pre slit area. L. Pasquini July 2002

  32. SPECTROSCOPY FEROS Optomechanics The single larger optical components in FEROS were the X-disperser prims and the main collimator L. Pasquini July 2002

  33. Calibrations: • Spectral flatfield • ThAr spectral lamp • Iodine absorption cell 3.6-m ESO telescope + HCFA Two-fiber mode Reference fiber Object fiber Mono mode Image Scrambler Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  34. SPECTROSCOPY HARPS optomechanics L. Pasquini July 2002

  35. Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  36. Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  37. Astrophysical niches of high-resolution spectroscopy ES0 Santiago, 2-3 Oct. 2001

  38. SPECTROSCOPY Summary of Characteristics UVES FEROS HARPS Pupil (cm) 20 13.5 20.8 Echelle 41.6,31.6 R4 79 R2 31.6 R4 R*A 40000 70000 90000 Xdisp Gratings(4) Prism Grism Camera F/1.8,2.5 F/3 F/5 CCD (15 mm/pix) 3*2X4K 2X4K 2*2X4K Arcs/Pix 0.22/0.16 .65 0.19 (Km/Pix) 1.6,1.2 3.0 0.7 Min.Order Sep. 10”,15” 30Pix 34 Pix Aperture variable (>0.2) 2.7” 1.” Coverage (nm) 285 or 485 560 300 L. Pasquini July 2002

  39. SPECTROSCOPY Summary of Characteristics Should note a few points: The use of a large (79 lines/mm) groove numbers allows to FEROS: a) To have a prism as X-disperser and still have a decent minimum separation: larger free spectral range b) On the other hand this would not allow higher resolution: with smaller slit higher magnificaion, less Km/sec/pix ---> No longer order coverage, CCD too small! c) HARPS can allow better sampling than UVES because 1) Spectral range limited at 690 nm in the red 2) Low S/N ratio observations are not the main driver! L. Pasquini July 2002

  40. Understanding K Giants results from radial velocity measurement Johny Setiawan, 04 June 2002

  41. People Johny Setiawan (KIS) Oskar von der Lühe (KIS) Luca Pasquini (ESO) Artie Hatzes (TLS, Tautenburg) Licio da Silva (ON, Brazil) Leo Girardi (Univ. Padova)

  42. QUESTION Do all giants show RV variations ? As suggested by the handful sofar sudied? What is causing these variations ? Pulsations? Activity-induced modulation? Planets ?

  43. 85 stars have been observed Oct 99 - Feb 02 77 stars have been analyzed for RV Variability ? Black: current targets Red : proposed new targets

  44. Fibre-fed Extended Range Optical Spectrograph Wavelength coverage 3700-8600 Å 39 orders, 2 fibres Resolution 48000 CCD 2098 x 4096 pixel RV accuracy 50 m/s (contract) 23 m/s (comissioning) 26 m/s (end of mission) Calibration modes: object - sky object - simult. calibration

  45. Results (1): The spectrograph accuracy Accuracy of standard star: HD 10700, G8V, mV=3.50 26 m/s (moderate, but still enough for K giants) Feb 01-Oct 01

  46. Results (2): Trend along the RGB 60-100 m/s 40-60 m/s 26-40 m/s Binaries not included in the figure

  47. Results (3): binary system Detected: 12 stars with stellar companions (binaries / multiple systems) Not yet in catalog m2sin i ~ 0.21 MSun at 1.0 AU m2sin i ~ 0.33 MSun at 2.4 AU

  48. Results (4): short, long, multi-periodic variation Observed: 46 stars show RV variations due to pulsations and/or rotation multi-periodic Short period (several days) Scargle periodogram: LP ~ 450 d SP ~ 14 d

  49. Results (5): comparingstellar parameters Computed: stellar radius, rotational velocity V sin i, rotation period

  50. Results (6): stellar activities HD 50778: RV variation long period, estimated radius ~ 19.8 RSun A B C D Activity index = (A+B)/(C+D), Choi et al. 1995