gravitational redshifts, and other wavelength shifts in ...dainis/presentations/vilnius_2011/... ·...
TRANSCRIPT
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Gravitational redshifts, and other wavelength shifts in stellar spectra
Dainis Dravins – Lund Observatory
www.astro.lu.se/~dainis
KVA
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Exactly 100 years ago
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A.Einstein, Annalen der Physik 340, 848 (1911)
Predicted effects by gravity on light
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Foreground galaxy cluster manually retouched away
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STRONG LENSING WEAK LENSING MICROLENSING
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Already long before Einstein…
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John Mitchell (1784)
Predicting gravitational effects on light
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Predicting gravitational effects on light
John Mitchell (1784)
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Predicting gravitational effects on light
John Mitchell (1784)
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Predicting gravitational effects on light
Pierre-Simon Laplace (1796)
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Verifying Einstein ?
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Klaus Hentschel: Erwin Finlay Freundlich and Testing Einstein’s Theory of Relativity, Archive for History of Exact Sciences 47, 243 (1994)
Freundlich’s attempts to verify relativity theory (I)
Erwin Finlay Freundlich (1885-1964) worked to experimentally verify the predictions from Einstein’s theory of relativity and the effects of gravity on light.
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Freundlich’s attempts to verify relativity theory (II)
Klaus Hentschel: Erwin Finlay Freundlich and Testing Einstein’s Theory of Relativity, Archive for History of Exact Sciences 47, 243 (1994)
Einsteinturm, Potsdam-Telegrafenberg
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Nature 306, 727 (1983)
Unethical falsifications in astronomy ?
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QJRAS 26, 279 (1985)
Controversial interpretations of history
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Actual gravitational redshift in white dwarfs
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X-ray spectra for early (top), and late phases of the bursts from neutron stars.
Red: Absorption lines from the circumstellar medium
Blue: Photospheric absorption lines at redshift Z = 0.35
J.Cottam, F.Paerels, M.Mendez: Gravitationally redshifted absorption lines in the X-ray burst spectra of a neutron star, Nature 420, 51
Gravitational redshift in neutron stars
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Gravitational redshift in the laboratory
R.V.Pound & G.A.Rebka: Gravitational Red-Shift in Nuclear Resonance, Phys.Rev.Lett. 3, 439 (1959)
Robert Pound
Glen Rebka
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Stellar spectroscopy
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EFFECTS ON SPECTRAL LINES
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L.Lindegren & D.Dravins: The fundamental definition of “radial velocity, A&A 401, 1185
Mechanisms causing wavelength shifts
The process includes: motion of the object; its emission of an electromagnetic signal; its propagation through space; motion of the observer; and the reception of the signal.
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R.F.Griffin: Spectroscopic Binaries near the North Galactic Pole. Paper 6: BD 33° 2206, J.Astrophys.Astron. 3, 383 (1982)
Expected gravitational redshifts
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Expected gravitational redshifts
D. Dravins
IAU Symp. 210
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Radial velocities without spectroscopy
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Astrometric radial velocities I
Dravins, Lindegren & Madsen, A&A 348, 1040
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Astrometric radial velocities II
Dravins, Lindegren & Madsen, A&A 348, 1040
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Astrometric radial
velocities from
perspective acceleration
Dravins, Lindegren & Madsen, A&A
348, 1040
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Astrometric radial velocities III
Dravins, Lindegren & Madsen, A&A 348, 1040
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STARPATHS (200,000 y)
Madsen, Dravins & Lindegren, A&A 381, 446
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Pleiades from Hipparcos Proper motions over 120,000 years
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Hyades from Hipparcos D. Dravins, IAU Symp. 215 (2004)
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Hyades lineshifts Madsen, Dravins & Lindegren, A&A 381, 446
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S.Madsen, D.Dravins, H.-G.Ludwig, L.Lindegren: Intrinsic spectral blueshifts in rapidly rotating stars?, A&A 411, 581
Apparent radial velocity vs. rotation?
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Differential velocities within open clusters
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B.Nordström, J.Andersen, M.I.Andersen: Critical tests of stellar evolution in open clusters II. Membership, duplicity, and stellar and
dynamical evolution in NGC 3680, Astron. Astrophys. 322, 460
Different “velocities” ─ giants vs. dwarfs?
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Dean Jacobsen, astrophoto.net
M 67
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L.Pasquini, C.Melo, C.Chavero, D.Dravins, H.-G.Ludwig, P.Bonifacio, R.De La Reza:
Gravitational redshifts in main-sequence and giant stars, A&A 526, A127 (2011)
Searching for gravitational redshifts in M67
M67 (NGC 2682) open cluster in Cancer contains some 500 stars;
age about 2,6 Gy, distance 850 pc.
M67 color–magnitude diagram with well-developed giant branch.
Filled squares denote single stars.
Dean Jacobsen, astrophoto.net
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L.Pasquini, C.Melo, C.Chavero, D.Dravins, H.-G.Ludwig, P.Bonifacio, R.De La Reza:
Gravitational redshifts in main-sequence and giant stars, A&A 526, A127 (2011)
Searching for gravitational redshifts in M67
Radial velocities in M67 with a superposed Gaussian centered on
Vr = 33.73, σ = 0.83 km s−1
Radial velocities in M67: No difference seen between giants (red)
and dwarfs (dashed)
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Real line formation
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Solar disk
June 12, 2009
GONG/Teide
AN ”IDEAL” STAR ?
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Granulation near the limb (towards the top) at 488 nm; Swedish 1-m solar telescope, La Palma
A REAL STAR
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Solar Optical Telescope on board HINODE (Solar-B) G-band (430nm) & Ca II H (397nm) movies
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Spectral scan
across the solar surface.
Left: H-alpha line
Right: Slit-jaw image
Big Bear Solar Observatory
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“Wiggly” spectral lines
of solar granulation
“Wiggly" spectral lines in the solar photosphere
inside and outside a region of activity, reflecting
rising and sinking motions in granulation (wavelength increases to the right).
The central part crosses a magnetically active region
with reduced velocity amplitudes. (W.Mattig)
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“Wiggly” spectral lines
of stellar granulation
(modeled)
Disk-center Fe I profiles from 3-D hydrodynamic model of the metal-poor star HD 140283 in NLTE and LTE.
Top: Synthetic “wiggly-line” spectra across stellar surface. Curves show equivalent widths W along the slit.
Bottom: Spatially resolved profiles; average is red-dotted.
N.G.Shchukina, J.Trujillo Bueno, M.Asplund, Astrophys.J. 618, 939 (2005)
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Spatially resolved line profiles of the Fe I 608.27 nm line (exc = 2.22 eV) in a 3-D solar simulation.
The thick red line denotes the spatially averaged profile.
The steeper temperature structures in upflows tend to make their lines stronger (blue-shifted components).
M.Asplund: New Light on Stellar Abundance Analyses: Departures from LTE and Homogeneity, Ann.Rev.Astron.Astrophys. 43, 481
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Solar-type granulation causes
convective lineshifts on order 300 m/s
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”INVERTED” GRANULATION & CONVECTIVE REDSHIFTS ?
Simulated (top) and observed (Dutch Open Telescope) solar images in continuum (left) and
Ca II H wing (right).
(Leenaarts & Wedemeyer-Böhm, Astron.Astrophys. 431, 687, 2005)
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Other stars
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A.S.Brun, A.Palacios: Numerical Simulations of a Rotating Red Giant Star. I. Three-dimensional Models of Turbulent Convection and
Associated Mean Flows, ApJ 702, 1078
3-D modeling of stellar hydrodynamics
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Cool supergiant (”Betelgeuse”)
Bernd Freytag (Uppsala)
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STELLAR CONVECTION – White dwarf vs. Red giant
Snapshots of emergent intensity during granular evolution on a 12,000 K white dwarf (left) and a 3,800 K red giant. Horizontal areas differ by dozen orders of magnitude: 7x7 km2
for the white dwarf, and 23x23 RSun2 for the giant. (H.-G. Ludwig)
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CORRUGATED STELLAR
SURFACES ?
Synthetic images
[negative] of
granulation in four
stellar models
From top:
Procyon (F5 IV-V),
Alpha Cen A (G2 V),
Beta Hyi (G2 IV), &
Alpha Cen B (K1 V).
Disk center (=1),
and two positions
towards the limb
D.Dravins & Å.Nordlund
Stellar Granulation IV.
Line Formation in
Inhomogeneous
Stellar Photospheres
A&A 228, 84
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Fe I-line bisectors in Sun and Procyon
(F5 IV-V) Average bisectors for Fe I lines of different strength,
produced from a time-dependent 3-D model
C.Allende Prieto, M.Asplund, R.J.García López, D.L.Lambert: Signatures of Convection in the Spectrum of Procyon:
Fundamental Parameters and Iron Abundance, Astrophys.J. 567, 544
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Bisectors of the same
spectral line in different
stars Adapted from
Dravins & Nordlund, A&A 228, 203
From left:
Procyon (F5 IV-V),
Beta Hyi (G2 IV),
Alpha Cen A (G2 V),
Alpha Cen B (K1 V).
Velocity [m/s]
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Non-LTE effects on spectral line wavelength
shifts
Adapted from
Dravins & Nordlund, A&A 228, 184
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L.Pasquini, C.Melo, C.Chavero, D.Dravins, H.-G.Ludwig, P.Bonifacio, R.De La Reza:
Gravitational redshifts in main-sequence and giant stars, A&A 526, A127 (2011)
Searching for gravitational redshifts in M67
Gravitational redshift predictions vs. mass/radius ratio (M/R) (dashed red)
do not agree with observations.
Calculated convective wavelength shifts for Fe I lines in dwarf (red crosses)
and giant models (squares).
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Spatially resolved stellar spectroscopy
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Solar granulation near the limb (upward on the image)
Filtergram at 488 nm; Swedish 1-m Solar Telescope on La Palma (G.Scharmer & M.G.Löfdahl)
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Simulated intensities approaching
the solar limb
Mats Carlsson, Oslo; in
Å.Nordlund, R.F.Stein, M.Asplund:
Solar Surface Convection, Living Reviews in Solar
Physics, 2009
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Exoplanet transits
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EFFECT OF TRANSIT GEOMETRY ON THE ROSSITER EFFECT FOR HD209458
Left: Geometry of the crossing for 3 cases
Right: Radial- velocity anomalies for these cases, for different stellar rotation Vsini
D.Queloz, A.Eggenberger, M.Mayor, C.Perrier, J.L.Beuzit, D.Naef, J.P.Sivan & S.Udry
Detection of a spectroscopic transit by the planet orbiting the star HD 209458
Astron.Astrophys. 359, L13
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RADIAL-VELOCITY
RESIDUALS FOR
THE STAR HD209458
TOP:
Outside planetary transit,
residuals are random errors.
BOTTOM:
During transit
(dashed line),
Rossiter effect appears.
ELODIE observations
D.Queloz, A.Eggenberger, M.Mayor,
C.Perrier, J.L.Beuzit, D.Naef
J.P.Sivan & S.Udry
Detection of a spectroscopic transit by
the planet orbiting the star HD 209458
Astron.Astrophys. 359, L13
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Exoplanet transits (Rossiter-McLaughlin effect)
When an exoplanet transits a stellar disk,
successive center-to-limb contributions
to the integrated line profile are occulted,
with different effects for stars of different
rotational velocities.
Hiva Pazira (Lund Observatory)
Spatially resolved stellar spectroscopy
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Synthetic line profiles
across stellar disks
Examples of synthetic line profiles from
hydrodynamic simulations of a solar-type star.
Curves are time-averaged line profiles, at
different positions and angles on the stellar disk.
Black curve is line profile at disk-center;
gradually lower intensities of blue, green, and
red curves reflect the limb darkening.
Solar model; Fe I, 620 nm, 1 eV.
Disk locations µ=1, 0.87, 0.59, 0.21;
azimuthal angles 0, 90, 180, 270°
Simulation by Hans-Günter Ludwig (Landessternwarte Heidelberg)
Spatially resolved stellar spectroscopy
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Doppler imaging
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DOPPLER
IMAGING
OF
STELLAR
SURFACES
S.S.Vogt, G.D.Penrod,
PASP 95, 565
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Doppler imaging of stellar surfaces
For a star with a dark spot close to
the equator, spectral line profiles
are affected throughout their whole
Width, as the spot is carried around
the star by rotation.
(Jean-François Donati)
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Doppler imaging of stellar surfaces
If the spot is located close to the pole,
spectral lines are only affected in their
core regions; the difference with the
previous case enables one to recover
information on both latitude and longitude
of starspots.
(Jean-François Donati)
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Spectroscopy at very & extremely large telescopes
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Visual high-resolution spectrometers at 8-10 m telescopes
Telescope SALT Keck I VLT
Kueyen
HET Subaru LBT
Diameter [m] 10 10 8.2 9.2 8.2 2 8.4
Spectrometer HRS HIRES UVES HRS HDS PEPSI
Maximum R 65,000 84,000 110,000 120,000 160,000 320,000
Wavelengths [µm] 0.37– 0.89 0.3 – 1.0 0.3 – 1.1 0.39 – 1.1 0.3 – 1.0 0.38 – 0.91
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Potsdam Echelle Polarimetric and Spectroscopic Instrument @ Large Binocular Telescope
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2080 cm R4 echelle grating for
PEPSI
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HE 1523−0901: A strongly r-process-enhanced metal-poor star, [Fe/H] = − 2.95 , with detected uranium
(Figure by Klaus Strassmeier)
At B=12.1, PEPSI @ LBT needs 9 hours to reach S/N=850 at R=300,000
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Resolving power and
spectral range of proposed
E-ELT spectrographs
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Pasquini et al.: CODEX: the high resolution visual spectrograph for the E-ELT
Proc. SPIE 7014, 70141I (2008)
Optical arrangement of multi-camera CODEX design
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40-m
European
Extremely
Large
Telescope
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E-ELT on Cerro Armazones (artist’s impression)
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Hiva Pazira (Lund Observatory)
Spatially resolved spectroscopy with ELTs
Left: Hydrodynamic simulation of the supergiant Betelgeuse (B.Freytag) Right: Betelgeuse imaged with ESO’s 8.2 m VLT (Kervella et al., A&A, 504, 115)
Top right: 40-m E-ELT diffraction limits at 550 nm & 1.04 μm..
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Grand challenge: Design an efficient
R = 1,000,000 high-fidelity
spectrometer for E-ELT !
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