LISA spectrograph
Long slit Intermediate resolution Spectrograph for Astronomy
Performances and application
Christian Buil
Active Spectroscopy in Astronomy
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Spectrograph resolution categories ( R = l/dl )
Lhires R = 16000
High resolution
Medium resolution
(or intermediate)
Low resolution
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eShel R = 11000
LISA
R = 500 to 1000
Star Analyser
R = 100 to 200
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Spectral resolution (R) and luminosity (L) : a complementary effort
R x L = constant
Faint object spectroscopy
The example of Star Analyser : very low resolution, very high luminosity
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Planetary nebulae NGC 2392 – 15 x 30 seconds
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Faint object spectroscopy
But do not mystake luminosity and detectivity !
One limitation of slitless spectroscopy : sky background pollution
The symbiotic star V1016 Cyg
Another limitation of SA : optical aberration
Chromatic coma : a source of detectivity degradation (bad capacity to concentrate energy)
Grism improvement
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Faint object spectroscopy
The importance of an entrance slit
Large slit
Narrow slit
The sky background level if proportionnal to the slit wide
The backgroung photon noise is proportionnal to the square root of slit wide
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The LISA concept (1/2)
-
Ajustable entrance slit by step (from 15 microns to 100 microns)
(capacity to optimise spectral resolution to a specific target)
-
Fast input beam : up to f/5 input i.e. high luminosity spectrograph (reduce potential
guidance problem because shorter focal length, capture of faint surface objet like galaxies,
comets, …
-
Optimized spectral dispersion to modern camera (2 A / pixel sampling on a popular KAF8300
CCD ship)
-
Balance between power resolution capacity and scientific interest (R = 500 to 1000
typically) – Sodium doublet is just separated with a 23 microns slit
2D spectrum of moon surface
Mg I,2,3
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Na
DA, D2
Halpha
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The LISA concept (2/2)
-
Wide spectral range in one shot : 3950 A – 7200 A (+ IR option)
-
Integrated calibration system (neon lamp + tungsten lamp) : easy to use and standard
pipeline processing. Possibility to fully automatize acquisition.
-
Compact and moderate weigth : adaptable on small refractor and refractor.
-
Low cost : large diffusion if possible!
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Optical design
Internal grandissement G = 0,603
For example: if the telescope focal / diameter
ratio is 6, the final F/D is 6 x 0,603 = 3,6
(LISA is equivalent to a focal reducer).
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Mechanical design
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Mechanical design
Calibration unit
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Ajustable grating angle
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Pointing and guidance system
High reflectivity slit
Very constant edge
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High quality slit image on the guidance camera
(here M104 galaxy with a Watec 120N)
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LISA on a Celestron 11 telescope
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Calibration module (spectral calibration and flat-field)
Electromagnetic system – 12 V power – Remote operation possible
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Interfaces
Optimal input focal ratio f/5 to f/7
Fast adaptation for CCD camera and DSRL
A fast Newton telescope is ideal (achromatism)
For SC Telescope : focal reducer
(here a Baader Alan Gee - final ratio f/6.8)
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Example of setup with Atik CCD cameras
Atik 314L for spectra acquistion (1390 x 1040 x 6.45 µm pixel size)
Readout noise : 4.5 e-, Camera gain : 0.250 e-/ADU, typical quantum efficiency @ 656 nm : 55%
Atik Titan for pointing and guiding functions
(faint object identification capability + rudimentary photometry measure on the targets)
Low cost solution for LISA, low mass on the telescope, high performances
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Amovible entrance slit
High precision chromium serigraphy
15 – 19 – 23 – 32 microns (option 50 – 75 – 100 microns + 19 microns hole)
Slit 23 microns – R = 1100
W = 2,5 arcsec on C11 f/6.8
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Slit 50 microns – R = 600
W = 5.4 arcsec on C11 f/6.8
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Automatised processing
Rlhires application
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Automatic spectral calibration by using observed type A, B or G
star spectra and internal neon lamp spectrum
Fit dispersion law with a 3e order polynomial function (typical RMS error : 0.3 to 0.4 A)
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Many tools available : computation of heliocentric velocity, H2O removal, atmopsheric
transmission, spectra database, …. French/english interface
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Limit magnitude
Integration time : 1 hour (6 x 600 sec)
Signal to noise ratio = 10 (@ Halpha)
Type A0V star – Seeing = 3 arcsec
CCD KAF-8300 (Binning 1 x1)
Altitude 0 m - Suburban
Altitude 3000 m – Dark sky
Slit 23 µm
R = 1100
Slit 50 µm
R = 600
Slit 100 µm
R = 290
D = 12.8 cm
F/D = 8
12.5
13.1
13.4
D = 28 cm
F/D = 6.8
13.6
14.6
D = 35 cm
F/D = 6.8
13.9
D = 50 cm
F/D = 6.0
D = 100 cm
F/D = 6.0
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Slit 23 µm
R = 1100
Slit 50 µm
R = 600
Slit 100 µm
R = 290
D = 12.8 cm
F/D = 8
13.1
13.6
13.9
15.0
D = 28 cm
F/D = 6.8
14.5
15.2
15.6
14.9
15.4
D = 35 cm
F/D = 6.8
14.8
15.6
16.1
14.4
15.5
16.2
D = 50 cm
F/D = 6.0
15.3
16.3
16.9
15.2
16.3
17.2
D = 100 cm
F/D = 6.0
16.1
17.3
18.2
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Limit magnitude (function of detector type)
Integration time : 1 hour (6 x 600 sec)
Signal to noise ratio = 10 (@ Halpha)
Type A0V star – Seeing = 3 arcsec
Altitude 3000 m – Dark sky
CCD KAF-8300 (Binning 2 x2)
CCD KAF-3200 (Binning 2 x2)
Slit 50 µm
R = 600
Slit 100 µm
R = 280
D = 12.8 cm
F/D = 8
14.2
14.5
15.8
D = 28 cm
F/D = 6.8
15.8
15.8
16.2
D = 35 cm
F/D = 6.8
D = 50 cm
F/D = 6.0
16.4
17.0
D = 100 cm
F/D = 6.0
17.4
18.3
Slit 50 µm
R = 600
Slit 100 µm
R = 280
D = 12.8 cm
F/D = 8
13.7
14.0
D = 28 cm
F/D = 6.8
15.4
D = 35 cm
F/D = 6.8
Slit 50 µm
R = 600
Slit 100 µm
R = 280
D = 12.8 cm
F/D = 8
14.3
14.7
16.2
D = 28 cm
F/D = 6.8
16.0
16.3
16.2
16.7
D = 35 cm
F/D = 6.8
16.4
16.8
D = 50 cm
F/D = 6.0
16.9
17.5
D = 50 cm
F/D = 6.0
17.1
17.6
D = 100 cm
F/D = 6.0
17.8
18.7
D = 100 cm
F/D = 6.0
18.1
19.0
3 hours integration (18 x 600 sec) – Slit 50 µm – D = 28 cm F/D = 6.8
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CCD ICX285AL (Binning 2 x2)
M = 16.1 (KAF-8300)
M = 16.5 (KAF-3200)
M = 16.6 (ICX424AL)
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Observation with LISA spectrograph
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Typical aspect of LISA 2D spectra
Symbiotic star V1016 Cyg
Star Analyser
2D spectrum before sky removal (23 µm slit)
2D spectrum after sky substraction
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Symbiotic star V1016 Cyg (V = 11.2) : lines identification
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First step : observation of normal stars (1/2)
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First step : observation of normal stars (2/2)
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Survey of know Be Star + and detection of new Be star
Beta Lyrae (Shelyak) – 15 x 30 s
Rapid scan of B and A star for Halpha emission signature (5-10 minutes exposure)
(list of nearly 1000 stars – magnitude < 10)
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Faint Be stars observation (BeSS)
V = 6.09 – 9 x 120 s
Essen - 7 May 2011 V = 8.62 – 6 x 300 s (new BeSS entry)
V = 4.74 – 8 x 60 s
V = 8.63 – 7 x 300 s (new BeSS entry)
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Survey of cataclysmic
(novae like)
SS Cyg outburst (V = 8.7) – April 4.1, 2011
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List of cataclysmic star (François Teyssier)
…
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Outburst of cataclysmic V694 Mon
High velocity wind – Fast evolution
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V694 Mon – Visible + IR capacity of LISA spectrograph
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Recurent nova T Pyxidis : day to day monitoring of profile evolution
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Observation at very low angular elevation : associated problem
T Pyxidis declinaison = -32 degrees
T Pyxidis 2D spectrum
6 arcsec refraction
at 12 degree elevation
Paralactic angle
Horizon
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Nova Sagittarii 2011 #2 (V5588 Sgr)
V = 13.2
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Eruption of Herbig Ae/Be star Z CMa
Vis + IR spectrum
Detail of IR spectrum
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MIRA star
R Leo at V = 8.5
Wide band spectrum
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Wolf-Rayet star HD 56925
WR 7 – V = 11.7
HD 56925 in NGC 2359 nebula
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Messier 1 (Crab nebulae) - 5 x 600 s @ R = 600
R Mon in NGC 2261 nebula
3 x 600 s @ R = 1000
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SUPERNOVA
SN 2011ae in MCG-3-30-19
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SUPERNOVA
SN 2011by in NGC 3979
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Messier 104
Sombrero galaxy
Audela autoguiding
2D spectrum
Na rest = 5892.9 A - Na observed = 5916.9 A – z = (5916.9 – 5892.9) / 5892.9 = 0.0041 (17 Mpc)
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Active galaxies (Seyfert)
NGC 4151
NGC 4051
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Quasar 3C273
LISA infrared version
Observed Halpha at 7584 A
z = (7584 - 6563)/6563 = 0.155
(official z = 0.158)
McDonald 2,1 m
K. Thompson AJ, 395, 404,417, 1992
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Quasar Mrk 205 observation
(V = 15.5)
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Quasar Mrk 205
7 x 600 sec. – 50 µm slit
Observed z = 0.0710 (official value z = 0.0705)
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Thank you
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