View
214
Download
0
Tags:
Embed Size (px)
Citation preview
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 1
Hommage to Hommage to Henrietta Leavitt Henrietta Leavitt from the CoRoT Teamfrom the CoRoT Team
1908
2008
Annie BAGLIN, Merième CHADID, Zoltan KOLLATH, Michel AUVERGNE
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 2
A stellar photometer in A stellar photometer in spacespace
* Ultra high relative photometry 100 to 1000 times more accurate than from ground
•Very long continuous durationsMore than 150 days
Dedicated to time variability from minutes to monthsDedicated to time variability from minutes to months
The CoRot product : Light curves
For 679 days in orbit
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 3
The focal planeThe focal plane
*
*
**
*
*
* *
*
*
•
•
•
•
•
1.3 °
field of view
Seismology field highly defocussed
main target (≤ 6)
12000 targetssampling 8.5 min (32 s.)
secondary targets (≤ 9)
10 targetssampling 1 s to 32s
Exoplanet fieldOn focus + bi-prism
faint stars (11-16)
Aperture photometry on selected targets to reduce the TM flow
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 4
Seismology Targets Seismology Targets already observedalready observed
6 Delta Scuti, 2 known gam Dor
10 B stars, Beta Ceph,
3 Be
10 giants (G,F)
14 A/early F stars ?2 Am, 7 Ap,
9 solar-like puls. cand.
(one observed twice)The classical HR diagram and the known class of variables
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 5
Solar like starsSolar like stars
6th mag
White noise
granulation
oscillations Eric Michel andThe SWG
Detection and measurement of oscillations and granulation in several stars
First interpretations show the presence of unexpected mechanisms of mixing in the stellar core
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 6
The Instability StripThe Instability Strip
Cepheids
RRLyrae
Delta ScutiDelta Scutis
in the seismology field high accuracy
Large number of modes ?
RR Lyrae
Continuous, ampl variations
Blasko effect
CepheidsLow amplitudesDouble modesStrange modes?
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 7
Delta scuti starsDelta scuti stars
2 days 2 days
2 days 3 days
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 8
In delta scuti stars A very rich In delta scuti stars A very rich spectrumspectrum
Eric Michel and the SWG
Ground based observations
The zoom below shows for the delat scuti star a very rich signal absent in another target of the same magnitude
This signal is real…..needs interpretation….not easy!
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 9
NGC2264 CCD E1
Seismology, variability Seismology, variability in the exoplanet fieldin the exoplanet field
*Data collected for the exoplanet search, R< 16, ~5500 stars per CCDPresently ~ 88 000 observed
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 10
Variables are everywhereVariables are everywhere
40%variables
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 11
Automatic classificationAutomatic classification
29 classes
Being Improved
…..
•4 first runs •IRa01, SRc01, LRc01, LRa01• 200 SPB• 190 Beta Cephei• 32 Dor• 1230 Delta Scuti• 8 RR Lyrae• 10 classical cepheids, 2 double mode• 5800 low amplitude Cepheids ?
A lot of uncertianties• New classes?
Debosscher et al.,
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 12
RR Lyrae: RRab with Blashko RR Lyrae: RRab with Blashko effecteffect
150 days
M. Chadid et al.
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 13
The Blazhko frequencyThe Blazhko frequency
Blazhko frequency
0.0369 c/d (27.1003 d)
and its harmonic 0.0746 c/d
For the first time
the Blazhko frequency is directly
measured in the Fourier spectrum.
The Blazhko effect reduces
the amplitude by over 50%.
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 14
First detection of an overtoneFirst detection of an overtone
For the first time in a RR ab star,
additional mode: at 4.0323 c/d
and half of it: 2.0162
with harmonics up to 5thharmonic.
Ratio to the fundamental frequency is 0.7177.
fundamental and first overtone double mode
pulsator...
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 15
Classical CepheidsClassical Cepheids
Rare objects but several (10) detections in the exo field
Amplitude (mag) 0.1Period (days) 30
Amplitude 0.5Period 6
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 16
Smaller and smaller?Smaller and smaller?
Amplitude 0.035Period 6
Amplitude 0.03Period 1.6
Amplitude 0.02Period 5
Amplitude 0.02Period 1.2
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 17
Probably a binary…..Probably a binary…..
Sometimes curious objects, be cautiousThe two very small repeating spikes in phase cast doubts on the pulsation nature of the variationOnly a very small sampling can reveal that as they last oy 4 hours
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 18
Strange Cepheids in the Strange Cepheids in the CoRoT targetsCoRoT targets
There seem to be CoRTt variables in the predicted domain of strange modesGround base observation are in progress to obtain precise stellar parameters
(Zoltan Kollath et al.)
Thanks to Henrietta Swan Leavitt, Harvard CfA November 5th 2008 19
A Double mode cepheidA Double mode cepheid
f1: 0.778 c/dF2: 0.971 c/d
More candidates….
More candidates to come…..