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MOST Guide Star Photometry
Overview
Statistics
Recent Results
by
Rainer Kuschnig &
the MOST Team
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Photometry Sources
Science CCD
open field
direct imaging
Fabry target
Guide stars
Direct imaging micro Lens Array
targets
Star Tracker CCD
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Star Photometry
• typically 4-8 guide stars, in special cases up to 20 are monitored
for any given primary target
• the magnitude range is 7-10.5, about 80% are of ‘known’ (listed)
spectral type
• exposure time is usually 1.5 sec (range from 0.3 to 1.5 applied)
• no images are recovered, the image data is processed on
board: a mean background value is removed and the signal is
the sum of high signal pixels (exceeding the background and
a 20 ADU threshold)
• for the brightest guide stars noise levels as low as 30ppm and
high duty cycle can be achieved over 3 weeks of data collection
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Star Photometry
1.5 sec exposure
calculate background
apply threshold
Sigexp = S (Ipix > backgr+threshold)
Sigtot = S N*Sigexp
-> stored in the science data stream
N = integer (target sampling time / guide Star exposure Time)
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Stars - Stats
time base:
7 to 47 days
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Stars – Scatter
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
Recently Observed Targets
observing period July - Nov 2005
WR103
HD179949
HD209458
HD224930
Kap1Ceti&
NGC752
Eps Eridani
+ 4
+ 2
+ 2
+ 3
+ 4
+ 2
+ 2
DI
DI
DI
DI
DI
DI
DI
and 20 Guide Stars
and 10 Guide Stars
and 5 Guide Stars
and 4 Guide Stars
and 5 Guide Stars
and 20 Guide Stars
and 4 Guide Stars
68 in total
over 300 stars measured in all 3 modes:
Fabry / Direct Imaging / Guide Star photometry
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
ALL TARGETS – SKY MAP
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
OFF-CVZ Observations: WR103
WR103
20 guide stars
4 field stars
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
OFF-CVZ: WR103 Guide Stars results
besides the unprecedented photometry for WR103 nine of
the twenty guide stars revealed variability
slowly pulsating Be (SPBe) star
- ‘classical’ SPB star
- gam Dor star
- variable B2Ib/II star
- B9(p?) star with rotation modulation
- delta Scuti star
- two K star variables
- two unknown type variables
-
50% duty cycle – 37 days
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Star: HD163868
MOST data
Observed and Modeled Frequencies
Published in ApJL 2005 (6 weeks after the run)
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Star Photometry
B5II/III – SPB star – 16 modes
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Star Photometry
B5II/III – SPB star – 16 modes
V=9.3
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Star Photometry
B2Ib/II
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Star Photometry
B8(p?) star – 2.4d period
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Star Photometry
B8(p?) star – 2.4d period
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Star Photometry
A3 – del Scuti
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Star Photometry
K0 star
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Star Photometry
unknown spectral type
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Star Photometry
K5 star
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Star Photometry
unknown spectral type
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
MOST Guide Star Photometry
gam Dor star
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
“A BAD COMPARISON STAR”
HD209775 is an F0 (V=7.59) field star close to (~1.2deg)
the well known exo-planet transiting system HD209458
Henry & Henry 2000 (IBVS #4826) checked this star for
suitability asa photometric comparison star for HD209458
and found based on 2 nights (each a few hours) that this
Object is of delta Scuti nature and hence of no use in the
context of their HD209458 study
……… but it was certainly found useful as a MOST
Guide Star
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
HD209775 – MOST Observations
HD209775 was one of 5 GUIDE STAR used
to point to HD209458 (transiting planet system)
MOST collected data during a ‘test’ run (~15days)
in 2004 to probe the eclipse phase of HD209458
clearly revealing its multi-mode delta Scuti type
pulsation modes (~20)
……….. nice but not quite outstanding …….
this year we went back and observed it (and HD209458)
for 45 days essentially without gaps and the recent
results are in fact quite unique with about 80 modes
identified
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
HD209775 ~80 pulsation modes
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
HD209775 ~80 pulsation modes
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC
HD209775 ~80 pulsation modes
COROT WEEK - 6-9 Dec 2005 – ESA/ESTEC