Transcript The DWARF project

The DWARF project: Vidojevica
Vince Oliver, Astronomical observatory of Belgrade
Outline
* Will talk about the Serbian side of the DWARF
project
The DWARF: “Definition”
• DWARF is an international project aimed at
detection of circumbinary extrasolar planets
using the timing of the minima of low-mass
eclipsing binaries.
The DWARF: Recall
• In general, we can consider 2 types of binaryplanet= configurations:
P-type
circumbinary extrasolar planet
(Kepler-16: Saturn-mas planet orbitin K+M dwarfs with P~229days)
S-type (planet orbit one star and Pbin>>Ppla)
P-type (planet orbit both stars and Ppla>>Pbin)
The DWARF: Program stars
• Starting sample of program stars consist 45 stars that
can be sorted into 3 groups:
(i) systems with K or/and M dwarf components
(ii) systems with hot subdwarf (sdO or sdB) and K or
M dwarf components,
(iii) post-common envelope systems with a white dwarf
(WD) component.
The DWARF: Program stars
Porbit < 5 days => to cover the minima
R=10-17mag => 20-200cm telescopes
The DWARF: Detection
In general, we have 3 principal techniques:
(i) precise radial-velocity measurements to
detect the wobble of the binary mass center,
BUTof transits of the
(ii) Photometric detection
The
timingacross
technique
proved
to be
the best
planet(s)
the disks
of the
components
forinner
detecting
circumbinary
planets
of the
binary,
and
(iii) timing of the inner binary eclipse
The DWARF: Timing technique
• The timing technique = precisely measure of the exact instant
of some well-defined and repeating feature of the binary light
curve (e.g. minimum)
e.g. Kepler 16
The DWARF: Members
Huge network consisting of 37 institutes/observatories
18 countries
1. Slovakia
2. Germany
3. Russia
4. Ukraine
5. Turkey
6. Egipt
7. Italy
8. Croatia
9. Greece
10. Bulgaria
11. Austria
12. Korea
13. Poland
14. Romania
15. Portugal
16. Czech Republic
17. Hungary
18. Serbia
The DWARF: Teles/Instruments
• Telescope sizes: 20 – 200 cm.
• Types: Cass, Schmidt-Cass, RC, few Newtons
• FOV: 7’x7’ – 132’ x 132’
AOB: Serbian side of the DWARF
project
• Project ”Stellar Physics” at the AOB participate in the
DWARF project since may 2012
• People currently involved in the project:
Dr Gojko Djurasevic
Dr Istvan Vince
Monika Jurkovic
Dr Oliver Vince
ASV: Equipment
1.
2.
3.
4.
Observatory is on the Vidojevica mountain: 1150m
60cm telescope (Cass, Astro System Austria)
ALTA Apogee U42 (2048x2048, 15’x15’ FOV, 0.46 “/pix)
Optec filter wheel (Bessel filters: B V R I)
ASV: Controlling softwares
• Telescope control: Autoslew control. soft. (P. Keller)
• Camera/filter control: MaxImDL imaging softw.
• Dome control: DomeControl soft. (Nikola & Laza)
ASV: Observation
• Automatized inVisual Basic Scripting language
Calibration
module
Master
frame
module
Preobservation
module
Observation
module
- Setup the accurate time
-Waits the sunset (using TheShy6 planetary program)
-Takes 5 FF frames with 5sec exposures in each band with highest S/N
-Takes 10 dark frames with 5sec exposure for making master flat
-Takes 10 bias frames for master bias
-Takes 10 dark frames with 180sec exposure for scalable master dark
- Makes master bias, dark and flat frames
-Chose the object which has an observable minima on that day
-Slew the telescope to the object
-Checks the FOV and correct it if needed
-Automatically finds the optimal exposure time for each filter
LOOP
-Makes an exposure
-Calibrates the images
-Do photometry on the fly
- corrects the exposure time if needed
-Check RA, DEC and correct if there is a shift
NEXT
ASV: VBScript output
So far we have minima of 3 objects:
HAT-192-0001841
1. HAT-192-0001841; Vmax=14; I band; texp=45s;
Binary
S/N=254;
system:
noK+M
binning
dwarfs
2. HS 2231+2441; Vmax=14; V band; texp=23s; S/N=79;
Observedwith
in I binning
band
3. NSVS 14256825; Vmax=13.2; V band ; texp=23;
Without
S/N=180;
binning
with binning
Vmax = 14 mag
Final reduction, calibration and photometry is performed
P ~ 0.31inday
the IRAF package
m ~ 0.6 mag
~ 0.02 mag
This project is the first automatized project in
Serbia astronomy
ASV: Our experience
• Our experience shows that there are at least 3
negative effects for observation:
1. Shutter delay: affects the timing of the minima
2. Shutter effect: affects the LC
3. Non-linearity of the CCD : affects the LC
ASV: Our experience
1. Shutter delay: is a result of finite time for
shutter to START to open
e.g. ALTA Apogee E47 has 0.42 sec delay
e.g. ALTA Apogee U42 has nearly 0 sec delay
Consequently: OBS-TIME written in the image
header is not the true one
Opinion: Each DWARF member should test their
CCD for this effect and correct it if needed
ASV: Our expirience
2. Shutter effect: is a result of a finite time for shutter to open
and close – it is not instant event but it is a process
e.g. FF with 0.02s (still present for 3sec exposure time)
When to wary?: FF frames are usually taken with 1-5 sec where
the effect is still severe
Consequence: Calibration and photometry is incorrect
Opinion: Small exposures should be avoided or to correct for
this effect
ASV: Our experience
3. Non-linearity: for instance, if we want 0.01
photometric precision we need to be within 1% of the
linarity range with both, Comp and Variable star
e.g. ALTA Apogee U42 is linear 3000-47000
ASV: How can 1.5m telescope help in
this project?
Theory: Expected precision of the minimum
N
t ~
A
N-number of the sampling points;
A-aperture size
Practice: We can calculate the recommended texp
for a given telescope, CCD, and star brightness
combination in order to achieve the required precision
ASV: How can 1.5m telescope help?
Our case: in order to achieve t < 1s, the program
stars can be rawly divided into 4 groups:
30s, 60s, 120s, 240s
However: there are problematic cases:
- faint stars producing small S/N
- stars observed in I band (CCD is ~20% less sensitive then in V band)
Solution:
- binning can help in some cases (faster readout, greater S/N)
- Larger aperture (greater S/N, better sampling)
Conclusions
• Serbia became eligible to be a part of nice
observational projects like DWARF with the
60cm telescope
• 1.5m telescope will improve the current
position in the observation