STARE Operations Experience and its Data Quality Control

IAC

Roi Alonso

Hans Deeg

Juan A. Belmonte

HAO BoulderTim Brown

David Charbonneau

STARE Operations Experience and its Data Quality Control

Potsdam, July04 #2

STARE telescope• Stellar Astrophysics and Research on Exoplanets.• HAO, NASA funding; IAC logistics and personnel.• Detection of first planet transit in 1999, during commision at

HAO• Located at Teide Observatory, Tenerife since July 2001• Schmidt optics, 10.1 cm Ø,

f=286mm. • CCD: 2k x 2k Loral, 15m pix• 6.1x6.1 deg2 FOV, 10.8 arcsec/pix • R, V, B manual filters.

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Potsdam, July04 #3

Transit Detection Observations

STARE observation strategy:• One (two) field observed all night, typ. declination 30°-40°.• Observation of a field for 2 - 3 months ( 150-400 hrs)• R band exposures of 100 sec, 13 sec readout• typical field: few 1000 stars rms < 1%

Requirements :

•precision F/F better than 0.5%

•observational coverage O(103-4) hrs

•data points every few minutes

•surveying thousands of stars

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Potsdam, July04 #4

In collaboration with similar projects

• PSST: Lowell Obsv., Arizona. T. Dunham, G. Mandushev

• SLEUTH: Mt. Palomar, California. D. Charbonneau, F. O’Donovan

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Instrument control

• Hardware: 2 PCs: {Dome, Mount},{CCD,guiding}• Optical fiber interfaces computers telescope dome• Control software

– Unified user interface withVisual C++ (Windows98)

– Telescope: Orchestrate Scripting Software (Software Bisque):

– Dome: AutomaDome (Software Bisque):

– CCD: Pixel View (Pixel Vision)

STARE Operations Experience and its Data Quality Control

Potsdam, July04 #6DLT, DVD

Operations schemeoperator opens dome, starts scriptAfternoon

Nightfall; if fieldhigh enough

End of night/fieldtoo low

Morning

script starts observations

PC butch (script) PC sundance

Mount+dome CCD+autoguide

script return telesc. to home pos

operator closes dome, saves data (2Gb/night)

Observingperiod

operator watchesweather;

closes if needed

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Potsdam, July04 #7

Data reduction schemeraw data saved on DLT, now DVDTeide Obsv

IDL programs: quality control, image processing, photometry, classification, transit search

IAC, La Laguna

PSST Lowell, Sleuth Palomar

Confirmation of events in other’s data.

Combination of data from 3 sites and transit search in combined data

Future

HAO, BoulderCoordination of follow-up obsv.

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STARE statusField

 Observing

dateObserving

nights (Teide)Stars with

rms<1%

Observing time (h) (Teide)

Coll. Telesc.

Status

Jul-Oct 01 38 of 91 ~7300 195 1 Reduced

Boo1 Abr-Jul 02 39 of 118 ~1500 238 2 Reduced Teide and

Lowell

Cyg1 Jul-Oct 02 16 of 78 ~7300 67 2 Reduced Teide

Per2 Oct-Nov 02 30 of 58 ~6300 193 2 Reduced Teide

Cnc0 Feb-May 03 16 of 89 ? 127 2 Reduced Reduced Lowell

Her0 May-Jun 03 44 of 54 ~1600 291 3 Reduced All

Lyr0 Jul-Sep 03 ~50 of 68 ? 367 3 Red. Teide Lowell

Cyg0

42 And Sep03-Jan04 56 of 121 ~3000 397 3 Not reduced

27 Lyn Jan-Mar04 29 of 61 ? 103 3 Not reduced

Since March: Technical problems (110V supply, UPS)

Instrumental & atmospheric sources of false alarms

Sources : instrumental:•guiding errors (moving psf over zones with varying flat-field correct.)•temperature/focus variations

Sources : atmospheric:•unrecognized extinction variations (cirrus, dust)•simple high-sigma events in photon noise (star, sky), scintillation

“Transits are rare events in hugh data sets which compete with other rare events to become detected”

False alarm: any event that appears to be a transit, but isn’t

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Astron. source of false alarms(Brown 2003)

Confusion from:• grazing eclisping binaries

• diluted eclising binaries (by foreground star)

• diluted eclising binaries (triple sys)

• Planetary transits

We look for:

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Data quality control Photometric, moon rise

extinction sky bright.

guiding alignment

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Data quality control Cirrus in early night

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Data quality control Dusty night

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Data quality control guiding unstable, moon setting

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Follow-up tecniques for transit candidates

• Careful interpretation of the lightcurve:– non-transit-like shape, search for primary/secondary eclipses– verify that transit is compatible with planet (Seager & Mallén-Ornelas, 2003)

• Multicolor transit photometry (incidentially with higher spatial resolution)– detects many cases of Ecl. binaries.

• Imaging with very high resolution (adapt. optics)– indicates if there are nearby stars, potentially Ecl. Binaries

• Radial velocity measures– low res: may detect Ecl. binaries (false alarm rejection)

– high res: independent verification of planet

Reject astronomical sources of false alarms by a sequence of tests, from simple (light) to sophisticated (resource-intensive) ones:

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Summary and future• Routine transit search operation since 2001

• Operations will continue for at least 3 years

• Well-coordinated collaboration is in place for follow-up observations. Sequence of methods to reject false alarms.

• Some interesting planet candidates which need final verifications.