Summary details for XO Exoplanet Archive-ETSS Data Sets


Two Canon Mark 1 cameras with EF2000 Canon lenses (200mm focal length, f/1.8).
Aperture: 11 cm.
Location: Haleakala, Maui, Hawaii.


1024 x 1024 Apogee Ap8p thinned CCD with 24-micron pixels.
Pixel scale: 25.4 arcsec / pixel.
Field of view: 7.2° x 7.2°.
Filter: W(XO) Edmunds Optics Inc NT54-517, flat throughput between 400nm and 700nm.

Observed Region

A 7 x 7 square degree region centered on RA = 240 degrees and Dec = +31 degrees.


The XO-DR1 data were obtained in drift-scan mode. Aperture photometry was used for simplicity and reliability. Both cameras were always pointed at the same field to increase signal-to-noise ratio (twice the number of photons) and to provide redundancy for verification and stability purposes. Effective exposure cadence is 10 minutes, exposure time is ~54s. For specific details on calibration and relative photometry, we refer the reader to the paper referenced below, specifically to section 5.4.

The Exoplanet Archive attempted to detect all stars in this data release in the 2MASS catalog by performing a coordinate match search with a radius of 20 arcsec. The resulting 2MASS entry (if available) with the smallest distance was designated a match, and its JHK magnitudes were assigned to the XO counterpart.

Data Ranges

The data parameters fall into the following approximate ranges:

Field Min Max
HJD of the
2453080.138 2453566.054
J 2MASS magnitude 3.555 17.240
H 2MASS magnitude 2.577 16.522
K 2MASS magnitude 2.324 17.056
Total number of stars - 2047
Number of epochs 11 3451


Figure 1

Figure 1: Standard deviation σ of the differential instrumental magnitudes estimated by each camera in a 54 s exposure made every 10 minutes, plotted with respect to the visual magnitude of each of the 1874 stars in a representative field at moderate Galactic latitude. Galactic coordinates of the center of the field are indicated. The σ is estimated from > 1000 observations per star, after calibration and iterative rejection of outliers. The expected performance (e.g., Everett & Howell 2001) is plotted as a solid line, which is the quadrature sum of three components: Poisson noise of photons from the sky (steeper sloped line) and the star (shallower sloped line) and a constant fractional error (horizontal line) attributed to scintillation and imperfect calibration. Stars brighter than V ≈ 9 are saturated and have σ ≈ 0.015 mag. Two stars known to exhibit transits, HD 209458 and TrES-1, are illustrated as squares located at their mean brightnesses and transit depths in the V band.

Download Data Sets

XO summary file IPAC ASCII format table
XO light curves Download scripts

Primary References