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Data release description


The release notes for each field

are included in each field folder.





RELEASE 5 DATA

The latest reduction of Cru/Car field (the Release R5) is now available.

The release 5 columns description is here: DR5-descr.pdf



RELEASE 4 DATA

The latest reduction of CasCep field included an additional parameter, the Release R4, is now available.

PSF blur 1(Column 7 in reformatted data file):

PPSF blur 1 - is the sum of squared, normalized intensities (sum of normalized image energy). The higher - the more sharp is the PSF.

PSF blur 2 (Column 8 in reformatted data file):

PSF blur 2 - is the blur measured using the correlation of image with its shifted copy in all 4 directions.

RTS indicator (Column 9 in reformatted data file):

RTS indicator - columns in differential image should be of 0 intensity (or around 0). The maximum (negative or positive) of all columns is given in this parameter. The higher this value, the higher propable offset of the photometry.RTS indicator meant the "median of columns".

The release4 has now 9 columns which are:

column 1HJDHeliocentric Julian Date at start of exposure
column 2Flux [ADU/sec] Signal extracted from image per second
column 3PSF-XCen Profile centre of gravity with respect to raster origin [pixel]
column 4PSF-YCenProfile centre of gravity with respect to raster origin [pixel]
column 5CCDTCCD Temperature [C]
column 6JD as given in the according FITS filesJulian Date at start of exposue
column 7PSFC1PSF blurring coeffient 1
column 8PSFC2PSF blurring coeffient 2
column 9RTSCRTS estimate coeffient


RELEASE 3 DATA

The differences between release 2 and release 3 data are that Adam has added two coefficients which may help to decorrelate instrumental effects. This applies to chopping data only! The FLAG column is now replaced and one more column is added which makes a total of 8 columns.

The two new columns are called PSFC and RTSC and the respective descriptions are taken from an email (Aug 3 2015) Adam sent out given here (full e-mail decribing the reduction AdamPopowicz chop reduction notes):

PSFC (Column 7 in reformatted data file):

We know that PSF shape influences the measurement. This appeared to be crucial and we (Andrzej and I) have some improved results after the blurring decorrelation. So we would like to have a nice PSF blurring coefiicient I have proposed about 5 of them and Andrzej checked which, after the decorrelation, gives the best accuracy. The selected is based on the autocorrelation of images. I work on the masked image so that only the star PSF is analysed. The pixels intensities are divided by the sum of intensities of all pixels. This way we have the PSF scaled so that the star intensity variability does not disturb the blurring coefficient, which is defined as: Q = A/ mean(A(n-1)).

The A is the maximum of autocorrelation of the image (i.e. A = sum(p(n)2), where p(n) is n-th pixel in the image). So we can say that it is the sum of squared pixels intensities. The A(n-1) is the sum of the intensity multiplication of image A with the same image A shifted by one pixel. The "mean" stands for the mean value of the previous for 8 directions of shifting. If the star is sharp, than the A is much larger than mean(A(n-1)), if it is blurred the both are close. An example of a dependency for exemplary star in currently analysed field is given in attachment- It surely will improve Your results. This coefficients are given in column 6 (after time, mag, temp, x_pos, y _pos).

RTSC (Column 8 in reformatted data file):

I have also added the next column which corresponds to the probability of RTS in data. It is simply the maximum of the image I(N+1)-I(N-1) masked by the PSF detected in I(N) (i.e. it shows the probably RTS impact of current N photometry). However it may be of limited use since it only signals if the RTS may appear for a give measurement. Please look at the example2.png, where You can see that for larger RTS estimated maxima we have much less points but they have larger spread (optically it may not be so visible but it is - the points are better concentrated around 0 for small RTS maximal values than it is for e.g. 600 and above, for this particular case the MAD for RTS maximum below 200 (4200points) is 244ADU while for those above 600 (500 points) is 430ADU). There is no trend downside or upside because the RTS will influence the photometry in both sides (RTS may be due to the dark current generation drop or increase) so not much chance for any decorrelation. This coefficient is given in the last column.

The release3 has now 8 columns which are:

column 1HJD
column 2Flux [ADU/sec]
column 3PSF-XCen
column 4PSF-YCen
column 5CCD Temperature [C]
column 6JD as given in the according FITS files
column 7PSFC
column 8RTSC



BRITE 2022. Last updated on 2022-06-02.