Gaia Alerts Meeting INAF-OABO, 29/09/2011

Gaia Science Alerts TEST at LOIANO

29-30 Jul 2011

G. Altavilla - INAF Osservatorio Astronomico di Bologna

BFOSC@1.52m Cassini TelescopeField of View: 13'x12.6'Pixel scale: 0.58 arsec/pixelLat. 44 15 33 N, Long. 11 20 02E,785m asl

UBVRI,GunnV~22 in 30min, V~6-7 in 2-3 sec;

(in spectroscopy V~18 in 30min, V~5-6 in 10sec)See here the comparison with other telescopes

1.5m, imaging ok,“wide” field useful for relative photometry

CRTS Transient ID CSS110610:141829+354249 14 18 28.52 +35 42 49.4 mag~18 images bias & flat corrected, astrometry and phot. catalogues (SExtractor) everything on the fly, while observing (in two!)151.fits > 110610_R.cat 2m152.fits > 110610_B.cat 10m153.fits > 110610_V.cat 5m154.fits > 110610_Rbis.cat 5m155.fits > 110610_Bbis.cat 10m156.fits > 110610_Vbis.cat 5m157.fits > 110610_R3.cat 5m

http://nesssi.cacr.caltech.edu/catalina/20110610/1106101350644123477.html

Ra/Dec or Long/Lat wcs rms: 0.193 0.149

110610, V 5min

110610

(R)(R)(R)

(V)(V)

(B)

(B)

B matched to gV,R matched to r

only zero point correction applied,no colour term

By Sergey Koposov

110610, Current CRTS lightcurve

2522

CRTS Transient ID CSS110621:201624-090333 20 16 24.2 -09 03 33.2 mag~16images bias & flat corrected, astrometry and phot. catalogues (SExtractor) everything on the fly, while observing (in two!)564.fits > 110621_B 5m565.fits > 110621_V 3m566.fits> 110621_R 2m

http://nesssi.cacr.caltech.edu/catalina/20110621/1106210091084179317.html

Ra/Dec or Long/Lat wcs rms: 0.187 0.213 (arcsec arcsec)

110621, V 3m

110621

(B)

(V)

(R)B,V matched to USNO phot BR matched to USNO phot R

only zero point correction applied,no colour term

By Sergey Koposov

110621, Current CRTS lightcurve

2523

Test successful

Fast reaction (target selected in the afternoon, observed and analysedIn the night)

Big errorbars due to the cross-correlation with other photometric systems and tothe missing colour term correction.

First target: clear, airmass ~1.2, seeing ~1.5”Second targert: veils, airmass ~1.7, seeing ~2”Useful to compare the results under different sky conditions

Conclusions/comments

Target selection: “by hand”, in contact with Cambridge (L. Wyrzykowski, S. Koposv, and A. Mahabal from CRTS). Options: web page to be checked manually, skyalert, email, automatic system, iphone....

Data aquisition: no problem (at least for imaging and during the nights devoted to this programme, no real ToO)

Data reduction: possible to measure the targets at the telescope while observing, provided that bias and flat images have already been acquired, but 2 observers areneeded (especially if the observational programme is made up by short exposures). Since data products are expected by the following day, an observer can acquire the data to be reduced by other people the following morning (efficient transfer of data and calibration to be set up).

Software used: Iraf (+wcstools+internet connection), SExtractor.Astrometric solution with an Iraf script of my own (can be adapted at other telescopes)very simple: in the best case the image name and the FWHM in pixel is enough.GSC2 reference catalogue.Sometimes an interactive shift of the solution may be necessary or, in the worst case,the coordinates of the center mut be specified manually in the parameters.

The photometric catalogues produced by SExtractor (I used aperture magnitudes with 3 different radii), together with the images header must be sent to Cambridge by email... (better automated system? how? To whom? Skyalert portfolio?).

Cambridge people calibrate the magnitudes by comparison with the catalogue mag of the fieldsstars. Hence Ra Dec and instrumental magnitudes are required, toghether with other info that can be retrieved from the images headers (JD for the light curve ecc..)

By the way, both targets were blazars