SDSS griz photometry SDSS griz photometry ((first experiences at Baja Observatoryfirst experiences at Baja Observatory))

T. Hegedüs – A. Szing – J. Vinkó* Baja Astronomical Observatory, * Szeged University

KOLOS 2013

Sloan Digital Sky Survey (2000-…)

First Standardized photometric system: Johnson’s UBV (1950…)

Harold Lester Johnson (April 17, 1921 – April 2, 1980)

UBV system: based on photomultipliers (basically blue-sensitive)

Apache Point Observatory (New Mexico, US)D=2,5 m RC telescope – at 2788 m altitude 65% clear sky 3 deg. large field of view 30 x 4 Mpixels CCD (cooled to -80C LN)

Filter λc (Å) FWHM (Å)u' 3543 570g' 4770 1370r' 6231 1370i' 7625 1530z' 9134 950

44

33

22

11

b+iga=rr'

b+zra='zr

b+ira='ir

b+rga='rg

obsobs

obs

obs

obs

58x58 mmMade by Omega Optical

Supported by Masaryk Univ.Brno (Cz) & Szeged University (Hu)

AverageAverage scatter at Baja (July-August scatter at Baja (July-August 20132013))

SN 2012htSN 2012ht

SN 2013dySN 2013dy

SN 2013dfSN 2013df

SN 2013SN 2013ejej

New griz photometry project: monitoring blazars in Kepler field

2541 BZBJ1838+4802 18 38 49.0 +48 02 34.0 0 16.2 BL Lac2606 BZQJ1949+5041 19 49 43.3 +50 41 31.9 1.929 15.7 QSO RLoud flat radio sp.2618 BZBJ2001+4352 20 01 12.8 +43 52 51.9 0 15 BL Lac2635 BZBJ2012+4628 20 12 05.5 +46 28 54.9 0 16.8 BL Lac

Problem: there are no ‘griz’ standards near this area!

Solution ???Solution ???

One possible solution: usage of previous UBVRI standards and try to transform

For Kepler-field blazars we selected NGC7790 open cluster’s standards.

At the SDSS web site:http://www.sdss.org/dr7/algorithms/sdssUBVRITransform.html#Jordi2006

One can find the possible linear formulae (Jordi et al., 2006)

UBVRcIc -> ugriz================

Transformation

u-g = (0.750 ± 0.050)*(U-B) + (0.770 ± 0.070)*(B-V) + (0.720 ± 0.040)

* g-V = (0.630 ± 0.002)*(B-V) - (0.124 ± 0.002)

g-B = (-0.370 ± 0.002)*(B-V) - (0.124 ± 0.002)

* g-r = (1.646 ± 0.008)*(V-R) - (0.139 ± 0.004)

g-i = (1.481 ± 0.004)*(V-I) - (0.536 ± 0.004) if V-I <= 1.8

g-i = (0.83 ± 0.01)*(V-I) + (0.60 ± 0.03) if V-I > 1.8

* r-i = (1.007 ± 0.005)*(R-I) - (0.236 ± 0.003)

* r-z = (1.584 ± 0.008)*(R-I) - (0.386 ± 0.005)

r-R = (0.267 ± 0.005)*(V-R) + (0.088 ± 0.003) if V-R <= 0.93

r-R = (0.77 ± 0.04)*(V-R) - (0.37 ± 0.04) if V-R > 0.93

i-I = (0.247 ± 0.003)*(R-I) + (0.329 ± 0.002)

(Jordi et al. (2006)

New experiment: another SDSS system on 50 cm RC telescope

Just for fun… (2013. 11. 15. BART-1, Baja Observatory, Hu

Comet LovejoyComet Lovejoy

Thank you for your attention!