{
  "bibcode": "2002GCN..1563....1C",
  "body": "Covino S., Malesani D., Ghisellini G., Stefanon M., Tavecchio F. (INAF-OAB), \nCovone G., Fugazza D. (INAF-TNG), Di Paola A., Israel G.L. (INAF-OAR), \nMannucci F. (IRA-CNR), Masetti N. (IASF-CNR), Pian E. ((INAF-OAT), on behalf \nof a larger Italian collaboration, report:\n\n\nWe observed the varying source (VS) in the field of XRF 020903 (Ricker et al., \nGCN 1530; Soderberg et al., GCN 1554) on Oct 1.9 UT, with the Italian 3.5m \nTNG telescope, using BVRI filters. Seeing conditions were moderate (about 1.5 \narcsec) and airmass about 1.6. Magnitudes were derived by PSF fitting \nphotometry. One standard star field was also observed under clear (but not \nphotometric) conditions; therefore a small zeropoint offset is still \npossible. The magnitudes for the VS are the following:\n\nFilter  UT     Magnitude\n-----------------------------\n B      1.941  21.87 +- 0.06\n V      1.932  21.14 +- 0.04\n R      1.916  20.60 +- 0.09\n I      1.919  20.29 +- 0.07\n\n\nFor comparison, we also report the magnitudes of some nearby USNO stars; \nU0675_37142330 is named \"star 1\" in Soderberg et al. finding chart.\n\nU0675_37143953 U0675_37141960 U0675_37142330\n----------------------------------------------\nB 18.54 +- 0.02  19.51 +- 0.02  17.14 +- 0.01\nV 17.77 +- 0.01  19.02 +- 0.01  16.40 +- 0.01\nR 17.21 +- 0.04  18.63 +- 0.04  15.92 +- 0.03\nI 16.81 +- 0.03  18.36 +- 0.03  15.58 +- 0.03\n\n\nBased on the photometry performed at the TNG, we re-analyzed data obtained on \nSep., 29.9 UT with the Asiago telescope (GCN 1561). Seeing conditions were \nmediocre (about 2 arcsec) and airmass about 2. Magnitudes were again derived \nby PSF fitting photometry. We report the following results for the VS:\n\nFilter  UT      Magnitude\n-----------------------------\n V      29.923  20.94 +- 0.12\n R      29.931  20.42 +- 0.10\n I      29.937  19.98 +- 0.13\n\nThe source has simultaneously faded by about 0.2 mag in all V, R and I bands \nbetween Sep 29.9 and Oct 1.9. Comparing with the R-band measurement by \nSoderberg et al. on Sep 28.3, the source appears fainter by more than 1 \nmagnitude.\n\n\nA color-color diagram, together with a BVRI spectrum and a light curve are \nshown at the web page: http://www.merate.mi.astro.it/~malesani/XRF020903 .\n\nThe values reported here supersede those in our GCN 1561, that were based on a \nmisidentification of the reference star. We apologize for any inconvenience \nthis may have caused.\n\nDetailed analsys of these data is still in progress, and more observations \nwill be performed in the next few days.\n\n\nThis message may be cited.",
  "circularId": 1563,
  "createdOn": 1033634601000,
  "email": "covino@merate.mi.astro.it",
  "subject": "XRF020903: TNG and Asiago photometry",
  "submitter": "Stefano Covino at Brera Astronomical Observatory  <covino@merate.mi.astro.it>"
}