{
  "body": "A.M. Soderberg, P.A. Price, D.W. Fox, S.R. Kulkarni, S.G. Djorgovski, E.\nBerger and F. Harrison, S. Yost (Caltech); M. Hamuy and S. Shectman (OCIW);\nE. Armstrong, C. Espaillat N. Mirabal and J. Halpern (Columbia); and\nJ. Kemp (Joint Astronomy Center and Columbia) report:\n\nWe imaged the entire error-box of XRF 020903 with the Palomar 200-inch\ntelescope + Large Format Camera (LFC) on Sep 4.3 UT (epoch 1) and Sep 10.3\nUT (epoch 2) in Steidel R-band.  Visual comparison of these images with\nthe Digitised Sky Survey and with each other did not reveal any obvious\ntransient.  Recently, we undertook a more detailed analysis, namely\nPSF-matched image subtraction of these two epochs, and found\nan optical transient (OT) located at coordinates:\n\n\t  RA: 22:48:42.34   Dec: -20:46:09.3   J2000\n\nwith a bright elliptical galaxy 4 arcsec SE (hereafter G2).\n\nThe source is also present in images from the MSO 50-inch telescope\n(GCN #1533) when the second epoch LFC image is subtracted.\n\nUpon discovery of the OT, we immediately pursued further observations,\nthereby obtaining a third epoch of imaging with the MDM 1.3-meter\ntelescope on Sep 28.3 UT in the R-band.  Initial photometry demonstrates\nthat the object has re-brightened by ~ 0.3-0.4 mag between epochs 2 and\n3.  We propose that this optical rebrightening is from an associated\nsupernova, peaking between ~7-24 days after the initial XRF trigger.\n\nSpectroscopic observations by M. Hamuy and S. Shectman for the source were\nalso obtained with the Magellan 6.5m telescopes (Baade+LDSS2, Clay+B&C) on\nSep 28.1 UT.  We detect narrow emission lines from an underlying host\ngalaxy (hereafter G1) are (Halpha, Hbeta, Hgamma, [O III], [Ne III],\n[O II]) at a mean redshift of z = 0.25 +/- 0.01.  Subtraction of the\nemission lines reveals a continuum that is consistent with a SN-like\ntransient near maximum.  In particular, the spectrum reveals\ndeficit of emission at rest wavelengths < 4000A, as would be expected\nfrom a SN.\n\nSpectra of G2 (R ~ 17 mag) reveal it to be an elliptical galaxy at\nz = 0.23 and therefore is not associated with the optical transient.\n\nIf the OT is indeed associated with XRF020903, it is the first known\noptical afterglow of an XRF, and may be the most nearby cosmological high\nenergy transient known yet.  Parenthetically we note that microlensing\nfrom G2 may result in sharp variations of the light curve (see\nGarnavich, Loeb and Stanek, 2000). We encourage further monitoring of\nthis OT/SN.\n\nA web page summarizing the discovery and subsequent observations can be\nfound at:\n\thttp://www.astro.caltech.edu/~ams/XrF.html\n\nThis message may be cited.\n\n[GCN OPS NOTE (29Sep02):  Three names were added to the author list.]",
  "circularId": 1554,
  "editedOn": 1777052640576,
  "submitter": "Alicia Soderberg at Caltech  <ams@astro.caltech.edu>",
  "version": 2,
  "eventId": "XRF 020903",
  "editedBy": "Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov>",
  "bibcode": "2002GCN..1554....1S",
  "subject": "XRF 020903: Supernova",
  "createdOn": 1033276348000,
  "email": "ams@astro.caltech.edu"
}