[vsnet-j 1994] The nature of SDSS "orphan GRB afterglow"

[Taichi Kato <tkato@kusastro.kyoto-u.ac.jp>]

The nature of SDSS "orphan GRB afterglow"

　アストロアーツのページでも紹介された、「光だけでみえた？ガンマ線バースト」
　ではないか、と言われた現象ですが、その後の調査で正体は違っていたようです。

　宇宙は怪しい話ばかりではないんだ、ということを実感しました(^^;)。

＃報道情報のその後の真相がフォローされるケースは少ないかも知れませんが、
＃プレスリリースニュースを当時出したところがどういった形でフォローをするのか
＃興味あるところです。

Paper: astro-ph/0202354
From: Avishay Gal-Yam <avishay@wise.tau.ac.il>
Date: Tue, 19 Feb 2002 16:22:26 GMT   (62kb)

Title: SDSS J124602.54+011318.8: A Highly Variable AGN, Not an Orphan GRB
  Afterglow
Authors: Avishay Gal-Yam, Eran O. Ofek, Alexei V. Filippenko, Ryan Chornock and
  Weidong Li
Comments: 14 pages, 5 figures, AASTEX 5.0.2, submitted to PASP
\\
  The optically variable source SDSS J124602.54+011318.8 first appears in Sloan
Digital Sky Survey (SDSS) data as a bright point source with nonstellar colors.
Subsequent SDSS imaging and spectroscopy showed that the point source declined
or disappeared, revealing an underlying host galaxy at z=0.385. Based on these
properties, the source was suggested to be a candidate ``orphan afterglow'': a
moderately beamed optical transient, associated with a gamma-ray burst (GRB)
whose highly beamed radiation cone does not include our line of sight. We
present new imaging and spectroscopic observations of this source. When
combined with a careful re-analysis of archival optical and radio data, the
observations prove that SDSS J124602.54+011318.8 is in fact an unusual
radio-loud AGN, probably in the BL Lac class. The object displays strong
photometric variability on time scales of weeks to years, including several
bright flares, similar to the one initially reported. The SDSS observations are
therefore almost certainly not related to a GRB. The optical spectrum of this
object dramatically changes in correlation with its optical brightness. At the
bright phase, weak, narrow oxygen emission lines and probably a broader H-alpha
line are superposed on a blue continuum. As the flux decreases, the spectrum
becomes dominated by the host galaxy light, with emerging stellar absorption
lines. The narrow and broad emission lines persist. We briefly discuss the
implications of this discovery on the study of AGNs and other optically
variable or transient phenomena.
\\ ( http://arXiv.org/abs/astro-ph/0202354 ,  62kb)

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