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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"
  1. GRB 090426B: Fermi GBM detection/observation
  2. GRB 090429B: Swift XRT refined analysis
  3. GRB 090429A: Enhanced Swift-XRT position
  4. Konus-Wind observation of very bright GRB 090427
  5. GRB 090428B: Fermi GBM detection
  6. GRB 090428: Fermi GBM detection
  7. GRB 090418A BVRcIc field calibration
  8. GRB 090426: GAO 150cm telescope Optical Observation
  9. GRB 090429B: RIMOTS optical upper limits
  10. GRB 090429B: Swift-BAT refined analysis
  11. GRB 090429A: Swift-BAT refined analysis
  12. GRB 090429B: Enhanced Swift-XRT position
  13. GRB 090429A - Correction to XRT position
  14. GRB090429B: Gemini-N infrared IR candidate
  15. GRB 090426: YNAO-GMG observations
  16. GRB 090429B: VLT upper limits
  17. GRB 090429B: GROND Observations
  18. GRB 090429B: Super-LOTIS early observations
  19. GRB 090429B: Swift detection of a burst
  20. GRB 090429: Swift detection of a burst
  21. GRB 090423: pseudo burst at z=1 and its relation to GRB 080913
  22. GRB 090424 : Multiband Optical observation from Nainital
  23. IPN triangulation of very bright GRB 090427
  24. GRB 090426: R-band limit
  25. GRB 090424: Continued R-band monitoring
  26. GRB 090423: CARMA mm observations
  27. GRB 090423: millimeter detection
  28. GRB 090426: Swift/BAT spectral lag results
  29. GRB 090425: Fermi GBM detection
  30. GRB 090424: Suzaku WAM observation of the prompt emission
  31. GRB 090426: VLT spectroscopy
  32. GRB 090426: GROND Observations of the Optical/NIR Afterglow
  33. GRB 090426: Near infrared observation with ISLE at OAO
  34. GRB 090426: Okayama MITSuME optical observation
  35. GRB090426 Swift/UVOT observations
  36. GRB 090426 Keck LRIS redshift
  37. GRB 090426: Swift-BAT refined analysis
  38. GRB 090426: Swift-XRT refined analysis
  39. GRB 090423: GROND second epoch imaging and refined SED
  40. Detection of bright radio afterglow of GRB 090424 with the VLA
  41. GRB 090426: Enhanced Swift-XRT position
  42. GRB090426: Observation for Optical counterpart from MIRO
  43. GRB 090426, RIMOTS optical upper limits
  44. GRB 090426: inspection of SDSS images
  45. GRB 090426: TNT confimation of optical counterpart
  46. GRB 090426: Swift detection of a burst with an optical counterpart
  47. GRB090424: R-band detection (37.5 hrs post-burst), jet break?
  48. GRB 090424: MASTER-Net prompt optical limit
  49. GRB 090423: Fermi GBM observation (correction of isotropic equivalent energy)
  50. GRB 090424: WHT ISIS spectroscopy
  51. VLA radio observation of high-z GRB 090423
  52. GRB090424: BVRI/R-band detection after 15 hrs burst
  53. GRB 090424 : Lulin 1m telescope optical observations
  54. GRB 090424: THO optical observations
  55. GRB 090424: GROND Observations of the Optical/NIR Afterglow
  56. GRB090423: Y-band limit
  57. GRB 090424 Gemini-South Redshift
  58. GRB 090423: Y-band field calibration update/correction
  59. GRB 090423: Swift/BAT spectral lag results
  60. GRB 090424 : TAOS optical detection
  61. GRB 090424 optical observations
  62. GRB 090424: Liverpool Telescope observations
  63. GRB 090424: Swift-XRT refined analysis
  64. GRB 090424: Optical observations from 1.23m CAHA
  65. GRB 090423: energetic, luminosity and jet break
  66. Swift/UVOT observations of GRB 090424
  67. GRB 090424: MASTER-Net prompt optical observations
  68. GRB 090424: Enhanced Swift-XRT position
  69. GRB 090424: Swift-BAT refined analysis
  70. GRB 090424: Fermi GBM Observation
  71. GRB 090423: Fermi GBM observation
  72. GRB 090422: Fermi GBM observation
  73. GRB 090423: Ep,i - Eiso correlation
  74. GRB 090424: SDSS Galaxy at the Swift position
  75. GRB 090424: TNT optical observations
  76. GRB 090424: ROTSE-III Confimation of Optical Counterpart
  77. GRB 090424: Swift detection of a burst with an optical counterpart
  78. GRB 090423: Refined TNG analysis
  79. GRB090423: Y-band field calibration
  80. GRB 090423 limiting magnitudes
  81. GRB 090423: VLT/ISAAC spectroscopy
  82. GRB 090423: Near infrared observation at Okayama Observatory
  83. GRB 090423: Deep z-band upper limit and confirmation of photo-z
  84. GRB 090423: TNG Amici spectrum
  85. GRB 090423: GROND detection and preliminary photo-z
  86. GRB 090423: NOT z-band limit
  87. GRB 090423: Correction to NIR photometry
  88. GRB 090423: Swift-XRT refined analysis
  89. GRB090418A Rc-band photometry
  90. GRB090423 - Swift/UVOT upper limits.
  91. GRB 090423: NIR photometry and evidence for spectral break
  92. GRB 090422: Swift-XRT refined analysis
  93. GRB090423, RIMOTS optical upper limits
  94. GRB 090423: UKIRT data further analysis
  95. GRB 090423: Enhanced Swift-XRT position
  96. GRB 090423: Swift-BAT refined analysis
  97. GRB 090422: Swift/UVOT Upper Limits
  98. GRB 090423: UKIRT K-band observations
  99. GRB 090423: P60 Observations
  100. GRB 090423: Faulkes Telescope South observations

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