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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 011121: HST Scheduled
  2. GRB011121: fainter still
  3. Correction: GCN1157 (GRB 011121)
  4. GRB011121: UBRI Observations
  5. GRB011121
  6. GRB 011121: Radio Observations
  7. GRB 011121 J-Band Astrometry
  8. GRB011121: continued decay
  9. GRB 011121: Detection of Bright IR Counterpart
  10. GRB011121: possible redshift, continued decay
  11. GRB011121: fading behavior
  12. GRB011121: possible optical counterpart
  13. GRB011121: BeppoSAX-WFC refined positions
  14. IPN triangulation of GRB011121
  15. BEPPOSAX GRB011121
  16. GRB 011030: TNG K-band observation
  17. XRF011030: J and K band observations
  18. GRB011030, optical observation
  19. XRF011030: Chandra Observations
  20. GRB 011030: K-band observations
  21. GRB011030: Z-band observations
  22. GRB 011030 R band observations
  23. GRB 011030 I-band Observation
  24. The X-ray Flash 011030 ('GRB 011030')
  25. Non-triggered burst 011030 ("GRB 011030")
  26. The Radio Afterglow from the X-ray Rich GRB 011030
  27. GRB 010921: HST Detection of the Afterglow and Host Galaxy
  28. GRB 970828: HST Observations of the Host Galaxy
  29. GRB 000131: HST Detection of the Host Galaxy
  30. GRB 970828: HST Observations of the Host Galaxy
  31. GRB010921, optical observation
  32. GRB 011019 optical observation
  33. Optical observation of SGR 1806-20 at the 6-m SAO telescope
  34. GRB011019: Subaru Optical Observations
  35. GRB 011030 I-band Observations
  36. GRB 011030 K-band Observations
  37. GRB010921, optical observations
  38. GRB 011030, WSRT radio observations
  39. GRB011030 - further refinement WFC position
  40. GRB 011030, Radio observations
  41. GRB011030: radio search
  42. GRB 011030, R-band observations
  43. X-ray rich GRB011030: BeppoSAX refined positions
  44. BeppoSAX ALERT: Possible X-ray rich GRB011030
  45. GRB 010921: Possible supernova component
  46. GRB011019: NEAT Optical Observations
  47. GRB011019: ROTSE-III optical observations
  48. GRB010921, optical observation at early time
  49. GRB 010921, I-band observations
  50. GRB011019: Optical observations
  51. GRB011019, optical observations -- correction
  52. GRB011019, optical observations
  53. GRB011019: A Faint, X-ray Rich GRB localized by HETE
  54. GRB010921: Spectroscopy of the Host Galaxy
  55. GRB 010921: The afterglow of HETE #1761
  56. Optical Observations of the field of HETE trigger #1793/GRB 011012?
  57. Optical Observations of the field of HETE trigger #1793/GRB 011012?
  58. GRB010923 as seen by BeppoSAX GRBM
  59. GRB010928(=H1770): Localization of a Long GRB by HETE
  60. GRB010923(=H1764): A Short Duration GRB Detected by HETE
  61. GRB010921, negative optical observations
  62. GRB010921 field photometry
  63. GRB010921 Optical Observations
  64. GRB 010921 DPOSS Images Available
  65. IPN triangulation of GRB010921 (=H1761)
  66. H1761: A Bright GRB Detected by HETE
  67. HETE Trigger #1760 (GRB 010920B?): new optical source = asteroid
  68. HETE Trigger #1760 (GRB 010920B?): a new optical source
  69. HETE Trigger #1759 (GRB 010920?) optical observations
  70. GRB001109, Host Galaxy Astrometry
  71. GRB000926, Host Galaxy Observations
  72. GRB001109, Host Galaxy Spectroscopic Observations
  73. Probable SGR or Short Duration GRB Detected by HETE
  74. GRB000926 Host Galaxy Observations
  75. GRB 010222: HST observations -- host galaxy and late-time decay
  76. BeppoSAX/GRBM detection of GRB 010801
  77. GCN and HETE status
  78. Dramatic Increase in the Rate of X-ray Bursts Reported by HETE
  79. BeppoSAX/GRBM detection of GRB010728
  80. GRB 010222 - WHT BVRI images
  81. SGR1900+14 burst seen by HETE: BeppoSAX data
  82. GRB 010629 Optical Observations
  83. GRB010629: Optical Observations
  84. SGR1900+14: High Fluence Burst Localized by HETE
  85. GRB010629, optical observations
  86. IPN triangulation of GRB010629
  87. GRB010629: A Burst Localized by HETE
  88. SGR1900+14: Second Burst Localized by HETE
  89. SGR1900+14: A Burst Localized by HETE
  90. Possible burst from SGR1806-20
  91. IPN detection of SGR1900+14
  92. SGR1806-20: A Second, Intense Burst Localized by HETE
  93. GRB 00630: Host Galaxy
  94. SGR1806-20: Localization by HETE
  95. IPN triangulation of GRB010613
  96. IPN triangulation of GRB010612
  97. IPN triangulation of GRB010612
  98. HETE Fully-Automated GCN Notices
  99. GRB000301C: Late-time HST/STIS observation
  100. GRB010518: a faint BeppoSAX detection

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