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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. GRB990627: BeppoSAX-WFC final location
  2. BeppoSAX: GRB990625
  3. Late-time HST/STIS Observation of GRB 990123
  4. GRB 990506 - clarification to GCN 352
  5. GRB 990506 - Optical Observations
  6. Optical Observations of GRB 990506
  7. GRB 990506 Radio Transient
  8. GRB990527 Optical Observations
  9. X-ray/GRB 1SAX J0835.9+5118, Optical Observation
  10. IPN error box for GRB990527
  11. Late Afterglows of GRBs 990510, 990123
  12. X-ray/GRB 1SAX J0835.9+5118, TNG V and R observations
  13. X-ray/GRB 1SAX J0835.9+5118, BATSE Observation
  14. X-ray/GRB 1SAX J0835.9+5118, Optical Observations
  15. GRB 990506 optical observation
  16. X-ray/GRB 1SAX J0835.9+5118, Optical Observation
  17. X-ray/GRB 1SAX J0835.9+5118, Optical Observation
  18. X-ray/GRB 1SAX J0835.9+5118, Optical Observation
  19. X-ray/GRB 1SAX J0835.9+5118, Optical Observation
  20. radio observations of X-ray/GRB transient field
  21. optical observation of the X-ray/GRB transient SAX J0835.9+5118
  22. Optical report on X-ray/GRB transient
  23. radio detection of X-ray/GRB transient
  24. BeppoSAX: A new fast X-ray transient
  25. GRB 990510: optical observations
  26. GRB990510: photometric and spectroscopic observations with the VLT
  27. GRB 990510: optical linear polarization
  28. GRB 990510: optical observations
  29. GRB990510, VI observations
  30. GRB 990506 R band observations
  31. GRB990510: X-ray afterglow
  32. GRB 990510: optical observation
  33. VLT spectrum of GRB990510
  34. GRB 990510: Broad Band Break
  35. GRB 990510: BATSE Observations
  36. GRB990510: optical observation
  37. GRB 990510 Optical Observations
  38. GRB 990510, BVI photometry
  39. GRB 990510 optical observations
  40. GRB 990510: BeppoSAX/GRBM observations
  41. GRB990510 optical observations
  42. GRB990510
  43. GRB 990510 optical observations
  44. GRB 990510 optical observations
  45. Galactic extinction towards GRB 990510
  46. GRB990510: NFI X-ray source
  47. GRB 990510 optical observations
  48. IPN localization of GRB990510
  49. GRB 990506 Radio Observations
  50. GRB 990123, optical monitoring
  51. GRB 990506: BATSE Observations
  52. GRB 990506, optical observations
  53. GRB 990510: Final BeppoSAX-WFC Coordinates
  54. GRB 990506, Optical Observations
  55. GRB 990506 optical observations
  56. GRB 990506 optical observations
  57. GRB 990506, optical observations
  58. GRB990506 observation plan
  59. Refined IPN error box for GRB990506
  60. GRB 990506: Limits on the possible optical transient
  61. GRB 990506, armchair astronomy
  62. GRB 990506, optical observations from +1 to +3 hours
  63. GRB 990506, optical observations
  64. GRB990506 Optical observations
  65. GRB990506 observation plan
  66. New IPN/RXTE error box for GRB990506
  67. IPN localization for GRB990506
  68. GRB 970228: Redshift and properties of the host galaxy
  69. IPN localization of GRB990427
  70. GRB981220 VLBA observations
  71. GRB980425 Optical observations of exponential decline at late time
  72. GRB990321 REFINED IPN ANNULUS
  73. GRB990323 PRECISE IPN POSITION
  74. GRB990321 IPN TRIANGULATION
  75. GRB 990316 Optical Observations
  76. GRB 990316, Radio observations
  77. GRB 990316, Optical observations
  78. GRB990316, Optical observations
  79. GRB 990316 optical observations
  80. GRB990316: simultaneous optical observation
  81. GRB990316 - Optical null results
  82. ASM/IPN error box for GRB 990308 (BATSE #7457)
  83. GRB990308 not a new SGR
  84. GRB 990308a and GRB 990308b
  85. GRB990308 (Trig. 7457), optical observations
  86. GRB990308, Possible new SGR~0209+70
  87. GRB981220, IPN localization
  88. GRB 981220, radio observations
  89. GRB 990123, Field Photometry
  90. GRB 990217 Optical Observations
  91. GRB 990217, radio observations
  92. BATSE Resumes Normal Operations
  93. BATSE Flight Anomaly
  94. GRB990217: BeppoSAX/GRBM data
  95. Optical Observations of GRB990217
  96. GRB990123: Caltech STIS Photometry and Images
  97. GRB990123 observations
  98. GRB990217 Optical observation
  99. GRB990217, WFC position
  100. GRB990123, Optical Observation

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