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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 210112A: AGILE detection
  2. GRB 210112A: Kitab a optical upper limit
  3. GRB 210104A: AROMA-N Optical Afterglow Detection
  4. GRB 210112A: Enhanced Swift-XRT position
  5. GRB 210112A: Swift detection of a burst with an optical counterpart
  6. NuEm-210111A: No counterpart candidates in INTEGRAL SPI-ACS and IBIS prompt observation
  7. AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-210111A
  8. GRB 210104A: Mondy optical observations, light curve
  9. MAXI GRB210110.64: Global MASTER-Net observations report
  10. GRB 210110A: MAXI/GSC detection
  11. GRB 210104A: Assy continued optical observations, correction to GCN circ. 29265
  12. GRB 210109A: MAXI/GSC detection
  13. GRB 201227A: continued Chilescope confirmation of variability of possible optical counterpart, redshift estimating
  14. Correction to GCN 29278: GRB 201216C XRT refined analysis
  15. GRB 210108A: BALROG localization (Fermi Trigger 631793415 / GRB 210108424)
  16. GRB 201216C: Swift-XRT refined Analysis
  17. GRB 210104A: SAO RAS optical observations
  18. GRB 201227A: ASIM observation
  19. GRB 210104A: GMG observations
  20. GRB210104A: VIRT optical transient detection.
  21. GRB 210104A: SARA-KP 0.9m Optical Afterglow Detection
  22. Fermi trigger No 631602681: Global MASTER-Net observations report
  23. GRB 210102B: further Swift-XRT observations
  24. GRB 210102B: Assy optical afterglow identification
  25. GRB 210104A: iTelescope optical upper limit
  26. GRB 210104A: CALET Gamma-Ray Burst Monitor detection
  27. Fermi trigger No 631584650: Global MASTER-Net observations report
  28. GRB 210104B: Swift-BAT refined analysis
  29. GRB 210104A: Assy continued optical observations
  30. Fermi GRB 210105A: Global MASTER-Net observations report
  31. GW170817: HST observations at 3.4 years from merger
  32. GRB 210104A: early ATLAS detections of the bright afterglow
  33. GRB 210105A: Fermi GBM Final Real-time Localization
  34. GRB 210104A: Swift-XRT refined Analysis
  35. GRB 210104B: Swift/UVOT Upper Limits
  36. Konus-Wind detection of GRB 210104A
  37. GRB 210104A: 1.3m DFOT Optical Afterglow Detection
  38. GRB 210104B: Swift-XRT refined Analysis
  39. GRB 210104B: Assy optical upper limit
  40. GRB 210104A: DOAO optical afterglow observations
  41. GRB 210104B: Enhanced Swift-XRT position
  42. GRB 210104A: Nanshan/NEXT optical powerlaw decay
  43. GRB 210104A: Swift-BAT refined analysis
  44. GRB 210104B: Nanshan/NEXT optical upper limit
  45. GRB 210104B: BOOTES network optical upper limit
  46. GRB 210104A: MASTER OT rebrightening detection
  47. GRB 210104A: Swift/UVOT Detection
  48. GRB 210104A: Fermi GBM detection
  49. GRB 210104A: Enhanced Swift-XRT position
  50. GRB 210102B: Tiled Swift observations
  51. GRB 210104B: Swift detection of a burst
  52. Swift GRB210104.88: Global MASTER-Net observations report
  53. GRB 210104A: MITSuME Ishigaki optical observation
  54. GRB 210102B: Assy optical observations
  55. Fermi GRB 210104A: Global MASTER-Net observations report
  56. GRB 210104A: Assy optical observations
  57. GRB 210104A: MITSuME Akeno optical observation
  58. GRB 210104A: BOOTES-4/MET early optical afterglow detection
  59. GRB 210104A: GWAC-F60A optical afterglow observations
  60. GRB 210104A: BALROG localization (Fermi Trigger 631452424 / GRB 210104477)
  61. GRB 210104A: Swift detection of a burst with a bright optical counterpart
  62. GRB 210104A: Fermi GBM Final Real-time Localization
  63. GRB 210102C: Swift-BAT refined analysis
  64. GRB 210102B: Swift-XRT observations
  65. Fermi GRB 210102C: Global MASTER-Net observations report
  66. GRB 210102C: Fermi GBM detection
  67. Swift GRB 210102C: Global MASTER-Net observations report
  68. GRB 210102C: Swift detection of a burst
  69. MAXI GRB210102.38: Global MASTER-Net observations report
  70. GRB 210102B: Tiled Swift observations
  71. GRB 210102B: MAXI/GSC detection
  72. Fermi GRB 210101A: Global MASTER-Net observations report
  73. INTEGRAL Weak #8913: AROMA-N Optical Observation
  74. Swift Trigger 1015615 is not a GRB
  75. Swift GRB210102.01: Global MASTER-Net observations report
  76. Fermi trigger No 631226368: Global MASTER-Net observations report
  77. Fermi trigger No 631119348: Global MASTER-Net observations report
  78. GRB 210101A: BALROG localization (Fermi Trigger 631205591 / GRB 210101620)
  79. GRB 210101A: Fermi GBM Final Real-time Localization
  80. Fermi trigger No 631113166: Global MASTER-Net observations report
  81. GRB 201229A: Swift/UVOT Detection
  82. Fermi trigger No 631118376: Global MASTER-Net observations report
  83. Fermi trigger No 631104264: Global MASTER-Net observations report
  84. GRB 201216C: TSHAO, Terskol, Mondy optical upper limits
  85. Baksan Neutrino Observatory Alert 201230.40: Global MASTER-Net observations report
  86. GRB 201227A: Chilescope optical observations, possible optical counterpart
  87. GRB 201227A: GRAWITA VST-ESO PARANAL observations
  88. GRB 201227A: Fermi GBM observation
  89. GRB 201229A: AbAO optical afterglow detection, TSHAO optical upper limit
  90. GRB 201229A: SAO RAS optical observations
  91. GRB 201229A: Nanshan/NEXT optical upper limit
  92. GRB 201227A: Swift-XRT observations
  93. GRB 201223A: SVOM-GWAC detected the optical counterpart during prompt emission phase
  94. GRB 201229A: Swift-XRT refined Analysis
  95. GRB 201229A: Swift-BAT refined analysis
  96. GRB 201104B: Maidanak and CrAO optical observations
  97. Fermi GRB 201229B: Global MASTER-Net observations report
  98. Konus-Wind observation of GRB 201227A
  99. GRB 201229B: BALROG localization (Fermi Trigger 630948017 / GRB 201229639)
  100. GRB 201229B: Fermi GBM Final Real-time Localization

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