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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 210930A: Swift-XRT refined Analysis
  2. Swift GRB 210930A: Global MASTER-Net observations report
  3. GRB 210930A: Enhanced Swift-XRT position
  4. Fermi trigger No 654658271: Global MASTER-Net observations report
  5. Fermi GRB 210929B: Global MASTER-Net observations report
  6. GRB 210930A: Swift detection of a burst
  7. GRB 210929B: Fermi GBM Final Real-time Localization
  8. Fermi-LAT Gamma-ray Observations of IceCubeCascade-210926A
  9. GRB 210929A: Fermi GBM Final Real-time Localization
  10. GRB 210927A: Zwicky Transient Facility Follow-Up of a Fermi Short GRB (Trigger 654396242)
  11. GRB 210925B: AstroSat CZTI detection
  12. IceCube-210922A: SMA observation for the JCMT candidate
  13. IPN triangulation of GRB 210925B
  14. GRB 210926A: AstroSat CZTI detection
  15. GRB 210919A: iTelescope T-11 upper limits
  16. IceCube-210926A: No neutrino counterpart candidates in ANTARES search
  17. GRB 210926A: GECAM detection
  18. GRB 210927A: Fermi GBM Final Real-time Localization
  19. GRB 210919A OSN 1.5m Source Confirmation
  20. GRB 210919A CAHA 2.2m Observations: Afterglow/Host Galaxy Candidate
  21. IceCube-210922A: JCMT/SCUBA2 observations
  22. GRB 210925A: GECAM detection
  23. GRB 210925A: Fermi GBM Final Real-time Localization
  24. GRB 210919A: Chandra rapid ToO upper limit
  25. GRB 210924A: Fermi GBM Final Real-time Localization
  26. IceCube-210922A: No Candidate Counterparts from Swift/XRT follow up observations
  27. IceCube-210922A: No significant detection in HAWC
  28. IceCube-210922A: No neutrino counterpart candidates in ANTARES search
  29. GRB 210923B: GECAM detection
  30. Retraction of Fermi GBM GRB 210923A: the trigger is not a GRB
  31. IceCube-210922A: Upper limits from a search for additional neutrino events in IceCube
  32. IceCube-210922A: Upper limits from Fermi-GBM Observations
  33. IceCube-210922A: No Candidate Counterparts from the Zwicky Transient Facility
  34. GECAM observations of a series of bursts from SGR J1935+2154 (2021-09-15T14 to 2021-09-23T14)
  35. GRB 210919A: DECam Upper Limits
  36. Fermi-LAT Gamma-ray Observations of IceCube-210922A
  37. Konus-Wind detection of a burst from SGR 1935+2154 on 2021 September 22
  38. GRB 210923A: Fermi GBM Final Real-time Localization
  39. IceCube Alert 210922.76: Global MASTER-Net observations report
  40. GRB 210919A: Swift-BAT refined analysis
  41. IceCube-210922A - IceCube observation of a high-energy neutrino candidate track-like event
  42. GRB 210912A: LBT optical observations
  43. GRB 210919A: Lowell Discovery Telescope upper limits (correction to GCN 30859)
  44. GRB 210919a: Lowell Discovery Telescope upper limits
  45. GRB210919A: Keck NIRC2 Kp band upper limits
  46. GRB 210919A: Swift/UVOT Upper Limits
  47. GRB 210919A: LOAO and LSGT optical upper limits
  48. GRB 210919A: MITSuME Akeno optical upper limits
  49. GRB 210919A: Swift-XRT refined Analysis
  50. GRB 210919B: Fermi GBM Final Real-time Localization
  51. GRB 210919A: NOT upper limits
  52. GRB 210919A: AbAO optical upper limit
  53. GRB 210919A: Enhanced Swift-XRT position
  54. GRB 210919A: LCO Optical Upper Limit
  55. GRB 210919A: BOOTES-2/TELMA optical upper limit
  56. Swift GRB 210919A: Global MASTER-Net observations report
  57. GRB 210919A: Swift detection of a short burst
  58. Swift trigger 1073821: detection of IGR J16418-4532
  59. GRB 210912A: BOOTES-5/JGT optical afterglow candidate (Correction to GCNC 30823)
  60. GRB 210917A: Fermi GBM Final Real-time Localization
  61. GRB 210812A is not a compelling example of a lensed GRB
  62. GECAM observations of bursts from SGR J1935+2154 (2021-09-13T01 to 2021-09-15T14)
  63. GRB 210909A: Detection by GRBAlpha
  64. GRB 210912A: Swift-BAT refined analysis
  65. Konus-Wind observation of the recent SGR 1935+2154 activity
  66. GRB 210912A: Tautenburg observations
  67. GECAM observations of bursts from SGR J1935+2154 (2021-09-12T05 to 2021-09-13T01)
  68. AGILE observations of two bright bursts from SGR 1935+2154
  69. GRB 210912A: CAHA 2.2m Detection
  70. GRB 210912A: Swift-XRT refined Analysis
  71. GRB 210912A: Swift/UVOT Detection
  72. Fermi GBM observation of another bright burst in the direction of SGR 1935+2154
  73. GRB 210912A: Enhanced Swift-XRT position
  74. GRB 210912A: Host-galaxy candidate in PanSTARRS
  75. Fermi trigger No 653151835: Global MASTER-Net observations report
  76. Fermi trigger No 653124492: Global MASTER-Net observations report
  77. Fermi trigger No 653122278: Global MASTER-Net observations report
  78. GRB 210912A: Mondy optical afterglow confirmation
  79. Swift GRB 210912A: Global MASTER-Net observations report
  80. GRB 210912A: BOOTES-5/JGT optical afterglow candidate
  81. GECAM observations of bursts from SGR J1935+2154 (2021-09-11T07 to 2021-09-12T08)
  82. GRB 210912B: Fermi GBM Final Real-time Localization
  83. GRB 210912A: Swift detection of a burst
  84. Fermi trigger No 653093506: Global MASTER-Net observations report
  85. Fermi trigger No 653066776: Global MASTER-Net observations report
  86. Fermi trigger No 653084584: Global MASTER-Net observations report
  87. Fermi trigger No 653083551: Global MASTER-Net observations report
  88. Fermi trigger No 653079281: Global MASTER-Net observations report
  89. Fermi trigger No 653066130: Global MASTER-Net observations report
  90. Fermi trigger No 653072474: Global MASTER-Net observations report
  91. Fermi trigger No 653071808: Global MASTER-Net observations report
  92. Fermi trigger No 653054042: Global MASTER-Net observations report
  93. Fermi trigger No 653049776: Global MASTER-Net observations report
  94. Fermi trigger No 653022153: Global MASTER-Net observations report
  95. Fermi trigger No 653031163: Global MASTER-Net observations report
  96. Swift GRB210910.42: Global MASTER-Net observations report
  97. Fermi GBM observation of a bright flare in the direction of SGR 1935+2154
  98. Fermi trigger No 653010039: Global MASTER-Net observations report
  99. Konus-Wind detection of the second intermediate flare from SGR 1935+2154
  100. IPN triangulation of a bright burst from SGR 1935+2154

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