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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"

11556 results found.

  1. GRB 250702F: REM optical afterglow detection
  2. GRB 250702F: DDOTI Optical Observation
  3. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  4. GRB 250703A: Fermi GBM Final Real-time Localization
  5. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  6. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  7. Fermi GRB 250702E: Global MASTER-Net observations report
  8. Fermi GRB 250702B: Global MASTER-Net observations report
  9. GRB 250702D, C, E: Swift/BAT-GUANO localization skymap of a burst or galactic transient
  10. GRB 250702F: GTC/OSIRIS+ spectroscopic redshift z = 1.520
  11. GRB 250702F: NOT observations of the optical afterglow
  12. GRB 250702F: MASTER optical afterglow observation
  13. Fermi GRB 250702F: Global MASTER-Net observations report
  14. Fermi GRB 250702C: Global MASTER-Net observations report
  15. GRB 250702F: GOTO optical counterpart detection
  16. GRB 250702F: Ondrejov D50 optical afterglow detection
  17. GRB 250702F: Swift detection of a burst with an optical counterpart
  18. GRB 250702F: Fermi GBM Final Real-time Localization
  19. Fermi GBM Triggers 250702B, C, D and E are likely from the same source
  20. GRB 250702E: Fermi GBM Final Real-time Localization
  21. GRB 250702A: Fermi GBM Detection
  22. GRB 250702D: Fermi GBM Final Localization Correction
  23. GRB 250702C: Fermi GBM Final Real-time Localization
  24. GRB 250702B: Fermi GBM Final Real-time Localization
  25. GRB 250702A: BALROG localization (Fermi Trigger 773142852 / GRB 250702413)
  26. GRB 250702A: Fermi GBM Final Real-time Localization
  27. Fermi Gamma-ray Burst Monitor trigger 772838080/250628885 is not a GRB
  28. Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
  29. GRB 250628C: Fermi GBM Final Real-time Localization
  30. Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
  31. GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
  32. Fermi GRB 250626A: Global MASTER-Net observations report
  33. GRB 250625A: Leavitt Observatory afterglow detection
  34. Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
  35. Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
  36. GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
  37. GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
  38. GRB 250626A: Fermi GBM Final Real-time Localization
  39. Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
  40. GRB 250625A: SVOM/C-GFT upper limit in early phase
  41. GRB 250625A: GECAM-B detection
  42. GRB 250625A: ABObservatory afterglow detection
  43. GRB 250625A: OHP/T193 optical detection
  44. GRB 250625A: COLIBRÍ optical observations
  45. GRB 250625A: Fermi-LAT detection
  46. GRB 250625A: JinShan optical observations
  47. GRB250625A: Fermi GBM Observation
  48. GRB 250625A: NOT z-band upper limit
  49. GRB 250625A: SVOM/VT optical confirmation
  50. GRB 250620B: Fermi GBM Observation
  51. GRB 250625A: SAO RAS possible optical afterglow
  52. Fermi GRB 250625A: Global MASTER-Net observations report
  53. GRB 250625A: Swift detection of a burst
  54. GRB 250625A: Fermi GBM Final Real-time Localization
  55. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  56. GRB 250620A: AstroSat CZTI detection
  57. GRB 250620C: AstroSat CZTI detection
  58. Fermi GRB 250624A: Global MASTER-Net observations report
  59. GRB 250624A: Fermi GBM Final Real-time Localization
  60. Fermi GRB 250623A: Global MASTER-Net observations report
  61. GRB 250623A: Fermi GBM Final Real-time Localization
  62. GRB 250521A: VZLUSAT-2 detection
  63. Fermi trigger No 772190032: Global MASTER-Net observations report
  64. Konus-Wind detection of GRB 250620C
  65. IPN triangulation of GRB 250620C (long/bright)
  66. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  67. GRB 250620C: SVOM/GRM observation
  68. GRB 250620A: SVOM/GRM observation of a short burst
  69. GRB250620A: Fermi GBM Observation
  70. Fermi GRB 250621A: Global MASTER-Net observations report
  71. GRB 250619B: Fermi GBM Observation
  72. GRB 250621A: Fermi GBM Final Real-time Localization
  73. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  74. GRB250620C: Fermi GBM Observation
  75. GRB 250506A - SVOM/ECLAIRs Refined analysis
  76. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  77. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  78. GRB 250620C: Fermi GBM Final Real-time Localization
  79. Fermi trigger No 772128434: Global MASTER-Net observations report
  80. GRB 250620B: Fermi GBM Final Real-time Localization
  81. GRB 250620A: Fermi GBM Final Real-time Localization
  82. GRB 250617B: Nickel telescope optical observations
  83. GRB 250619B: Fermi GBM Final Real-time Localization
  84. Fermi trigger No 772058337: Global MASTER-Net observations report
  85. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  86. GRB 250619A: Fermi GBM Final Real-time Localization
  87. GRB 250617B: Assy AZT-20 Optical Observations
  88. Fermi GRB 250617A: Global MASTER-Net observations report
  89. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  90. GRB 250617B: COLIBRÍ optical observations
  91. GRB 250617B: NOT NIR observations of the afterglow
  92. GRB 250617B: SVOM/VT optical observation
  93. Fermi trigger No 771886893: Global MASTER-Net observations report
  94. GRB 250617B: GOTO optical upper limit
  95. GRB 250617B: Fermi GBM Observation
  96. GRB 250617B: Fermi GBM Final Localization
  97. GRB 250617A: Fermi GBM Final Real-time Localization
  98. IPN triangulation of GRB 250612C (short/hard)
  99. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  100. Konus-Wind detection of GRB 250612C (short/hard with extended emission)

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