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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. The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580
  2. GRB 241018A: Maidanak optical observations
  3. GRB 250620C: AstroSat CZTI detection
  4. Fermi GRB 250624A: Global MASTER-Net observations report
  5. GRB 250624A: Fermi GBM Final Real-time Localization
  6. sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
  7. Fermi GRB 250623A: Global MASTER-Net observations report
  8. GRB 250623A: Fermi GBM Final Real-time Localization
  9. GRB 250521A: VZLUSAT-2 detection
  10. GRB 250617B: Swift-BAT refined analysis
  11. Fermi trigger No 772190032: Global MASTER-Net observations report
  12. Konus-Wind detection of GRB 250620C
  13. IPN triangulation of GRB 250620С (long/bright)
  14. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  15. GRB 250620C: SVOM/GRM observation
  16. GRB 250620A: SVOM/GRM observation of a short burst
  17. GRB250620A: Fermi GBM Observation
  18. GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  19. Fermi GRB 250621A: Global MASTER-Net observations report
  20. GRB 250619B: Fermi GBM Observation
  21. GRB 250621A: Fermi GBM Final Real-time Localization
  22. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  23. GRB250620C: Fermi GBM Observation
  24. GRB 250506A - SVOM/ECLAIRs Refined analysis
  25. The EP-WXT trigger 01709179071 is likely a flaring star
  26. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  27. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  28. GRB 250620C: Fermi GBM Final Real-time Localization
  29. Fermi trigger No 772128434: Global MASTER-Net observations report
  30. GRB 250620B: Fermi GBM Final Real-time Localization
  31. GRB 250620A: Fermi GBM Final Real-time Localization
  32. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  33. GRB 250617B: Nickel telescope optical observations
  34. GRB 250619B: Fermi GBM Final Real-time Localization
  35. Fermi trigger No 772058337: Global MASTER-Net observations report
  36. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  37. GRB 250615A: Kilonova-Catcher optical upper limits
  38. GRB 250619A: Fermi GBM Final Real-time Localization
  39. GRB 250617B: Assy AZT-20 Optical Observations
  40. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  41. Fermi GRB 250617A: Global MASTER-Net observations report
  42. GRB 250615A/EP250615a: FTW optical and NIR observations
  43. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  44. GRB 250617B: Swift/UVOT Detection
  45. GRB 250617B: Kilonova-Catcher optical afterglow detection
  46. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  47. GRB 250617B: COLIBRÍ optical observations
  48. GRB 250617B: NOT NIR observations of the afterglow
  49. GRB 250617B: Swift-XRT refined Analysis
  50. GRB 250617B: SVOM/VT optical observation
  51. GRB 250617B: NUTTelA-TAO early time optical observations
  52. Fermi trigger No 771886893: Global MASTER-Net observations report
  53. Swift GRB 250617B: Global MASTER-Net observations report
  54. GRB 250617B: GOTO optical upper limit
  55. GRB 250617B: Enhanced Swift-XRT position
  56. GRB 250617B: Fermi GBM Observation
  57. GRB 250615A: Swift-BAT refined analysis
  58. The EP-WXT trigger 01709178990 is likely a flaring star
  59. GRB 250617B: Fermi GBM Final Localization
  60. GRB 250617B: Ondrejov D50 optical afterglow detection
  61. GRB 250617B: SAO RAS optical observations
  62. GRB 250617B: Swift detection of a burst with an optical counterpart
  63. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  64. GRB 250617A: Fermi GBM Final Real-time Localization
  65. IPN triangulation of GRB 250612C (short/hard)
  66. EP#01709178975: Swift-XRT counterpart detection
  67. EP-WXT trigger 01709178975: GOTO optical upper limit
  68. The EP-WXT trigger 01709178975 is likely a flaring star
  69. Konus-Wind detection of GRB 250615A / EP250615a
  70. GRB 250615A / EP250615a: AstroSat CZTI detection
  71. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  72. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  73. GRB 250615A: COLIBRÍ optical upper limit
  74. GRB 250615A: DDOTI Optical Upper Limit
  75. GRB 250615A: Swift/UVOT Upper Limits
  76. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  77. GRB 250615A: Swift-XRT refined Analysis
  78. sb25061207/SVOM: T120 OHP optical upper limit
  79. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  80. Fermi trigger No 771752663: Global MASTER-Net observations report
  81. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  82. The EP-WXT trigger 01709178875 is likely a flaring star
  83. GRB 250615A: Enhanced Swift-XRT position
  84. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  85. GRB 250615A: Prompt enhanced Swift-XRT position
  86. GRB 250615A: Swift detection of a burst
  87. Swift GRB 250615A: Global MASTER-Net observations report
  88. Fermi trigger No 771718064: Global MASTER-Net observations report
  89. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  90. GRID detection of GRB 250612C
  91. sb25061207: Mephisto optical upper limits
  92. IceCube alert 141029_8144692 retraction
  93. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  94. GRB 250614A: Fermi GBM Final Real-time Localization
  95. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  96. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  97. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  98. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  99. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  100. Fermi trigger No 771494087: Global MASTER-Net observations report

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