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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 250620B: Fermi GBM Final Real-time Localization
  2. GRB 250620A: Fermi GBM Final Real-time Localization
  3. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  4. GRB 250617B: Nickel telescope optical observations
  5. GRB 250619B: Fermi GBM Final Real-time Localization
  6. Fermi trigger No 772058337: Global MASTER-Net observations report
  7. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  8. GRB 250615A: Kilonova-Catcher optical upper limits
  9. GRB 250619A: Fermi GBM Final Real-time Localization
  10. GRB 250617B: Assy AZT-20 Optical Observations
  11. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  12. Fermi GRB 250617A: Global MASTER-Net observations report
  13. GRB 250615A/EP250615a: FTW optical and NIR observations
  14. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  15. GRB 250617B: Swift/UVOT Detection
  16. GRB 250617B: Kilonova-Catcher optical afterglow detection
  17. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  18. GRB 250617B: COLIBRÍ optical observations
  19. GRB 250617B: NOT NIR observations of the afterglow
  20. GRB 250617B: Swift-XRT refined Analysis
  21. GRB 250617B: SVOM/VT optical observation
  22. GRB 250617B: NUTTelA-TAO early time optical observations
  23. Fermi trigger No 771886893: Global MASTER-Net observations report
  24. Swift GRB 250617B: Global MASTER-Net observations report
  25. GRB 250617B: GOTO optical upper limit
  26. GRB 250617B: Enhanced Swift-XRT position
  27. GRB 250617B: Fermi GBM Observation
  28. GRB 250615A: Swift-BAT refined analysis
  29. The EP-WXT trigger 01709178990 is likely a flaring star
  30. GRB 250617B: Fermi GBM Final Localization
  31. GRB 250617B: Ondrejov D50 optical afterglow detection
  32. GRB 250617B: SAO RAS optical observations
  33. GRB 250617B: Swift detection of a burst with an optical counterpart
  34. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  35. GRB 250617A: Fermi GBM Final Real-time Localization
  36. IPN triangulation of GRB 250612C (short/hard)
  37. EP#01709178975: Swift-XRT counterpart detection
  38. EP-WXT trigger 01709178975: GOTO optical upper limit
  39. The EP-WXT trigger 01709178975 is likely a flaring star
  40. Konus-Wind detection of GRB 250615A / EP250615a
  41. GRB 250615A / EP250615a: AstroSat CZTI detection
  42. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  43. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  44. GRB 250615A: COLIBRÍ optical upper limit
  45. GRB 250615A: DDOTI Optical Upper Limit
  46. GRB 250615A: Swift/UVOT Upper Limits
  47. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  48. GRB 250615A: Swift-XRT refined Analysis
  49. sb25061207/SVOM: T120 OHP optical upper limit
  50. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  51. Fermi trigger No 771752663: Global MASTER-Net observations report
  52. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  53. The EP-WXT trigger 01709178875 is likely a flaring star
  54. GRB 250615A: Enhanced Swift-XRT position
  55. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  56. GRB 250615A: Prompt enhanced Swift-XRT position
  57. GRB 250615A: Swift detection of a burst
  58. Swift GRB 250615A: Global MASTER-Net observations report
  59. Fermi trigger No 771718064: Global MASTER-Net observations report
  60. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  61. GRID detection of GRB 250612C
  62. sb25061207: Mephisto optical upper limits
  63. IceCube alert 141029_8144692 retraction
  64. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  65. GRB 250614A: Fermi GBM Final Real-time Localization
  66. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  67. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  68. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  69. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  70. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  71. Fermi trigger No 771494087: Global MASTER-Net observations report
  72. sb25061218: Swift-XRT observations
  73. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  74. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  75. sb25061207: EP-FXT follow-up observation and afterglow candidate
  76. GRB 250612B: Fermi GBM Observation
  77. EP250612a: SVOM/VT optical candidate
  78. Fermi trigger No 771424081: Global MASTER-Net observations report
  79. EP250612a: Global MASTER-Net observations report
  80. GRB 250612C: Fermi GBM Observation
  81. sb25061218: SVOM detection of a X-ray transient
  82. sb25061207: Swift-XRT observations
  83. EP250612a/GRB 250612B: JinShan optical upper limit
  84. EP 250612a: AST3-3 Yaoan Optical Observation
  85. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  86. sb25061207: SVOM/VT optical counterpart
  87. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  88. GRB 250610B: Swift-XRT refined Analysis
  89. GRB 250612C: Fermi GBM Final Real-time Localization
  90. EP250610a: Upper limit from Fermi-GBM Observations
  91. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  92. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  93. EP250612a: Einstein Probe detection of an X-ray transient
  94. GRB 250610B: Liverpool Telescope continued monitoring
  95. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  96. sb25061207: SVOM detection of a X-ray transient
  97. EP250610a: continuous follow-up observations with EP-FXT
  98. GRB 250610B - SVOM/ECLAIRs refined analysis
  99. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  100. Swift GRB250612.04: Global MASTER-Net observations report

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