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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"

5049 results found.

  1. GRB 250725A: PRIME near-infrared observations
  2. GRB250727A: SVOM/VT optical upper limit
  3. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  4. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  5. GRB 250725A: Swift-XRT refined Analysis
  6. GRB 250725A: Fermi GBM Observation
  7. GRB 250725A: Fermi-LAT detection
  8. GRB 250725A: Fermi GBM Final Real-time Localization
  9. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  10. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  11. GRB 250721A: MAXI/GSC detection
  12. Fermi trigger No 774730635: Global MASTER-Net observations report
  13. GRB 250713A: SVOM/C-GFT upper limit
  14. Fermi GRB 250711A: Global MASTER-Net observations report
  15. GRB 250709A: Fermi GBM Final Localization
  16. IceCube-250706A: EP-FXT follow-up observations
  17. GRB 250706A: Swift-XRT refined Analysis
  18. GRB250706B: Swift-XRT counterpart detection
  19. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  20. EP250704a / GRB250704B: Swift-XRT counterpart detection
  21. GRB 250704A: Swift-XRT afterglow detection
  22. GRB 250702F: GROWTH-India Telescope optical observations
  23. Fermi GRB 250703A: Global MASTER-Net observations report
  24. GRB 250702F: NOT observations of the optical afterglow
  25. GRB 250702F: MASTER optical afterglow observation
  26. Fermi GRB 250702F: Global MASTER-Net observations report
  27. Swift GRB 250702F: Global MASTER-Net observations report
  28. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  29. GRB 250628A: Swift-XRT refined Analysis
  30. Fermi GRB 250626A: Global MASTER-Net observations report
  31. GRB 250625A: Swift-XRT refined Analysis
  32. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  33. Fermi GRB 250624A: Global MASTER-Net observations report
  34. GRB 250624A: Fermi GBM Final Real-time Localization
  35. Fermi GRB 250623A: Global MASTER-Net observations report
  36. Fermi GRB 250621A: Global MASTER-Net observations report
  37. GRB 250617B: Swift-XRT refined Analysis
  38. GRB 250617B: SVOM/VT optical observation
  39. GRB 250617B: Swift detection of a burst with an optical counterpart
  40. GRB 250615A: Swift-XRT refined Analysis
  41. The EP-WXT trigger 01709178875 is likely a flaring star
  42. Fermi trigger No 771424081: Global MASTER-Net observations report
  43. EP250612a: Global MASTER-Net observations report
  44. EP250610a: Upper limit from Fermi-GBM Observations
  45. GRB 250610B: LT detection of the optical counterpart
  46. EP250610a: Global MASTER-Net observations report
  47. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  48. Fermi trigger No 771072240: Global MASTER-Net observations report
  49. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  50. GRB 250609A: Fermi GBM Final Real-time Localization
  51. GRB 250605A: Swift-XRT refined Analysis
  52. Fermi trigger No 770867684: Global MASTER-Net observations report
  53. The EP-WXT trigger 01709177837 is likely a flaring star
  54. GRB 250601A: VLT/FORS2 Optical Observation
  55. GRB 250601A: Fermi GBM Observation
  56. GRB 250603A: Swift-XRT refined Analysis
  57. Fermi GRB 250601A: Global MASTER-Net observations report
  58. Fermi trigger No 770470765: Global MASTER-Net observations report
  59. GRB 250531A: Fermi GBM Final Real-time Localization
  60. GRB 250530C: Swift-XRT refined Analysis
  61. EP J1350.0-8622: EP-FXT follow-up observation
  62. GRB 250529B: Fermi GBM Final Real-time Localization
  63. GRB 250520A: Gemini-South optical afterglow detection
  64. Fermi trigger No 770058372: Global MASTER-Net observations report
  65. Fermi trigger No 770047117: Global MASTER-Net observations report
  66. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  67. EP250526a: Global MASTER-Net observations report
  68. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  69. Fermi GRB 250523A: Global MASTER-Net observations report
  70. Fermi trigger No 769611916: Global MASTER-Net observations report
  71. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  72. Fermi GRB 250522B: Global MASTER-Net observations report
  73. GRB 250522A: Fermi GBM Final Real-time Localization
  74. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  75. GRB 250520A: Swift-XRT refined Analysis
  76. Fermi GRB 250516A: Global MASTER-Net observations report
  77. GRB 250516A: Swift-XRT refined Analysis
  78. Fermi GRB 250512A: Global MASTER-Net observations report
  79. EP250512a: Global MASTER-Net observations report
  80. Fermi GRB 250510C: Global MASTER-Net observations report
  81. GRB 250510C: Fermi GBM Final Real-time Localization
  82. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  83. GRB 250509A: Swift-XRT refined Analysis
  84. EP250508a: Liverpool Telescope optical upper limits
  85. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  86. EP250508a: Global MASTER-Net observations report
  87. GRB 250504A: Swift-XRT refined Analysis
  88. Fermi GRB 250502B: Global MASTER-Net observations report
  89. GRB 250430A: SVOM/VT optical observations
  90. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  91. Fermi trigger No 767623859: Global MASTER-Net observations report
  92. EP250428b: SAO RAS optical upper limit
  93. GRB 250424A: LCO optical observation
  94. EP250427a: TRT optical counterpart detection
  95. GRB 250424A: WINTER J-band detection
  96. GRB 250424A: EIRSAT-1 GMOD Detection
  97. GRB 250424A: SVOM/VT optical observation
  98. GRB 250424A: Swift-XRT refined Analysis
  99. GRB 250424A: AstroSat CZTI detection of a bright long burst
  100. GRB 250424A: BlackGEM optical afterglow detection

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