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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"

5157 results found.

  1. GRB 250805A: Swift-XRT refined Analysis
  2. GRB 250805A: Enhanced Swift-XRT position
  3. GRB 250805A: Swift-XRT observations
  4. GRB 250805A: Swift detection of a burst
  5. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  6. EP250711a: CrAO and Assy optical observations
  7. EP250730a: Global MASTER-Net observations report
  8. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  9. GRB 250725A: PRIME near-infrared observations
  10. GRB250727A: SVOM/VT optical upper limit
  11. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  12. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  13. GRB 250725A: Swift-XRT refined Analysis
  14. GRB 250725A: Fermi GBM Observation
  15. GRB 250725A: Fermi-LAT detection
  16. GRB 250725A: Fermi GBM Final Real-time Localization
  17. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  18. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  19. GRB 250721A: MAXI/GSC detection
  20. Fermi trigger No 774730635: Global MASTER-Net observations report
  21. GRB 250713A: SVOM/C-GFT upper limit
  22. Fermi GRB 250711A: Global MASTER-Net observations report
  23. GRB 250709A: Fermi GBM Final Localization
  24. IceCube-250706A: EP-FXT follow-up observations
  25. GRB 250706A: Swift-XRT refined Analysis
  26. GRB250706B: Swift-XRT counterpart detection
  27. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  28. EP250704a / GRB250704B: Swift-XRT counterpart detection
  29. GRB 250704A: Swift-XRT afterglow detection
  30. GRB 250702F: GROWTH-India Telescope optical observations
  31. Fermi GRB 250703A: Global MASTER-Net observations report
  32. GRB 250702F: NOT observations of the optical afterglow
  33. GRB 250702F: MASTER optical afterglow observation
  34. Fermi GRB 250702F: Global MASTER-Net observations report
  35. Swift GRB 250702F: Global MASTER-Net observations report
  36. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  37. GRB 250628A: Swift-XRT refined Analysis
  38. Fermi GRB 250626A: Global MASTER-Net observations report
  39. GRB 250625A: Swift-XRT refined Analysis
  40. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  41. Fermi GRB 250624A: Global MASTER-Net observations report
  42. GRB 250624A: Fermi GBM Final Real-time Localization
  43. Fermi GRB 250623A: Global MASTER-Net observations report
  44. Fermi GRB 250621A: Global MASTER-Net observations report
  45. GRB 250617B: Swift-XRT refined Analysis
  46. GRB 250617B: SVOM/VT optical observation
  47. GRB 250617B: Swift detection of a burst with an optical counterpart
  48. GRB 250615A: Swift-XRT refined Analysis
  49. The EP-WXT trigger 01709178875 is likely a flaring star
  50. Fermi trigger No 771424081: Global MASTER-Net observations report
  51. EP250612a: Global MASTER-Net observations report
  52. EP250610a: Upper limit from Fermi-GBM Observations
  53. GRB 250610B: LT detection of the optical counterpart
  54. EP250610a: Global MASTER-Net observations report
  55. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  56. Fermi trigger No 771072240: Global MASTER-Net observations report
  57. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  58. GRB 250609A: Fermi GBM Final Real-time Localization
  59. GRB 250605A: Swift-XRT refined Analysis
  60. Fermi trigger No 770867684: Global MASTER-Net observations report
  61. The EP-WXT trigger 01709177837 is likely a flaring star
  62. GRB 250601A: VLT/FORS2 Optical Observation
  63. GRB 250601A: Fermi GBM Observation
  64. GRB 250603A: Swift-XRT refined Analysis
  65. Fermi GRB 250601A: Global MASTER-Net observations report
  66. Fermi trigger No 770470765: Global MASTER-Net observations report
  67. GRB 250531A: Fermi GBM Final Real-time Localization
  68. GRB 250530C: Swift-XRT refined Analysis
  69. EP J1350.0-8622: EP-FXT follow-up observation
  70. GRB 250529B: Fermi GBM Final Real-time Localization
  71. GRB 250520A: Gemini-South optical afterglow detection
  72. Fermi trigger No 770058372: Global MASTER-Net observations report
  73. Fermi trigger No 770047117: Global MASTER-Net observations report
  74. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  75. EP250526a: Global MASTER-Net observations report
  76. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  77. Fermi GRB 250523A: Global MASTER-Net observations report
  78. Fermi trigger No 769611916: Global MASTER-Net observations report
  79. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  80. Fermi GRB 250522B: Global MASTER-Net observations report
  81. GRB 250522A: Fermi GBM Final Real-time Localization
  82. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  83. GRB 250520A: Swift-XRT refined Analysis
  84. Fermi GRB 250516A: Global MASTER-Net observations report
  85. GRB 250516A: Swift-XRT refined Analysis
  86. Fermi GRB 250512A: Global MASTER-Net observations report
  87. EP250512a: Global MASTER-Net observations report
  88. Fermi GRB 250510C: Global MASTER-Net observations report
  89. GRB 250510C: Fermi GBM Final Real-time Localization
  90. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  91. GRB 250509A: Swift-XRT refined Analysis
  92. EP250508a: Liverpool Telescope optical upper limits
  93. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  94. EP250508a: Global MASTER-Net observations report
  95. GRB 250504A: Swift-XRT refined Analysis
  96. Fermi GRB 250502B: Global MASTER-Net observations report
  97. GRB 250430A: SVOM/VT optical observations
  98. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  99. Fermi trigger No 767623859: Global MASTER-Net observations report
  100. EP250428b: SAO RAS optical upper limit

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