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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"

4873 results found.

  1. GRB 250814A: Swift-XRT refined Analysis
  2. GRB 240814A: Fermi GBM Observation
  3. GRB 250814A: DDOTI Optical Upper Limit
  4. IceCube Alert 250813.14: Global MASTER-Net observations report
  5. LIGO/Virgo/KAGRA S250813k: Identification of a GW compact binary merger candidate
  6. Corrected Swift-XRT Refined Analysis of GRB 250809A
  7. GRB 250809A: Swift-XRT refined Analysis
  8. GRB 250807B: SVOM/VT optical observation
  9. Fermi GRB 250808A: Global MASTER-Net observations report
  10. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  11. GRB 250807B: Swift-XRT refined Analysis
  12. EP 250807.979: GOTO optical upper limit
  13. IceCube Alert 250804.84: Global MASTER-Net observations report
  14. GRB 250806A: Swift-XRT counterpart detection
  15. EP250806a: COLIBRÍ optical upper limit
  16. GRB 250805A: SVOM/VT optical counterpart
  17. GRB 250805A: Swift-XRT refined Analysis
  18. GRB 250805A: Enhanced Swift-XRT position
  19. GRB 250805A: Swift-XRT observations
  20. GRB 250805A: Swift detection of a burst
  21. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  22. EP250711a: CrAO and Assy optical observations
  23. EP250730a: Global MASTER-Net observations report
  24. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  25. GRB 250725A: PRIME near-infrared observations
  26. GRB250727A: SVOM/VT optical upper limit
  27. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  28. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  29. GRB 250725A: Swift-XRT refined Analysis
  30. GRB 250725A: Fermi GBM Observation
  31. GRB 250725A: Fermi-LAT detection
  32. GRB 250725A: Fermi GBM Final Real-time Localization
  33. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  34. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  35. GRB 250721A: MAXI/GSC detection
  36. Fermi trigger No 774730635: Global MASTER-Net observations report
  37. GRB 250713A: SVOM/C-GFT upper limit
  38. Fermi GRB 250711A: Global MASTER-Net observations report
  39. GRB 250709A: Fermi GBM Final Localization
  40. IceCube-250706A: EP-FXT follow-up observations
  41. GRB 250706A: Swift-XRT refined Analysis
  42. GRB250706B: Swift-XRT counterpart detection
  43. EP250704a / GRB 250704B: Pan-STARRS iz-band imaging and photometry
  44. EP250704a / GRB250704B: Swift-XRT counterpart detection
  45. GRB 250704A: Swift-XRT afterglow detection
  46. GRB 250702F: GROWTH-India Telescope optical observations
  47. Fermi GRB 250703A: Global MASTER-Net observations report
  48. GRB 250702F: NOT observations of the optical afterglow
  49. GRB 250702F: MASTER optical afterglow observation
  50. Fermi GRB 250702F: Global MASTER-Net observations report
  51. Swift GRB 250702F: Global MASTER-Net observations report
  52. LIGO/Virgo/KAGRA S250701bp: Identification of a GW compact binary merger candidate
  53. GRB 250628A: Swift-XRT refined Analysis
  54. Fermi GRB 250626A: Global MASTER-Net observations report
  55. GRB 250625A: Swift-XRT refined Analysis
  56. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  57. Fermi GRB 250624A: Global MASTER-Net observations report
  58. GRB 250624A: Fermi GBM Final Real-time Localization
  59. Fermi GRB 250623A: Global MASTER-Net observations report
  60. Fermi GRB 250621A: Global MASTER-Net observations report
  61. GRB 250617B: Swift-XRT refined Analysis
  62. GRB 250617B: SVOM/VT optical observation
  63. GRB 250617B: Swift detection of a burst with an optical counterpart
  64. GRB 250615A: Swift-XRT refined Analysis
  65. The EP-WXT trigger 01709178875 is likely a flaring star
  66. Fermi trigger No 771424081: Global MASTER-Net observations report
  67. EP250612a: Global MASTER-Net observations report
  68. EP250610a: Upper limit from Fermi-GBM Observations
  69. GRB 250610B: LT detection of the optical counterpart
  70. EP250610a: Global MASTER-Net observations report
  71. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  72. Fermi trigger No 771072240: Global MASTER-Net observations report
  73. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  74. GRB 250609A: Fermi GBM Final Real-time Localization
  75. GRB 250605A: Swift-XRT refined Analysis
  76. Fermi trigger No 770867684: Global MASTER-Net observations report
  77. The EP-WXT trigger 01709177837 is likely a flaring star
  78. GRB 250601A: VLT/FORS2 Optical Observation
  79. GRB 250601A: Fermi GBM Observation
  80. GRB 250603A: Swift-XRT refined Analysis
  81. Fermi GRB 250601A: Global MASTER-Net observations report
  82. Fermi trigger No 770470765: Global MASTER-Net observations report
  83. GRB 250531A: Fermi GBM Final Real-time Localization
  84. GRB 250530C: Swift-XRT refined Analysis
  85. EP J1350.0-8622: EP-FXT follow-up observation
  86. GRB 250529B: Fermi GBM Final Real-time Localization
  87. GRB 250520A: Gemini-South optical afterglow detection
  88. Fermi trigger No 770058372: Global MASTER-Net observations report
  89. Fermi trigger No 770047117: Global MASTER-Net observations report
  90. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  91. EP250526a: Global MASTER-Net observations report
  92. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  93. Fermi GRB 250523A: Global MASTER-Net observations report
  94. Fermi trigger No 769611916: Global MASTER-Net observations report
  95. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  96. Fermi GRB 250522B: Global MASTER-Net observations report
  97. GRB 250522A: Fermi GBM Final Real-time Localization
  98. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  99. GRB 250520A: Swift-XRT refined Analysis
  100. Fermi GRB 250516A: Global MASTER-Net observations report

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