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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"

11757 results found.

  1. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  2. GRB250620A: Fermi GBM Observation
  3. Fermi GRB 250621A: Global MASTER-Net observations report
  4. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  5. GRB250620C: Fermi GBM Observation
  6. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  7. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  8. GRB 250620C: Fermi GBM Final Real-time Localization
  9. Fermi trigger No 772128434: Global MASTER-Net observations report
  10. GRB 250620B: Fermi GBM Final Real-time Localization
  11. GRB 250620A: Fermi GBM Final Real-time Localization
  12. Fermi trigger No 772058337: Global MASTER-Net observations report
  13. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  14. GRB 250617B: Assy AZT-20 Optical Observations
  15. GRB 250615A/EP250615a: FTW optical and NIR observations
  16. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  17. GRB 250617B: COLIBRÍ optical observations
  18. GRB 250617B: Swift-XRT refined Analysis
  19. GRB 250617B: Swift detection of a burst with an optical counterpart
  20. EP#01709178975: Swift-XRT counterpart detection
  21. Konus-Wind detection of GRB 250615A / EP250615a
  22. GRB 250615A / EP250615a: AstroSat CZTI detection
  23. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  24. Fermi trigger No 771752663: Global MASTER-Net observations report
  25. sb25061218: Swift-XRT observations
  26. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  27. EP250612a: SVOM/VT optical candidate
  28. sb25061207: Swift-XRT observations
  29. GRB 250610B: Swift-XRT refined Analysis
  30. EP250612a: Einstein Probe detection of an X-ray transient
  31. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  32. sb25061207: SVOM detection of a X-ray transient
  33. Swift GRB250612.04: Global MASTER-Net observations report
  34. GRB 250610B: Swift-XRT counterpart detection
  35. GRB 250610B: SVOM/VT optical counterpart
  36. GRB 250610B: OHP/T120 optical counterpart candidate
  37. GRB 250610B: GOTO optical upper limit
  38. EP250610a: Global MASTER-Net observations report
  39. GRB 250610B: SVOM detection of a long burst
  40. EP250610a: Swift-XRT counterpart detection
  41. EP250610a: Einstein Probe detection of an X-ray transient
  42. Fermi trigger No 771072240: Global MASTER-Net observations report
  43. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  44. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  45. GRB 250605A: Swift-XRT refined Analysis
  46. Fermi GRB 250606A: Global MASTER-Net observations report
  47. Fermi trigger No 770867684: Global MASTER-Net observations report
  48. GRB 250605A: LT optical observations
  49. Konus-Wind detection of GRB 250601A
  50. Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
  51. Swift GRB250603.05: Global MASTER-Net observations report
  52. GRB 250602A: Fermi-LAT detection
  53. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  54. Fermi GRB 250531A: Global MASTER-Net observations report
  55. EP#01709177494: Swift-XRT counterpart detection of known source
  56. GRB 250530C: Swift-XRT refined Analysis
  57. GRB 250530C: Swift detection of a burst
  58. GRB 250530A: Swift-XRT counterpart detection
  59. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  60. EP J1350.0-8622: EP-FXT follow-up observation
  61. Fermi trigger No 770058372: Global MASTER-Net observations report
  62. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  63. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  64. GRB 250314A: CIDER NB1008 upper limit
  65. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  66. Fermi GRB 250523A: Global MASTER-Net observations report
  67. Fermi trigger No 769611916: Global MASTER-Net observations report
  68. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  69. GRB 250520A: GRBAlpha detection
  70. EP#01709176612: Swift-XRT counterpart detection of flaring star
  71. Fermi trigger No 769533898: Global MASTER-Net observations report
  72. GRB 250521D: LAST tentative optical counterpart candidate
  73. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  74. Konus-Wind detection of GRB 250520A (short/hard)
  75. Konus-Wind detection of GRB 250516B
  76. GRB 250520A: Gemini-South optical observations
  77. GRB 250520A: REM optical/NIR early observations
  78. GRB 250520B: Fermi GBM Final Real-time Localization
  79. GRB 250520A: COLIBRÍ optical upper limit
  80. GRB 250520A: DDOTI Optical Upper Limit
  81. GRB 250520A: AstroSat CZTI detection of a short burst
  82. GRB 250520A: GOTO optical upper limit
  83. Swift GRB 250520A: Global MASTER-Net observations report
  84. GRB 250516A: Swift-BAT refined analysis
  85. GRB 250516A: COLIBRÍ optical upper limit
  86. Konus-Wind detection of GRB 250516A
  87. Fermi GRB 250516A: Global MASTER-Net observations report
  88. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  89. GRB 250516A: Swift-XRT refined Analysis
  90. GRB 250516A: Swift detection of a burst
  91. GRB 250512B / EP250512a: SVOM/GRM analysis
  92. GRB 250515A: GOTO candidate optical counterpart
  93. GRB 250515A: Fermi GBM Final Localization
  94. Konus-Wind detection of GRB 250512B / EP250512a
  95. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  96. Konus-Wind detection of GRB 250506A
  97. GRB 250507B: AstroSat CZTI detection
  98. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  99. EP250512a: Global MASTER-Net observations report
  100. GRB 250512B/EP250512a:SVOM/VT bright optical counterpart

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