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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"

27398 results found.

  1. GRB 250520A: Gemini-South optical observations
  2. GRB 250520A: Swift-XRT refined Analysis
  3. GRB 250520A: REM optical/NIR early observations
  4. GRB 250520A：SVOM/VT optical candidate
  5. GRB 250520A: COLIBRÍ optical upper limit
  6. GRB 250520A: DDOTI Optical Upper Limit
  7. GRB 250520A: AstroSat CZTI detection of a short burst
  8. GRB 250520A: Enhanced Swift-XRT position
  9. GRB 250520A: Swift detection of a burst
  10. GRB 250516A: Swift-BAT refined analysis
  11. GRB 250516A: COLIBRÍ optical upper limit
  12. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  13. GRB 250515A: Swift-XRT observations
  14. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  15. GRB 250515A: 1.6m Mephisto optical detection
  16. GRB 250516A: Fermi GBM Observation
  17. GRB 250516A: Swift-XRT refined Analysis
  18. GRB 250516A: Swift/UVOT Detection
  19. GRB 250516B: GECAM-B detection of a bright long burst
  20. GRB 250516A: Enhanced Swift-XRT position
  21. GRB 250516A: Swift detection of a burst
  22. MAXI GRB250515.65: Global MASTER-Net observations report
  23. GRB 250424A: COLIBRÍ detection of the associated supernova
  24. GRB 250502A: TESS observations
  25. GRB 250509A: Swift-BAT refined analysis
  26. Fermi GRB 250512A: Global MASTER-Net observations report
  27. EP250512a/GRB 250512B: REM optical/NIR observations
  28. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  29. GRB 250507B: AstroSat CZTI detection
  30. EP250511a: Gemini optical counterpart observation
  31. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  32. EP250511a: Mephisto optical upper limits
  33. GRB 250512B: SVOM detection of a burst
  34. EP250512a: Einstein Probe detection of an X-ray transient
  35. EP250511a: REM optical/NIR observations
  36. EP250511a: Einstein Probe follow-up obsevation and refined analysis
  37. EP250511a: COLIBRÍ optical counterpart candidate
  38. EP250511a: BOOTES-5 optical upper limit
  39. EP250511a: Einstein Probe detection of an X-ray transient
  40. EP250508a: Gemini NIR upper limits
  41. GRB 250510B: Fermi GBM Observation
  42. GRB 250510A: Swift-XRT observations
  43. GRB 250509A: Fermi GBM Observation
  44. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  45. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  46. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  47. GRB 250509A: Swift-XRT refined Analysis
  48. GRB 250510A: SVOM possible detection of a burst
  49. GRB 250507A: J-band observations with WINTER
  50. GRB 250509A: Enhanced Swift-XRT position
  51. GRB 250509A: Swift detection of a burst
  52. GRB 250506A: NOT optical upper limits
  53. EP250508a: Liverpool Telescope optical upper limits
  54. EP250508a: KAIT optical upper limit
  55. GRB 250507A: KAIT optical upper limit
  56. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  57. GRB 250505B: SVOM/GRM observation of a short burst
  58. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  59. EP250508a: REM optical/NIR observations
  60. GRB 250506A: Swift-XRT afterglow detection
  61. EP250508a: COLIBRÍ Optical Limit
  62. EP250508a: Einstein Probe detection of an X-ray transient
  63. GRB 250507A: Swift-XRT refined Analysis
  64. IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube
  65. GRB 250506A: Swift/UVOT Upper Limits
  66. GRB 250507A: follow-up observation with EP-FXT
  67. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  68. GRB 250507A: REM optical/NIR observations
  69. GRB 250507A: SVOM/VT optical upper limit
  70. GRB 250506A: Swift-XRT observations
  71. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  72. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  73. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  74. GRB 250507A: SVOM detection of a long burst
  75. GRB 250506A: Mephisto optical upper limits
  76. GRB 250504A: EIRSAT-1 GMOD Detection
  77. GRB 250502A: Bassano Bresciano Observatory upper limit
  78. GRB 250506A: Xinglong 2.16m optical upper limit
  79. SVOM/sb25050601: EP-FXT observations
  80. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  81. GRB 250506A: REM optical/NIR upper limits
  82. GRB 250506A: Fermi GBM Observation
  83. GRB 250506A: Swift XRT observations and possible counterpart detection
  84. GRB 250506A: TRT optical observations
  85. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  86. GRB 250506A: SVOM detection of a burst
  87. GRB 250504A: Swift-BAT refined analysis
  88. GRB 250430A: Swift-BAT refined analysis
  89. GRB 250504A: Swift-XRT refined Analysis
  90. GRB 250504A: VLT/X-shooter upper limits
  91. GRB 250504A: REM optical/NIR observations
  92. GRB 250502A: REM optical/NIR observations
  93. GRB 250504A: MeerLICHT optical afterglow detection
  94. GRB 250504A: Fermi GBM Observation
  95. GRB 250504A: Enhanced Swift-XRT position
  96. Fermi GRB 250504A: Global MASTER-Net observations report
  97. GRB 250504A: Swift detection of a burst
  98. GRB 250502A: Swift/UVOT Follow up
  99. GRB 250502A: Mondy and Tien-Shan Optical Observations
  100. GRB 250502A: KAIT optical observations

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