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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"

21467 results found.

  1. GRB 250520A: GRBAlpha detection
  2. GRB 250521B: SVOM/VT optical upper limit
  3. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  4. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  5. EP#01709176612: Swift-XRT counterpart detection of flaring star
  6. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  7. GRB 250521B: Swift ToO observations
  8. Konus-Wind detection of GRB 250520A (short/hard)
  9. GRB 250520A: VLT/FORS2 Optical Observation
  10. GRB 250520A: Swift/UVOT Upper Limits
  11. IPN triangulation of GRB 250516B
  12. GRB 250520A: J-band observations with WINTER
  13. GRB 250520A: Gemini-South optical observations
  14. GRB 250520A: Swift-XRT refined Analysis
  15. GRB 250520A: REM optical/NIR early observations
  16. GRB 250520A:SVOM/VT optical candidate
  17. GRB 250520A: COLIBRÍ optical upper limit
  18. GRB 250520A: DDOTI Optical Upper Limit
  19. GRB 250520A: AstroSat CZTI detection of a short burst
  20. GRB 250520A: SVOM/GRM observation
  21. GRB 250520A: Enhanced Swift-XRT position
  22. GRB 250520A: GOTO optical upper limit
  23. GRB 250520A: Prompt enhanced Swift-XRT position
  24. GRB 250520A: Swift detection of a burst
  25. Swift GRB 250520A: Global MASTER-Net observations report
  26. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  27. GRB 250516A: Swift-BAT refined analysis
  28. GRB 250516A: COLIBRÍ optical upper limit
  29. Konus-Wind detection of GRB 250516A
  30. GRB 250515A: Swift-XRT observations
  31. Swift GRB 250516A: Global MASTER-Net observations report
  32. GRB 250516A: AstroSat CZTI detection
  33. GRB 250516A: Fermi GBM Observation
  34. GRB 250516A: Swift-XRT refined Analysis
  35. GRB 250516A: Swift/UVOT Detection
  36. GRB 250515A: Swift ToO observations
  37. GRB 250516A: Enhanced Swift-XRT position
  38. GRB 250516A: Swift detection of a burst
  39. GRB 250509A: Swift-BAT refined analysis
  40. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  41. GRB 250510B: Fermi GBM Observation
  42. GRB 250510A: Swift-XRT observations
  43. GRB 250509A: Fermi GBM Observation
  44. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  45. GRB 250509A: Swift-XRT refined Analysis
  46. GRB 250507A: J-band observations with WINTER
  47. GRB 250509A: Enhanced Swift-XRT position
  48. GRB 250509A: Prompt enhanced Swift-XRT position
  49. Swift GRB 250509A: Global MASTER-Net observations report
  50. GRB 250509A: Swift detection of a burst
  51. GRB 250506A: NOT optical upper limits
  52. GRB 250506A: GECAM detection
  53. GRB 250506A: Swift-XRT afterglow detection
  54. GRB 250506A: SVOM/VT optical upper limit
  55. GRB 250507A: Swift-XRT refined Analysis
  56. GRB 250506A: Swift/UVOT Upper Limits
  57. GRB 250430A / EP250430a: AstroSat CZTI detection
  58. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  59. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  60. GRB 250506A: Swift-XRT observations
  61. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  62. GRB 250504A: EIRSAT-1 GMOD Detection
  63. GRB 250506A: Swift ToO observations
  64. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  65. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  66. GRB 250506A: Swift XRT observations and possible counterpart detection
  67. GRB 250506A: TRT optical observations
  68. GRB 250504A: Swift-BAT refined analysis
  69. GRB 250430A: Swift-BAT refined analysis
  70. GRB 250504A: Swift-XRT refined Analysis
  71. GRB 250504A: VLT/X-shooter upper limits
  72. GRB 250504A: SVOM/VT upper limit
  73. GRB 250504A: REM optical/NIR observations
  74. GRB 250504A: MeerLICHT optical afterglow detection
  75. GRB 250504A: Fermi GBM Observation
  76. GRB 250504A: Enhanced Swift-XRT position
  77. GRB 250504A: Swift detection of a burst
  78. Swift GRB250504.98: Global MASTER-Net observations report
  79. GRB 250502A: Swift/UVOT Follow up
  80. GRB 250502A: Mondy and Tien-Shan Optical Observations
  81. GRB 250502A: Swift-XRT afterglow detection
  82. GRB 250502A: Swift ToO observations
  83. GRB 250430A: Swift-XRT refined Analysis
  84. GRB 250430A: Swift/UVOT Detection
  85. GRB 250430A: Enhanced Swift-XRT position
  86. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  87. GRB 250430A: NUTTelA-TAO Early Measurements
  88. GRB 250430A: DDOTI Optical Observations
  89. GRB 250430A: Leavitt Observatory optical upper limit
  90. GRB 250430A: Bassano Bresciano Observatory upper limit
  91. GRB 250430A : MITSuME Akeno optical upper limits
  92. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  93. EP250430a/GRB 250430A: Einstein Probe WXT detection of the X-ray prompt emission
  94. GRB 250424A: CALET Gamma-Ray Burst Monitor detection
  95. GRB 250430A: AKO Optical Afterglow Detection
  96. GRB 250430A: Swift detection of a burst with optical counterpart
  97. Swift GRB250430.73: Global MASTER-Net observations report
  98. GRB 250427A: Swift/UVOT Detection
  99. EP250427a: EP-FXT follow-up observations
  100. GRB 250427A: Swift-XRT refined Analysis

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