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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"

21455 results found.

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

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