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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"

895 results found.

  1. MAXI GRB260827.40: Global MASTER-Net observations report
  2. GRB260708B: MAXI/GSC detection
  3. GRB 260616C: GECAM-B observation of a burst
  4. GRB260616C: MAXI/GSC detection
  5. GRB 260531A: MAXI/GSC detection
  6. GRB 260510C: Glowbug gamma-ray detection
  7. GRB 260510C: CALET Gamma-Ray Burst Monitor detection
  8. GRB 260510C: Fermi GBM Observation
  9. GRB 260510C: AstroSat CZTI detection
  10. GRB 260510C: EP-FXT follow-up observation
  11. GRB 260510C: SVOM/VT optical upper limits
  12. GRB 260510C: MAXI/GSC detection
  13. GRID detection of GRB 260401A
  14. GRB 260401A: SVOM/GRM observation
  15. GRB 260401A: GECAM-B observation
  16. GRB 260401A: Fermi GBM Observation
  17. GRB 260401A: NuSTAR detection of prompt emission
  18. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  19. GRB 260401A: MAXI/GSC detection
  20. Konus-Wind detection of GRB 260226A
  21. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  22. GRB 260206A: Swift-XRT observations
  23. GRB 260206A: Tiled Swift observations
  24. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  25. GRID detection of GRB 260131A/B
  26. GRB 260131A/B: EP/FXT X-ray afterglow detection
  27. GRB 260131A: NOT spectroscopic redshift z = 1.434
  28. Konus-Wind detection of GRB 260131A/B
  29. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  30. GRB 260131A/B: Fermi GBM Observation
  31. GRB 260131B: MAXI/GSC detection
  32. GRB 260120B: Swift/UVOT Detection
  33. GRB 251220A: MAXI/GSC detection
  34. GRB 251201A: GECAM-B observation of a burst
  35. GRB 251201A: SVOM/GRM observation of a burst
  36. GRB 251201A: MAXI/GSC detection
  37. SVOM GRB 251129A : MASTER optical counterpart detection
  38. Fermi GRB 251125B: Global MASTER-Net observations report
  39. GRB 251112B: MAXI/GSC detection
  40. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  41. GRB 251028A: Insight-HXMT/HE detection
  42. Konus-Wind detection of GRB 251028A
  43. GRB 251028A: GECAM-B detection
  44. GRB 251028A: SVOM/GRM observation
  45. GRB 251028A: Fermi GBM Observation
  46. GRB 251028A: Glowbug gamma-ray detection
  47. GRB 251028A: MAXI/GSC detection
  48. GRB 251024A: Swift-BAT refined analysis
  49. GRB 251023B: Glowbug gamma-ray detection
  50. GRB 251023B / EP#01709247298: COLIBRÍ optical counterpart candidate
  51. GRB 251023B: CALET Gamma-Ray Burst Monitor detection
  52. EP#01709247298: Swift-XRT counterpart detection
  53. GRB 251023B / MAXI J0451+122: MAXI/GSC detection
  54. GRB 250911A: MAXI/GSC detection
  55. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  56. GRB 250830B: Swift-XRT afterglow detection
  57. LIGO/Virgo/KAGRA S250831cc: Coverage and upper limits from MAXI/GSC observations
  58. GRB 250830B: Swift-XRT observations
  59. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  60. LIGO/Virgo/KAGRA S250830bp: Coverage and upper limits from MAXI/GSC observations
  61. GRB 250830B: Swift ToO observations
  62. GRB 250830B: MAXI/GSC detection
  63. GRB 250830A / MAXI J0853+337: MAXI/GSC detection
  64. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  65. GRB 250721A: Fermi GBM Observation
  66. GRB 250721A: Swift-XRT observations
  67. GRB 250721A: Tiled Swift observations
  68. GRB 250721A: MAXI/GSC detection
  69. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  70. LIGO/Virgo/KAGRA S250704ab: Coverage and upper limits from MAXI/GSC observations
  71. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  72. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  73. GRBs 250702B,C,D,E / EP250702a: Konus-Wind detection of a hard X-ray transient activity
  74. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  75. GRB 250625A: Swift/UVOT Upper Limits
  76. GRB 250620A: AstroSat CZTI detection
  77. GRB 250527B: Swift-XRT observations
  78. GRB 250527B: Tiled Swift observations
  79. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  80. MAXI GRB250515.65: Global MASTER-Net observations report
  81. GRB 250507B: AstroSat CZTI detection
  82. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  83. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  84. GRB 250331A: MAXI/GSC detection
  85. EP250311a/GRB 250311A: Correction to EP-WXT detection time
  86. EP250311a/GRB 250311A: EP-FXT follow-up observation
  87. GRB 250311A: Swift-XRT observations
  88. GRB 250311A/EP250311a: TRT optical upper limit
  89. GRB 250311A: Tiled Swift observations
  90. EP250311a/GRB 250311A: EP-WXT detection
  91. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  92. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  93. GRB 250207B: Swift-XRT observations
  94. GRB 250207B: Tiled Swift observations
  95. GRB 250207B: MAXI/GSC detection
  96. LIGO/Virgo/KAGRA S250206dm: Coverage and upper limits from MAXI/GSC observations
  97. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  98. Fermi GRB 250128A: Global MASTER-Net observations report
  99. GRB 250126A: CALET Gamma-Ray Burst Monitor detection
  100. GRB 250126A: MAXI/GSC detection

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