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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"

2406 results found.

  1. GRB 260424B: AstroSat CZTI detection
  2. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  3. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  4. GRB 260424B: Glowbug gamma-ray detection of a short burst
  5. GRB 260424B: COLIBRÍ optical upper limit
  6. Konus-Wind detection of GRB 260424B
  7. IPN triangulation of GRB 260424B (short)
  8. GRB 260424B: SVOM/GRM detection of a short burst
  9. GRB 260401A: cubesat Avion detection
  10. GRB 260421B: Kilonova-Catcher optical afterglow detection
  11. GRB 260421B: Insight-HXMT/HE detection
  12. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  13. GRB 260421B: SVOM/ECLAIRs refined analysis
  14. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  15. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  16. GRB 260421B: SVOM/GRM observation
  17. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  18. GRB 260421B: EP-FXT follow-up observation
  19. GRB 260421B: LCO optical counterpart detection
  20. GRB 260421B: Fermi GBM Observation
  21. GRB 260412A: SVOM/ECLAIRs refined analysis
  22. GRB 260421B: SVOM/VT optical observations
  23. GRB 260421B: VLT/X-shooter spectroscopic redshift z = 2.115
  24. GRB 260421B: BOOTES-7 early optical afterglow detection
  25. GRB 260421B: LCO optical afterglow confirmation
  26. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  27. GRB 260421B: TRT optical counterpart detection
  28. GRB 260421B: SVOM detection of a long burst
  29. GRB 260412A: LCOGT Optical Upper Limits
  30. GRB 260417A: SVOM/GRM observation
  31. Konus-Wind detection of GRB 260411B
  32. IPN triangulation of GRB 260411B
  33. EP260416a: WFST optical observations and rebrightening
  34. EP260416a: SVOM/VT optical observation
  35. GOTO26djh/AT2026jpw: SVOM/VT optical observation
  36. GRB 260411B: Glowbug gamma-ray detection
  37. GRB 260412A: Insight-HXMT/HE detection
  38. GRB 260410B: Insight-HXMT/HE detection
  39. GRB 260411B: GECAM-B observation of a long burst
  40. EP260321a: SVOM/VT optical observations and color changes around peak
  41. GRB 260412A: GECAM-B observation of a long burst
  42. GRB 260412A: Fermi GBM Observation
  43. GRB 260411B: Fermi-LAT detection
  44. GRB 260412A: SVOM detection of a long burst
  45. GRB 260410B: Fermi GBM Observation
  46. GRB 260411A: SVOM/GRM observation
  47. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  48. GRB 260411B: SVOM/GRM observation of a long burst
  49. GRB 260410B: SVOM/GRM detection of a short faint burst
  50. EP260409a: SVOM/VT optical upper limits
  51. GRB 260402A: SVOM/ECLAIRs refined analysis
  52. EP260402a / GRB 260402A: Mephisto optical upper limits
  53. GRID detection of GRB 260401A
  54. EP260405a: SVOM/VT optical upper limits
  55. GRB 260330B: SVOM/VT further optical observation
  56. GRB 260330B: SVOM/ECLAIRs refined analysis
  57. GRB 260330B: SVOM/VT optical candidate
  58. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  59. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  60. GRB 260402A: WINTER J-band upper limit
  61. GRB260402A: GROWTH-India Telescope optical upper limit
  62. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  63. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  64. GRB 260401A: SVOM/GRM observation
  65. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  66. GRB 260402A: Kilonova-Catcher optical upper limit
  67. GRB 260402A: MASTER optical observations
  68. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  69. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  70. GRB 260402A: SVOM detection of a burst
  71. GRB 260401A: NuSTAR detection of prompt emission
  72. GRB 260330B: SVOM/VT optical upper limits
  73. Konus-Wind detection of GRB 260316B
  74. GRB 260321A: SVOM/ECLAIRs refined analysis
  75. Fermi GBM Sub-Threshold Detection of GRB 260330B
  76. GRB 260330B: LCO optical upper limits
  77. GRB 260330B: SVOM detection of a burst
  78. EP260327a: SVOM/VT optical upper limits
  79. GRB 260307B: ATCA Radio Upper Limits
  80. IPN triangulation of GRB 260320A
  81. IPN triangulation of GRB 260316B
  82. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  83. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  84. GRB 260320A: Glowbug gamma-ray detection
  85. GRB 260321A: EP-FXT follow-up observation
  86. GRB 260321A: SVOM/VT optical upper limits
  87. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  88. EP260321a: SVOM/VT optical upper limit
  89. Fermi GBM Sub-Threshold Detection of GRB 260321A
  90. GRB 260321A: SVOM detection of a burst
  91. GRB 260318A: Glowbug gamma-ray detection
  92. GRB 260320A: NuSTAR detection of prompt emission
  93. GRB 260318A: SVOM/GRM observation
  94. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  95. GRB 260316B: GECAM-B observation
  96. GRB 260316B: SVOM/GRM observation
  97. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  98. GRB 260316B: AstroSat CZTI detection
  99. EP260314a: COLIBRÍ optical upper limit
  100. EP260314a: refined analysis of the EP-WXT and EP-FXT observations

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