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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"

3728 results found.

  1. IceCube Alert 260825A: Global MASTER-Net observations report
  2. GRB 260822A: GOTO optical counterpart detection
  3. GRB260822B: Fermi GBM Final Localization
  4. GRB 260818B: VLA radio observations
  5. EP260806a: SAO RAS multicolor optical observations
  6. EP260812a: SVOM/C-GFT optical upper limit
  7. GRB 260808B: SVOM/VT optical afterglow confirmation
  8. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  9. GRB 260808B: SVOM/VT optical candidate from VHF data
  10. EP260806a: Einstein Probe detection of an X-ray transient
  11. SN 2026stf / GRB 260708A: ATLAS forced photometry
  12. Fermi GRB 260805A: Global MASTER-Net observations report
  13. GRB 260803A: Fermi GBM Final Real-time Localization
  14. Fermi GRB 260802B: Global MASTER-Net observations report
  15. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  16. GRB260730A: Fermi GBM Final Localization
  17. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  18. GRB 260727A: AbAO and SAO RAS optical observations
  19. EP260728a: EP-FXT follow-up observation
  20. EP260727a: 1.5m OSN optical counterpart detection
  21. GRB 260726A: Liverpool Telescope optical observations
  22. GRB 260727A: Liverpool Telescope optical upper limits
  23. EP260727a: Liverpool Telescope confirmation of optical counterpart
  24. GRB 260728A: Fermi GBM Final Localization
  25. GRB 260726A: SVOM/VT optical candidate
  26. EP260723a: SVOM/VT optical observation
  27. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  28. Fermi GRB 260718A: Global MASTER-Net observations report
  29. GRB260708B: MAXI/GSC detection
  30. Fermi GBM Sub-Threshold Detection of GRB 260705A
  31. GRB 260705A: SVOM detection of a burst
  32. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  33. Fermi trigger No 804552016: Global MASTER-Net observations report
  34. Fermi GRB 260628A: Global MASTER-Net observations report
  35. GRB 260628A: Fermi GBM Final Real-time Localization
  36. Konus-Wind detection of GRB 260623B / EP260623a
  37. IPN triangulation of GRB 260605A
  38. GRB 260604A: 239Alferov CubeSat detection
  39. GRB 260506B: cubesat Avion detection
  40. EP260616a/GRB260616B: COLIBRÍ optical upper limit
  41. GRB 260614A: AstroSat CZTI detection
  42. The EP-WXT trigger 01709269893 is likely a flaring star
  43. The EP-WXT trigger 01709269488 is likely a flaring star
  44. GRB 260610B / AT2026owq: SVOM/VT optical observations
  45. GRB 260515A: SOAR optical observations
  46. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  47. GRB 260604C: GOTO detections of the optical afterglow
  48. Fermi GRB 260604C: Global MASTER-Net observations report
  49. Fermi GRB 260604C: Global MASTER-Net observations report
  50. EP260602d: Optical Upper limits with kinder observations
  51. Fermi GRB 260602B: Global MASTER-Net observations report
  52. Fermi GRB 260602B: Global MASTER-Net observations report
  53. Fermi GRB 260601A: Global MASTER-Net observations report
  54. Fermi trigger No 801900520: Global MASTER-Net observations report
  55. GRB 260527A / EP260527a: VLA radio detection
  56. Fermi GRB 260529A: Global MASTER-Net observations report
  57. EP260527a: COLIBRÍ optical detection
  58. Fermi trigger No 801580882: Global MASTER-Net observations report
  59. Fermi GRB 260525A: Global MASTER-Net observations report
  60. GRB 260523B: AstroSat CZTI detection
  61. Fermi GRB 260522A: Global MASTER-Net observations report
  62. Fermi GRB 260516C: Global MASTER-Net observations report
  63. GRB 260516D: SVOM possible detection of a burst
  64. GRID detection of GRB 260507A
  65. SVOM GRB 260515A: Global MASTER-Net observations report
  66. Fermi GRB 260514A: Global MASTER-Net observations report
  67. Fermi GRB 260512A: Global MASTER-Net observations report
  68. GRB 260506A: Glowbug gamma-ray detection of a short burst
  69. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  70. Fermi GRB 260510A: Global MASTER-Net observations report
  71. GRB 260507A: Fermi GBM Final Real-time Localization
  72. GRB 260506A: Fermi GBM Final Real-time Localization
  73. Fermi GRB 260504A: Global MASTER-Net observations report
  74. Fermi GRB 260429A: Global MASTER-Net observations report
  75. GRB 260428A: AstroSat CZTI detection
  76. Fermi GRB 260428A: Global MASTER-Net observations report
  77. GRB 260424B: COLIBRÍ optical upper limit
  78. GRB 260428A: Fermi GBM Final Real-time Localization
  79. GRB 260401A: cubesat Avion detection
  80. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  81. EP260416a: Mondy optical observations
  82. GRB 260419A: AstroSat CZTI detection
  83. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  84. Fermi GRB 260421C: Global MASTER-Net observations report
  85. Fermi GRB 260421B: Global MASTER-Net observations report
  86. GRB 260421B: BOOTES-7 early optical afterglow detection
  87. EP260417a: Global MASTER-Net observations report
  88. Fermi GRB 260417A: Global MASTER-Net observations report
  89. EP260416a: Global MASTER-Net observations report
  90. GRB 260415B: NuSTAR detection of long prompt emission
  91. EP260321a: SVOM/VT optical observations and color changes around peak
  92. GRB 260411A: Fermi GBM Final Real-time Localization
  93. EP260405a: GMOS-N optical upper limits
  94. EP260405a: SVOM/VT optical upper limits
  95. Fermi trigger No 797039833: Global MASTER-Net observations report
  96. EP260403a: LCO optical counterpart detection
  97. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  98. EP260329b: GOTO detection of optical counterpart
  99. Fermi trigger No 796485221: Global MASTER-Net observations report
  100. GRB 260327A: Insight-HXMT/HE detection

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