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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"

5514 results found.

  1. EP260601a/GRB 260601B: EP-FXT follow-up observation
  2. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  3. Fermi trigger No 802141998: Global MASTER-Net observations report
  4. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  5. EP260602a: COLIBRÍ optical observations
  6. GRB260601B/EP260601a: NOT near-infrared observations
  7. SVOM GRB260603.23: Global MASTER-Net observations report
  8. Fermi GRB 260602B: Global MASTER-Net observations report
  9. Fermi GRB 260602B: Global MASTER-Net observations report
  10. EP260602a: SVOM/VT optical candidate
  11. Fermi trigger No 801900520: Global MASTER-Net observations report
  12. GRB 260531A: MAXI/GSC detection
  13. IPN triangulation of GRB 260527A / EP260527a
  14. GRB 260529A: GOTO tentative optical afterglow candidate
  15. Fermi GRB 260529A: Global MASTER-Net observations report
  16. Fermi trigger No 801580882: Global MASTER-Net observations report
  17. Fermi GRB 260526A: Global MASTER-Net observations report
  18. GRB 260522A: GOTO optical upper limit
  19. GRB 260307A: TERI Gamma-ray detection
  20. GRB 260519B: Fermi GBM Final Localization
  21. GRB 260516D: GOTO optical counterpart detection
  22. GRB 260516D: GTC/OSIRIS+ spectroscopic redshift z = 1.801
  23. Fermi GRB 260516C: Global MASTER-Net observations report
  24. EP260514a: SVOM/VT optical candidate
  25. Fermi GRB 260516B: Global MASTER-Net observations report
  26. EP260514a: COLIBRÍ optical upper limits
  27. SVOM GRB 260515A: Global MASTER-Net observations report
  28. SVOM GRB 260515A: MASTER OT J151044.43+243321.7 optical counterpart detection
  29. Fermi GRB 260512A: Global MASTER-Net observations report
  30. GRB 260511B: further SAO RAS optical observations
  31. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  32. GRB 260511B: LCO optical counterpart detection
  33. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) further optical observations
  34. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  35. GRB 260511B: SVOM detection of a burst
  36. GRB 260510C: EP-FXT follow-up observation
  37. Fermi GRB 260511A: Global MASTER-Net observations report
  38. GRB 260510C: MAXI/GSC detection
  39. SVOM GRB 260509A: MASTER-OAFA optical observation
  40. Fermi GRB 260510A: Global MASTER-Net observations report
  41. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  42. GRB 260509A: SVOM detection of a burst
  43. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  44. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  45. IPN triangulation of GRB 260428A
  46. SVOM GRB 260504B: MASTER-OAFA optical observations
  47. Fermi GRB 260504A: Global MASTER-Net observations report
  48. EP260430a: LCO optical upper limits
  49. EP260430a: Global MASTER-Net observations report
  50. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  51. Fermi trigger No 798737427: Global MASTER-Net observations report
  52. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  53. Fermi GRB 260421C: Global MASTER-Net observations report
  54. Fermi GRB 260421B: Global MASTER-Net observations report
  55. Fermi GRB 260421A: Global MASTER-Net observations report
  56. EP260416a: VLT/FORS2 spectroscopic redshift confirmation
  57. EP260417a: Global MASTER-Net observations report
  58. Fermi GRB 260417A: Global MASTER-Net observations report
  59. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  60. EP260416a: COLIBRÍ optical counterpart candidate
  61. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  62. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  63. Fermi trigger No 797912738: Global MASTER-Net observations report
  64. GRB 260410A: Glowbug gamma-ray detection of a short burst
  65. GRB 260410A: Insight-HXMT/HE detection
  66. Konus-Wind detection of GRB 260410A (short/hard)
  67. EP260321a: SVOM/VT optical observations and color changes around peak
  68. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  69. GRB 260410A: COLIBRÍ optical upper limit
  70. GRB 260410A: Fermi GBM Observation
  71. GRB 260410A: Fermi-LAT detection
  72. GRB 260410A: Fermi GBM Final Real-time Localization
  73. EP260409a: COLIBRÍ optical upper limits
  74. EP260403a: Mephisto optical upper limits
  75. EP260321a: Upper limits from VLA radio observations
  76. EP260405a: Global MASTER-Net observations report
  77. Fermi trigger No 797039833: Global MASTER-Net observations report
  78. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  79. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  80. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  81. GRB 260330B: SVOM/ECLAIRs refined analysis
  82. EP260403a: LCO optical observations of the counterpart
  83. EP260403a: LCO optical counterpart detection
  84. GRB 260330B: SVOM/VT optical candidate
  85. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  86. GRB 260403A: AstroSat CZTI detection
  87. EP260324A / AT 2026hir: COLIBRÍ optical observations
  88. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  89. EP260329b: Mondy and Assy-Turgen optical upper limits
  90. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  91. EP260321a :Xinglong optical observations
  92. EP260327a: Xinglong optical upper limit
  93. EP260329b: GOTO detection of optical counterpart
  94. GRB 260330B: SVOM/VT optical upper limits
  95. GRB 260321A: SVOM/ECLAIRs refined analysis
  96. EP260329b: J-band upper limits with WINTER
  97. EP260329a: J-band upper limit with WINTER
  98. GRB 260330A: Glowbug gamma-ray detection
  99. GRB 260310A: VLA Multi-frequency Radio Observations
  100. Fermi GBM Sub-Threshold Detection of GRB 260330B

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