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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"

5111 results found.

  1. IceCube Alert 260825A: Global MASTER-Net observations report
  2. IceCube-Cascade 260824A: Upper limits from a search for additional neutrino events in IceCube
  3. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  4. GRB 260820A: Insight-HXMT/HE detection
  5. GRB260820A: Fermi GBM Final Real-Time Localization
  6. GRB 260818B: NOT optical upper limits
  7. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  8. GRB 260808B: SVOM/VT optical afterglow confirmation
  9. GRB 260808C: Fermi GBM Final Real-time Localization
  10. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  11. SN 2026stf / GRB 260708A: ATLAS forced photometry
  12. Fermi GRB 260802B: Global MASTER-Net observations report
  13. EP260731a: Einstein Probe detection of an X-ray transient
  14. GRB260730A: Fermi GBM Final Localization
  15. EP260728a: COLIBRÍ optical upper limit
  16. Fermi GRB 260726A: Global MASTER-Net observations report
  17. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  18. GRB 260602B: cubesat Avion detection
  19. EP260723a: EP-FXT follow-up observation
  20. IPN triangulation of GRB 260706B
  21. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  22. EP260723a: Liverpool Telescope likely optical counterpart
  23. Fermi trigger No 806104130: Global MASTER-Net observations report
  24. IceCube Alert 260709A: Global MASTER-Net observations report
  25. GRB 260705B: SVOM/GRM observation
  26. EP260707a: Einstein Probe detection of an X-ray transient
  27. GRB 260706A: SVOM/ECLAIRs refined analysis
  28. GRB 260704A: SVOM detection of a possible GRB
  29. Fermi GRB 260703A: Global MASTER-Net observations report
  30. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  31. Fermi trigger No 804552016: Global MASTER-Net observations report
  32. GRB 260628A: Fermi GBM Final Real-time Localization
  33. EP260626a: Liverpool Telescope upper limits
  34. EP260623a: Liverpool Telescope optical observations
  35. Fermi GBM trigger 804010507/260624677 is not a GRB
  36. GRB 260624A: Fermi GBM Final Real-time Localization
  37. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  38. GRB 260623A: Fermi GBM Final Real-time Localization
  39. The EP-WXT trigger 01709271197 is likely a flaring star
  40. GRB 260604A: 239Alferov CubeSat detection
  41. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  42. GRB 260429A: cubesat Avion detection
  43. GRB260616C: MAXI/GSC detection
  44. EP260610b: MAO/AZT-22 optical observations
  45. GRB 260610A: Fermi GBM Final Real-time Localization
  46. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  47. GRB 260604A: SVOM/GRM detection
  48. GRB 260604C: 6 GHz VLA observations
  49. GRB 260604A: Glowbug gamma-ray detection
  50. Fermi GRB 260604C: Global MASTER-Net observations report
  51. Fermi GRB 260604C: Global MASTER-Net observations report
  52. GRB 260604A: Fermi GBM Final Real-time Localization
  53. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  54. Fermi GRB 260602B: Global MASTER-Net observations report
  55. Fermi GRB 260602B: Global MASTER-Net observations report
  56. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  57. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  58. Fermi GRB 260601A: Global MASTER-Net observations report
  59. Fermi trigger No 801900520: Global MASTER-Net observations report
  60. GRB 260531B: Fermi GBM Final Real-time Localization
  61. IPN triangulation of GRB 260527A / EP260527a
  62. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  63. Fermi trigger No 801580882: Global MASTER-Net observations report
  64. Fermi GRB 260526A: Global MASTER-Net observations report
  65. Fermi GRB 260522A: Global MASTER-Net observations report
  66. GRB 260511A: iTelescope T-75 optical detection
  67. GRB 260520A: Fermi GBM Final Localization
  68. Konus-Wind detection of GRB 260518A
  69. GRB 260421B: radio detection with the VLA
  70. Fermi GRB 260516C: Global MASTER-Net observations report
  71. Fermi GRB 260516B: Global MASTER-Net observations report
  72. SVOM GRB 260515A: Global MASTER-Net observations report
  73. EP260514a: Global MASTER-Net observations report
  74. GRB 260513A: Fermi GBM Final Real-time Localization
  75. Konus-Wind detection of GRB 260511B
  76. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  77. GRB 260511B: SAO RAS optical observations
  78. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  79. GRB 260510C: AstroSat CZTI detection
  80. Fermi GRB 260511A: Global MASTER-Net observations report
  81. GRB 260511A: LCO optical afterglow detection
  82. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  83. GRB 260510C: MAXI/GSC detection
  84. SVOM GRB 260509A: MASTER-OAFA optical observation
  85. Fermi GRB 260510A: Global MASTER-Net observations report
  86. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  87. EP260502a is likely a flaring star
  88. GRB 260421B: radio observation with the VLA
  89. IPN triangulation of GRB 260429A
  90. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  91. GRB 260429A: SVOM/GRM observation of a short burst
  92. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  93. GRB 260424B: AstroSat CZTI detection
  94. GRB 260429A: Fermi GBM Detection
  95. GRB 260429A: Fermi GBM Final Real-time Localization
  96. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  97. GRB 260424B: Glowbug gamma-ray detection of a short burst
  98. Konus-Wind detection of GRB 260424B
  99. GRB 260424C: Fermi GBM Final Localization
  100. IPN triangulation of GRB 260424B (short)

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