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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"

5132 results found.

  1. GRB 260915A: SVOM/ECLAIRs refined analysis
  2. GRB 260917B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  3. GRB 260917A: BALROG localization (Fermi Trigger 811304653 / GRB 260917100)
  4. GRB 260917A: Fermi GBM Final Real-time Localization
  5. Fermi trigger No 811304653: Global MASTER-Net observations report
  6. GRB 260909A: NOEMA detection
  7. EP Alert 260914.53: Global MASTER-Net observations report
  8. EP Alert 260909.53: Global MASTER-Net observations report
  9. GRB 260909A: Mondy optical observations and afterglow candidate
  10. The EP-WXT trigger 01709306297 is likely the known LMXB 4U 1745-203
  11. Fermi GRB 260907B: Global MASTER-Net observations report
  12. EP Alert 260903.62: Global MASTER-Net observations report
  13. SVOM GRB260903A: Global MASTER-Net observations report
  14. Konus-Wind detection of GRB 260829A
  15. EP260901a: Global MASTER-Net observations report
  16. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  17. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  18. MAXI GRB260827.40: Global MASTER-Net observations report
  19. The EP-WXT trigger 01709291839 is likely the known LMXB 4U 1745-203
  20. EP260822a: Global MASTER-Net observations report
  21. GRB 260809A: SVOM/ECLAIRs refined analysis
  22. IceCube Alert 260825A: Global MASTER-Net observations report
  23. IceCube-Cascade 260824A: Upper limits from a search for additional neutrino events in IceCube
  24. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  25. GRB 260820A: Insight-HXMT/HE detection
  26. GRB260820A: Fermi GBM Final Real-Time Localization
  27. GRB 260818B: NOT optical upper limits
  28. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  29. GRB 260808B: SVOM/VT optical afterglow confirmation
  30. GRB 260808C: Fermi GBM Final Real-time Localization
  31. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  32. SN 2026stf / GRB 260708A: ATLAS forced photometry
  33. Fermi GRB 260802B: Global MASTER-Net observations report
  34. EP260731a: Einstein Probe detection of an X-ray transient
  35. GRB260730A: Fermi GBM Final Localization
  36. EP260728a: COLIBRÍ optical upper limit
  37. Fermi GRB 260726A: Global MASTER-Net observations report
  38. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  39. GRB 260602B: cubesat Avion detection
  40. EP260723a: EP-FXT follow-up observation
  41. IPN triangulation of GRB 260706B
  42. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  43. EP260723a: Liverpool Telescope likely optical counterpart
  44. Fermi trigger No 806104130: Global MASTER-Net observations report
  45. IceCube Alert 260709A: Global MASTER-Net observations report
  46. GRB 260705B: SVOM/GRM observation
  47. EP260707a: Einstein Probe detection of an X-ray transient
  48. GRB 260706A: SVOM/ECLAIRs refined analysis
  49. GRB 260704A: SVOM detection of a possible GRB
  50. Fermi GRB 260703A: Global MASTER-Net observations report
  51. GRB 260610B / AT2026owq: SAO RAS, CrAO and INASAN further optical observations and light curve
  52. Fermi trigger No 804552016: Global MASTER-Net observations report
  53. GRB 260628A: Fermi GBM Final Real-time Localization
  54. EP260626a: Liverpool Telescope upper limits
  55. EP260623a: Liverpool Telescope optical observations
  56. Fermi GBM trigger 804010507/260624677 is not a GRB
  57. GRB 260624A: Fermi GBM Final Real-time Localization
  58. EP260623a: FRAM-ORM detection of the optical afterglow rise, peak and decay
  59. GRB 260623A: Fermi GBM Final Real-time Localization
  60. The EP-WXT trigger 01709271197 is likely a flaring star
  61. GRB 260604A: 239Alferov CubeSat detection
  62. GRB 260610B/AT2026owq: 1.3m DFOT optical rebrightening detection
  63. GRB 260429A: cubesat Avion detection
  64. GRB260616C: MAXI/GSC detection
  65. EP260610b: MAO/AZT-22 optical observations
  66. GRB 260610A: Fermi GBM Final Real-time Localization
  67. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  68. GRB 260604A: SVOM/GRM detection
  69. GRB 260604C: 6 GHz VLA observations
  70. GRB 260604A: Glowbug gamma-ray detection
  71. Fermi GRB 260604C: Global MASTER-Net observations report
  72. Fermi GRB 260604C: Global MASTER-Net observations report
  73. GRB 260604A: Fermi GBM Final Real-time Localization
  74. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  75. Fermi GRB 260602B: Global MASTER-Net observations report
  76. Fermi GRB 260602B: Global MASTER-Net observations report
  77. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  78. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  79. Fermi GRB 260601A: Global MASTER-Net observations report
  80. Fermi trigger No 801900520: Global MASTER-Net observations report
  81. GRB 260531B: Fermi GBM Final Real-time Localization
  82. IPN triangulation of GRB 260527A / EP260527a
  83. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  84. Fermi trigger No 801580882: Global MASTER-Net observations report
  85. Fermi GRB 260526A: Global MASTER-Net observations report
  86. Fermi GRB 260522A: Global MASTER-Net observations report
  87. GRB 260511A: iTelescope T-75 optical detection
  88. GRB 260520A: Fermi GBM Final Localization
  89. Konus-Wind detection of GRB 260518A
  90. GRB 260421B: radio detection with the VLA
  91. Fermi GRB 260516C: Global MASTER-Net observations report
  92. Fermi GRB 260516B: Global MASTER-Net observations report
  93. SVOM GRB 260515A: Global MASTER-Net observations report
  94. EP260514a: Global MASTER-Net observations report
  95. GRB 260513A: Fermi GBM Final Real-time Localization
  96. Konus-Wind detection of GRB 260511B
  97. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  98. GRB 260511B: SAO RAS optical observations
  99. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  100. GRB 260510C: AstroSat CZTI detection

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