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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"

5152 results found.

  1. GRB 260531B: Fermi GBM Final Real-time Localization
  2. IPN triangulation of GRB 260527A / EP260527a
  3. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  4. Fermi trigger No 801580882: Global MASTER-Net observations report
  5. Fermi GRB 260526A: Global MASTER-Net observations report
  6. Fermi GRB 260522A: Global MASTER-Net observations report
  7. GRB 260511A: iTelescope T-75 optical detection
  8. GRB 260520A: Fermi GBM Final Localization
  9. Konus-Wind detection of GRB 260518A
  10. GRB 260421B: radio detection with the VLA
  11. Fermi GRB 260516C: Global MASTER-Net observations report
  12. Fermi GRB 260516B: Global MASTER-Net observations report
  13. SVOM GRB 260515A: Global MASTER-Net observations report
  14. EP260514a: Global MASTER-Net observations report
  15. GRB 260513A: Fermi GBM Final Real-time Localization
  16. Konus-Wind detection of GRB 260511B
  17. GRB 260511B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  18. GRB 260511B: SAO RAS optical observations
  19. GRB 260511B: SVOM/COLIBRÍ (FM-GFT) optical observations
  20. GRB 260510C: AstroSat CZTI detection
  21. Fermi GRB 260511A: Global MASTER-Net observations report
  22. GRB 260511A: LCO optical afterglow detection
  23. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  24. GRB 260510C: MAXI/GSC detection
  25. SVOM GRB 260509A: MASTER-OAFA optical observation
  26. Fermi GRB 260510A: Global MASTER-Net observations report
  27. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  28. EP260502a is likely a flaring star
  29. GRB 260421B: radio observation with the VLA
  30. IPN triangulation of GRB 260429A
  31. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  32. GRB 260429A: SVOM/GRM observation of a short burst
  33. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  34. GRB 260424B: AstroSat CZTI detection
  35. GRB 260429A: Fermi GBM Detection
  36. GRB 260429A: Fermi GBM Final Real-time Localization
  37. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  38. GRB 260424B: Glowbug gamma-ray detection of a short burst
  39. Konus-Wind detection of GRB 260424B
  40. GRB 260424C: Fermi GBM Final Localization
  41. IPN triangulation of GRB 260424B (short)
  42. GRB 260401A: cubesat Avion detection
  43. GRB 260424A: AstroSat CZTI detection of a long burst
  44. GRB 260421B: 3.6m DOT optical observation
  45. EP-WXT trigger 01709260362: FRAM-ORM optical observations confirm flaring star G 151-9
  46. Fermi GRB 260421C: Global MASTER-Net observations report
  47. Fermi GRB 260421B: Global MASTER-Net observations report
  48. EP260416a: Optical follow-up observations with Kinder
  49. Fermi GRB 260417B: Global MASTER-Net observations report
  50. EP260417a: Global MASTER-Net observations report
  51. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  52. Fermi GRB 260417A: Global MASTER-Net observations report
  53. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  54. GRB 260411B: COLIBRÍ optical observations
  55. EP260405a: Global MASTER-Net observations report
  56. The EP-WXT trigger 01709259621 is likely a flaring star
  57. Fermi trigger No 797039833: Global MASTER-Net observations report
  58. GRB 260401A: SVOM/GRM observation
  59. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  60. EP260329b: Mondy and Assy-Turgen optical upper limits
  61. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  62. Fermi trigger No 796485221: Global MASTER-Net observations report
  63. EP260327a: COLIBRÍ optical upper limits
  64. EP260327a: Global MASTER-Net observations report
  65. IPN triangulation of GRB 260316B
  66. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  67. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  68. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  69. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  70. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  71. Fermi GRB 260323A: Global MASTER-Net observations report
  72. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  73. IceCube-260315A: COLIBRÍ optical observations
  74. Fermi trigger No 795185313: Global MASTER-Net observations report
  75. IceCube Alert 260315A: Global MASTER-Net observations report
  76. Fermi GRB 260314A: Global MASTER-Net observations report
  77. Fermi GRB 260313A: Global MASTER-Net observations report
  78. GRB 260310A: potential optical counterpart
  79. Fermi GRB 260311B: Global MASTER-Net observations report
  80. GRB 260311B: Fermi GBM Final Real-time Localization
  81. EP260306a: Mondy optical upper limit
  82. Fermi GRB 260310B: Global MASTER-Net observations report
  83. GRB 260307B: SVOM/ECLAIRs refined analysis
  84. GRB 260208A: radio detection with the VLA
  85. GRB 260207A: TESS Detection and Possible VLA Counterpart
  86. GRB 260303B: AstroSat CZTI detection
  87. GRB 260304A: AstroSat CZTI detection of a long burst
  88. GRB 260303B: NuSTAR detection of prompt emission
  89. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  90. GRB 260303B: Fermi GBM Final Real-time Localization
  91. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  92. EP260227A: 3.6m DOT optical afterglow detection
  93. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  94. LAT GRB260226.44: Global MASTER-Net observations report
  95. EP260214a: VLA 6 GHz detection
  96. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  97. EP260126a: VLA 6 GHz detection
  98. EP260223a: Liverpool Telescope upper limits
  99. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  100. EP260223a: Xinglong optical upper limit

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