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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"
  1. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  2. EP260809a: Einstein Probe detection of an X-ray transient
  3. GRB 260808B: SVOM/VT optical afterglow confirmation
  4. GRB 260808C: Fermi GBM Final Real-time Localization
  5. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  6. GRB 260808B: SVOM/VT optical candidate from VHF data
  7. GRB 260808B: SVOM detection of a faint burst
  8. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  9. Fermi GRB 260808A: Global MASTER-Net observations report
  10. GRB 260808A: Fermi GBM Final Real-time Localization
  11. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  12. IceCube Alert 260807A: Global MASTER-Net observations report
  13. IceCube-260805A: One candidate from the Zwicky Transient Facility
  14. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  15. GRB 260807A: SVOM possible detection of a faint burst
  16. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  17. EP260806a: COLIBRÍ optical observations
  18. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  19. EP260806a: SVOM/VT optical observation
  20. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  21. EP260806a: OSIRIS+/GTC redshift z=0.089
  22. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  23. EP260806a: LCO likely optical counterpart
  24. EP260806a: Einstein Probe detection of an X-ray transient
  25. GRB 260715A: cubesat Avion detection
  26. GRB 260709A: cubesat Avion detection
  27. GRB 260708A: cubesat Avion detection
  28. SN 2026stf / GRB 260708A: ATLAS forced photometry
  29. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  30. GRB 260730B: Glowbug gamma-ray detection
  31. GRB 260805C: Glowbug gamma-ray detection
  32. GRB 260805B: Glowbug gamma-ray detection
  33. Fermi GRB 260805A: Global MASTER-Net observations report
  34. GRB 260805B: Fermi GBM Final Localization
  35. GRB 260804A: Glowbug gamma-ray detection
  36. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  37. GRB 260805A: Fermi GBM Final Localization
  38. AT 2026wki: EP/FXT follow-up observations
  39. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  40. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  41. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  42. GRB 260804A: Fermi GBM Final Real-time Localization
  43. GRB 260708A: LCO further optical observations show supernova features
  44. GRB 260803A: Fermi GBM Final Real-time Localization
  45. Fermi GRB 260802B: Global MASTER-Net observations report
  46. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  47. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  48. GRB 260802A: SVOM/VT optical upper limits from VHF data
  49. GRB 260802A: LCO optical upper limits
  50. GRB 260802B: Fermi GBM Final Localization
  51. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  52. The EP-WXT trigger 01709277420 is likely a flaring star
  53. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  54. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  55. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  56. GRB 260731A: AstroSat CZTI detection of a long burst
  57. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  58. GRB 260730B: AstroSat CZTI detection
  59. EP260731a: COLIBRÍ optical upper limit
  60. EP260731a: NOT optical upper limit
  61. GRB 260730B: NuSTAR detection of prompt emission
  62. EP260731a: Einstein Probe detection of an X-ray transient
  63. GRB 260727A: SVOM/ECLAIRs refined analysis
  64. GRB 260726A: SVOM/ECLAIRs refined analysis
  65. GRB260730A: Fermi GBM Final Localization
  66. EP260728a: COLIBRÍ optical upper limit
  67. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  68. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  69. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  70. EP260729a: Einstein Probe detection of an X-ray transient
  71. EP260727a: SAO RAS optical observations
  72. GRB 260727A: AbAO and SAO RAS optical observations
  73. EP260728a: EP-FXT follow-up observation
  74. GRB 260726A: EP-FXT follow-up observations
  75. EP260728a: Einstein Probe detection of a fast X-ray transient
  76. GRB 260727A: SVOM/GRM observation
  77. GRB 260726A: Fermi GBM Observation
  78. EP260727a: 1.5m OSN optical counterpart detection
  79. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  80. EP260727a: OHP/T193 optical observations
  81. Konus-Wind detection of GRB 260727A
  82. GRB 260726A: Liverpool Telescope optical observations
  83. GRB 260727A: Liverpool Telescope optical upper limits
  84. EP260727a: Liverpool Telescope confirmation of optical counterpart
  85. EP260727a: NUTTELA-TAO Early Optical Limits
  86. GRB 260728A: Fermi GBM Final Localization
  87. GRB 260727A: EP/FXT follow-up observations
  88. EP260727a: Einstein Probe detection of an X-ray transient
  89. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  90. GRB 260727A: Glowbug gamma-ray detection
  91. GRB 260726A: J-band upper limit with WINTER
  92. GRB 260727A: J-band upper limit with WINTER
  93. GRB 260726A: SVOM/VT optical candidate
  94. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  95. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  96. EP260723a: SVOM/ECLAIRs Upper Limit
  97. GRB 260727A: GOTO early optical upper limit
  98. GRB 260727A: AstroSat CZTI detection
  99. GRB 260727A: Kilonova-Catcher optical upper limit
  100. GRB 260727A: LCO optical upper limits

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