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

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