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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. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  2. GRB 260730B: Glowbug gamma-ray detection
  3. GRB 260805C: Glowbug gamma-ray detection
  4. GRB 260805B: Glowbug gamma-ray detection
  5. Fermi GRB 260805A: Global MASTER-Net observations report
  6. GRB 260805B: Fermi GBM Final Localization
  7. GRB 260804A: Glowbug gamma-ray detection
  8. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  9. GRB 260805A: Fermi GBM Final Localization
  10. AT 2026wki: EP/FXT follow-up observations
  11. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  12. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  13. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  14. GRB 260804A: Fermi GBM Final Real-time Localization
  15. GRB 260708A: LCO further optical observations show supernova features
  16. GRB 260803A: Fermi GBM Final Real-time Localization
  17. Fermi GRB 260802B: Global MASTER-Net observations report
  18. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  19. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  20. GRB 260802A: SVOM/VT optical upper limits from VHF data
  21. GRB 260802A: LCO optical upper limits
  22. GRB 260802B: Fermi GBM Final Localization
  23. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  24. The EP-WXT trigger 01709277420 is likely a flaring star
  25. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  26. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  27. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  28. GRB 260731A: AstroSat CZTI detection of a long burst
  29. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  30. GRB 260730B: AstroSat CZTI detection
  31. EP260731a: COLIBRÍ optical upper limit
  32. EP260731a: NOT optical upper limit
  33. GRB 260730B: NuSTAR detection of prompt emission
  34. EP260731a: Einstein Probe detection of an X-ray transient
  35. GRB 260727A: SVOM/ECLAIRs refined analysis
  36. GRB 260726A: SVOM/ECLAIRs refined analysis
  37. GRB260730A: Fermi GBM Final Localization
  38. EP260728a: COLIBRÍ optical upper limit
  39. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  40. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  41. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  42. EP260729a: Einstein Probe detection of an X-ray transient
  43. EP260727a: SAO RAS optical observations
  44. GRB 260727A: AbAO and SAO RAS optical observations
  45. EP260728a: EP-FXT follow-up observation
  46. GRB 260726A: EP-FXT follow-up observations
  47. EP260728a: Einstein Probe detection of a fast X-ray transient
  48. GRB 260727A: SVOM/GRM observation
  49. GRB 260726A: Fermi GBM Observation
  50. EP260727a: 1.5m OSN optical counterpart detection
  51. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  52. EP260727a: OHP/T193 optical observations
  53. Konus-Wind detection of GRB 260727A
  54. GRB 260726A: Liverpool Telescope optical observations
  55. GRB 260727A: Liverpool Telescope optical upper limits
  56. EP260727a: Liverpool Telescope confirmation of optical counterpart
  57. EP260727a: NUTTELA-TAO Early Optical Limits
  58. GRB 260728A: Fermi GBM Final Localization
  59. GRB 260727A: EP/FXT follow-up observations
  60. EP260727a: Einstein Probe detection of an X-ray transient
  61. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  62. GRB 260727A: Glowbug gamma-ray detection
  63. GRB 260726A: J-band upper limit with WINTER
  64. GRB 260727A: J-band upper limit with WINTER
  65. GRB 260726A: SVOM/VT optical candidate
  66. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  67. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  68. EP260723a: SVOM/ECLAIRs Upper Limit
  69. GRB 260727A: GOTO early optical upper limit
  70. GRB 260727A: AstroSat CZTI detection
  71. GRB 260727A: Kilonova-Catcher optical upper limit
  72. GRB 260727A: LCO optical upper limits
  73. GRB 260727B: Fermi GBM Final Real-time Localization
  74. Fermi GRB 260726A: Global MASTER-Net observations report
  75. GRB 260727A: SVOM detection of a bright long burst
  76. GRB 260726A: SVOM detection of a burst
  77. GRB 260726A: Fermi GBM Final Real-time Localization
  78. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  79. EP260723a: further EP-FXT follow-up observation
  80. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  81. EP260725a: EP-WXT detection of an X-ray transient
  82. GRB 260616A: cubesat Avion detection
  83. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  84. GRB 260602B: cubesat Avion detection
  85. GRB 260601A: cubesat Avion detection
  86. EP260723a: EP-FXT follow-up observation
  87. IPN triangulation of GRB 260706B
  88. GRB 260718A: SVOM/ECLAIRs refined analysis
  89. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  90. EP260723a: SVOM/VT optical observation
  91. EP260723a: COLIBRÍ optical observations
  92. EP260723a: NOT optical conterpart confirmation
  93. EP260723a: Liverpool Telescope likely optical counterpart
  94. EP260723a: EP-WXT detection of a fast X-ray transient
  95. GRB 260723A: Fermi GBM Final Localization
  96. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  97. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  98. IceCube Alert 260722A: Global MASTER-Net observations report
  99. Konus-Wind detection of GRB 260721A
  100. GRB 260722A: Fermi GBM Final Real-time Localization

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