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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 260804A: Glowbug gamma-ray detection
  2. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  3. GRB 260805A: Fermi GBM Final Localization
  4. AT 2026wki: EP/FXT follow-up observations
  5. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  6. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  7. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  8. GRB 260804A: Fermi GBM Final Real-time Localization
  9. GRB 260708A: LCO further optical observations show supernova features
  10. GRB 260803A: Fermi GBM Final Real-time Localization
  11. Fermi GRB 260802B: Global MASTER-Net observations report
  12. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  13. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  14. GRB 260802A: SVOM/VT optical upper limits from VHF data
  15. GRB 260802A: LCO optical upper limits
  16. GRB 260802B: Fermi GBM Final Localization
  17. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  18. The EP-WXT trigger 01709277420 is likely a flaring star
  19. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  20. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  21. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  22. GRB 260731A: AstroSat CZTI detection of a long burst
  23. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  24. GRB 260730B: AstroSat CZTI detection
  25. EP260731a: COLIBRÍ optical upper limit
  26. EP260731a: NOT optical upper limit
  27. GRB 260730B: NuSTAR detection of prompt emission
  28. EP260731a: Einstein Probe detection of an X-ray transient
  29. GRB 260727A: SVOM/ECLAIRs refined analysis
  30. GRB 260726A: SVOM/ECLAIRs refined analysis
  31. GRB260730A: Fermi GBM Final Localization
  32. EP260728a: COLIBRÍ optical upper limit
  33. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  34. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  35. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  36. EP260729a: Einstein Probe detection of an X-ray transient
  37. EP260727a: SAO RAS optical observations
  38. GRB 260727A: AbAO and SAO RAS optical observations
  39. EP260728a: EP-FXT follow-up observation
  40. GRB 260726A: EP-FXT follow-up observations
  41. EP260728a: Einstein Probe detection of a fast X-ray transient
  42. GRB 260727A: SVOM/GRM observation
  43. GRB 260726A: Fermi GBM Observation
  44. EP260727a: 1.5m OSN optical counterpart detection
  45. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  46. EP260727a: OHP/T193 optical observations
  47. Konus-Wind detection of GRB 260727A
  48. GRB 260726A: Liverpool Telescope optical observations
  49. GRB 260727A: Liverpool Telescope optical upper limits
  50. EP260727a: Liverpool Telescope confirmation of optical counterpart
  51. EP260727a: NUTTELA-TAO Early Optical Limits
  52. GRB 260728A: Fermi GBM Final Localization
  53. GRB 260727A: EP/FXT follow-up observations
  54. EP260727a: Einstein Probe detection of an X-ray transient
  55. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  56. GRB 260727A: Glowbug gamma-ray detection
  57. GRB 260726A: J-band upper limit with WINTER
  58. GRB 260727A: J-band upper limit with WINTER
  59. GRB 260726A: SVOM/VT optical candidate
  60. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  61. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  62. EP260723a: SVOM/ECLAIRs Upper Limit
  63. GRB 260727A: GOTO early optical upper limit
  64. GRB 260727A: AstroSat CZTI detection
  65. GRB 260727A: Kilonova-Catcher optical upper limit
  66. GRB 260727A: LCO optical upper limits
  67. GRB 260727B: Fermi GBM Final Real-time Localization
  68. Fermi GRB 260726A: Global MASTER-Net observations report
  69. GRB 260727A: SVOM detection of a bright long burst
  70. GRB 260726A: SVOM detection of a burst
  71. GRB 260726A: Fermi GBM Final Real-time Localization
  72. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  73. EP260723a: further EP-FXT follow-up observation
  74. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  75. EP260725a: EP-WXT detection of an X-ray transient
  76. GRB 260616A: cubesat Avion detection
  77. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  78. GRB 260602B: cubesat Avion detection
  79. GRB 260601A: cubesat Avion detection
  80. EP260723a: EP-FXT follow-up observation
  81. IPN triangulation of GRB 260706B
  82. GRB 260718A: SVOM/ECLAIRs refined analysis
  83. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  84. EP260723a: SVOM/VT optical observation
  85. EP260723a: COLIBRÍ optical observations
  86. EP260723a: NOT optical conterpart confirmation
  87. EP260723a: Liverpool Telescope likely optical counterpart
  88. EP260723a: EP-WXT detection of a fast X-ray transient
  89. GRB 260723A: Fermi GBM Final Localization
  90. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  91. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  92. IceCube Alert 260722A: Global MASTER-Net observations report
  93. Konus-Wind detection of GRB 260721A
  94. GRB 260722A: Fermi GBM Final Real-time Localization
  95. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  96. Fermi GBM trigger 806384210/260722151 is not a GRB
  97. GRB 260721A: NuSTAR detection of prompt emission
  98. Konus-Wind detection of GRB 260714B
  99. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  100. GRB 260705A: Retraction of optical counterpart

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