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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 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  2. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  3. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  4. GRB 260731A: AstroSat CZTI detection of a long burst
  5. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  6. GRB 260730B: AstroSat CZTI detection
  7. EP260731a: COLIBRÍ optical upper limit
  8. EP260731a: NOT optical upper limit
  9. GRB 260730B: NuSTAR detection of prompt emission
  10. EP260731a: Einstein Probe detection of an X-ray transient
  11. GRB 260727A: SVOM/ECLAIRs refined analysis
  12. GRB 260726A: SVOM/ECLAIRs refined analysis
  13. GRB260730A: Fermi GBM Final Localization
  14. EP260728a: COLIBRÍ optical upper limit
  15. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  16. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  17. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  18. EP260729a: Einstein Probe detection of an X-ray transient
  19. EP260727a: SAO RAS optical observations
  20. GRB 260727A: AbAO and SAO RAS optical observations
  21. EP260728a: EP-FXT follow-up observation
  22. GRB 260726A: EP-FXT follow-up observations
  23. EP260728a: Einstein Probe detection of a fast X-ray transient
  24. GRB 260727A: SVOM/GRM observation
  25. GRB 260726A: Fermi GBM Observation
  26. EP260727a: 1.5m OSN optical counterpart detection
  27. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  28. EP260727a: OHP/T193 optical observations
  29. Konus-Wind detection of GRB 260727A
  30. GRB 260726A: Liverpool Telescope optical observations
  31. GRB 260727A: Liverpool Telescope optical upper limits
  32. EP260727a: Liverpool Telescope confirmation of optical counterpart
  33. EP260727a: NUTTELA-TAO Early Optical Limits
  34. GRB 260728A: Fermi GBM Final Localization
  35. GRB 260727A: EP/FXT follow-up observations
  36. EP260727a: Einstein Probe detection of an X-ray transient
  37. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  38. GRB 260727A: Glowbug gamma-ray detection
  39. GRB 260726A: J-band upper limit with WINTER
  40. GRB 260727A: J-band upper limit with WINTER
  41. GRB 260726A: SVOM/VT optical candidate
  42. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  43. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  44. EP260723a: SVOM/ECLAIRs Upper Limit
  45. GRB 260727A: GOTO early optical upper limit
  46. GRB 260727A: AstroSat CZTI detection
  47. GRB 260727A: Kilonova-Catcher optical upper limit
  48. GRB 260727A: LCO optical upper limits
  49. GRB 260727B: Fermi GBM Final Real-time Localization
  50. Fermi GRB 260726A: Global MASTER-Net observations report
  51. GRB 260727A: SVOM detection of a bright long burst
  52. GRB 260726A: SVOM detection of a burst
  53. GRB 260726A: Fermi GBM Final Real-time Localization
  54. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  55. EP260723a: further EP-FXT follow-up observation
  56. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  57. EP260725a: EP-WXT detection of an X-ray transient
  58. GRB 260616A: cubesat Avion detection
  59. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  60. GRB 260602B: cubesat Avion detection
  61. GRB 260601A: cubesat Avion detection
  62. EP260723a: EP-FXT follow-up observation
  63. IPN triangulation of GRB 260706B
  64. GRB 260718A: SVOM/ECLAIRs refined analysis
  65. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  66. EP260723a: SVOM/VT optical observation
  67. EP260723a: COLIBRÍ optical observations
  68. EP260723a: NOT optical conterpart confirmation
  69. EP260723a: Liverpool Telescope likely optical counterpart
  70. EP260723a: EP-WXT detection of a fast X-ray transient
  71. GRB 260723A: Fermi GBM Final Localization
  72. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  73. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  74. IceCube Alert 260722A: Global MASTER-Net observations report
  75. Konus-Wind detection of GRB 260721A
  76. GRB 260722A: Fermi GBM Final Real-time Localization
  77. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  78. Fermi GBM trigger 806384210/260722151 is not a GRB
  79. GRB 260721A: NuSTAR detection of prompt emission
  80. Konus-Wind detection of GRB 260714B
  81. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  82. GRB 260705A: Retraction of optical counterpart
  83. GRB 260714B: Insight-HXMT/HE detection
  84. GRB 260718A: EP-FXT follow-up observation
  85. Fermi trigger No 806104130: Global MASTER-Net observations report
  86. Fermi GRB 260718A: Global MASTER-Net observations report
  87. GRB 260718A: LCO optical upper limits
  88. GRB 260711A: SVOM/GRM observation
  89. GRB 260710A: SVOM/GRM observation
  90. GRB 260718A: Fermi GBM Observation
  91. GRB 260718A : GRANDMA and KNC upper limits
  92. GRB 260718A: SVOM/VT optical upper limits
  93. GRB 260718A: SVOM/VT optical upper limits from VHF data
  94. GRB 260718A: SVOM detection of a burst
  95. GRB 260714B: SVOM/GRM observation
  96. GRB 260310A / AT2026fgk: Late-time Chandra Detection
  97. GRB 260714B: GECAM-B observation of a burst
  98. GRB 260618B: EP-FXT follow-up observation upper limit
  99. GRB 260714B: COLIBRÍ optical counterpart candidate
  100. IceCube-260708A: Follow-up studies of cosmic-ray origin of high-energy neutrino alert

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