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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/VT optical upper limit
  2. GRB 260802A: SVOM/VT optical upper limits from VHF data
  3. GRB 260802A: LCO optical upper limits
  4. GRB 260802B: Fermi GBM Final Localization
  5. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  6. The EP-WXT trigger 01709277420 is likely a flaring star
  7. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  8. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  9. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  10. GRB 260731A: AstroSat CZTI detection of a long burst
  11. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  12. GRB 260730B: AstroSat CZTI detection
  13. EP260731a: COLIBRÍ optical upper limit
  14. EP260731a: NOT optical upper limit
  15. GRB 260730B: NuSTAR detection of prompt emission
  16. EP260731a: Einstein Probe detection of an X-ray transient
  17. GRB 260727A: SVOM/ECLAIRs refined analysis
  18. GRB 260726A: SVOM/ECLAIRs refined analysis
  19. GRB260730A: Fermi GBM Final Localization
  20. EP260728a: COLIBRÍ optical upper limit
  21. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  22. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  23. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  24. EP260729a: Einstein Probe detection of an X-ray transient
  25. EP260727a: SAO RAS optical observations
  26. GRB 260727A: AbAO and SAO RAS optical observations
  27. EP260728a: EP-FXT follow-up observation
  28. GRB 260726A: EP-FXT follow-up observations
  29. EP260728a: Einstein Probe detection of a fast X-ray transient
  30. GRB 260727A: SVOM/GRM observation
  31. GRB 260726A: Fermi GBM Observation
  32. EP260727a: 1.5m OSN optical counterpart detection
  33. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  34. EP260727a: OHP/T193 optical observations
  35. Konus-Wind detection of GRB 260727A
  36. GRB 260726A: Liverpool Telescope optical observations
  37. GRB 260727A: Liverpool Telescope optical upper limits
  38. EP260727a: Liverpool Telescope confirmation of optical counterpart
  39. EP260727a: NUTTELA-TAO Early Optical Limits
  40. GRB 260728A: Fermi GBM Final Localization
  41. GRB 260727A: EP/FXT follow-up observations
  42. EP260727a: Einstein Probe detection of an X-ray transient
  43. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  44. GRB 260727A: Glowbug gamma-ray detection
  45. GRB 260726A: J-band upper limit with WINTER
  46. GRB 260727A: J-band upper limit with WINTER
  47. GRB 260726A: SVOM/VT optical candidate
  48. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  49. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  50. EP260723a: SVOM/ECLAIRs Upper Limit
  51. GRB 260727A: GOTO early optical upper limit
  52. GRB 260727A: AstroSat CZTI detection
  53. GRB 260727A: Kilonova-Catcher optical upper limit
  54. GRB 260727A: LCO optical upper limits
  55. GRB 260727B: Fermi GBM Final Real-time Localization
  56. Fermi GRB 260726A: Global MASTER-Net observations report
  57. GRB 260727A: SVOM detection of a bright long burst
  58. GRB 260726A: SVOM detection of a burst
  59. GRB 260726A: Fermi GBM Final Real-time Localization
  60. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  61. EP260723a: further EP-FXT follow-up observation
  62. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  63. EP260725a: EP-WXT detection of an X-ray transient
  64. GRB 260616A: cubesat Avion detection
  65. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  66. GRB 260602B: cubesat Avion detection
  67. GRB 260601A: cubesat Avion detection
  68. EP260723a: EP-FXT follow-up observation
  69. IPN triangulation of GRB 260706B
  70. GRB 260718A: SVOM/ECLAIRs refined analysis
  71. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  72. EP260723a: SVOM/VT optical observation
  73. EP260723a: COLIBRÍ optical observations
  74. EP260723a: NOT optical conterpart confirmation
  75. EP260723a: Liverpool Telescope likely optical counterpart
  76. EP260723a: EP-WXT detection of a fast X-ray transient
  77. GRB 260723A: Fermi GBM Final Localization
  78. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  79. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  80. IceCube Alert 260722A: Global MASTER-Net observations report
  81. Konus-Wind detection of GRB 260721A
  82. GRB 260722A: Fermi GBM Final Real-time Localization
  83. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  84. Fermi GBM trigger 806384210/260722151 is not a GRB
  85. GRB 260721A: NuSTAR detection of prompt emission
  86. Konus-Wind detection of GRB 260714B
  87. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  88. GRB 260705A: Retraction of optical counterpart
  89. GRB 260714B: Insight-HXMT/HE detection
  90. GRB 260718A: EP-FXT follow-up observation
  91. Fermi trigger No 806104130: Global MASTER-Net observations report
  92. Fermi GRB 260718A: Global MASTER-Net observations report
  93. GRB 260718A: LCO optical upper limits
  94. GRB 260711A: SVOM/GRM observation
  95. GRB 260710A: SVOM/GRM observation
  96. GRB 260718A: Fermi GBM Observation
  97. GRB 260718A : GRANDMA and KNC upper limits
  98. GRB 260718A: SVOM/VT optical upper limits
  99. GRB 260718A: SVOM/VT optical upper limits from VHF data
  100. GRB 260718A: SVOM detection of a burst

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