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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+521421: EP-FXT follow-up observation
  2. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  3. GRB 260802A: SVOM/VT optical upper limits from VHF data
  4. GRB 260802A: LCO optical upper limits
  5. GRB 260802B: Fermi GBM Final Localization
  6. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  7. The EP-WXT trigger 01709277420 is likely a flaring star
  8. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  9. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  10. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  11. GRB 260731A: AstroSat CZTI detection of a long burst
  12. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  13. GRB 260730B: AstroSat CZTI detection
  14. EP260731a: COLIBRÍ optical upper limit
  15. EP260731a: NOT optical upper limit
  16. GRB 260730B: NuSTAR detection of prompt emission
  17. EP260731a: Einstein Probe detection of an X-ray transient
  18. GRB 260727A: SVOM/ECLAIRs refined analysis
  19. GRB 260726A: SVOM/ECLAIRs refined analysis
  20. GRB260730A: Fermi GBM Final Localization
  21. EP260728a: COLIBRÍ optical upper limit
  22. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  23. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  24. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  25. EP260729a: Einstein Probe detection of an X-ray transient
  26. EP260727a: SAO RAS optical observations
  27. GRB 260727A: AbAO and SAO RAS optical observations
  28. EP260728a: EP-FXT follow-up observation
  29. GRB 260726A: EP-FXT follow-up observations
  30. EP260728a: Einstein Probe detection of a fast X-ray transient
  31. GRB 260727A: SVOM/GRM observation
  32. GRB 260726A: Fermi GBM Observation
  33. EP260727a: 1.5m OSN optical counterpart detection
  34. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  35. EP260727a: OHP/T193 optical observations
  36. Konus-Wind detection of GRB 260727A
  37. GRB 260726A: Liverpool Telescope optical observations
  38. GRB 260727A: Liverpool Telescope optical upper limits
  39. EP260727a: Liverpool Telescope confirmation of optical counterpart
  40. EP260727a: NUTTELA-TAO Early Optical Limits
  41. GRB 260728A: Fermi GBM Final Localization
  42. GRB 260727A: EP/FXT follow-up observations
  43. EP260727a: Einstein Probe detection of an X-ray transient
  44. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  45. GRB 260727A: Glowbug gamma-ray detection
  46. GRB 260726A: J-band upper limit with WINTER
  47. GRB 260727A: J-band upper limit with WINTER
  48. GRB 260726A: SVOM/VT optical candidate
  49. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  50. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  51. EP260723a: SVOM/ECLAIRs Upper Limit
  52. GRB 260727A: GOTO early optical upper limit
  53. GRB 260727A: AstroSat CZTI detection
  54. GRB 260727A: Kilonova-Catcher optical upper limit
  55. GRB 260727A: LCO optical upper limits
  56. GRB 260727B: Fermi GBM Final Real-time Localization
  57. Fermi GRB 260726A: Global MASTER-Net observations report
  58. GRB 260727A: SVOM detection of a bright long burst
  59. GRB 260726A: SVOM detection of a burst
  60. GRB 260726A: Fermi GBM Final Real-time Localization
  61. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  62. EP260723a: further EP-FXT follow-up observation
  63. EP260725a: EP-FXT follow-up observation and association with a bright flaring star
  64. EP260725a: EP-WXT detection of an X-ray transient
  65. GRB 260616A: cubesat Avion detection
  66. EP260723a: Continued Liverpool Telescope observations suggest hours long optical plateau or rebrightening
  67. GRB 260602B: cubesat Avion detection
  68. GRB 260601A: cubesat Avion detection
  69. EP260723a: EP-FXT follow-up observation
  70. IPN triangulation of GRB 260706B
  71. GRB 260718A: SVOM/ECLAIRs refined analysis
  72. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  73. EP260723a: SVOM/VT optical observation
  74. EP260723a: COLIBRÍ optical observations
  75. EP260723a: NOT optical conterpart confirmation
  76. EP260723a: Liverpool Telescope likely optical counterpart
  77. EP260723a: EP-WXT detection of a fast X-ray transient
  78. GRB 260723A: Fermi GBM Final Localization
  79. IceCube-260722A: Upper limits from a search for additional neutrino events in IceCube
  80. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  81. IceCube Alert 260722A: Global MASTER-Net observations report
  82. Konus-Wind detection of GRB 260721A
  83. GRB 260722A: Fermi GBM Final Real-time Localization
  84. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  85. Fermi GBM trigger 806384210/260722151 is not a GRB
  86. GRB 260721A: NuSTAR detection of prompt emission
  87. Konus-Wind detection of GRB 260714B
  88. SVOM trigger sb26071506: SVOM/VT confirmation of a stellar flare
  89. GRB 260705A: Retraction of optical counterpart
  90. GRB 260714B: Insight-HXMT/HE detection
  91. GRB 260718A: EP-FXT follow-up observation
  92. Fermi trigger No 806104130: Global MASTER-Net observations report
  93. Fermi GRB 260718A: Global MASTER-Net observations report
  94. GRB 260718A: LCO optical upper limits
  95. GRB 260711A: SVOM/GRM observation
  96. GRB 260710A: SVOM/GRM observation
  97. GRB 260718A: Fermi GBM Observation
  98. GRB 260718A : GRANDMA and KNC upper limits
  99. GRB 260718A: SVOM/VT optical upper limits
  100. GRB 260718A: SVOM/VT optical upper limits from VHF data

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