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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"

32484 results found.

  1. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  2. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  3. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  4. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  5. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  6. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  7. GRB 260809A: NOT optical observations
  8. GRB260809A: MAO/AZT-22 optical observations
  9. GRB260809A: OHP/T193 optical observations
  10. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  11. GRB 260809A: SVOM/VT optical counterpart
  12. EP260809a: J-band upper limit with WINTER
  13. GRB 260808B: J-band upper limit with WINTER
  14. GRB 260808B: SVOM/ECLAIRs refined analysis
  15. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  16. GRB 260808B: Liverpool Telescope optical observations
  17. GRB 260808B: NOT optical observations
  18. GRB 260808B: LCO optical observations
  19. GRB 260808A: NuSTAR detection of prompt emission
  20. EP260809a: COLIBRÍ optical observations
  21. EP260809a: LCO optical observation
  22. GRB260808B: OHP/T193 optical observations
  23. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  24. GRB 260808B: SVOM/VT optical afterglow confirmation
  25. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  26. GRB 260808B: SVOM/VT optical candidate from VHF data
  27. Fermi GRB 260808A: Global MASTER-Net observations report
  28. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  29. IceCube-260805A: One candidate from the Zwicky Transient Facility
  30. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  31. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  32. EP260806a: COLIBRÍ optical observations
  33. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  34. EP260806a: SVOM/VT optical observation
  35. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  36. EP260806a: OSIRIS+/GTC redshift z=0.089
  37. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  38. EP260806a: LCO likely optical counterpart
  39. GRB 260715A: cubesat Avion detection
  40. GRB 260709A: cubesat Avion detection
  41. GRB 260708A: cubesat Avion detection
  42. SN 2026stf / GRB 260708A: ATLAS forced photometry
  43. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  44. GRB 260730B: Glowbug gamma-ray detection
  45. GRB 260805B: Glowbug gamma-ray detection
  46. Fermi GRB 260805A: Global MASTER-Net observations report
  47. GRB 260804A: Glowbug gamma-ray detection
  48. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  49. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  50. GRB 260708A: LCO further optical observations show supernova features
  51. Fermi GRB 260802B: Global MASTER-Net observations report
  52. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  53. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  54. GRB 260802A: SVOM/VT optical upper limits from VHF data
  55. GRB 260802A: LCO optical upper limits
  56. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  57. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  58. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  59. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  60. GRB 260730B: AstroSat CZTI detection
  61. EP260731a: COLIBRÍ optical upper limit
  62. EP260731a: NOT optical upper limit
  63. GRB 260730B: NuSTAR detection of prompt emission
  64. GRB 260727A: SVOM/ECLAIRs refined analysis
  65. GRB 260726A: SVOM/ECLAIRs refined analysis
  66. EP260728a: COLIBRÍ optical upper limit
  67. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  68. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  69. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  70. EP260727a: SAO RAS optical observations
  71. GRB 260727A: AbAO and SAO RAS optical observations
  72. EP260728a: EP-FXT follow-up observation
  73. GRB 260726A: EP-FXT follow-up observations
  74. GRB 260727A: SVOM/GRM observation
  75. GRB 260726A: Fermi GBM Observation
  76. EP260727a: 1.5m OSN optical counterpart detection
  77. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  78. EP260727a: OHP/T193 optical observations
  79. Konus-Wind detection of GRB 260727A
  80. GRB 260726A: Liverpool Telescope optical observations
  81. GRB 260727A: Liverpool Telescope optical upper limits
  82. EP260727a: Liverpool Telescope confirmation of optical counterpart
  83. EP260727a: NUTTELA-TAO Early Optical Limits
  84. GRB 260727A: EP/FXT follow-up observations
  85. EP260727a: Einstein Probe detection of an X-ray transient
  86. GRB 260727A: Glowbug gamma-ray detection
  87. GRB 260726A: J-band upper limit with WINTER
  88. GRB 260727A: J-band upper limit with WINTER
  89. GRB 260726A: SVOM/VT optical candidate
  90. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  91. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  92. EP260723a: SVOM/ECLAIRs Upper Limit
  93. GRB 260727A: GOTO early optical upper limit
  94. GRB 260727A: AstroSat CZTI detection
  95. GRB 260727A: Kilonova-Catcher optical upper limit
  96. GRB 260727A: LCO optical upper limits
  97. Fermi GRB 260726A: Global MASTER-Net observations report
  98. GRB 260726A: SVOM detection of a burst
  99. IceCube-260722A: Classification of ZTF26abjbxfs/SN 2026vts as a Type Ia Supernova
  100. EP260723a: further EP-FXT follow-up observation

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