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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"

42564 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. The EP-WXT trigger 01709278015 is likely a flaring star
  6. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  7. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  8. GRB 260809A: NOT optical observations
  9. GRB260809A: MAO/AZT-22 optical observations
  10. GRB260809A: OHP/T193 optical observations
  11. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  12. GRB 260809A: SVOM/VT optical counterpart
  13. EP260809a: J-band upper limit with WINTER
  14. GRB 260808B: J-band upper limit with WINTER
  15. GRB 260808B: SVOM/ECLAIRs refined analysis
  16. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  17. GRB 260809A: SVOM detection of a faint burst
  18. GRB 260808B: Liverpool Telescope optical observations
  19. GRB 260808B: NOT optical observations
  20. GRB 260808B: LCO optical observations
  21. GRB 260808A: NuSTAR detection of prompt emission
  22. EP260809a: COLIBRÍ optical observations
  23. EP260809a: LCO optical observation
  24. EP260809a: OHP/T193 optical observations
  25. GRB260808B: OHP/T193 optical observations
  26. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  27. EP260809a: Einstein Probe detection of an X-ray transient
  28. GRB 260808B: SVOM/VT optical afterglow confirmation
  29. GRB 260808C: Fermi GBM Final Real-time Localization
  30. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  31. GRB 260808B: SVOM/VT optical candidate from VHF data
  32. GRB 260808B: SVOM detection of a faint burst
  33. Fermi GRB 260808A: Global MASTER-Net observations report
  34. GRB 260808A: Fermi GBM Final Real-time Localization
  35. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  36. IceCube Alert 260807A: Global MASTER-Net observations report
  37. IceCube-260805A: One candidate from the Zwicky Transient Facility
  38. GRB 260807A: SVOM possible detection of a faint burst
  39. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  40. EP260806a: COLIBRÍ optical observations
  41. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  42. EP260806a: SVOM/VT optical observation
  43. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  44. EP260806a: OSIRIS+/GTC redshift z=0.089
  45. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  46. EP260806a: LCO likely optical counterpart
  47. EP260806a: Einstein Probe detection of an X-ray transient
  48. GRB 260715A: cubesat Avion detection
  49. GRB 260709A: cubesat Avion detection
  50. GRB 260708A: cubesat Avion detection
  51. SN 2026stf / GRB 260708A: ATLAS forced photometry
  52. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  53. GRB 260730B: Glowbug gamma-ray detection
  54. GRB 260805C: Glowbug gamma-ray detection
  55. GRB 260805B: Glowbug gamma-ray detection
  56. Fermi GRB 260805A: Global MASTER-Net observations report
  57. GRB 260805B: Fermi GBM Final Localization
  58. GRB 260804A: Glowbug gamma-ray detection
  59. GRB 260805A: Fermi GBM Final Localization
  60. AT 2026wki: EP/FXT follow-up observations
  61. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  62. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  63. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  64. GRB 260804A: Fermi GBM Final Real-time Localization
  65. GRB 260708A: LCO further optical observations show supernova features
  66. GRB 260803A: Fermi GBM Final Real-time Localization
  67. Fermi GRB 260802B: Global MASTER-Net observations report
  68. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  69. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  70. GRB 260802A: SVOM/VT optical upper limits from VHF data
  71. GRB 260802A: LCO optical upper limits
  72. GRB 260802B: Fermi GBM Final Localization
  73. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  74. The EP-WXT trigger 01709277420 is likely a flaring star
  75. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  76. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  77. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  78. GRB 260731A: AstroSat CZTI detection of a long burst
  79. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  80. GRB 260730B: AstroSat CZTI detection
  81. EP260731a: NOT optical upper limit
  82. GRB 260730B: NuSTAR detection of prompt emission
  83. EP260731a: Einstein Probe detection of an X-ray transient
  84. GRB 260727A: SVOM/ECLAIRs refined analysis
  85. GRB 260726A: SVOM/ECLAIRs refined analysis
  86. GRB260730A: Fermi GBM Final Localization
  87. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  88. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  89. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  90. EP260729a: Einstein Probe detection of an X-ray transient
  91. EP260727a: SAO RAS optical observations
  92. GRB 260727A: AbAO and SAO RAS optical observations
  93. EP260728a: EP-FXT follow-up observation
  94. GRB 260726A: EP-FXT follow-up observations
  95. EP260728a: Einstein Probe detection of a fast X-ray transient
  96. GRB 260727A: SVOM/GRM observation
  97. GRB 260726A: Fermi GBM Observation
  98. EP260727a: 1.5m OSN optical counterpart detection
  99. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  100. EP260727a: OHP/T193 optical observations

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