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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"

45415 results found.

  1. GRB260809A: OHP/T193 optical observations
  2. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  3. GRB 260809A: SVOM/VT optical counterpart
  4. EP260809a: J-band upper limit with WINTER
  5. GRB 260808B: J-band upper limit with WINTER
  6. GRB 260808B: SVOM/ECLAIRs refined analysis
  7. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  8. GRB 260809A: SVOM detection of a faint burst
  9. GRB 260808B: Liverpool Telescope optical observations
  10. GRB 260808B: NOT optical observations
  11. GRB 260808B: LCO optical observations
  12. GRB 260808A: NuSTAR detection of prompt emission
  13. EP260809a: COLIBRÍ optical observations
  14. EP260809a: LCO optical observation
  15. EP260809a: OHP/T193 optical observations
  16. GRB260808B: OHP/T193 optical observations
  17. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  18. EP260809a: Einstein Probe detection of an X-ray transient
  19. GRB 260808B: SVOM/VT optical afterglow confirmation
  20. GRB 260808C: Fermi GBM Final Real-time Localization
  21. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  22. GRB 260808B: SVOM/VT optical candidate from VHF data
  23. GRB 260808B: SVOM detection of a faint burst
  24. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  25. Fermi GRB 260808A: Global MASTER-Net observations report
  26. GRB 260808A: Fermi GBM Final Real-time Localization
  27. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  28. IceCube Alert 260807A: Global MASTER-Net observations report
  29. IceCube-260805A: One candidate from the Zwicky Transient Facility
  30. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  31. GRB 260807A: SVOM possible detection of a faint burst
  32. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  33. EP260806a: COLIBRÍ optical observations
  34. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  35. EP260806a: SVOM/VT optical observation
  36. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  37. EP260806a: OSIRIS+/GTC redshift z=0.089
  38. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  39. EP260806a: LCO likely optical counterpart
  40. EP260806a: Einstein Probe detection of an X-ray transient
  41. GRB 260715A: cubesat Avion detection
  42. GRB 260709A: cubesat Avion detection
  43. GRB 260708A: cubesat Avion detection
  44. SN 2026stf / GRB 260708A: ATLAS forced photometry
  45. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  46. GRB 260730B: Glowbug gamma-ray detection
  47. GRB 260805C: Glowbug gamma-ray detection
  48. GRB 260805B: Glowbug gamma-ray detection
  49. Fermi GRB 260805A: Global MASTER-Net observations report
  50. GRB 260805B: Fermi GBM Final Localization
  51. GRB 260804A: Glowbug gamma-ray detection
  52. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  53. GRB 260805A: Fermi GBM Final Localization
  54. AT 2026wki: EP/FXT follow-up observations
  55. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  56. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  57. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  58. GRB 260804A: Fermi GBM Final Real-time Localization
  59. GRB 260708A: LCO further optical observations show supernova features
  60. GRB 260803A: Fermi GBM Final Real-time Localization
  61. Fermi GRB 260802B: Global MASTER-Net observations report
  62. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  63. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  64. GRB 260802A: SVOM/VT optical upper limits from VHF data
  65. GRB 260802A: LCO optical upper limits
  66. GRB 260802B: Fermi GBM Final Localization
  67. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  68. The EP-WXT trigger 01709277420 is likely a flaring star
  69. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  70. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  71. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  72. GRB 260731A: AstroSat CZTI detection of a long burst
  73. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  74. GRB 260730B: AstroSat CZTI detection
  75. EP260731a: COLIBRÍ optical upper limit
  76. EP260731a: NOT optical upper limit
  77. GRB 260730B: NuSTAR detection of prompt emission
  78. EP260731a: Einstein Probe detection of an X-ray transient
  79. GRB 260727A: SVOM/ECLAIRs refined analysis
  80. GRB 260726A: SVOM/ECLAIRs refined analysis
  81. GRB260730A: Fermi GBM Final Localization
  82. EP260728a: COLIBRÍ optical upper limit
  83. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  84. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  85. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  86. EP260729a: Einstein Probe detection of an X-ray transient
  87. EP260727a: SAO RAS optical observations
  88. GRB 260727A: AbAO and SAO RAS optical observations
  89. EP260728a: EP-FXT follow-up observation
  90. GRB 260726A: EP-FXT follow-up observations
  91. EP260728a: Einstein Probe detection of a fast X-ray transient
  92. GRB 260727A: SVOM/GRM observation
  93. GRB 260726A: Fermi GBM Observation
  94. EP260727a: 1.5m OSN optical counterpart detection
  95. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  96. EP260727a: OHP/T193 optical observations
  97. Konus-Wind detection of GRB 260727A
  98. GRB 260726A: Liverpool Telescope optical observations
  99. GRB 260727A: Liverpool Telescope optical upper limits
  100. EP260727a: Liverpool Telescope confirmation of optical counterpart

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