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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 260808B: NOT optical observations
  2. GRB 260808B: LCO optical observations
  3. GRB 260808A: NuSTAR detection of prompt emission
  4. EP260809a: COLIBRÍ optical observations
  5. EP260809a: LCO optical observation
  6. EP260809a: OHP/T193 optical observations
  7. GRB260808B: OHP/T193 optical observations
  8. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  9. EP260809a: Einstein Probe detection of an X-ray transient
  10. GRB 260808B: SVOM/VT optical afterglow confirmation
  11. GRB 260808C: Fermi GBM Final Real-time Localization
  12. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  13. GRB 260808B: SVOM/VT optical candidate from VHF data
  14. GRB 260808B: SVOM detection of a faint burst
  15. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  16. Fermi GRB 260808A: Global MASTER-Net observations report
  17. GRB 260808A: Fermi GBM Final Real-time Localization
  18. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  19. IceCube Alert 260807A: Global MASTER-Net observations report
  20. IceCube-260805A: One candidate from the Zwicky Transient Facility
  21. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  22. GRB 260807A: SVOM possible detection of a faint burst
  23. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  24. EP260806a: COLIBRÍ optical observations
  25. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  26. EP260806a: SVOM/VT optical observation
  27. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  28. EP260806a: OSIRIS+/GTC redshift z=0.089
  29. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  30. EP260806a: LCO likely optical counterpart
  31. EP260806a: Einstein Probe detection of an X-ray transient
  32. GRB 260715A: cubesat Avion detection
  33. GRB 260709A: cubesat Avion detection
  34. GRB 260708A: cubesat Avion detection
  35. SN 2026stf / GRB 260708A: ATLAS forced photometry
  36. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  37. GRB 260730B: Glowbug gamma-ray detection
  38. GRB 260805C: Glowbug gamma-ray detection
  39. GRB 260805B: Glowbug gamma-ray detection
  40. Fermi GRB 260805A: Global MASTER-Net observations report
  41. GRB 260805B: Fermi GBM Final Localization
  42. GRB 260804A: Glowbug gamma-ray detection
  43. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  44. GRB 260805A: Fermi GBM Final Localization
  45. AT 2026wki: EP/FXT follow-up observations
  46. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  47. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  48. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  49. GRB 260804A: Fermi GBM Final Real-time Localization
  50. GRB 260708A: LCO further optical observations show supernova features
  51. GRB 260803A: Fermi GBM Final Real-time Localization
  52. Fermi GRB 260802B: Global MASTER-Net observations report
  53. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  54. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  55. GRB 260802A: SVOM/VT optical upper limits from VHF data
  56. GRB 260802A: LCO optical upper limits
  57. GRB 260802B: Fermi GBM Final Localization
  58. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  59. The EP-WXT trigger 01709277420 is likely a flaring star
  60. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  61. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  62. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  63. GRB 260731A: AstroSat CZTI detection of a long burst
  64. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  65. GRB 260730B: AstroSat CZTI detection
  66. EP260731a: COLIBRÍ optical upper limit
  67. EP260731a: NOT optical upper limit
  68. GRB 260730B: NuSTAR detection of prompt emission
  69. EP260731a: Einstein Probe detection of an X-ray transient
  70. GRB 260727A: SVOM/ECLAIRs refined analysis
  71. GRB 260726A: SVOM/ECLAIRs refined analysis
  72. GRB260730A: Fermi GBM Final Localization
  73. EP260728a: COLIBRÍ optical upper limit
  74. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  75. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  76. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  77. EP260729a: Einstein Probe detection of an X-ray transient
  78. EP260727a: SAO RAS optical observations
  79. GRB 260727A: AbAO and SAO RAS optical observations
  80. EP260728a: EP-FXT follow-up observation
  81. GRB 260726A: EP-FXT follow-up observations
  82. EP260728a: Einstein Probe detection of a fast X-ray transient
  83. GRB 260727A: SVOM/GRM observation
  84. GRB 260726A: Fermi GBM Observation
  85. EP260727a: 1.5m OSN optical counterpart detection
  86. EP260727a:refined analysis of the EP-WXT and EP-FXT observation
  87. EP260727a: OHP/T193 optical observations
  88. Konus-Wind detection of GRB 260727A
  89. GRB 260726A: Liverpool Telescope optical observations
  90. GRB 260727A: Liverpool Telescope optical upper limits
  91. EP260727a: Liverpool Telescope confirmation of optical counterpart
  92. EP260727a: NUTTELA-TAO Early Optical Limits
  93. GRB 260728A: Fermi GBM Final Localization
  94. GRB 260727A: EP/FXT follow-up observations
  95. EP260727a: Einstein Probe detection of an X-ray transient
  96. The EP-WXT trigger 01709276927 (EP260727a?): NOT likely optical counterpart
  97. GRB 260727A: Glowbug gamma-ray detection
  98. GRB 260726A: J-band upper limit with WINTER
  99. GRB 260727A: J-band upper limit with WINTER
  100. GRB 260726A: SVOM/VT optical candidate

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