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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. GRB260808B: MAO/AZT-22 optical observations
  2. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  3. GRB 260809A: J-band upper limit with WINTER
  4. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  5. GRB 260806A: Glowbug gamma-ray detection
  6. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  7. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  8. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  9. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  10. The EP-WXT trigger 01709278015 is likely a flaring star
  11. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  12. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  13. GRB 260809A: NOT optical observations
  14. GRB260809A: MAO/AZT-22 optical observations
  15. GRB260809A: OHP/T193 optical observations
  16. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  17. GRB 260809A: SVOM/VT optical counterpart
  18. EP260809a: J-band upper limit with WINTER
  19. GRB 260808B: J-band upper limit with WINTER
  20. GRB 260808B: SVOM/ECLAIRs refined analysis
  21. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  22. GRB 260809A: SVOM detection of a faint burst
  23. GRB 260808B: Liverpool Telescope optical observations
  24. GRB 260808B: NOT optical observations
  25. GRB 260808B: LCO optical observations
  26. GRB 260808A: NuSTAR detection of prompt emission
  27. EP260809a: COLIBRÍ optical observations
  28. EP260809a: LCO optical observation
  29. EP260809a: OHP/T193 optical observations
  30. GRB260808B: OHP/T193 optical observations
  31. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  32. EP260809a: Einstein Probe detection of an X-ray transient
  33. GRB 260808B: SVOM/VT optical afterglow confirmation
  34. GRB 260808C: Fermi GBM Final Real-time Localization
  35. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  36. GRB 260808B: SVOM/VT optical candidate from VHF data
  37. GRB 260808B: SVOM detection of a faint burst
  38. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  39. Fermi GRB 260808A: Global MASTER-Net observations report
  40. GRB 260808A: Fermi GBM Final Real-time Localization
  41. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  42. IceCube Alert 260807A: Global MASTER-Net observations report
  43. IceCube-260805A: One candidate from the Zwicky Transient Facility
  44. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  45. GRB 260807A: SVOM possible detection of a faint burst
  46. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  47. EP260806a: COLIBRÍ optical observations
  48. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  49. EP260806a: SVOM/VT optical observation
  50. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  51. EP260806a: OSIRIS+/GTC redshift z=0.089
  52. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  53. EP260806a: LCO likely optical counterpart
  54. EP260806a: Einstein Probe detection of an X-ray transient
  55. GRB 260715A: cubesat Avion detection
  56. GRB 260709A: cubesat Avion detection
  57. GRB 260708A: cubesat Avion detection
  58. SN 2026stf / GRB 260708A: ATLAS forced photometry
  59. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  60. GRB 260730B: Glowbug gamma-ray detection
  61. GRB 260805C: Glowbug gamma-ray detection
  62. GRB 260805B: Glowbug gamma-ray detection
  63. Fermi GRB 260805A: Global MASTER-Net observations report
  64. GRB 260805B: Fermi GBM Final Localization
  65. GRB 260804A: Glowbug gamma-ray detection
  66. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  67. GRB 260805A: Fermi GBM Final Localization
  68. AT 2026wki: EP/FXT follow-up observations
  69. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  70. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  71. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  72. GRB 260804A: Fermi GBM Final Real-time Localization
  73. GRB 260708A: LCO further optical observations show supernova features
  74. GRB 260803A: Fermi GBM Final Real-time Localization
  75. Fermi GRB 260802B: Global MASTER-Net observations report
  76. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  77. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  78. GRB 260802A: SVOM/VT optical upper limits from VHF data
  79. GRB 260802A: LCO optical upper limits
  80. GRB 260802B: Fermi GBM Final Localization
  81. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  82. The EP-WXT trigger 01709277420 is likely a flaring star
  83. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  84. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  85. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  86. GRB 260731A: AstroSat CZTI detection of a long burst
  87. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  88. GRB 260730B: AstroSat CZTI detection
  89. EP260731a: COLIBRÍ optical upper limit
  90. EP260731a: NOT optical upper limit
  91. GRB 260730B: NuSTAR detection of prompt emission
  92. EP260731a: Einstein Probe detection of an X-ray transient
  93. GRB 260727A: SVOM/ECLAIRs refined analysis
  94. GRB 260726A: SVOM/ECLAIRs refined analysis
  95. GRB260730A: Fermi GBM Final Localization
  96. EP260728a: COLIBRÍ optical upper limit
  97. EP260727a: VLT/X-shooter spectroscopic redshift z = 2.817
  98. The EP-WXT trigger 01709277130 (EP260729a): refined EP-WXT analysis and association with a flaring star
  99. EP 260729a: Ondrejov D50 optical detection supports stellar flare origin
  100. EP260729a: Einstein Probe detection of an X-ray transient

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