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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"

45435 results found.

  1. GRB 260813A: BALROG localization (Fermi Trigger 808341387 / GRB 260813803)
  2. GRB 260813A: Fermi GBM Final Real-time Localization
  3. EP260812a: NOT and Liverpool Telescope upper limits:
  4. EP260812b: Liverpool Telescope observations
  5. EP260812b: GOTO detection of the optical counterpart
  6. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  7. EP260812a: SVOM/C-GFT optical upper limit
  8. EP260812b: COLIBRÍ optical observations
  9. EP260812b: SVOM/VT optical observation
  10. GRB 260808A: SVOM/GRM observation
  11. EP260812b: Einstein Probe detection of an X-ray transient
  12. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  13. Fermi GBM Sub-Threshold Detection of GRB 260809A
  14. GRB 260810A: Glowbug gamma-ray detection
  15. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  16. GRB 260810A: AstroSat CZTI detection of a long burst
  17. EP260812a: Einstein Probe detection of an X-ray transient
  18. GRB 260809A: SAO RAS optical observations
  19. GRB 260808B: SAO RAS optical observations
  20. GRB 260808B: SVOM/VT optical re-brightening at day 3
  21. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  22. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  23. GRB 260808A: GECAM-B observation
  24. GRB 260807A: SVOM/ECLAIRs refined analysis
  25. EP260806a: MAO/AZT-22 optical observations
  26. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  27. GRB260808B: MAO/AZT-22 optical observations
  28. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  29. GRB 260809A: J-band upper limit with WINTER
  30. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  31. GRB 260806A: Glowbug gamma-ray detection
  32. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  33. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  34. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  35. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  36. The EP-WXT trigger 01709278015 is likely a flaring star
  37. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  38. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  39. GRB 260809A: NOT optical observations
  40. GRB260809A: MAO/AZT-22 optical observations
  41. GRB260809A: OHP/T193 optical observations
  42. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  43. GRB 260809A: SVOM/VT optical counterpart
  44. EP260809a: J-band upper limit with WINTER
  45. GRB 260808B: J-band upper limit with WINTER
  46. GRB 260808B: SVOM/ECLAIRs refined analysis
  47. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  48. GRB 260809A: SVOM detection of a faint burst
  49. GRB 260808B: Liverpool Telescope optical observations
  50. GRB 260808B: NOT optical observations
  51. GRB 260808B: LCO optical observations
  52. GRB 260808A: NuSTAR detection of prompt emission
  53. EP260809a: COLIBRÍ optical observations
  54. EP260809a: LCO optical observation
  55. EP260809a: OHP/T193 optical observations
  56. GRB260808B: OHP/T193 optical observations
  57. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  58. EP260809a: Einstein Probe detection of an X-ray transient
  59. GRB 260808B: SVOM/VT optical afterglow confirmation
  60. GRB 260808C: Fermi GBM Final Real-time Localization
  61. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  62. GRB 260808B: SVOM/VT optical candidate from VHF data
  63. GRB 260808B: SVOM detection of a faint burst
  64. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  65. Fermi GRB 260808A: Global MASTER-Net observations report
  66. GRB 260808A: Fermi GBM Final Real-time Localization
  67. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  68. IceCube Alert 260807A: Global MASTER-Net observations report
  69. IceCube-260805A: One candidate from the Zwicky Transient Facility
  70. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  71. GRB 260807A: SVOM possible detection of a faint burst
  72. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  73. EP260806a: COLIBRÍ optical observations
  74. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  75. EP260806a: SVOM/VT optical observation
  76. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  77. EP260806a: OSIRIS+/GTC redshift z=0.089
  78. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  79. EP260806a: LCO likely optical counterpart
  80. EP260806a: Einstein Probe detection of an X-ray transient
  81. GRB 260715A: cubesat Avion detection
  82. GRB 260709A: cubesat Avion detection
  83. GRB 260708A: cubesat Avion detection
  84. SN 2026stf / GRB 260708A: ATLAS forced photometry
  85. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  86. GRB 260730B: Glowbug gamma-ray detection
  87. GRB 260805C: Glowbug gamma-ray detection
  88. GRB 260805B: Glowbug gamma-ray detection
  89. Fermi GRB 260805A: Global MASTER-Net observations report
  90. GRB 260805B: Fermi GBM Final Localization
  91. GRB 260804A: Glowbug gamma-ray detection
  92. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  93. GRB 260805A: Fermi GBM Final Localization
  94. AT 2026wki: EP/FXT follow-up observations
  95. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  96. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  97. IceCube-Cascade 260801A: Upper limits from a search for additional neutrino events in IceCube
  98. GRB 260804A: Fermi GBM Final Real-time Localization
  99. GRB 260708A: LCO further optical observations show supernova features
  100. GRB 260803A: Fermi GBM Final Real-time Localization

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