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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"

26338 results found.

  1. GRB 260818A: SVOM/ECLAIRs refined analysis
  2. GRB 260818B: NOT optical upper limits
  3. GRB 260810A: SVOM/GRM observation
  4. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  5. GRB260818A: EP-FXT follow-up observation
  6. GRB 260818B: LCO optical upper limits
  7. GRB 260818B: SVOM detection of a short burst
  8. SVOM trigger sb26081806 is not a GRB
  9. EP260806a: SAO RAS multicolor optical observations
  10. GRB 260818A: LCO optical upper limits
  11. EP260812a: AbAO optical upper limit
  12. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  13. GRB 260810A: Insight-HXMT/HE detection
  14. GRB 260818A: SVOM possible detection of a long and faint GRB
  15. EP260806a: SVOM/ECLAIRs detection through targeted search
  16. EP260806a: NUTTELA-TAO optical observations
  17. EP260812a: AZT-22 optical upper limit
  18. EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
  19. EP260806a: WFST optical observations
  20. EP260812b: Optical upper limit with Kinder
  21. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  22. GRB 260808B: Liverpool Telescope further optical observations
  23. EP260812a: NOT and Liverpool Telescope upper limits:
  24. EP260812b: GOTO detection of the optical counterpart
  25. EP260812a: refined analysis of the EP-WXT and autonomous EP-FXT observation
  26. EP260812a: SVOM/C-GFT optical upper limit
  27. EP260812b: COLIBRÍ optical observations
  28. EP260812b: SVOM/VT optical observation
  29. GRB 260808A: SVOM/GRM observation
  30. EP260812b: Einstein Probe detection of an X-ray transient
  31. Fermi GBM Sub-Threshold Detection of GRB 260809A
  32. GRB 260810A: Glowbug gamma-ray detection
  33. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  34. GRB 260810A: AstroSat CZTI detection of a long burst
  35. EP260812a: Einstein Probe detection of an X-ray transient
  36. GRB 260809A: SAO RAS optical observations
  37. GRB 260808B: SAO RAS optical observations
  38. GRB 260808B: SVOM/VT optical re-brightening at day 3
  39. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  40. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  41. GRB 260808A: GECAM-B observation
  42. GRB 260807A: SVOM/ECLAIRs refined analysis
  43. EP260806a: MAO/AZT-22 optical observations
  44. GRB260808B: MAO/AZT-22 optical observations
  45. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  46. GRB 260809A: J-band upper limit with WINTER
  47. GRB 260806A: Glowbug gamma-ray detection
  48. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  49. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  50. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  51. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  52. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  53. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  54. GRB 260809A: NOT optical observations
  55. GRB260809A: MAO/AZT-22 optical observations
  56. GRB 260809A: SVOM/VT optical counterpart
  57. EP260809a: J-band upper limit with WINTER
  58. GRB 260808B: J-band upper limit with WINTER
  59. GRB 260808B: SVOM/ECLAIRs refined analysis
  60. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  61. GRB 260809A: SVOM detection of a faint burst
  62. GRB 260808B: Liverpool Telescope optical observations
  63. GRB 260808B: NOT optical observations
  64. GRB 260808B: LCO optical observations
  65. GRB 260808A: NuSTAR detection of prompt emission
  66. EP260809a: COLIBRÍ optical observations
  67. EP260809a: LCO optical observation
  68. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  69. EP260809a: Einstein Probe detection of an X-ray transient
  70. GRB 260808B: SVOM/VT optical afterglow confirmation
  71. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  72. GRB 260808B: SVOM/VT optical candidate from VHF data
  73. GRB 260808B: SVOM detection of a faint burst
  74. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  75. IceCube-260805A: One candidate from the Zwicky Transient Facility
  76. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  77. GRB 260807A: SVOM possible detection of a faint burst
  78. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  79. EP260806a: COLIBRÍ optical observations
  80. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  81. EP260806a: SVOM/VT optical observation
  82. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  83. EP260806a: OSIRIS+/GTC redshift z=0.089
  84. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  85. EP260806a: LCO likely optical counterpart
  86. EP260806a: Einstein Probe detection of an X-ray transient
  87. GRB 260715A: cubesat Avion detection
  88. GRB 260709A: cubesat Avion detection
  89. GRB 260708A: cubesat Avion detection
  90. SN 2026stf / GRB 260708A: ATLAS forced photometry
  91. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  92. GRB 260730B: Glowbug gamma-ray detection
  93. GRB 260805C: Glowbug gamma-ray detection
  94. GRB 260805B: Glowbug gamma-ray detection
  95. GRB 260804A: Glowbug gamma-ray detection
  96. GRB 260805A: Fermi GBM Final Localization
  97. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  98. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  99. GRB 260708A: LCO further optical observations show supernova features
  100. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation

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