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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. SVOM trigger sb26081806 is not a GRB
  2. EP260806a: SAO RAS multicolor optical observations
  3. GRB 260818A: LCO optical upper limits
  4. EP260812a: AbAO optical upper limit
  5. GRB 260818A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  6. GRB 260810A: Insight-HXMT/HE detection
  7. GRB 260818A: SVOM possible detection of a long and faint GRB
  8. EP260806a: SVOM/ECLAIRs detection through targeted search
  9. EP260806a: NUTTELA-TAO optical observations
  10. The EP-WXT trigger 01709281429 is likely a flaring star
  11. EP260812a: AZT-22 optical upper limit
  12. EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
  13. EP260806a: WFST optical observations
  14. The EP-WXT trigger 01709280562 is likely a flaring star
  15. EP260812b: Optical upper limit with Kinder
  16. The EP-WXT trigger 01709279838 is likely a flaring star
  17. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  18. GRB 260808B: Liverpool Telescope further optical observations
  19. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  20. GRB 260813A: BALROG localization (Fermi Trigger 808341387 / GRB 260813803)
  21. GRB 260813A: Fermi GBM Final Real-time Localization
  22. EP260812a: NOT and Liverpool Telescope upper limits:
  23. EP260812b: Liverpool Telescope observations
  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. EP trigger #01709278129 (EP260812b?): NOT optical counterpart
  32. Fermi GBM Sub-Threshold Detection of GRB 260809A
  33. GRB 260810A: Glowbug gamma-ray detection
  34. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  35. GRB 260810A: AstroSat CZTI detection of a long burst
  36. EP260812a: Einstein Probe detection of an X-ray transient
  37. GRB 260809A: SAO RAS optical observations
  38. GRB 260808B: SAO RAS optical observations
  39. GRB 260808B: SVOM/VT optical re-brightening at day 3
  40. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  41. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  42. GRB 260808A: GECAM-B observation
  43. GRB 260807A: SVOM/ECLAIRs refined analysis
  44. EP260806a: MAO/AZT-22 optical observations
  45. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  46. GRB260808B: MAO/AZT-22 optical observations
  47. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  48. GRB 260809A: J-band upper limit with WINTER
  49. EP260809a: VLT/X-shooter spectroscopic redshift z = 3.07
  50. GRB 260806A: Glowbug gamma-ray detection
  51. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  52. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  53. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  54. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  55. The EP-WXT trigger 01709278015 is likely a flaring star
  56. GRB 260809A: SVOM/COLIBRÍ (FM-GFT) optical observation
  57. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) optical observation
  58. GRB 260809A: NOT optical observations
  59. GRB260809A: MAO/AZT-22 optical observations
  60. GRB260809A: OHP/T193 optical observations
  61. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  62. GRB 260809A: SVOM/VT optical counterpart
  63. EP260809a: J-band upper limit with WINTER
  64. GRB 260808B: J-band upper limit with WINTER
  65. GRB 260808B: SVOM/ECLAIRs refined analysis
  66. EP260809a:refined analysis of the EP-WXT and autonomous EP-FXT observation
  67. GRB 260809A: SVOM detection of a faint burst
  68. GRB 260808B: Liverpool Telescope optical observations
  69. GRB 260808B: NOT optical observations
  70. GRB 260808B: LCO optical observations
  71. GRB 260808A: NuSTAR detection of prompt emission
  72. EP260809a: COLIBRÍ optical observations
  73. EP260809a: LCO optical observation
  74. EP260809a: OHP/T193 optical observations
  75. GRB260808B: OHP/T193 optical observations
  76. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  77. EP260809a: Einstein Probe detection of an X-ray transient
  78. GRB 260808B: SVOM/VT optical afterglow confirmation
  79. GRB 260808C: Fermi GBM Final Real-time Localization
  80. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  81. GRB 260808B: SVOM/VT optical candidate from VHF data
  82. GRB 260808B: SVOM detection of a faint burst
  83. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  84. Fermi GRB 260808A: Global MASTER-Net observations report
  85. GRB 260808A: Fermi GBM Final Real-time Localization
  86. EP260806a: ZTF serendipitous detection of ZTF26abmjjnm / AT 2026yeh
  87. IceCube Alert 260807A: Global MASTER-Net observations report
  88. IceCube-260805A: One candidate from the Zwicky Transient Facility
  89. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  90. GRB 260807A: SVOM possible detection of a faint burst
  91. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  92. EP260806a: COLIBRÍ optical observations
  93. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  94. EP260806a: SVOM/VT optical observation
  95. EP260806a: Liverpool Telescope observations of the counterpart show a blue colour
  96. EP260806a: OSIRIS+/GTC redshift z=0.089
  97. EP260731a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  98. EP260806a: LCO likely optical counterpart
  99. EP260806a: Einstein Probe detection of an X-ray transient
  100. GRB 260715A: cubesat Avion detection

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