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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"

15247 results found.

  1. GRB 260903A: NOT optical observations and afterglow fading
  2. NuSTAR Transient 260828: SOAR Optical Upper Limits
  3. GRB 260903A: Retraction of optical counterpart of GCN 45501
  4. GRB 260831A: GECAM-B observation
  5. GRB 260827A: Insight-HXMT/HE detection
  6. GRB 260903A: SVOM detection of a soft faint burst
  7. Konus-Wind detection of GRB 260829A
  8. GRB 260829A: SVOM/GRM observation
  9. GRB 260818A: ATCA detection of a candidate radio counterpart
  10. IceCube-260827A: No transient candidates from the Zwicky Transient Facility
  11. GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical variation of nova V* GK Per
  12. SVOM trigger sb26083106 is not a GRB
  13. GRB 260829A: AstroSat CZTI detection
  14. GRB 260827A: SVOM/GRM observation
  15. NuSTAR 260828: a 1100s hard X-ray transient
  16. GRB 260831B: SVOM detection of a possible burst
  17. Fermi-LAT Gamma-ray Observations of IceCube-260827A
  18. Fermi-LAT Gamma-ray Observations of IceCube-260825A
  19. GRB 260829A: GECAM-B observation of a long burst
  20. GRB 260825A: SVOM/GRM observation of a long burst
  21. GRB 260825A: GECAM-B observation
  22. GRB 260829A: Fermi GBM Detection
  23. GRB 260825A: AstroSat CZTI detection
  24. IceCube-260827A: Upper limits from a search for additional neutrino events in IceCube
  25. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  26. IceCube-260825A: Upper limits from a search for additional neutrino events in IceCube
  27. GRB 260818B: VLT optical and nIR observations
  28. IceCube-260827A - IceCube observation of a high-energy neutrino candidate track-like event
  29. GRB 260818B: 6 GHz VLA observations
  30. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  31. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  32. GRB 260808B: SAO RAS observations of the optical rebrightening
  33. IceCube-260825A: No transient candidates from the Zwicky Transient Facility
  34. GRB 260809A: SVOM/ECLAIRs refined analysis
  35. IceCube-Cascade 260824A: Upper limits from a search for additional neutrino events in IceCube
  36. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  37. GRB 260822A: PRIME near-infrared upper limits from multiple epochs
  38. GRB 260818A: further EP-FXT observations and X-ray afterglow confirmation
  39. GRB 260822A: Retraction of GOTO optical counterpart detection GCN 45431
  40. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  41. GRB 260822A: GROWTH-India Telescope Upper Limits
  42. GRB 260822A: SVOM detection of a short burst
  43. Fermi-LAT Gamma-ray Observations of IceCube-260821A
  44. Fermi-LAT Gamma-ray Observations of IceCube-260807A
  45. IceCube-260821A: Upper limits from a search for additional neutrino events in IceCube
  46. GRB 260818B: SVOM/C-GFT optical upper limit
  47. EP260731a: SVOM/ECLAIRs detection through offline targeted search
  48. GRB 260820A: Insight-HXMT/HE detection
  49. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  50. GRB 260818B: SVOM/GRM observation
  51. GRB 260818B: Insight-HXMT detection
  52. GRB 260818A: J-band observations with WINTER
  53. GRB 260818B: SVOM/ECLAIRs refined analysis
  54. GRB 260818A: SVOM/ECLAIRs refined analysis
  55. GRB 260810A: SVOM/GRM observation
  56. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  57. GRB 260818B: SVOM detection of a short burst
  58. GRB 260818A: LCO optical upper limits
  59. EP260812a: AbAO optical upper limit
  60. GRB 260810A: Insight-HXMT/HE detection
  61. GRB 260818A: SVOM possible detection of a long and faint GRB
  62. EP260806a: SVOM/ECLAIRs detection through targeted search
  63. EP260812b: GTC/OSIRIS+ tentative spectroscopic redshift z = 2.034
  64. EP260806a: WFST optical observations
  65. EP260812b: Optical upper limit with Kinder
  66. GRB 260805D: SVOM/GRM detection of a possible magnetar burst
  67. GRB 260808B: Liverpool Telescope further optical observations
  68. GRB 260808B: GTC/OSIRIS+ spectroscopic redshift z = 1.295
  69. EP260812a: NOT and Liverpool Telescope upper limits:
  70. EP260812b: COLIBRÍ optical observations
  71. GRB 260808A: SVOM/GRM observation
  72. GRB 260808B: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical rebrightening
  73. GRB 260810A: AstroSat CZTI detection of a long burst
  74. GRB 260317A: SVOM/ECLAIRs detection through offline targeted search and its possible association to magnetar 1E 1841-04.5
  75. GRB 260806A: CALET Gamma-Ray Burst Monitor detection
  76. GRB 260808A: GECAM-B observation
  77. GRB 260807A: SVOM/ECLAIRs refined analysis
  78. IceCube-260807A: Upper limits from a search for additional neutrino events in IceCube
  79. GRB260808B: MAO/AZT-22 optical observations
  80. GRB 250607A: SVOM/ECLAIRs detection through offline targeted search
  81. GRB 260808A: CALET Gamma-Ray Burst Monitor detection
  82. GRB 260805C: CALET Gamma-Ray Burst Monitor detection
  83. GRB 260804A: CALET Gamma-Ray Burst Monitor detection
  84. GRB260809A/EPF_J234751.2+210212: EP-FXT follow-up observation
  85. GRB260809A: MAO/AZT-22 optical observations
  86. IceCube-260805A: Upper limits from a search for additional neutrino events in IceCube
  87. GRB 260808B: SVOM/ECLAIRs refined analysis
  88. GRB 260809A: SVOM detection of a faint burst
  89. GRB 260808B: Liverpool Telescope optical observations
  90. GRB 260808B: SVOM detection of a faint burst
  91. IceCube-260805A: One candidate from the Zwicky Transient Facility
  92. GRB 260807A: SVOM possible detection of a faint burst
  93. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  94. EP260806a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  95. EP260806a: SVOM/VT optical observation
  96. GRB 260715A: cubesat Avion detection
  97. GRB 260709A: cubesat Avion detection
  98. GRB 260708A: cubesat Avion detection
  99. SN 2026stf / GRB 260708A: ATLAS forced photometry
  100. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event

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