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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"

37503 results found.

  1. GRB 260808B: Liverpool Telescope optical observations
  2. GRB 260808B: NOT optical observations
  3. GRB 260808B: LCO optical observations
  4. GRB 260808A: NuSTAR detection of prompt emission
  5. GRB260808B: OHP/T193 optical observations
  6. GRB 260808B / EPF_J230056.0+082842: EP-FXT follow-up observation
  7. GRB 260808B: SVOM/VT optical afterglow confirmation
  8. GRB 260808C: Fermi GBM Final Real-time Localization
  9. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  10. GRB 260808B: SVOM/VT optical candidate from VHF data
  11. GRB 260808B: SVOM detection of a faint burst
  12. GRB 260808A: BALROG localization (Fermi Trigger 807850307 / GRB 260808119)
  13. Fermi GRB 260808A: Global MASTER-Net observations report
  14. GRB 260808A: Fermi GBM Final Real-time Localization
  15. GRB 260807A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  16. GRB 260807A: SVOM possible detection of a faint burst
  17. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  18. GRB 260715A: cubesat Avion detection
  19. GRB 260709A: cubesat Avion detection
  20. GRB 260708A: cubesat Avion detection
  21. SN 2026stf / GRB 260708A: ATLAS forced photometry
  22. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  23. GRB 260730B: Glowbug gamma-ray detection
  24. GRB 260805C: Glowbug gamma-ray detection
  25. GRB 260805B: Glowbug gamma-ray detection
  26. Fermi GRB 260805A: Global MASTER-Net observations report
  27. GRB 260805B: Fermi GBM Final Localization
  28. GRB 260804A: Glowbug gamma-ray detection
  29. GRB 260805B: BALROG localization (Fermi Trigger 807622617 / GRB 260805484)
  30. GRB 260805A: Fermi GBM Final Localization
  31. GRB 260730B: CALET Gamma-Ray Burst Monitor detection
  32. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  33. GRB 260804A: Fermi GBM Final Real-time Localization
  34. GRB 260708A: LCO further optical observations show supernova features
  35. GRB 260803A: Fermi GBM Final Real-time Localization
  36. Fermi GRB 260802B: Global MASTER-Net observations report
  37. GRB 260802A / EP J223759.5+521421: EP-FXT follow-up observation
  38. GRB 260802A / EP J223759.5+531421: SVOM/VT optical upper limit
  39. GRB 260802A: SVOM/VT optical upper limits from VHF data
  40. GRB 260802A: LCO optical upper limits
  41. GRB 260802B: Fermi GBM Final Localization
  42. GRB 260802A / EP J223759.5+531421: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  43. GRB 260802A/EP J223759.5+531421: SVOM detection of a possible magnetar burst
  44. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  45. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  46. GRB 260731A: AstroSat CZTI detection of a long burst
  47. Fermi-LAT Gamma-ray Observations of IceCube-260722A
  48. GRB 260730B: AstroSat CZTI detection
  49. GRB 260730B: NuSTAR detection of prompt emission
  50. GRB 260727A: SVOM/ECLAIRs refined analysis
  51. GRB 260726A: SVOM/ECLAIRs refined analysis
  52. GRB260730A: Fermi GBM Final Localization
  53. EP260727a: SAO RAS optical observations
  54. GRB 260727A: AbAO and SAO RAS optical observations
  55. GRB 260726A: EP-FXT follow-up observations
  56. GRB 260727A: SVOM/GRM observation
  57. GRB 260726A: Fermi GBM Observation
  58. Konus-Wind detection of GRB 260727A
  59. GRB 260726A: Liverpool Telescope optical observations
  60. GRB 260727A: Liverpool Telescope optical upper limits
  61. GRB 260728A: Fermi GBM Final Localization
  62. GRB 260727A: EP/FXT follow-up observations
  63. GRB 260727A: Glowbug gamma-ray detection
  64. GRB 260726A: J-band upper limit with WINTER
  65. GRB 260727A: J-band upper limit with WINTER
  66. GRB 260726A: SVOM/VT optical candidate
  67. GRB 260726A: SVOM ECLAIRs improved position and MXT possible detection of a counterpart
  68. GRB 260727A / SVOM sb26072702: RAPAS optical non-detection
  69. GRB 260727A: GOTO early optical upper limit
  70. GRB 260727A: AstroSat CZTI detection
  71. GRB 260727A: Kilonova-Catcher optical upper limit
  72. GRB 260727A: LCO optical upper limits
  73. GRB 260727B: Fermi GBM Final Real-time Localization
  74. Fermi GRB 260726A: Global MASTER-Net observations report
  75. GRB 260727A: SVOM detection of a bright long burst
  76. GRB 260726A: SVOM detection of a burst
  77. GRB 260726A: Fermi GBM Final Real-time Localization
  78. GRB 260616A: cubesat Avion detection
  79. GRB 260602B: cubesat Avion detection
  80. GRB 260601A: cubesat Avion detection
  81. IPN triangulation of GRB 260706B
  82. GRB 260718A: SVOM/ECLAIRs refined analysis
  83. Fermi Gamma-ray Burst Monitor trigger 806592752 / 260724564 is not a GRB
  84. GRB 260723A: Fermi GBM Final Localization
  85. Konus-Wind detection of GRB 260721A
  86. GRB 260722A: Fermi GBM Final Real-time Localization
  87. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  88. Fermi GBM trigger 806384210/260722151 is not a GRB
  89. GRB 260721A: NuSTAR detection of prompt emission
  90. Konus-Wind detection of GRB 260714B
  91. GRB 260705A: Retraction of optical counterpart
  92. GRB 260714B: Insight-HXMT/HE detection
  93. GRB 260718A: EP-FXT follow-up observation
  94. Fermi trigger No 806104130: Global MASTER-Net observations report
  95. Fermi GRB 260718A: Global MASTER-Net observations report
  96. GRB 260718A: LCO optical upper limits
  97. GRB 260711A: SVOM/GRM observation
  98. GRB 260710A: SVOM/GRM observation
  99. GRB 260718A: Fermi GBM Observation
  100. GRB 260718A : GRANDMA and KNC upper limits

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