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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

38640 results found.

  1. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  2. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  3. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  4. GRB 260208B: Fermi GBM Final Real-time Localization
  5. Fermi Gamma-ray Burst Monitor trigger 792220053/260208214 is not a GRB
  6. GRB 260208A: Fermi GBM Final Real-time Localization
  7. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  8. GRB 260207A : MASTER optical counterpart discovery
  9. GRB 260131A/B: Mondy and Terskol optical observations
  10. GRB 260206A: Swift-XRT observations
  11. GRB 260207B: Fermi GBM Final Real-time Localization
  12. GRB 260207A: Fermi GBM Final Localization
  13. EP260131a: VLA detection
  14. GRB 260206A: Tiled Swift observations
  15. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  16. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  17. GRB 260204A: Swift-XRT observations
  18. GRB 260204A: LCO optical afterglow detection
  19. GRB 260204A: SVOM/VT optical candidate
  20. GRB 260204A : MASTER Global robotic net optical observations
  21. Fermi GBM Sub-Threshold Detection of GRB 260204A
  22. GRB 260204A: GOTO optical upper limit
  23. GRB 260204A: LCO optical upper limits
  24. EP260110a: Late GTC/EMIR near-infrared observations
  25. GRB 260204B: Fermi GBM Final Real-time Localization
  26. GRB 260204A: SVOM detection of a burst
  27. GRB 260121A: 239Alferov CubeSat detection
  28. Konus-Wind detection of GRB 260121A
  29. GRB 260131A/B: OHP/T193 optical observations
  30. GRB 260131A: KAIT optical observations
  31. GRB 251230A: MeerLICHT afterglow detection
  32. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  33. GRID detection of GRB 260131A/B
  34. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  35. GRB 260130A: Insight-HXMT/HE detection
  36. GRB 260130A: GECAM-B observation of a short burst
  37. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  38. GRB 260131A/B: EP/FXT X-ray afterglow detection
  39. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  40. GRB 260127B: Insight-HXMT/HE detection
  41. GRB 260127B: GECAM-B observation of a short burst
  42. GRB 260127A: GECAM-B observation
  43. GRB 260131A: NOT spectroscopic redshift z = 1.434
  44. EP260131a: Liverpool Telescope optical upper limits
  45. EP260131a: COLIBRÍ further observations
  46. Konus-Wind detection of GRB 260128A / EP260128a
  47. GRB 260131A: Insight-HXMT/HE detection
  48. Konus-Wind detection of GRB 260131A/B
  49. EP260131a: SVOM/VT optical observation
  50. EP260131a: Xinglong optical upper limit
  51. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  52. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  53. GRB 260131A/B: Fermi GBM Observation
  54. EP260131a: COLIBRÍ observations of slow optical fading
  55. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  56. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  57. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  58. GRB 260131B: MAXI/GSC detection
  59. GRB 260131A: Fermi GBM Final Real-time Localization
  60. EP260131a: COLIBRÍ optical observations of the counterpart
  61. GRB 260127B: AstroSat CZTI detection
  62. GRB 260130A: Fermi GBM Detection
  63. EP260131a: Einstein Probe detection of an X-ray transient
  64. GRB 260127B: Fermi GBM Detection
  65. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  66. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  67. GRB 260130A: Fermi GBM Final Real-time Localization
  68. GRB 260128B: LCO optical upper limits
  69. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  70. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  71. IPN triangulation of GRB 260121A
  72. GRB 260129B: Fermi GBM Final Localization
  73. GRB 260128B: SVOM detection of a burst through offline search
  74. GRB 260129A: Fermi GBM Final Localization
  75. IPN triangulation of GRB 260127B (short)
  76. GRB 260127B: Swift-XRT observations
  77. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  78. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  79. EP260128a: NOT optical counterpart candidate
  80. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  81. EP260128a: Liverpool Telescope optical observations and possible counterpart
  82. EP260128a: LCO optical upper limits
  83. EP260126a: SVOM/VT optical upperlimit
  84. EP260128a: Einstein Probe detection of an X-ray transient
  85. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  86. GRB 260127A: Fermi GBM Observation
  87. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  88. GRB 260127A: COLIBRÍ optical observations
  89. GRB 260127A: NOT optical observations
  90. GRB 260127B: Swift ToO observations
  91. EP260126a: Seimei/TriCCS optical upper limit
  92. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  93. GRB 260127A: Swift-XRT refined Analysis
  94. GRB 260127B: GOTO candidate optical counterpart
  95. GRB 260127A: SVOM/C-GFT optical observations
  96. The EP-WXT trigger 01709253145 is likely a flaring star
  97. GRB 260127A: Enhanced Swift-XRT position
  98. GRB 260127B: Fermi GBM Final Real-time Localization
  99. GRB 260127A: Prompt enhanced Swift-XRT position
  100. GRB 260127A: LCO optical afterglow discovery

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