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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"

24279 results found.

  1. EP260210a: refined analysis of the EP-FXT observation
  2. EP260209a: Global MASTER-Net observations report
  3. EP260210a: Optical upper limits with Kinder observations
  4. IPN triangulation of GRB 260207B (short/hard with EE)
  5. GRB 260210C: Fermi GBM Final Real-time Localization
  6. GRB 260210B: Fermi GBM Final Real-time Localization
  7. EP260210a: SVOM/VT optical upper limit
  8. EP260210a: SVOM/C-GFT upper limit
  9. GRB 260208C: SVOM/GRM observation
  10. GRB260208A: Liverpool Telescope optical follow-up observations
  11. GRB 260208A: NuSTAR detection of prompt emission
  12. GRB 260208A: Fermi GBM Observation
  13. Fermi GRB 260209A: Global MASTER-Net observations report
  14. GRB 260208A: 1.3m DFOT optical detection
  15. Fermi GRB 260208C: Global MASTER-Net observations report
  16. GRB 260208B: SVOM/VT optical candidate
  17. GRB 260208A: GECAM-B observation of a bright burst
  18. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  19. GRB 260209A: Fermi GBM Final Real-time Localization
  20. GRB 260208A: SVOM/VT optical observation
  21. Fermi GRB 260208D: Global MASTER-Net observations report
  22. GRB 260208D: Fermi GBM Final Real-time Localization
  23. GRB 260208B: SVOM/GRM observation of a bright burst
  24. GRB 260208B: Fermi GBM Detection
  25. LAT GRB 260208B: Global MASTER-Net observations report
  26. GRB 260208B: Fermi-LAT detection
  27. GRB 260208C: Fermi GBM Final Real-time Localization
  28. GRB 260208A: Fermi-LAT detection
  29. GRB 260207B: GECAM-B observation
  30. GRB 260208A: Fermi GBM Classification Correction
  31. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  32. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  33. GRB 260208B: Fermi GBM Final Real-time Localization
  34. Fermi GRB 260208A: Global MASTER-Net observations report
  35. GRB 260208A: Fermi GBM Final Real-time Localization
  36. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  37. GRB 260207A : MASTER optical counterpart discovery
  38. Fermi GRB 260207B: Global MASTER-Net observations report
  39. GRB 260206A: Swift-XRT observations
  40. GRB 260207B: Fermi GBM Final Real-time Localization
  41. GRB 260207A: Fermi GBM Final Localization
  42. Fermi trigger No 792135758: Global MASTER-Net observations report
  43. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  44. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  45. GRB 260204A: LCO optical afterglow detection
  46. GRB 260204A: SVOM/VT optical candidate
  47. GRB 260204A : MASTER Global robotic net optical observations
  48. Fermi GBM Sub-Threshold Detection of GRB 260204A
  49. GRB 260204A: GOTO optical upper limit
  50. GRB 260204A: LCO optical upper limits
  51. EP260110a: Late GTC/EMIR near-infrared observations
  52. GRB 260204B: Fermi GBM Final Real-time Localization
  53. GRB 260204A: SVOM detection of a burst
  54. Konus-Wind detection of GRB 260121A
  55. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  56. GRB 260130A: GECAM-B observation of a short burst
  57. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  58. Konus-Wind detection of GRB 260128A / EP260128a
  59. Konus-Wind detection of GRB 260131A/B
  60. EP260131a: SVOM/VT optical observation
  61. EP260131a: Xinglong optical upper limit
  62. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  63. GRB 260131A/B: Fermi GBM Observation
  64. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  65. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  66. GRB 260131A: Fermi GBM Final Real-time Localization
  67. GRB 260130A: Fermi GBM Detection
  68. GRB 260127B: Fermi GBM Detection
  69. Fermi GRB 260130A: Global MASTER-Net observations report
  70. GRB 260130A: Fermi GBM Final Real-time Localization
  71. Fermi GRB 260129A: Global MASTER-Net observations report
  72. GRB 260128B: LCO optical upper limits
  73. IPN triangulation of GRB 260121A
  74. GRB 260127A: Swift-BAT refined analysis
  75. GRB 260129B: Fermi GBM Final Localization
  76. GRB 260128B: SVOM detection of a burst through offline search
  77. GRB 260129A: Fermi GBM Final Localization
  78. IPN triangulation of GRB 260127B (short)
  79. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  80. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  81. EP260126a: SVOM/VT optical upperlimit
  82. EP260128a: Global MASTER-Net observations report
  83. Fermi GRB 260127A: Global MASTER-Net observations report
  84. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  85. GRB 260127A: Fermi GBM Observation
  86. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  87. GRB 260127A: NOT optical observations
  88. EP260126a: Seimei/TriCCS optical upper limit
  89. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  90. GRB 260127A: Swift-XRT refined Analysis
  91. GRB 260127B: GOTO candidate optical counterpart
  92. GRB 260127A: SVOM/C-GFT optical observations
  93. The EP-WXT trigger 01709253145 is likely a flaring star
  94. Fermi GRB 260127B: Global MASTER-Net observations report
  95. GRB 260127B: Fermi GBM Final Real-time Localization
  96. Swift GRB 260127A: Global MASTER-Net observations report
  97. GRB 260127A: LCO optical afterglow discovery
  98. GRB 260127A: Fermi GBM Final Real-time Localization
  99. EP260126a: EP-FXT follow-up observation
  100. EP260126a: Optical upper limit with Kinder observations

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