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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"

32489 results found.

  1. GRB 260208A: Mondy optical observations (duplicate submission)
  2. GRB 260208A: Mondy optical observations
  3. GRB 260208A: 1.3m DFOT optical detection
  4. GRB 260208A: COLIBRÍ optical observations
  5. GRB 260208B: EP-FXT observation
  6. GRB 260208A: NOT spectroscopic redshift z = 2.36
  7. GRB 260208A: Liverpool Telescope optical detection
  8. Fermi GRB 260208C: Global MASTER-Net observations report
  9. GRB 260208B: SVOM/VT optical candidate
  10. GRB 260208A: GECAM-B observation of a bright burst
  11. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  12. GRB 260208A: SVOM/VT optical observation
  13. Fermi GRB 260208D: Global MASTER-Net observations report
  14. GRB 260208A: Swift-XRT observations
  15. GRB 260208B: Swift ToO observations
  16. GRB 260208B: SVOM/GRM observation of a bright burst
  17. GRB 260208B: Fermi GBM Detection
  18. GRB 260208B: Fermi-LAT detection
  19. GRB 260208A: Fermi-LAT detection
  20. GRB 260207B: GECAM-B observation
  21. GRB 260208A: Swift ToO observations
  22. GRB 260208A: Fermi GBM Classification Correction
  23. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  24. GRB 260208A : MASTER bright optical transient inside retracted Fermi error-box
  25. Fermi GRB 260208A: Global MASTER-Net observations report
  26. GRB 260207A : MASTER optical counterpart discovery
  27. GRB 260131A/B: Mondy and Terskol optical observations
  28. Fermi GRB 260207B: Global MASTER-Net observations report
  29. GRB 260206A: Swift-XRT observations
  30. EP260131a: VLA detection
  31. GRB 260206A: Tiled Swift observations
  32. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  33. GRB 260204A: Swift-XRT observations
  34. GRB 260204A: LCO optical afterglow detection
  35. GRB 260204A: SVOM/VT optical candidate
  36. GRB 260204A : MASTER Global robotic net optical observations
  37. Fermi GBM Sub-Threshold Detection of GRB 260204A
  38. GRB 260204A: GOTO optical upper limit
  39. GRB 260204A: LCO optical upper limits
  40. EP260110a: Late GTC/EMIR near-infrared observations
  41. GRB 260121A: 239Alferov CubeSat detection
  42. Konus-Wind detection of GRB 260121A
  43. GRB 260131A/B: OHP/T193 optical observations
  44. GRB 260131A: KAIT optical observations
  45. GRB 251230A: MeerLICHT afterglow detection
  46. GRB 260131A: FTW optical and NIR observations
  47. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  48. GRID detection of GRB 260131A/B
  49. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  50. GRB 260130A: Insight-HXMT/HE detection
  51. GRB 260130A: GECAM-B observation of a short burst
  52. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  53. GRB 260131A/B: EP/FXT X-ray afterglow detection
  54. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  55. GRB 260127B: Insight-HXMT/HE detection
  56. GRB 260127B: GECAM-B observation of a short burst
  57. GRB 260127A: GECAM-B observation
  58. GRB 260131A: NOT spectroscopic redshift z = 1.434
  59. EP260131a: Liverpool Telescope optical upper limits
  60. EP260131a: COLIBRÍ further observations
  61. Konus-Wind detection of GRB 260128A / EP260128a
  62. GRB 260131A: Insight-HXMT/HE detection
  63. Konus-Wind detection of GRB 260131A/B
  64. EP260131a: SVOM/VT optical observation
  65. EP260131a: Xinglong optical upper limit
  66. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  67. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  68. GRB 260131A/B: Fermi GBM Observation
  69. EP260131a: COLIBRÍ observations of slow optical fading
  70. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  71. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  72. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  73. EP260131a: COLIBRÍ optical observations of the counterpart
  74. GRB 260127B: AstroSat CZTI detection
  75. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  76. Fermi GRB 260130A: Global MASTER-Net observations report
  77. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  78. Fermi GRB 260129A: Global MASTER-Net observations report
  79. GRB 260128B: LCO optical upper limits
  80. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  81. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  82. IPN triangulation of GRB 260121A
  83. GRB 260127A: Swift-BAT refined analysis
  84. IPN triangulation of GRB 260127B (short)
  85. GRB 260127B: Swift-XRT observations
  86. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  87. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  88. EP260128a: NOT optical counterpart candidate
  89. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  90. EP260128a: Liverpool Telescope optical observations and possible counterpart
  91. EP260128a: LCO optical upper limits
  92. EP260126a: SVOM/VT optical upperlimit
  93. EP260128a: Global MASTER-Net observations report
  94. Fermi GRB 260127A: Global MASTER-Net observations report
  95. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  96. GRB 260127A: Fermi GBM Observation
  97. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  98. GRB 260127A: COLIBRÍ optical observations
  99. GRB 260127A: NOT optical observations
  100. GRB 260127B: Swift ToO observations

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