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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"

36029 results found.

  1. Swift GRB 251230A: Global MASTER-Net observations report
  2. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  3. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  4. GRB 251226A: Glowbug gamma-ray detection
  5. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  6. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  7. Fermi GRB 251228A: Global MASTER-Net observations report
  8. GRB 251228A: Fermi GBM Final Real-time Localization
  9. GRB 251226A: SVOM/GRM observation
  10. GRB 251226A: GECAM-B detection
  11. Fermi Gamma-ray Burst Monitor trigger 788368008/251225630 is not a GRB
  12. GRB 251222A: NUTTelA-TAO Early Measurements
  13. GRB 251222A/EP251222b: Optical detection with Kinder observations
  14. GRB 251221A: Swift-BAT refined analysis
  15. GRB 251222A/EP251222b: FTW optical and NIR observations
  16. GRB 251205A: Kilonova-Catcher optical afterglow detection
  17. GRB 251222A: AbAO optical observations
  18. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  19. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  20. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  21. GRB 251222A: ZTSH BVRI optical observations
  22. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  23. GRB 251222A: Continued 1.3m DFOT optical observation
  24. GRB 251222A: Fermi GBM Observation
  25. EP251220a: CrAO ZTSh optical observations
  26. GRB 251222A / EP251222b: GECAM-B observation
  27. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  28. Konus-Wind detection of GRB 251222A / EP251222b
  29. GRB 251222A: Swift-XRT afterglow detection
  30. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  31. GRB 251222A / EP251222b: GOTO optical counterpart detection
  32. GRB 251222A / EP251222b: LCO optical observations
  33. GRB 251222A: 1.3m DFOT optical detection
  34. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  35. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  36. EP251222b/GRB 251222A: SVOM/GRM observation
  37. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  38. GRB 251222A: PRIME near-infrared detection
  39. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  40. GRB 251222A: NOT optical observations
  41. IPN triangulation of GRB 251220B (short)
  42. GRB 251222A: Swift ToO observations
  43. GRB 251222A: BALROG localization (Fermi Trigger / GRB 251222712)
  44. GRB 251222A: SVOM/VT optical candidate
  45. GRB 251222A: SVOM detection of a long burst
  46. GRB 251222A: Fermi GBM Final Real-time Localization
  47. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  48. GRB 251221A: PRIME near-infrared observation
  49. GRB 251221A: UAFO and Mondy optical upper limit
  50. GRB 251221A: Swift-XRT refined Analysis
  51. GRB 251221A: Swift/UVOT Upper Limits
  52. Fermi Gamma-ray Burst Monitor trigger 788028118/251221696 is not a GRB
  53. GRB 251221A: Enhanced Swift-XRT position
  54. GRB 251221A: Fermi GBM Observation
  55. GRB 251221B: Fermi GBM Final Real-time Localization
  56. GRB 251220B: SVOM/GRM observation of a short burst
  57. GRB 251221A: COLIBRÍ detection of the optical counterpart
  58. GRB 251221A: Swift detection of a burst
  59. GRB 251221A: Fermi GBM Final Real-time Localization
  60. GRB 251220B: Fermi GBM Final Real-time Localization
  61. GRB 251219A: SVOM/GRM observation of a short burst
  62. GRB 251219A: GECAM-B detection of a possible magnetar X-ray burst from SGR 1830-0645
  63. GRB 251220A: MAXI/GSC detection
  64. GRB 251215A: Swift-XRT afterglow detection
  65. GRB 251214B: VIRT Optical Upper Limit
  66. Fermi GRB 251217A: Global MASTER-Net observations report
  67. GRB 251217A: Fermi GBM Final Real-time Localization
  68. GRB 251215A: Swift/UVOT Upper LImits
  69. GRB 251215A: Fermi GBM Observation
  70. Fermi GRB 251216A: Global MASTER-Net observations report
  71. GRB 251202A/EP251202a: Koshka optical upper limit
  72. GRB 251214B: Mondy optical upper limit
  73. GRB 251215A: COLIBRÍ optical upper limit
  74. GRB 251216A: Fermi GBM Final Real-time Localization
  75. EP251214b: KAIT optical upper limit
  76. GRB 251215A: Swift-XRT observations
  77. Fermi GRB 251215A: Global MASTER-Net observations report
  78. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  79. GRB 251215A: Glowbug gamma-ray detection
  80. GRB 251214B: UAFO optical upper limit
  81. GRB 251214B: VLT/X-shooter observations
  82. GRB 251213A: GRID-10B observation
  83. GRB 251214B: Swift-BAT refined analysis
  84. GRB 251202A: radio detection with the VLA
  85. GRB 251214B: AbAO optical observations
  86. GRB 251214B: LCO detection of the optical counterpart
  87. GRB 251209A: GECAM-B observation of a long burst
  88. GRB 251214D: GECAM-B observation of a long burst
  89. GRB 251214B: Fermi GBM Observation
  90. GRB 251209A: Insight-HXMT/HE detection
  91. GRB 251215A: Swift ToO observations
  92. GRID detection of GRB 251213A
  93. GRB 251203B: AbAO optical observations
  94. GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst
  95. GRB 251214B: GECAM-B observation of a long burst
  96. GRB 251214B: Swift-XRT refined Analysis
  97. GRB 251213A: SVOM/GRM observation
  98. EP251214a: KAIT optical upper limit
  99. GRB 251214D: AstroSat CZTI detection of a long burst
  100. GRB 251213A: AstroSat CZTI detection

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