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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"

35946 results found.

  1. Fermi Gamma-ray Burst Monitor trigger 776705265/250812644 is not a GRB
  2. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  3. GRB 250812A: SVOM/VT optical afterglow confirmation
  4. GRB 250812A: Swift-XRT afterglow detection
  5. GRB 250812A: TRT likely optical counterpart detection
  6. GRB 250812A: SVOM detection of a faint long burst
  7. GRB 250809A: Swift-BAT refined analysis
  8. Fermi Gamma-ray Burst Monitor trigger 776620220/250811660 is not a GRB
  9. GRB 250807A: Swift-BAT refined analysis
  10. GRB 250809A: Swift/UVOT Detection
  11. Corrected Swift-XRT Refined Analysis of GRB 250809A
  12. GRB 250809A: Swift-XRT refined Analysis
  13. GRB 250807B: SVOM/VT optical observation
  14. GRB 250809A: LCOGT Optical Upper Limits
  15. GRB 250702B: Chandra X-ray Detection
  16. Fermi GRB 250808A: Global MASTER-Net observations report
  17. Fermi Gamma-ray Burst Monitor trigger 776449964/250809689 is not a GRB
  18. GRB 250808A: VLT X-shooter candidate counterpart
  19. GRB 250809A: Prompt enhanced Swift-XRT position
  20. GRB 250809A: Swift detection of a gamma ray burst
  21. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  22. GRB 250808A: Fermi GBM Observation
  23. GRB 250808A: Swift-XRT candidate counterpart detection
  24. GRB 250807A: SVOM/VT optical continued observation
  25. EP-WXT trigger 01709195487: KAIT confirmation of the stellar flare
  26. GRB 250808A: SVOM detection of a long burst
  27. GRB 250808A: Fermi GBM Final Real-time Localization
  28. Konus-Wind detection of GRB 250807A
  29. GRB 250807B: Swift/UVOT Detection
  30. GRB 250807B: Kilonova-Catcher optical afterglow detection
  31. GRB 250807A: Swift/UVOT Detection
  32. GRB 250807A: Swift-XRT refined Analysis
  33. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  34. GRB 250806A: SVOM/MXT refined analysis
  35. GRB 250806A: SVOM/ECLAIRs refined analysis
  36. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  37. GRB 250804B: Insight-HXMT detection
  38. GRB 250807A: SVOM/GRM observation
  39. GRB 250807A: AstroSat CZTI detection of bright long burst
  40. GRB 250807B: Swift-XRT refined Analysis
  41. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  42. GRB 250807B: NTT optical observations
  43. GRB 250807A: SVOM/VT optical observation
  44. EP250806a: Upper limit from Fermi-GBM Observations
  45. GRB 250807B: Enhanced Swift-XRT position
  46. GRB 250807A: Enhanced Swift-XRT position
  47. GRB 250807B: Swift detection of a burst with an optical counterpart.
  48. GRB 250805A: Kilonova-Catcher optical upper limits
  49. GRB 250805A: Swift/UVOT Upper Limits
  50. GRB 250806A: Swift/UVOT U-band detection
  51. GRB 250807A: Swift detection of a burst with an optical counterpart
  52. GRB 250806A: EP-FXT observation
  53. GRB 250806A: J-band upper limit from WINTER
  54. GRB 250805A: Swift-BAT refined analysis
  55. GRB 250806A: KAIT optical upper limit
  56. GRB 250806A: SVOM/VT refined analysis
  57. GRB 250806A: Swift-XRT counterpart detection
  58. GRB 250806A: Kilonova-Catcher optical upper limits
  59. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  60. GRB 250806A: SVOM/VT optical upper limit
  61. GRB 250806A: SVOM detection of a soft burst
  62. GRB 250805A: SVOM/VT optical counterpart
  63. GRB 250805A: ESO/VLT observations
  64. GRB 250805A: Swift-XRT refined Analysis
  65. GRB 250804B: Swift-XRT observations
  66. GRB 250805A: Enhanced Swift-XRT position
  67. GRB 250804C: AstroSat CZTI detection of a long burst
  68. GRB 250805A: TRT optical upper limits
  69. GRB 250805A: Swift-XRT observations
  70. GRB 250805A: Swift detection of a burst
  71. GRB 250804B: Tiled Swift observations
  72. GRB 250804B: SVOM/GRM observation of a short burst
  73. GRB 250804A: Fermi GBM Final Localization
  74. Fermi Gamma-ray Burst Monitor trigger 775945985/250803856 is not a GRB
  75. GRB 250702B: SMA observations
  76. EP250711a: CrAO and Assy optical observations
  77. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  78. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  79. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  80. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  81. GRB 250725A: AstroSat CZTI detection
  82. GRB 250727A: EP-FXT follow-up observation
  83. GRB 250725A: PRIME near-infrared observations
  84. GRB: Clarification on Gamma-Ray Burst Naming Convention
  85. GRB 250728A: Swift-XRT observations
  86. GRB 250727A: SVOM/ECLAIRs refined analysis
  87. GRB 250728A: COLIBRÍ optical upper limit
  88. GRB 250728A: Fermi GBM Observation
  89. GRB 250728A: Swift ToO observations
  90. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  91. GRB 250727A: AST3-2 Upper limit
  92. GRB 250727A: EP-FXT counterpart detection
  93. GRB250727A: SVOM/VT optical upper limit
  94. GRB 250727A: Swift-XRT observations
  95. GRB 250727A: SVOM detection of a burst
  96. GRB 250725A: Swift-XRT refined Analysis
  97. GRB 250725A: Fermi GBM Observation
  98. GRB 250725A: Swift-BAT refined analysis
  99. Konus-Wind detection of GRB 250725A
  100. GRB 250725A: SVOM/GRM observation

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