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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"

36156 results found.

  1. GRB 250807A: Swift-XRT refined Analysis
  2. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  3. GRB 250806A: SVOM/MXT refined analysis
  4. GRB 250806A: SVOM/ECLAIRs refined analysis
  5. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  6. GRB 250804B: Insight-HXMT detection
  7. GRB 250807A: SVOM/GRM observation
  8. GRB 250807A: AstroSat CZTI detection of bright long burst
  9. GRB 250807B: Swift-XRT refined Analysis
  10. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  11. GRB 250807B: NTT optical observations
  12. GRB 250807A: SVOM/VT optical observation
  13. EP250806a: Upper limit from Fermi-GBM Observations
  14. GRB 250807B: Enhanced Swift-XRT position
  15. GRB 250807A: Enhanced Swift-XRT position
  16. GRB 250807B: Swift detection of a burst with an optical counterpart.
  17. GRB 250805A: Kilonova-Catcher optical upper limits
  18. GRB 250805A: Swift/UVOT Upper Limits
  19. GRB 250806A: Swift/UVOT U-band detection
  20. GRB 250807A: Swift detection of a burst with an optical counterpart
  21. GRB 250806A: EP-FXT observation
  22. GRB 250806A: J-band upper limit from WINTER
  23. GRB 250805A: Swift-BAT refined analysis
  24. GRB 250806A: KAIT optical upper limit
  25. GRB 250806A: SVOM/VT refined analysis
  26. GRB 250806A: Swift-XRT counterpart detection
  27. GRB 250806A: Kilonova-Catcher optical upper limits
  28. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  29. GRB 250806A: SVOM/VT optical upper limit
  30. GRB 250806A: SVOM detection of a soft burst
  31. GRB 250805A: SVOM/VT optical counterpart
  32. GRB 250805A: ESO/VLT observations
  33. GRB 250805A: Swift-XRT refined Analysis
  34. GRB 250804B: Swift-XRT observations
  35. GRB 250805A: Enhanced Swift-XRT position
  36. GRB 250804C: AstroSat CZTI detection of a long burst
  37. GRB 250805A: TRT optical upper limits
  38. GRB 250805A: Swift-XRT observations
  39. GRB 250805A: Swift detection of a burst
  40. GRB 250804B: Tiled Swift observations
  41. GRB 250804B: SVOM/GRM observation of a short burst
  42. GRB 250804A: Fermi GBM Final Localization
  43. Fermi Gamma-ray Burst Monitor trigger 775945985/250803856 is not a GRB
  44. GRB 250702B: SMA observations
  45. EP250711a: CrAO and Assy optical observations
  46. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  47. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  48. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  49. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  50. GRB 250725A: AstroSat CZTI detection
  51. GRB 250727A: EP-FXT follow-up observation
  52. GRB 250725A: PRIME near-infrared observations
  53. GRB: Clarification on Gamma-Ray Burst Naming Convention
  54. GRB 250728A: Swift-XRT observations
  55. GRB 250727A: SVOM/ECLAIRs refined analysis
  56. GRB 250728A: COLIBRÍ optical upper limit
  57. GRB 250728A: Fermi GBM Observation
  58. GRB 250728A: Swift ToO observations
  59. GRB 250728A: Swift/BAT-GUANO arcminute localization of a short burst
  60. GRB 250727A: AST3-2 Upper limit
  61. GRB 250727A: EP-FXT counterpart detection
  62. GRB250727A: SVOM/VT optical upper limit
  63. GRB 250727A: Swift-XRT observations
  64. GRB 250727A: SVOM detection of a burst
  65. GRB 250725A: Swift-XRT refined Analysis
  66. GRB 250725A: Fermi GBM Observation
  67. GRB 250725A: Swift-BAT refined analysis
  68. Konus-Wind detection of GRB 250725A
  69. GRB 250725A: SVOM/GRM observation
  70. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  71. GRB 250725A: Swift/UVOT Upper Limits
  72. GRB 250725A: Fermi-LAT detection
  73. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  74. GRB 250725A: BOOTES-7 early optical detection
  75. GRB 250725A: SVOM/VT optical candidate
  76. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  77. GRB 250725A: Enhanced Swift-XRT position
  78. GRB 250725A: Swift detection of a burst
  79. Swift GRB 250725A: Global MASTER-Net OT detection
  80. GRB 250725A: Fermi GBM Final Real-time Localization
  81. Fermi GRB 250725A: Global MASTER-Net observations report
  82. Swift GRB 250725A: Global MASTER-Net observations report
  83. GRB 250723B: Fermi GBM Final Real-time Localization
  84. GRB 250721A: Fermi GBM Observation
  85. GRB 250723A: Fermi GBM Final Real-time Localization
  86. Swift-BAT trigger 1334535 is not a GRB
  87. GRB 250721A: Swift-XRT observations
  88. GRB 250722A: Fermi GBM Final Real-time Localization
  89. GRB 250713A : SVOM/ECLAIRs refined analysis
  90. GRB 250717B: SVOM/GRM observation
  91. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  92. GRB 250721A: Tiled Swift observations
  93. GRB 250721A: MAXI/GSC detection
  94. GRB 250721A: Fermi GBM Final Localization
  95. GRB 250720B: Fermi GBM Final Localization Correction
  96. GRB 250720A: Fermi GBM Final Localization
  97. LIGO/Virgo/KAGRA S250720j: Retraction of GW compact binary merger candidate
  98. Fermi Gamma-ray Burst Monitor trigger 774670514/250720094 is not a GRB
  99. GRB 250717B: COLIBRÍ optical upper limit
  100. LIGO/Virgo/KAGRA S250711q: Upper limits from Swift/BAT-GUANO

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