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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"

1589 results found.

  1. GRB 251002A: AKO Early Optical Afterglow Detection
  2. GRB 251002A: Swift-XRT afterglow detection
  3. GRB 251002A: Kilonova-Catcher optical afterglow detection
  4. GRB 251002A: AbAO optical observations
  5. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  6. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  7. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  8. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  9. GRB 251002A: EP-FXT counterpart detection
  10. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  11. GRB 251002A: BOOTES-6 early optical detection
  12. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  13. GRB 251002A: LCO optical observation
  14. GRB 251002A: SVOM/VT optical observation
  15. GRB 251002A: SVOM detection of a burst
  16. GRB 251001A: SVOM/GRM observation
  17. GRB 251001B: SVOM/VT optical observation
  18. GRB 250930A: SVOM/GRM observation
  19. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  20. GRB 250916A: SVOM/VT optical observation
  21. GRB 250924A: SVOM/GRM observation
  22. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  23. GRB 250925A: SVOM/GWAC-F60A upper limit
  24. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  25. GRB 250922A: SVOM/GRM observation
  26. GRB 250924A: SVOM/VT optical observation
  27. GRB 250920C: Kilonova-Catcher optical afterglow detection
  28. GRB 250922B: SVOM/GRM observation
  29. GRB 250919A / EP250919a: further LCO optical observation
  30. Konus-Wind detection of GRB 250920C
  31. GRB 250920C: KAIT optical observations
  32. GRB 250920C: COLIBRÍ optical observations
  33. GRB 250920C: NIR observations with WINTER
  34. Konus-Wind detection of GRB 250920A
  35. IPN triangulation of GRB 250920A (long/bright)
  36. GRB 250920C: SVOM/GRM observation
  37. GRB 250920A: NuSTAR detection of bright prompt emission
  38. GRB 250920B: Fermi GBM Observation
  39. GRB 250920A: Fermi GBM Detection
  40. GRB 250920A: SVOM/GRM observation
  41. GRB 250920B: SVOM/C-GFT optical observations
  42. GRB 250919A / EP250919a: LCO optical observation
  43. Konus-Wind detection of GRB 250919A
  44. GRB 250919A / EP250919a: Insight-HXMT detection
  45. GRB 250919A/EP250919a: SVOM/VT optical observation
  46. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  47. GRB 250919A: Glowbug gamma-ray detection
  48. GRB 250919A: Fermi GBM Observation
  49. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  50. GRB 250918A: SVOM/GRM observation
  51. GRB 250919A: Fermi-LAT detection
  52. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  53. GRB 250919A: SVOM/GRM observation of a very bright GRB
  54. GRB 250912A: SVOM/ECLAIRs refined analysis
  55. GRB 250910A: SVOM/ECLAIRs refined analysis
  56. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  57. SVOM/sb25091517: FRAM-ORM stellar flare - transient observation
  58. SVOM/sb25091517: SVOM detection of an X-ray transient
  59. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  60. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  61. GRB 250912A: Swift-XRT observations
  62. GRB250912A: VLT/HAWK-I follow-up observations
  63. GRB 250912A: VLT observations
  64. GRB 250912A: Fermi GBM Observation
  65. GRB 250912A: SVOM/GRM analysis suggests a possible short GRB with extended emission
  66. GRB 250912A:SVOM/VT optical upper limit
  67. GRB 250912A: LCO optical upper limit
  68. GRB 250912A: SVOM detection of a burst
  69. GRB 250910B: SVOM/GRM observation
  70. EP250911a: SVOM/VT optical observation
  71. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  72. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  73. GRB 250909B: Insight-HXMT detection
  74. GRB 250909B: SVOM/GRM observation
  75. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  76. GRB 250903A: SVOM/ECLAIRs refined analysis
  77. GRB 250910A: SVOM/VT optical upper limit
  78. GRB 250910A: LCO optical upper limit
  79. GRB 250910A: SVOM/MXT possible afterglow detection
  80. GRB 250910A: SVOM detection of a faint burst
  81. EP250908c: SVOM/VT optical observation
  82. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  83. EP250908b: SVOM/VT optical candidate
  84. GRB 250903A: Swift-XRT afterglow detection
  85. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  86. GRB 250901A - SVOM/ECLAIRs refined analysis
  87. GRB 250903A: Swift/UVOT detection
  88. GRB 250902B: CALET Gamma-Ray Burst Monitor detection
  89. GRB 250902A: CALET Gamma-Ray Burst Monitor detection
  90. GRB 250902A: VZLUSAT-2 detection
  91. GRB 250903A: Swift-XRT observations
  92. EP250903a: Swift-XRT observations
  93. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  94. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  95. GRB 250903A: EP-FXT counterpart detection
  96. GRB 250902A: GECAM-B detection
  97. GRB 250903A: LCO optical observation
  98. GRB 250903A: LCO optical afterglow detection
  99. GRB 250903A: SVOM/VT optical confirmation with VHF data
  100. EP250903a: SVOM/VT optical confirmation

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