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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"

19089 results found.

  1. EP 251220a: GOTO optical counterpart detection
  2. GRB 251221A: COLIBRÍ detection of the optical counterpart
  3. EP 251220a: COLIBRÍ detection of the optical counterpart
  4. GRB 251221A: Swift detection of a burst
  5. EP251220a: EP detection of a fast X-ray transient
  6. GRB 251219A: SVOM/GRM observation of a short burst
  7. GRB 251215A: Swift-XRT afterglow detection
  8. IceCube-251218A: COLIBRÍ optical upper limits
  9. GRB 251214B: VIRT Optical Upper Limit
  10. GRB 251215A: Swift/UVOT Upper LImits
  11. GRB 251202A/EP251202a: Koshka optical upper limit
  12. GRB 251214B: Mondy optical upper limit
  13. GRB 251215A: COLIBRÍ optical upper limit
  14. EP251214b: KAIT optical upper limit
  15. GRB 251215A: Swift-XRT observations
  16. EP251214a: Optical upper limit with Kinder observations
  17. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  18. GRB 251214B: UAFO optical upper limit
  19. GRB 251214B: VLT/X-shooter observations
  20. GRB 251202A: radio detection with the VLA
  21. EP251214b : Einstein Probe detection of a fast X-ray transient
  22. EP251214b : Einstein Probe detection of a fast X-ray transient
  23. GRB 251214B: AbAO optical observations
  24. GRB 251214B: LCO detection of the optical counterpart
  25. GRB 251215A: Swift ToO observations
  26. EP251214b (EP trigger 01709250023): LCO optical limits
  27. GRB 251203B: AbAO optical observations
  28. GRB 251214B: Swift-XRT refined Analysis
  29. GRB 251213A: SVOM/GRM observation
  30. EP251214a: KAIT optical upper limit
  31. GRB 251214D: AstroSat CZTI detection of a long burst
  32. GRB 251214B: Swift/UVOT Detection
  33. GRB 251214B: COLIBRÍ observations of the afterglow
  34. EP251214a: EP-FXT non-detection and upper limit
  35. GRB 251214B: 1.3m DFOT optical detection
  36. GRB 251214B: Enhanced Swift-XRT position
  37. GRB 251214B: Xinglong-2.16m optical observation
  38. GRB 251214B : MASTER optical afterglow detection
  39. GRB 251214B: SVOM/C-GFT optical observations
  40. EP251214a: COLIBRÍ optical upper limit
  41. EP251214.305: COLIBRÍ optical upper limit
  42. GRB 251214B: Swift detection of a burst with an optical counterpart
  43. EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A
  44. EP251212a: KAIT optical upper limit
  45. GRB 251211B: AstroSat CZTI detection
  46. EP251212a : COLIBRÍ optical upper limit
  47. EP251212a: Einstein Probe detection of an X-ray transient
  48. IceCube-251210A: DDOTI Optical Upper Limit
  49. GRB 251205A: 1.3m DFOT optical upper limit
  50. EP251124a: Mondy optical upper limit
  51. GRB 251129A/EP251129a: AbAO and Mondy optical observations
  52. EP251130a: Mondy and AbAO optical observations
  53. Fermi GBM Sub-Threshold Detection of GRB 251205A
  54. GRB 251208B: COLIBRÍ optical upper limits
  55. EP251118a / GRB 251118C: VLT/MUSE redshift confirmation
  56. GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  57. GRB 251208B: Swift-XRT afterglow detection
  58. GRB 251208D: LAST optical upper limit
  59. GRB 251208D: LCO analysis of the XRT sources
  60. GRB 251208B: GROWTH-India Telescope optical upper limits
  61. GRB 251205A: J-band detection with WINTER
  62. GRB 251208A: SVOM/GRM observation of a short burst
  63. GRB 251208C: SVOM/GRM observation of a short burst
  64. GRB 251205A: Liverpool Telescope further optical follow-up observations
  65. GRB 251208D: LCO optical upper limits
  66. GRB 251208B: Swift ToO observations
  67. GRB 251208D: SVOM possible detection of a faint burst
  68. GRB 251208C: Fermi GBM Final Real-time Localization
  69. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  70. GRB 251208B: Fermi GBM Final Real-time Localization
  71. GRB 251208A: Fermi GBM Final Real-time Localization
  72. GRB 251205A: Liverpool Telescope further optical follow-up observations
  73. GRB 251205A: GROWTH-India Telescope optical observations
  74. GRB 251205A: Swift/UVOT Detection
  75. GRB 251205A: Liverpool Telescope optical follow-up observations
  76. GRB 251203C: Swift/UVOT Upper Limit
  77. GRB 251205A: COLIBRÍ optical observations
  78. GRB 251205A: NOT optical observations
  79. GRB 251205A: Enhanced Swift-XRT position
  80. Swift GRB 251205A : MASTER OT detection with host galaxy
  81. GRB 251205A: Swift detection of a burst with an optical afterglow
  82. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  83. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  84. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  85. GRB 251202A: SVOM/GRM observation
  86. GRB 251203A: SVOM/GRM observation
  87. GRB 251203C: J-band observations with WINTER
  88. GRB 251203A: AstroSat CZTI detection
  89. GRB 251203C: SVOM/VT optical counterpart
  90. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  91. GRB 251203C: LCO optical upper limits
  92. GRB 251203B: LCO optical upper limits
  93. GRB 251203B: SVOM/VT optical observation
  94. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  95. GRB 251203C: SVOM detection of a burst
  96. GRB 251203B: SVOM detection of a burst
  97. GRB 251201B: Insight-HXMT/HE detection
  98. EP251130a: MAO/AZT-22 optical observations
  99. EP251202a/GRB 251202A: KAIT optical observations
  100. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory

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