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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').
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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"

16155 results found.

  1. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  2. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  3. EP251222a: VLT/FORS2 spectroscopic redshift z = 0.505
  4. GRB 251222A: ZTSH BVRI optical observations
  5. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  6. GRB 251222A: Continued 1.3m DFOT optical observation
  7. EP251220a: 3.6m DOT optical afterglow detection
  8. EP251220a: CrAO ZTSh optical observations
  9. EP251221a: Liverpool Telescope upper limits
  10. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  11. EP251222a: NTT/ULTRACAM optical observations
  12. EP251222a: GOTO optical upper limit
  13. GRB 251222A / EP251222b: GOTO optical counterpart detection
  14. GRB 251222A / EP251222b: LCO optical observations
  15. GRB 251222A: 1.3m DFOT optical detection
  16. GRB251221A: 7DT optical upper limits
  17. EP251222a: GSP Optical Counterpart Detection
  18. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  19. GRB 251222A / EP251222b: SVOM/VT optical rebrightening
  20. EP251222b/GRB 251222A: SVOM/GRM observation
  21. GRB 251222A: PRIME near-infrared detection
  22. EP251221a: NOT optical upper limit
  23. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  24. GRB 251222A: NOT optical observations
  25. GRB 251222A: SVOM/VT optical candidate
  26. EP251220a: PRIME upper limit
  27. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375
  28. EP251220a: NOT optical observations
  29. EP251220a: FTW optical and NIR observations
  30. GRB 251221A: UAFO and Mondy optical upper limit
  31. GRB 251221A: Swift/UVOT Upper Limits
  32. GRB 251220B: SVOM/GRM observation of a short burst
  33. EP 251220a: GOTO optical counterpart detection
  34. GRB 251221A: COLIBRÍ detection of the optical counterpart
  35. EP 251220a: COLIBRÍ detection of the optical counterpart
  36. GRB 251219A: SVOM/GRM observation of a short burst
  37. IceCube-251218A: COLIBRÍ optical upper limits
  38. GRB 251214B: VIRT Optical Upper Limit
  39. GRB 251215A: Swift/UVOT Upper LImits
  40. GRB 251202A/EP251202a: Koshka optical upper limit
  41. GRB 251214B: Mondy optical upper limit
  42. GRB 251215A: COLIBRÍ optical upper limit
  43. EP251214b: KAIT optical upper limit
  44. EP251214a: Optical upper limit with Kinder observations
  45. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  46. GRB 251214B: UAFO optical upper limit
  47. GRB 251214B: VLT/X-shooter observations
  48. GRB 251202A: radio detection with the VLA
  49. GRB 251214B: AbAO optical observations
  50. GRB 251214B: LCO detection of the optical counterpart
  51. EP251214b (EP trigger 01709250023): LCO optical limits
  52. GRB 251203B: AbAO optical observations
  53. GRB 251213A: SVOM/GRM observation
  54. EP251214a: KAIT optical upper limit
  55. GRB 251214B: Swift/UVOT Detection
  56. GRB 251214B: 1.3m DFOT optical detection
  57. GRB 251214B: Xinglong-2.16m optical observation
  58. GRB 251214B : MASTER optical afterglow detection
  59. GRB 251214B: SVOM/C-GFT optical observations
  60. EP251214a: COLIBRÍ optical upper limit
  61. EP251214.305: COLIBRÍ optical upper limit
  62. GRB 251214B: Swift detection of a burst with an optical counterpart
  63. EP251212a: KAIT optical upper limit
  64. EP251212a : COLIBRÍ optical upper limit
  65. IceCube-251210A: DDOTI Optical Upper Limit
  66. GRB 251205A: 1.3m DFOT optical upper limit
  67. EP251124a: Mondy optical upper limit
  68. GRB 251129A/EP251129a: AbAO and Mondy optical observations
  69. EP251130a: Mondy and AbAO optical observations
  70. GRB 251208B: COLIBRÍ optical upper limits
  71. EP251118a / GRB 251118C: VLT/MUSE redshift confirmation
  72. GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  73. GRB 251208D: LAST optical upper limit
  74. GRB 251208B: GROWTH-India Telescope optical upper limits
  75. GRB 251205A: J-band detection with WINTER
  76. GRB 251208A: SVOM/GRM observation of a short burst
  77. GRB 251208C: SVOM/GRM observation of a short burst
  78. GRB 251129A: e-MERLIN C-band observations
  79. GRB 251205A: Liverpool Telescope further optical follow-up observations
  80. GRB 251208D: LCO optical upper limits
  81. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  82. GRB 251205A: FTW optical and NIR observations
  83. GRB 251205A: Liverpool Telescope further optical follow-up observations
  84. GRB 251205A: ZTF and ATLAS optical afterglow detections
  85. GRB 251205A: GROWTH-India Telescope optical observations
  86. GRB 251205A: Liverpool Telescope optical follow-up observations
  87. GRB 251203C: Swift/UVOT Upper Limit
  88. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  89. GRB 251205A: COLIBRÍ optical observations
  90. GRB 251205A: GOTO optical afterglow detection
  91. GRB 251205A: NOT optical observations
  92. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  93. Swift GRB 251205A : MASTER OT detection with host galaxy
  94. GRB 251205A: Swift detection of a burst with an optical afterglow
  95. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  96. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  97. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  98. GRB 251202A: SVOM/GRM observation
  99. GRB 251203A: SVOM/GRM observation
  100. GRB 251201B: SALT spectroscopic redshift z = 1.599

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