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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"

26037 results found.

  1. EP251220a: 3.6m DOT optical afterglow detection
  2. GRB 251222A: Fermi GBM Observation
  3. GRB 251222A: Swift-XRT afterglow detection
  4. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  5. GRB 251222A / EP251222b: GOTO optical counterpart detection
  6. GRB 251222A: 1.3m DFOT optical detection
  7. GRB251221A: 7DT optical upper limits
  8. GRB 251222A: NOT optical observations
  9. IPN triangulation of GRB 251220B (short)
  10. GRB 251222A: Swift ToO observations
  11. GRB 251221A: PRIME near-infrared observation
  12. GRB 251221A: UAFO and Mondy optical upper limit
  13. GRB 251221A: Swift-XRT refined Analysis
  14. GRB 251221A: Swift/UVOT Upper Limits
  15. GRB 251221A: Enhanced Swift-XRT position
  16. GRB 251221A: Fermi GBM Observation
  17. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  18. GRB 251221A: COLIBRÍ detection of the optical counterpart
  19. GRB 251221A: Swift detection of a burst
  20. Swift GRB251221A: Global MASTER-Net observations report
  21. GRB 251215A: Swift-XRT afterglow detection
  22. GRB 251214B: VIRT Optical Upper Limit
  23. GRB 251215A: Swift/UVOT Upper LImits
  24. GRB 251215A: Fermi GBM Observation
  25. GRB 251214B: Mondy optical upper limit
  26. GRB 251215A: COLIBRÍ optical upper limit
  27. GRB 251215A: Swift-XRT observations
  28. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  29. GRB 251215A: Glowbug gamma-ray detection
  30. GRB 251214B: UAFO optical upper limit
  31. GRB 251214B: VLT/X-shooter observations
  32. GRB 251214B: Swift-BAT refined analysis
  33. GRB 251202A: radio detection with the VLA
  34. GRB 251214B: AbAO optical observations
  35. GRB 251214B: LCO detection of the optical counterpart
  36. GRB 251214B: Fermi GBM Observation
  37. GRB 251215A: Swift ToO observations
  38. EP251214b (EP trigger 01709250023): LCO optical limits
  39. GRB 251215A: Swift/BAT-GUANO arcminute localization of a burst
  40. GRB 251214B: Swift-XRT refined Analysis
  41. GRB 251214B: Swift/UVOT Detection
  42. GRB 251214B: COLIBRÍ observations of the afterglow
  43. GRB 251214B: 1.3m DFOT optical detection
  44. GRB 251214B: Enhanced Swift-XRT position
  45. GRB 251214B: Xinglong-2.16m optical observation
  46. GRB 251214B : MASTER optical afterglow detection
  47. GRB 251214B: SVOM/C-GFT optical observations
  48. Swift GRB 251214B: Global MASTER-Net observations report
  49. GRB 251214B: Swift detection of a burst with an optical counterpart
  50. EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A
  51. GRB 251205A: 1.3m DFOT optical upper limit
  52. GRB 251129A/EP251129a: AbAO and Mondy optical observations
  53. EP251130a: Mondy and AbAO optical observations
  54. Fermi GBM Sub-Threshold Detection of GRB 251205A
  55. GRB 251208B: COLIBRÍ optical upper limits
  56. EP251118a / GRB 251118C: VLT/MUSE redshift confirmation
  57. GRB 251208B: Swift-XRT afterglow detection
  58. GRB 251208D: LCO analysis of the XRT sources
  59. GRB 251208B: Fermi GBM Observation
  60. GRB 251208B: GROWTH-India Telescope optical upper limits
  61. GRB 251208D: Swift-XRT observations
  62. GRB 251208B: Swift ToO observations
  63. GRB 251208B: Fermi-LAT detection
  64. GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst
  65. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  66. GRB 251205A: ZTF and ATLAS optical afterglow detections
  67. GRB 251205A: GROWTH-India Telescope optical observations
  68. GRB 251205A: Swift-BAT refined analysis
  69. GRB 251205A: Swift-XRT refined Analysis
  70. GRB 251205A: Swift/UVOT Detection
  71. GRB 251203C: Swift/UVOT Upper Limit
  72. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  73. GRB 251205A: COLIBRÍ optical observations
  74. GRB 251205A: GOTO optical afterglow detection
  75. GRB 251205A: NOT optical observations
  76. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  77. GRB 251205A: Enhanced Swift-XRT position
  78. Swift GRB 251205A : MASTER OT detection with host galaxy
  79. GRB 251205A: Swift detection of a burst with an optical afterglow
  80. Swift GRB251205A: Global MASTER-Net observations report
  81. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  82. GRB 251202A: SVOM/GRM observation
  83. GRB 251201B: SALT spectroscopic redshift z = 1.599
  84. GRB 251129B: Glowbug gamma-ray detection of a short burst
  85. GRB 251203C: LCO optical afterglow confirmation
  86. GRB 251203C: SVOM/VT optical counterpart
  87. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  88. GRB 251203B: Swift-XRT observations
  89. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  90. GRB 251203B: LCO optical upper limits
  91. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  92. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  93. EP251130a: MAO/AZT-22 optical observations
  94. GRB 251202A / EP251202a: SVOM/VT optical observation
  95. GRB 251201B: Fermi GBM Observation
  96. EP251202a/GRB 251202A: KAIT optical observations
  97. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  98. IPN triangulation of GRB 251129B (short/hard)
  99. GRB251129A/EP251129a: Swift UVOT detection
  100. GRB 251202A: Fermi GBM Observation

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