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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"

21770 results found.

  1. GRB251230A: 7DT optical upper limits
  2. GRB 251230A: GOTO optical upper limit
  3. EP251229a: NOT optical upper limits
  4. GRB 251230A / EP251230a: SVOM/VT optical observation
  5. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  6. GRB 251230A: Enhanced Swift-XRT position
  7. GRB 251230A: Early optical counterpart detection by LCO.
  8. EP-WXT trigger 01709250662 Mephisto and 50cm telescope follow-up
  9. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  10. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  11. EP251229a: Einstein Probe detection of an X-ray transient
  12. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  13. GRB 251222A/EP251222b: 1.6m Mephisto optical followup
  14. GRB 251226A: SVOM/GRM observation
  15. IceCube Alert 251225.84: Global MASTER-Net observations report
  16. GRB 251222A: NUTTelA-TAO Early Measurements
  17. GRB 251222A/EP251222b: Optical detection with Kinder observations
  18. EP251222a: Optical upper limit with Kinder observations
  19. GRB 251222A/EP251222b: FTW optical and NIR observations
  20. GRB 251205A: Kilonova-Catcher optical afterglow detection
  21. GRB 251222A: AbAO optical observations
  22. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  23. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  24. GRB 251222A: ZTSH BVRI optical observations
  25. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  26. GRB 251222A: Continued 1.3m DFOT optical observation
  27. EP251220a: 3.6m DOT optical afterglow detection
  28. EP251220a: CrAO ZTSh optical observations
  29. EP251221a: PRIME upper limit
  30. EP251221a: Liverpool Telescope upper limits
  31. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  32. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  33. GRB 251222A: Swift-XRT afterglow detection
  34. GRB 251222A / EP251222b: LCO detection of the optical counterpart
  35. EP251222a: NTT/ULTRACAM optical observations
  36. EP251222a: GOTO optical upper limit
  37. GRB 251222A / EP251222b: GOTO optical counterpart detection
  38. GRB 251222A / EP251222b: LCO optical observations
  39. GRB 251222A: 1.3m DFOT optical detection
  40. GRB251221A: 7DT optical upper limits
  41. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  42. EP251222a: Einstein Probe detection of an X-ray transient
  43. GRB 251222A: PRIME near-infrared detection
  44. EP251221a: NOT optical upper limit
  45. GRB 251222A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  46. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  47. IPN triangulation of GRB 251220B (short)
  48. GRB 251222A: SVOM/VT optical candidate
  49. GRB 251222A: SVOM detection of a long burst
  50. EP251220a: PRIME upper limit
  51. GRB 251221A: PRIME near-infrared observation
  52. EP251220a: FTW optical and NIR observations
  53. GRB 251221A: UAFO and Mondy optical upper limit
  54. EP251221a: Einstein Probe detection of a fast X-ray transient
  55. GRB 251221A: Swift/UVOT Upper Limits
  56. GRB 251221A: Enhanced Swift-XRT position
  57. GRB 251220B: SVOM/GRM observation of a short burst
  58. EP251220a: COLIBRÍ confirmation of fading and photometric redshift upper limit of z < 3.4
  59. EP 251220a: GOTO optical counterpart detection
  60. GRB 251221A: COLIBRÍ detection of the optical counterpart
  61. EP 251220a: COLIBRÍ detection of the optical counterpart
  62. GRB 251221A: Swift detection of a burst
  63. EP251220a: EP detection of a fast X-ray transient
  64. GRB 251219A: SVOM/GRM observation of a short burst
  65. Fermi-LAT Gamma-ray Observations of IceCube-251218A
  66. GRB 251215A: Swift-XRT afterglow detection
  67. IceCube-251218A: COLIBRÍ optical upper limits
  68. GRB 251214B: VIRT Optical Upper Limit
  69. GRB 251215A: Swift/UVOT Upper LImits
  70. GRB 251202A/EP251202a: Koshka optical upper limit
  71. GRB 251214B: Mondy optical upper limit
  72. GRB 251215A: COLIBRÍ optical upper limit
  73. EP251214b: KAIT optical upper limit
  74. GRB 251215A: Swift-XRT observations
  75. EP251214a: Optical upper limit with Kinder observations
  76. GRB 251214B: 1.6m Mephisto observations with newly installed mosaic cameras
  77. GRB 251214B: UAFO optical upper limit
  78. GRB 251214B: VLT/X-shooter observations
  79. GRB 251202A: radio detection with the VLA
  80. EP251214b : Einstein Probe detection of a fast X-ray transient
  81. EP251214b : Einstein Probe detection of a fast X-ray transient
  82. GRB 251214B: AbAO optical observations
  83. GRB 251214B: LCO detection of the optical counterpart
  84. EP251214b (EP trigger 01709250023): LCO optical limits
  85. GRB 251203B: AbAO optical observations
  86. GRB 251213A: SVOM/GRM observation
  87. EP251214a: KAIT optical upper limit
  88. GRB 251214A: AstroSat CZTI detection
  89. GRB 251214B: Swift/UVOT Detection
  90. GRB 251214B: COLIBRÍ observations of the afterglow
  91. EP251214a: EP-FXT non-detection and upper limit
  92. GRB 251214B: 1.3m DFOT optical detection
  93. GRB 251214B: Enhanced Swift-XRT position
  94. GRB 251214B: Xinglong-2.16m optical observation
  95. GRB 251214B : MASTER optical afterglow detection
  96. GRB 251214B: SVOM/C-GFT optical observations
  97. EP251214a: COLIBRÍ optical upper limit
  98. EP251214.305: COLIBRÍ optical upper limit
  99. GRB 251214B: Swift detection of a burst with an optical counterpart
  100. EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A

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