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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"

15722 results found.

  1. GRB 250129A: COLIBRÍ Optical Observations
  2. GRB 250128B: VLA possible radio detection
  3. GRB 250129A: continued KAIT observations indicating steep decay after 28.5h
  4. GRB 250129A: iTelescope optical observation
  5. GRB 250129A: NOT optical observations of continuining activity
  6. GRB 250129a: Liverpool Telescope optical follow-up
  7. GRB 250129A: AKO Optical Afterglow Detection
  8. GRB 250129A: GRANDMA/TAROT optical afterglow detection
  9. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  10. Ep250125A: 1.3m DFOT optical upper limit
  11. GRB 250129A: Skynet optical observations
  12. GRB 250129A: KAIT optical observations of the rebrightening around 5.1 hours
  13. GRB 250128B: Gemini-North optical extended source detection
  14. GRB 250128B: TNG optical upper limit
  15. GRB 250129A: Swift/UVOT Detection
  16. GRB 250127A: CrAO and Terskol optical upper limits
  17. GRB 250128B: NOT optical upper limit
  18. GRB 250128B: VLT/FORS2 optical observations
  19. GRB 250129A: REM optical/NIR afterglow detection
  20. GRB 250129A: OHP/T193 optical and spectroscopy observations
  21. GRB 250129A: Early afterglow detection by LCO.
  22. GRB 250128B: OHP/T193 optical upper limit
  23. Swift GRB 250129A: Global MASTER-Net Slowly evolving LC detection
  24. GRB 250129A: LCO optical observations
  25. GRB 250129A: NOT optical observations and redshift confirmation
  26. GRB 250129A: GOTO optical observations show brightening afterglow
  27. GRB 250129A: VLT/X-shooter redshift of z = 2.151
  28. GRB 250129A: Swift detection of a burst with an optical counterpart
  29. Swift GRB 250129A: Global MASTER-Net OT detection
  30. GRB 250128B: GOTO optical upper limit
  31. GRB 250128B: LCO optical observations
  32. GRB 250127A: LCO optical upper limit
  33. EP250125a: Optical upper limit with Kinder observations
  34. EP250125a: REM optical counterpart detection
  35. EP250125a: Swift/XRT detection of a fading counterpart
  36. EP250125a: a new X-ray transient detected by Einstein Probe
  37. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  38. EP250108a: AbAO, CMO and Terskol optical upper limits
  39. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  40. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  41. EP 250108A: Late-time optical observation by LCO
  42. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  43. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  44. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  45. EP250108a / AT2025kg: GMG Optical Observations
  46. EP250108a / AT2025kg: VLA radio upper limit
  47. GRB 241217A / EP241217B: radio detection with the VLA
  48. GRB 250114B: Swift-XRT afterglow detection
  49. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  50. GRB 250114B: Liverpool Telescope optical upper limit
  51. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  52. GRB 250114A: LCO optical counterpart detection.
  53. GRB 250114B: OHP/T193 optical upper limit
  54. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  55. GRB 250114A: LCOGT optical afterglow i-band detection
  56. GRB 250114B : GIT optical upper limit
  57. EP250111a: SAO RAS optical upper limit
  58. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  59. GRB 250114A: REM detection of the optical and NIR counterpart
  60. Swift GRB250114A: Global MASTER-Net OT detection
  61. GRB 250114A: LCO optical observations
  62. GRB 250114A: TRT optical observations
  63. GRB 250114A: Swift detection of a burst with an optical counterpart
  64. GRB 250101A: Terskol Zeiss-2000 optical observations
  65. EP250108a / AT 2025kg: SAO RAS optical observations
  66. EP241021a: SMA radio observation
  67. GRB 250113A: SVOM/GRM observation of a long burst
  68. EP250109b: optical upper limits with the Liverpool Telescope
  69. EP250111a: KAIT optical observations
  70. GRB 250109A / EP250109a: Mephisto optical upper limits
  71. EP250108a: Mephisto detection
  72. EP250111a: Mondy optical observation
  73. EP250108a / AT 2025kg: LCO optical observations
  74. EP250111a: Swift/XRT detection and fading
  75. EP250108a / AT 2025kg: Swift UVOT detections
  76. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  77. EP250108a: optical follow-up observations with the Liverpool Telescope
  78. EP250111a: NOT likely optical counterpart
  79. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  80. EP250108a: further NOT optical observations
  81. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  82. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  83. GRB 250101A: CMO RC-500 optical observations
  84. GRB 250109A: Fermi GBM Observation
  85. EP250108a: NOT optical observations
  86. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  87. GRB 250109a: GMG Optical Upper Limit
  88. EP250109a: Swift/UVOT non-detection
  89. EP250108a: Liverpool Telescope likely optical counterpart
  90. GRB 250108B: Gemini-North likely redshift z = 2.197
  91. GRB 250108B: 1.3m DFOT upper limit
  92. GRB 250108B: REM optical/NIR upper limits
  93. EP250109a: SVOM/VT optical candidate
  94. GRB 250101A: Terskol K-800 optical observations
  95. EP250109a: GOTO optical upper limits
  96. GRB 250108A: Swift/UVOT Upper Limits
  97. GRB 250108A: NOT optical upper limit
  98. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  99. GRB 250103A: 1.6m Mephisto optical observations
  100. GRB 250108A:SVOM/VT optical candidate

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