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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"

16158 results found.

  1. GRB 250812A: EP-FXT counterpart detection
  2. EP 250812a: GOTO optical upper limit
  3. GRB 250812A: Kilonova-Catcher optical afterglow detection
  4. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  5. GRB 250812A: SVOM/VT optical afterglow confirmation
  6. GRB 250812A: TRT likely optical counterpart detection
  7. GRB 250812A: SVOM detection of a faint long burst
  8. GRB 250807B: SVOM/VT optical observation
  9. GRB 250809A: LCOGT Optical Upper Limits
  10. GRB 250808A: VLT X-shooter candidate counterpart
  11. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  12. GRB 250807A: SVOM/VT optical continued observation
  13. GRB 250808A: SVOM detection of a long burst
  14. GRB 250807B: Kilonova-Catcher optical afterglow detection
  15. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  16. EP250807a: NTT z-band optical upper limit
  17. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  18. GRB 250807A: SVOM/GRM observation
  19. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  20. GRB 250807B: NTT optical observations
  21. EP250807a: EP-WXT detection of a fast X-ray transient
  22. EP 250807.979: GOTO optical upper limit
  23. EP250807a: COLIBRÍ optical upper limit
  24. GRB 250807A: SVOM/VT optical observation
  25. GRB 250807B: Swift detection of a burst with an optical counterpart.
  26. GRB 250805A: Kilonova-Catcher optical upper limits
  27. GRB 250805A: Swift/UVOT Upper Limits
  28. EP250806a: Liverpool telescope optical upper limit
  29. GRB 250807A: Swift detection of a burst with an optical counterpart
  30. EP250802a: EP-FXT follow-up observation
  31. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  32. EP250806a: SVOM /VT optical candidate
  33. GRB 250806A: KAIT optical upper limit
  34. GRB 250806A: SVOM/VT refined analysis
  35. EP250806a: COLIBRÍ optical upper limit
  36. GRB 250806A: Kilonova-Catcher optical upper limits
  37. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  38. GRB 250806A: SVOM/VT optical upper limit
  39. GRB 250805A: SVOM/VT optical counterpart
  40. GRB 250805A: ESO/VLT observations
  41. GRB 250805A: TRT optical upper limits
  42. GRB 250804B: SVOM/GRM observation of a short burst
  43. EP250730a: SVOM/VT optical upper limit
  44. EP250802a: Liverpool Telescope optical upper limits
  45. EP250802a: GROWTH-India Telescope optical upper limit
  46. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  47. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  48. EP250711a: CrAO and Assy optical observations
  49. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  50. EP250730a: COLIBRÍ optical upper limit
  51. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  52. GRB 250725A: PRIME near-infrared observations
  53. GRB 250728A: COLIBRÍ optical upper limit
  54. GRB 250727A: AST3-2 Upper limit
  55. GRB250727A: SVOM/VT optical upper limit
  56. GRB 250725A: SVOM/GRM observation
  57. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  58. GRB 250725A: Swift/UVOT Upper Limits
  59. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  60. GRB 250725A: BOOTES-7 early optical detection
  61. GRB 250725A: SVOM/VT optical candidate
  62. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  63. Swift GRB 250725A: Global MASTER-Net OT detection
  64. SVOM J195836+32283/sb25072103: Second VT observation
  65. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  66. GRB 250717B: SVOM/GRM observation
  67. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  68. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  69. GRB 250717B: COLIBRÍ optical upper limit
  70. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  71. GRB 270713A: Kitab and AbAO Optical Observations
  72. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  73. GRB 250716A: GOTO tentative optical counterpart candidate
  74. GRB 250714A: SVOM/GRM observation
  75. GRB 250713A: Mephisto optical upper limits
  76. GRB 250713A: SVOM/VT optical upper limit
  77. GRB 250713A: NOT optical upper limits
  78. GRB 250706B/C: 7DT Follow-up Observations
  79. EP250711a: COLIBRÍ continuous optical observations
  80. GRB 250713A: JinShan optical upper limits
  81. GRB 250711A: DDOTI Optical Upper Limit
  82. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  83. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  84. GRB 250711A: SVOM/GRM observation
  85. EP250711a: NOT optical counterpart candidate
  86. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  87. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  88. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  89. EP/WXT 01709181970: GOTO observations confirm stellar variability
  90. EP250704a/GRB 250704B: 10 GHz VLA detection
  91. IceCube-250706A: No Candidates from WINTER
  92. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  93. GRB 250704B / EP250704a: VLA radio detection
  94. EP250704a/GRB250704B : HCT optical and NIR upper limits
  95. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  96. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  97. GRB 250702F: radio detection with the VLA
  98. GRB 250706B/C: VLT/X-shooter redshift z = 0.942
  99. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  100. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit

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