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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"

15993 results found.

  1. EP250812a: Nickel optical upper limit
  2. GRB 250812A: VLT X-shooter spectroscopic redshift confirmation z = 2.571
  3. GRB 250812A: NTT spectroscopic redshift z = 2.57
  4. GRB250812a: STEP/T80S Indication of slow decay of afterglow
  5. EP250812a: NOT, NTT, and GS observations
  6. GRB 250812A: Swift/UVOT Detection
  7. EP250812a: Liverpool Telescope upper limits
  8. EP250812a: SVOM/VT optical counterpart
  9. GRB 250812A: EP-FXT counterpart detection
  10. EP 250812a: GOTO optical upper limit
  11. GRB 250812A: Kilonova-Catcher optical afterglow detection
  12. GRB 250812A: SVOM/COLIBRÍ (FM-GFT) optical observations
  13. GRB 250812A: SVOM/VT optical afterglow confirmation
  14. GRB 250812A: TRT likely optical counterpart detection
  15. GRB 250812A: SVOM detection of a faint long burst
  16. GRB 250807B: SVOM/VT optical observation
  17. GRB 250809A: LCOGT Optical Upper Limits
  18. GRB 250808A: VLT X-shooter candidate counterpart
  19. GRB 250808A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  20. GRB 250807A: SVOM/VT optical continued observation
  21. GRB 250808A: SVOM detection of a long burst
  22. GRB 250807B: Kilonova-Catcher optical afterglow detection
  23. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  24. EP250807a: NTT z-band optical upper limit
  25. GRB 250806A: Mondy optical observations, and nearby bright galaxy photometry
  26. GRB 250807A: SVOM/GRM observation
  27. GRB 250806A: NOT z-band upper limit and host galaxy candidate
  28. GRB 250807B: NTT optical observations
  29. EP250807a: EP-WXT detection of a fast X-ray transient
  30. EP 250807.979: GOTO optical upper limit
  31. EP250807a: COLIBRÍ optical upper limit
  32. GRB 250807A: SVOM/VT optical observation
  33. GRB 250807B: Swift detection of a burst with an optical counterpart.
  34. GRB 250805A: Kilonova-Catcher optical upper limits
  35. GRB 250805A: Swift/UVOT Upper Limits
  36. EP250806a: Liverpool telescope optical upper limit
  37. GRB 250807A: Swift detection of a burst with an optical counterpart
  38. EP250802a: EP-FXT follow-up observation
  39. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  40. EP250806a: SVOM /VT optical candidate
  41. GRB 250806A: KAIT optical upper limit
  42. GRB 250806A: SVOM/VT refined analysis
  43. EP250806a: COLIBRÍ optical upper limit
  44. GRB 250806A: Kilonova-Catcher optical upper limits
  45. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  46. GRB 250806A: SVOM/VT optical upper limit
  47. GRB 250805A: SVOM/VT optical counterpart
  48. GRB 250805A: ESO/VLT observations
  49. GRB 250805A: TRT optical upper limits
  50. GRB 250804B: SVOM/GRM observation of a short burst
  51. EP250730a: SVOM/VT optical upper limit
  52. EP250802a: Liverpool Telescope optical upper limits
  53. EP250802a: GROWTH-India Telescope optical upper limit
  54. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  55. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  56. EP250711a: CrAO and Assy optical observations
  57. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  58. EP250730a: COLIBRÍ optical upper limit
  59. LIGO/Virgo/KAGRA S250725j: DECam DESGW Epoch 1-2 Candidates
  60. GRB 250725A: PRIME near-infrared observations
  61. GRB 250728A: COLIBRÍ optical upper limit
  62. GRB 250727A: AST3-2 Upper limit
  63. GRB250727A: SVOM/VT optical upper limit
  64. GRB 250725A: SVOM/GRM observation
  65. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  66. GRB 250725A: Swift/UVOT Upper Limits
  67. GRB 250725A: VLT/FORS2 spectroscopic redshift z = 5.26
  68. GRB 250725A: BOOTES-7 early optical detection
  69. GRB 250725A: SVOM/VT optical candidate
  70. GRB 250725A: MASTER-OAFA optical detection of very fast afterglow
  71. Swift GRB 250725A: Global MASTER-Net OT detection
  72. SVOM J195836+32283/sb25072103: Second VT observation
  73. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  74. GRB 250717B: SVOM/GRM observation
  75. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  76. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  77. GRB 250717B: COLIBRÍ optical upper limit
  78. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  79. GRB 270713A: Kitab and AbAO Optical Observations
  80. GRB 250716A: Lesedi Detection of Fading Optical Transient GOTO25eyp
  81. GRB 250716A: GOTO tentative optical counterpart candidate
  82. GRB 250714A: SVOM/GRM observation
  83. GRB 250713A: Mephisto optical upper limits
  84. GRB 250713A: SVOM/VT optical upper limit
  85. GRB 250713A: NOT optical upper limits
  86. GRB 250706B/C: 7DT Follow-up Observations
  87. EP250711a: COLIBRÍ continuous optical observations
  88. GRB 250713A: JinShan optical upper limits
  89. GRB 250711A: DDOTI Optical Upper Limit
  90. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate (duplicate submission)
  91. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  92. GRB 250711A: SVOM/GRM observation
  93. EP250711a: NOT optical counterpart candidate
  94. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  95. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  96. GRB 250702B,D,E/EP250702A: MeerKAT radio observations at 1.28GHz
  97. EP/WXT 01709181970: GOTO observations confirm stellar variability
  98. EP250704a/GRB 250704B: 10 GHz VLA detection
  99. IceCube-250706A: No Candidates from WINTER
  100. IceCube-250706A: No Candidates from the Zwicky Transient Facility

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