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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"

15683 results found.

  1. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  2. GRB 250919A/EP250919a: SVOM/VT optical observation
  3. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  4. GRB 250916A: Mondy R-band optical observations
  5. GRB 250918A: SVOM/GRM observation
  6. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  7. GRB 250919A: Swift-XRT afterglow detection
  8. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  9. GRB 250919A: SVOM/GRM observation of a very bright GRB
  10. EP250919a: Einstein Probe detection of an X-ray transient
  11. The EP-WXT trigger 01709243841: Las Cumbres discovery of the optical counterpart
  12. GRB 250916A: Fermi GBM Observation
  13. GRB 250916A: KAIT optical observations
  14. GRB 250916A: NuSTAR detection of the prompt emission
  15. GRB 250916A: further SAO RAS optical observations
  16. GRB 250917B: Swift/UVOT Upper Limits
  17. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  18. GRB 250916A: Swift-XRT observations
  19. GRB 250916A: MAO/AZT-22 optical observations
  20. GRB 250916A: SAO RAS optical observations
  21. GRB 250916A : GIT optical observations
  22. GRB250917B: WFST optical observations
  23. GRB 250916A: GOTO optical counterpart candidate
  24. EP250827b: VLA Observations
  25. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  26. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  27. GRB 250912A: VLT observations
  28. GRB 250912A:SVOM/VT optical upper limit
  29. GRB 250912A: LCO optical upper limit
  30. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  31. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  32. GRB 250910B: SVOM/GRM observation
  33. EP250911a: SVOM/VT optical observation
  34. GRB 250911A: MASTER optical counterpart observations
  35. EP250911a: SAO RAS optical observations
  36. EP250911a: Swift-XRT observations
  37. EP250911a: Optical detection with Kinder observations
  38. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  39. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  40. EP250911a: COLIBRÍ optical observations
  41. EP250911a: LCO optical counterpart discovery
  42. GRB 250911A: COLIBRÍ optical counterpart candidate
  43. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  44. GRB 250910A: SVOM/VT optical upper limit
  45. EP250908C: GROND observation of the fading optical counterpart
  46. GRB 250910A: LCO optical upper limit
  47. EP250908c: SVOM/VT optical observation
  48. EP250908c: VLT/FORS2 optical counterpart identification
  49. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  50. EP250908b: SVOM/VT optical candidate
  51. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  52. GRB 250903A: Swift-XRT afterglow detection
  53. EP250905a: Liverpool Telescope i-band upper limits
  54. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  55. EP250905a: Liverpool Telescope observations
  56. EP250905a: FTW one optical and multiple NIR counterpart candidates
  57. EP250905a: JinShan likely optical counterpart detection
  58. GRB 250905A: Swift/UVOT Upper Limits
  59. GRB250904A: Liverpool Telescope upper limits
  60. GRB 250903A: Swift/UVOT detection
  61. GRB 250905A: KAIT optical upper limit
  62. GRB 250904A: TRT optical counterpart detection
  63. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  64. GRB 250903A: Swift-XRT observations
  65. EP250903a: Swift-XRT observations
  66. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  67. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  68. GRB 250903A: EP-FXT counterpart detection
  69. GRB 250903A: LCO optical observation
  70. GRB 250903A: LCO optical afterglow detection
  71. GRB 250903A: SVOM/VT optical confirmation with VHF data
  72. EP250903a: SVOM/VT optical confirmation
  73. EP250901a: Mondy, Assy and SAO RAS optical limits
  74. Subject GRB 250903A: SVOM/MXT afterglow detection
  75. GRB 250903A: TRT optical counterpart detection
  76. GRB 250903A: SVOM detection of a burst
  77. EP250903a: TRT optical observations
  78. EP 250827B: Detection of supernova counterpart by LCO.
  79. EP/WXT01709201159: GOTO optical follow-up
  80. EP250827b / AT 2025wkm: TRT optical observations
  81. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  82. EP250827b: continued Liverpool Telescope observations
  83. GRB 250902B: SVOM/GRM observation
  84. GRB 250901A: Swift/UVOT Upper Limit
  85. GRB 250902A: SVOM/GRM observation
  86. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  87. GRB 250901A: EP-FXT follow-up observation
  88. GRB 250901A: NOT optical observations
  89. GRB 250901A: SVOM/VT optical afterglow with VHF data
  90. GRB 250901A: LCO optical upper limit
  91. EP250827b: Swift observations of AT 2025wkm
  92. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  93. EP250831a: NOT optical observations and tentative afterglow candidate
  94. EP250827b: FTW Observations of AT 2025wkm
  95. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  96. EP250901a: Mephisto optical upper limits
  97. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  98. EP250821a: SOAR observations
  99. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  100. EP250828a: refined analysis of the EP-WXT and EP-FXT observations

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