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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"

16079 results found.

  1. GRB 250918A: SVOM/GRM observation
  2. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  3. GRB 250919A: Swift-XRT afterglow detection
  4. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  5. GRB 250919A: SVOM/GRM observation of a very bright GRB
  6. EP250919a: Einstein Probe detection of an X-ray transient
  7. The EP-WXT trigger 01709243841: Las Cumbres discovery of the optical counterpart
  8. GRB 250916A: Fermi GBM Observation
  9. GRB 250916A: KAIT optical observations
  10. GRB 250916A: NuSTAR detection of the prompt emission
  11. GRB 250916A: further SAO RAS optical observations
  12. GRB 250917B: Swift/UVOT Upper Limits
  13. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  14. GRB 250916A: Swift-XRT observations
  15. GRB 250916A: MAO/AZT-22 optical observations
  16. GRB 250916A: SAO RAS optical observations
  17. GRB 250916A : GIT optical observations
  18. GRB250917B: WFST optical observations
  19. GRB 250916A: GOTO optical counterpart candidate
  20. EP250827b: VLA Observations
  21. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  22. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  23. GRB 250912A: VLT observations
  24. GRB 250912A:SVOM/VT optical upper limit
  25. GRB 250912A: LCO optical upper limit
  26. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  27. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  28. GRB 250910B: SVOM/GRM observation
  29. EP250911a: SVOM/VT optical observation
  30. GRB 250911A: MASTER optical counterpart observations
  31. EP250911a: SAO RAS optical observations
  32. EP250911a: Swift-XRT observations
  33. EP250911a: Optical detection with Kinder observations
  34. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  35. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  36. EP250911a: COLIBRÍ optical observations
  37. EP250911a: LCO optical counterpart discovery
  38. GRB 250911A: COLIBRÍ optical counterpart candidate
  39. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  40. GRB 250910A: SVOM/VT optical upper limit
  41. EP250908C: GROND observation of the fading optical counterpart
  42. GRB 250910A: LCO optical upper limit
  43. EP250908c: SVOM/VT optical observation
  44. EP250908c: VLT/FORS2 optical counterpart identification
  45. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  46. EP250908b: SVOM/VT optical candidate
  47. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  48. GRB 250903A: Swift-XRT afterglow detection
  49. EP250905a: Liverpool Telescope i-band upper limits
  50. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  51. EP250905a: Liverpool Telescope observations
  52. EP250905a: FTW one optical and multiple NIR counterpart candidates
  53. EP250905a: JinShan likely optical counterpart detection
  54. GRB 250905A: Swift/UVOT Upper Limits
  55. GRB250904A: Liverpool Telescope upper limits
  56. GRB 250903A: Swift/UVOT detection
  57. GRB 250905A: KAIT optical upper limit
  58. GRB 250904A: TRT optical counterpart detection
  59. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  60. GRB 250903A: Swift-XRT observations
  61. EP250903a: Swift-XRT observations
  62. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  63. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  64. GRB 250903A: EP-FXT counterpart detection
  65. GRB 250903A: LCO optical observation
  66. GRB 250903A: LCO optical afterglow detection
  67. GRB 250903A: SVOM/VT optical confirmation with VHF data
  68. EP250903a: SVOM/VT optical confirmation
  69. EP250901a: Mondy, Assy and SAO RAS optical limits
  70. Subject GRB 250903A: SVOM/MXT afterglow detection
  71. GRB 250903A: TRT optical counterpart detection
  72. GRB 250903A: SVOM detection of a burst
  73. EP250903a: TRT optical observations
  74. EP 250827B: Detection of supernova counterpart by LCO.
  75. EP/WXT01709201159: GOTO optical follow-up
  76. EP250827b / AT 2025wkm: TRT optical observations
  77. EP250827b: NOT spectroscopic observations and AT 2025wkm classification as a broad-lined type-Ic supernova
  78. EP250827b: continued Liverpool Telescope observations
  79. GRB 250902B: SVOM/GRM observation
  80. GRB 250901A: Swift/UVOT Upper Limit
  81. GRB 250902A: SVOM/GRM observation
  82. EP250828a: Early near-infrared follow-up with MIRAGE on the MDM 1.3m telescope
  83. GRB 250901A: EP-FXT follow-up observation
  84. GRB 250901A: NOT optical observations
  85. GRB 250901A: SVOM/VT optical afterglow with VHF data
  86. GRB 250901A: LCO optical upper limit
  87. EP250827b: Swift observations of AT 2025wkm
  88. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 1 Candidates
  89. EP250831a: NOT optical observations and tentative afterglow candidate
  90. EP250827b: FTW Observations of AT 2025wkm
  91. EP250827b: Contemporaneous detection of EP X-ray flare EP250827b and ZTF transient ZTF25abmpngy/AT2025wkm
  92. EP250901a: Mephisto optical upper limits
  93. GRB 250831A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  94. EP250821a: SOAR observations
  95. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  96. EP250828a: refined analysis of the EP-WXT and EP-FXT observations
  97. EP250828a: Optical counterpart detection with Kinder observations
  98. EP250828a: Liverpool Telescope upper limits
  99. EP-WXT trigger 01709200800 : KAIT optical observations
  100. EP250828a: KAIT optical upper limit

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