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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"

15714 results found.

  1. GRB 250924A: DDOTI Detection of the Optical Counterpart
  2. GRB 250924A: Swift detection of a burst with an optical counterpart
  3. GRB 250920B: AbAO optical upper limits
  4. GRB 250920C: KAIT optical observations
  5. GRB 250920C: VLT redshift confirmation z = 1.399
  6. EP250911a: e-MERLIN radio observations
  7. GRB 250920B: CrAO ZTSH optical observations
  8. GRB 250920C: SALT redshift confirmation
  9. GRB 250920C: COLIBRÍ optical observations
  10. GRB 250920B: SAO RAS optical observations
  11. GRB 250920C: NIR observations with WINTER
  12. GRB 250920B: NIR observations with WINTER
  13. GRB 250920C: PRIME near-infrared detection
  14. GRB 250916A: Swift/UVOT Detection
  15. GRB 250916A: CrAO ZTSh R-band optical observations
  16. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  17. GRB 250920B: Asiago optical observations
  18. GRB 250920B: Kitab-ISON optical upper limit
  19. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  20. GRB 250920C: SVOM/GRM observation
  21. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  22. GRB 250917B: KAIT optical upper limit
  23. GRB 250920C: GROWTH-India Telescope optical observations
  24. GRB 250916A: FTW optical and NIR observations of the counterpart
  25. GRB 250920B: FTW optical and NIR observations of the counterpart
  26. GRB 250920C: Optical counterpart detection by LCO
  27. GRB 250920A: SVOM/GRM observation
  28. GRB250920C: LCOGT Optical Detection
  29. GRB 250920B: SVOM/C-GFT optical observations
  30. GRB 250920C: GOTO optical counterpart candidate
  31. GRB 250919A / EP250919a: LCO optical observation
  32. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  33. GRB 250919A/EP250919a: SVOM/VT optical observation
  34. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  35. GRB 250916A: Mondy R-band optical observations
  36. GRB 250918A: SVOM/GRM observation
  37. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  38. GRB 250919A: Swift-XRT afterglow detection
  39. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  40. GRB 250919A: SVOM/GRM observation of a very bright GRB
  41. EP250919a: Einstein Probe detection of an X-ray transient
  42. The EP-WXT trigger 01709243841: Las Cumbres discovery of the optical counterpart
  43. GRB 250916A: Fermi GBM Observation
  44. GRB 250916A: KAIT optical observations
  45. GRB 250916A: NuSTAR detection of the prompt emission
  46. GRB 250916A: further SAO RAS optical observations
  47. GRB 250917B: Swift/UVOT Upper Limits
  48. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  49. GRB 250916A: Swift-XRT observations
  50. GRB 250916A: MAO/AZT-22 optical observations
  51. GRB 250916A: SAO RAS optical observations
  52. GRB 250916A : GIT optical observations
  53. GRB250917B: WFST optical observations
  54. GRB 250916A: GOTO optical counterpart candidate
  55. EP250827b: VLA Observations
  56. LIGO/Virgo/KAGRA S250818k: HCT optical follow-up
  57. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  58. GRB 250912A: VLT observations
  59. GRB 250912A:SVOM/VT optical upper limit
  60. GRB 250912A: LCO optical upper limit
  61. EP250908c: tentative VLT/FORS2 redshift z = 2.87
  62. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  63. GRB 250910B: SVOM/GRM observation
  64. EP250911a: SVOM/VT optical observation
  65. GRB 250911A: MASTER optical counterpart observations
  66. EP250911a: SAO RAS optical observations
  67. EP250911a: Swift-XRT observations
  68. EP250911a: Optical detection with Kinder observations
  69. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  70. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  71. EP250911a: COLIBRÍ optical observations
  72. EP250911a: LCO optical counterpart discovery
  73. GRB 250911A: COLIBRÍ optical counterpart candidate
  74. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  75. GRB 250910A: SVOM/VT optical upper limit
  76. EP250908C: GROND observation of the fading optical counterpart
  77. GRB 250910A: LCO optical upper limit
  78. EP250908c: SVOM/VT optical observation
  79. EP250908c: VLT/FORS2 optical counterpart identification
  80. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  81. EP250908b: SVOM/VT optical candidate
  82. EP#01709240652 (possibly EP250908a): FTW optical and NIR observations
  83. GRB 250903A: Swift-XRT afterglow detection
  84. EP250905a: Liverpool Telescope i-band upper limits
  85. LIGO/Virgo/KAGRA S250830bp: DECam DESGW Epoch 2 Candidates
  86. EP250905a: Liverpool Telescope observations
  87. EP250905a: FTW one optical and multiple NIR counterpart candidates
  88. EP250905a: JinShan likely optical counterpart detection
  89. GRB 250905A: Swift/UVOT Upper Limits
  90. GRB250904A: Liverpool Telescope upper limits
  91. GRB 250903A: Swift/UVOT detection
  92. GRB 250905A: KAIT optical upper limit
  93. GRB 250904A: TRT optical counterpart detection
  94. EP250827b: Gemini Spectroscopic Confirmation of AT2025wkm as a Ic-BL Supernova
  95. GRB 250903A: Swift-XRT observations
  96. EP250903a: Swift-XRT observations
  97. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  98. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  99. GRB 250903A: EP-FXT counterpart detection
  100. GRB 250903A: LCO optical observation

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