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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"

18104 results found.

  1. GRB 250920B: SVOM/C-GFT optical observations
  2. GRB 250919A / EP250919a: LCO optical observation
  3. GRB 250920C: Swift detection of a burst
  4. GRB 250919A / EP250919a: Insight-HXMT detection
  5. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  6. GRB 250919A/EP250919a: SVOM/VT optical observation
  7. GRB 250916A: Mondy R-band optical observations
  8. GRB 250918A: SVOM/GRM observation
  9. GRB 250919A: Swift-XRT afterglow detection
  10. GRB 250919A: SVOM/GRM observation of a very bright GRB
  11. EP250919a: Einstein Probe detection of an X-ray transient
  12. GRB 250916A: KAIT optical observations
  13. GRB 250917B: VLT/HAWK-I near-infrared observations
  14. GRB 250916A: further SAO RAS optical observations
  15. GRB 250912A: SVOM/ECLAIRs refined analysis
  16. GRB 250917B: Swift/UVOT Upper Limits
  17. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  18. GRB 250916A: MAO/AZT-22 optical observations
  19. GRB 250916A: SAO RAS optical observations
  20. GRB 250916A : GIT optical observations
  21. GRB250917B: WFST optical observations
  22. GRB 250916A: Swift ToO observations
  23. GRB 250917B: Swift detection of a short burst
  24. EP250916a: Einstein Probe detection of an X-ray transient
  25. SVOM/sb25091517: SVOM detection of an X-ray transient
  26. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  27. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  28. GRB250912A: VLT/HAWK-I follow-up observations
  29. GRB 250912A:SVOM/VT optical upper limit
  30. GRB 250912A: LCO optical upper limit
  31. GRB 250912A: SVOM detection of a burst
  32. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  33. GRB 250910B: SVOM/GRM observation
  34. EP250911a: SVOM/VT optical observation
  35. EP250911a: SAO RAS optical observations
  36. EP250911a: Optical detection with Kinder observations
  37. GRB 250911A: Swift/UVOT Detection
  38. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  39. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  40. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  41. EP250911a: COLIBRÍ optical observations
  42. EP250911a: Einstein Probe detection of an X-ray transient
  43. LIGO/Virgo/KAGRA S250911ac: Identification of a GW compact binary merger candidate
  44. GRB 250911A: Enhanced Swift-XRT position
  45. GRB 250911A: Swift-XRT observations
  46. GRB 250911A: COLIBRÍ optical counterpart candidate
  47. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  48. EP250910a/GRB 250910A: EP-WXT detection of a fast X-ray transient
  49. GRB 250909B: AstroSat CZTI detection of a long burst
  50. GRB 250910A: SVOM/VT optical upper limit
  51. GRB 250910A: LCO optical upper limit
  52. GRB 250910A: SVOM detection of a faint burst
  53. EP250908b/EP#01709240653: Swift/UVOT Detection
  54. EP250908c: refined analysis of the EP-WXT and EP-FXT observations
  55. EP250908c: SVOM/VT optical observation
  56. EP250908c: VLT/FORS2 optical counterpart identification
  57. EP250908b: SVOM/VT optical candidate (Coordinate supplement for GCN 41758)
  58. EP250908b: SVOM/VT optical candidate
  59. EP250908c: Einstein Probe detection of an X-ray transient
  60. EP250908b: EP-WXT detection of a fast X-ray transient and EP-FXT observation
  61. GRB 250903A: Swift-XRT afterglow detection
  62. SVOM/sb25090605: detection of an X-ray transient from the LMXB 4U 0513-40
  63. EP250905a: Liverpool Telescope i-band upper limits
  64. LIGO/Virgo/KAGRA S250830bp: DECam/SOAR GW-MMADS updates
  65. EP250905a: Liverpool Telescope observations
  66. EP250905a: refined analysis of the EP-WXT and EP-FXT observations
  67. EP250905b: EP-WXT detection of a fast X-ray transient
  68. EP250905a: JinShan likely optical counterpart detection
  69. GRB 250905A: Swift/UVOT Upper Limits
  70. GRB 250901A - SVOM/ECLAIRs refined analysis
  71. EP250905a: Einstein Probe detection of an X-ray transient
  72. GRB250904A: Liverpool Telescope upper limits
  73. GRB 250905A: Enhanced Swift-XRT position
  74. GRB 250904A: Swift/UVOT Detection
  75. GRB 250903A: Swift/UVOT detection
  76. EP detected a brightening of LMXB 1ES 1735-26.9
  77. GRB 250905A: KAIT optical upper limit
  78. GRB 250905A: Swift detection of a burst
  79. GRB 250904A: Enhanced Swift-XRT position
  80. GRB 250904A: TRT optical counterpart detection
  81. GRB 250904A: Swift detection of a burst
  82. GRB 250902A: VZLUSAT-2 detection
  83. LIGO/Virgo/KAGRA S250904cv: Identification of a GW compact binary merger candidate
  84. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  85. EP-WXT trigger 01709201209: Liverpool Telescope upper limits
  86. GRB 250830C: VZLUSAT-2 detection
  87. EP250903a: refined analysis of the EP-WXT and EP-FXT observations
  88. LIGO/Virgo/KAGRA S250904br: Identification of a GW compact binary merger candidate
  89. LIGO/Virgo/KAGRA S250904ae: Identification of a GW compact binary merger candidate
  90. GRB 250903A: LCO optical observation
  91. GRB 250903A: LCO optical afterglow detection
  92. GRB 250903A: SVOM/VT optical confirmation with VHF data
  93. EP250901a: Mondy, Assy and SAO RAS optical limits
  94. GRB 250903A: TRT optical counterpart detection
  95. EP250903a: TRT optical observations
  96. EP250903a: Einstein Probe detection of an X-ray transient
  97. EP 250827B: Detection of supernova counterpart by LCO.
  98. GRB 250902B: SVOM/GRM observation
  99. EP250827b: SVOM/VT observation of AT 2025wkm
  100. LIGO/VIRGO/KAGRA S250818k: No evidence for radio variability of AT2025ulz in MeerKAT 3 GHz data

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