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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"

23403 results found.

  1. GRB 250924A: 1.6m Mephisto optical upper limits
  2. GRB 250924A: SAO RAS optical observations
  3. GRB 250924A: AstroSat CZTI detection
  4. GRB 250914A: AstroSat CZTI detection
  5. GRB 250920B: AstroSat CZTI detection
  6. GRB 250924A: SVOM/VT optical observation
  7. GRB 250924A: Swift/UVOT Detection
  8. GRB 250924A: Swift-XRT refined Analysis
  9. GRB 250924A: Enhanced Swift-XRT position
  10. GRB 250924A: J-band detection with WINTER
  11. GRB 250924A: GROWTH-India Telescope Upper Limits
  12. GRB 250924A: Mondy optical observations, afterglow fading
  13. GRB 250924A: Kilonova-Catcher optical afterglow detection
  14. GRB 250920C: Kilonova-Catcher optical afterglow detection
  15. GRB 250922B: SVOM/GRM observation
  16. GRB 250920C: TRT optical observation
  17. GRB 250924A: COLIBRÍ optical observations
  18. GRB 250919A / EP250919a: further LCO optical observation
  19. GRB 250924A: DDOTI Detection of the Optical Counterpart
  20. GRB 250924A: Swift detection of a burst with an optical counterpart
  21. GRB 250920B: AbAO optical upper limits
  22. GRB 250920C: KAIT optical observations
  23. GRB 250920B: CrAO ZTSH optical observations
  24. GRB 250920C: COLIBRÍ optical observations
  25. GRB 250920B: SAO RAS optical observations
  26. GRB 250920C: NIR observations with WINTER
  27. GRB 250920B: NIR observations with WINTER
  28. GRB 250920C: PRIME near-infrared detection
  29. IPN triangulation of GRB 250920A (long/bright)
  30. GRB 250916A: Swift/UVOT Detection
  31. GRB 250920B: Glowbug gamma-ray detection
  32. GRB 250916A: CrAO ZTSh R-band optical observations
  33. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  34. GRB 250920B: Asiago optical observations
  35. GRB 250920B: Kitab-ISON optical upper limit
  36. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  37. GRB 250920C: SVOM/GRM observation
  38. GRB 250920A: NuSTAR detection of bright prompt emission
  39. GRB 250920C: GROWTH-India Telescope optical observations
  40. GRB 250920C: Enhanced Swift-XRT position
  41. GRB 250920C: Swift/UVOT Detection
  42. GRB 250920A: Fermi GBM Detection
  43. GRB 250920B: Swift/UVOT Detection
  44. GRB 250920C: Optical counterpart detection by LCO
  45. GRB 250920A: SVOM/GRM observation
  46. GRB250920C: LCOGT Optical Detection
  47. GRB 250920B: Enhanced Swift-XRT position
  48. GRB 250920B: SVOM/C-GFT optical observations
  49. GRB 250919A / EP250919a: LCO optical observation
  50. GRB 250920C: Swift detection of a burst
  51. GRB 250920A: AstroSat CZTI detection
  52. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  53. GRB 250919A/EP250919a: SVOM/VT optical observation
  54. GRB 250916A: Mondy R-band optical observations
  55. GRB 250919A: Glowbug gamma-ray detection
  56. GRB 250919A: Fermi GBM Observation
  57. GRB 250918A: SVOM/GRM observation
  58. GRB 250919A: Swift-XRT afterglow detection
  59. GRB 250919A: SVOM/GRM observation of a very bright GRB
  60. EP250919a: Einstein Probe detection of an X-ray transient
  61. GRB 250916A: KAIT optical observations
  62. GRB 250917B: VLT/HAWK-I near-infrared observations
  63. GRB 250916A: further SAO RAS optical observations
  64. LIGO/Virgo/KAGRA S250918aw: 1 counterpart neutrino candidate event from an IceCube neutrino search
  65. GRB 250917B: Swift/UVOT Upper Limits
  66. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  67. GRB 250916A: Swift-XRT observations
  68. EP250916a: EP-FXT follow-up observation
  69. GRB 250916A: MAO/AZT-22 optical observations
  70. GRB 250916A: SAO RAS optical observations
  71. GRB 250916A : GIT optical observations
  72. LIGO/Virgo/KAGRA S250917aq: Three counterpart neutrino candidates from IceCube neutrino searches
  73. GRB 250916A: Glowbug gamma-ray detection
  74. GRB250917B: WFST optical observations
  75. GRB 250917B: Swift-XRT observations
  76. LIGO/Virgo/KAGRA S250917aq: Identification of a GW compact binary merger candidate
  77. GRB 250917B: Swift detection of a short burst
  78. GRB 250916A: GOTO optical counterpart candidate
  79. GRB 250910A: SVOM/ECLAIRs refined analysis
  80. EP250916a: Einstein Probe detection of an X-ray transient
  81. EP250827b: VLA Observations
  82. SVOM/sb25091517: Confirmation of a stellar flare by SVOM/VT
  83. SVOM/sb25091517: SVOM detection of an X-ray transient
  84. GRB 250912A: Swift/BAT-GUANO localization skymap of a possibly short burst
  85. GRB 250912A: SVOM/COLIBRÍ (FM-GFT) optical observations
  86. GRB 250912A: Swift-XRT observations
  87. GRB250912A: VLT/HAWK-I follow-up observations
  88. GRB 250912A:SVOM/VT optical upper limit
  89. GRB 250912A: LCO optical upper limit
  90. GRB 250912A: SVOM detection of a burst
  91. LIGO/Virgo/KAGRA S250912s: 2 counterpart neutrino candidate events from an IceCube neutrino search
  92. LIGO/Virgo/KAGRA S250912f: Identification of a GW compact binary merger candidate
  93. EP250911a: refined analysis of the EP-WXT and EP-FXT observations
  94. GRB 250910B: SVOM/GRM observation
  95. EP250911a: SVOM/VT optical observation
  96. EP250911a: SAO RAS optical observations
  97. EP250911a: Swift-XRT observations
  98. EP250911a: Optical detection with Kinder observations
  99. GRB 250911A: Swift/UVOT Detection
  100. GRB 250910A / EP250910a: Swift-XRT afterglow detection

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