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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"

21771 results found.

  1. GRB 251002A: LCO optical observation
  2. GRB 251002A: SVOM/VT optical observation
  3. GRB 251002A: SVOM detection of a burst
  4. GRB 251001B: Swift-BAT refined analysis
  5. GRB 251001A: SVOM/GRM observation
  6. GRB 251001B: Swift/UVOT Detection
  7. GRB 251001B: COLIBRÍ optical observations
  8. GRB 251001B: SVOM/VT optical observation
  9. GRB 251001B: NOT optical observations
  10. GRB 251001B: Fermi GBM Observation
  11. GRB 251001B: Enhanced Swift-XRT position
  12. GRB 251001B: LCOGT Optical Observations
  13. GRB 250930A: SVOM/GRM observation
  14. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  15. GRB 251001B: Swift detection of a burst
  16. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  17. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  18. GRB 250925A: MAO/AZT-22 optical observations
  19. GRB 250925A: Mondy I-band optical observations
  20. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  21. GRB 250924A: SVOM/GRM observation
  22. GRB 250925A: Swift-XRT refined Analysis
  23. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  24. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  25. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  26. GRB 250925A: Mondy and AbAO optical observations
  27. GRB 250925A: SVOM/GWAC-F60A upper limit
  28. GRB 250925A/EP250925a: EP-WXT detection
  29. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  30. GRB 250925A : MITSuME Akeno optical upper limits
  31. GRB 250925A: JinShan optical observations
  32. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  33. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  34. GRB250925A: Liverpool Telescope optical observations
  35. GRB 250925A: NOT optical afterglow candidate
  36. GRB 250925A: Leavitt Observatory optical upper limit
  37. GRB 250925A: Enhanced Swift-XRT position
  38. GRB 250925A: GROWTH-India Telescope Upper Limits
  39. GRB 250922A: SVOM/GRM observation
  40. GRB 250924A: 1.6m Mephisto optical upper limits
  41. GRB 250924A: SAO RAS optical observations
  42. GRB 250924A: AstroSat CZTI detection
  43. GRB 250924A: SVOM/VT optical observation
  44. GRB 250924A: Swift/UVOT Detection
  45. GRB 250924A: Enhanced Swift-XRT position
  46. GRB 250924A: J-band detection with WINTER
  47. GRB 250924A: GROWTH-India Telescope Upper Limits
  48. GRB 250924A: Mondy optical observations, afterglow fading
  49. GRB 250924A: Kilonova-Catcher optical afterglow detection
  50. GRB 250920C: Kilonova-Catcher optical afterglow detection
  51. GRB 250922B: SVOM/GRM observation
  52. GRB 250920C: TRT optical observation
  53. GRB 250924A: COLIBRÍ optical observations
  54. GRB 250919A / EP250919a: further LCO optical observation
  55. GRB 250924A: DDOTI Detection of the Optical Counterpart
  56. GRB 250924A: Swift detection of a burst with an optical counterpart
  57. GRB 250920B: AbAO optical upper limits
  58. Konus-Wind detection of GRB 250920C
  59. GRB 250920C: KAIT optical observations
  60. EP250911a: e-MERLIN radio observations
  61. GRB 250920B: CrAO ZTSH optical observations
  62. GRB 250920C: COLIBRÍ optical observations
  63. GRB 250920B: SAO RAS optical observations
  64. GRB 250920C: NIR observations with WINTER
  65. GRB 250920B: NIR observations with WINTER
  66. GRB 250920C: PRIME near-infrared detection
  67. Konus-Wind detection of GRB 250920B
  68. Konus-Wind detection of GRB 250920A
  69. Konus-Wind detection of GRB 250911A
  70. GRB 250916A: Swift/UVOT Detection
  71. GRB 250916A: CrAO ZTSh R-band optical observations
  72. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  73. GRB 250920B: Asiago optical observations
  74. GRB 250920B: Kitab-ISON optical upper limit
  75. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  76. GRB 250920C: SVOM/GRM observation
  77. GRB 250917B: KAIT optical upper limit
  78. GRB 250920A: NuSTAR detection of bright prompt emission
  79. GRB 250920C: GROWTH-India Telescope optical observations
  80. GRB 250920C: Enhanced Swift-XRT position
  81. GRB 250916A: FTW optical and NIR observations of the counterpart
  82. GRB 250920C: Swift/UVOT Detection
  83. GRB 250920B: Swift/UVOT Detection
  84. GRB 250920C: Optical counterpart detection by LCO
  85. GRB 250920A: SVOM/GRM observation
  86. GRB250920C: LCOGT Optical Detection
  87. GRB 250920B: Enhanced Swift-XRT position
  88. GRB 250920B: SVOM/C-GFT optical observations
  89. GRB 250919A / EP250919a: LCO optical observation
  90. GRB 250920C: Swift detection of a burst
  91. GRB 250920B: Swift detection of a burst with a bright optical counterpart.
  92. GRB 250919A/EP250919a: SVOM/VT optical observation
  93. GRB 250916A: Mondy R-band optical observations
  94. GRB 250919A: Fermi GBM Observation
  95. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  96. GRB 250918A: SVOM/GRM observation
  97. GRB 250919A: Swift-XRT afterglow detection
  98. GRB 250919A: Fermi-LAT detection
  99. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  100. GRB 250919A: SVOM/GRM observation of a very bright GRB

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