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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"

23111 results found.

  1. GRB 251006B/EP251006a: EP-WXT detection
  2. LIGO/Virgo/KAGRA S251006dd: Identification of a GW compact binary merger candidate
  3. GRB 251006B: Fermi GBM Final Real-time Localization
  4. GRB 251006A (short): Glowbug gamma-ray detection
  5. GRB 251005C: COLIBRÍ optical observations
  6. GRB 251003A: LAST optical observations
  7. GRB 251002A: LAST optical observations
  8. GRB 251006A: Fermi GBM Final Real-time Localization
  9. GRB 251005C: AstroSat CZTI detection
  10. GRB 251005C: Swift/UVOT Upper Limits
  11. GRB 250902A: MSU cubesats detection
  12. GRB 251005C: Swift-XRT refined Analysis
  13. GRB 251005C: Fermi GBM Observation
  14. GRB 251005C: GOTO optical upper limits
  15. GRB 251005C: Swift detection of a burst
  16. GRB 251003A: J-band detection with WINTER
  17. GRB 251002A: NIR observations with WINTER
  18. GRB 251003A: Swift-BAT refined analysis
  19. GRB 251001B: NIR observations with WINTER
  20. GRB 251003A: Swift/UVOT Upper Limits
  21. GRB 251001A: AstroSat CZTI detection
  22. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  23. GRB 251003A: Swift-XRT refined Analysis
  24. GRB 251003A: COLIBRÍ photometric redshift
  25. GRB 251003A: GOTO detection of the optical counterpart
  26. GRB 251002A: GOTO detection of optical counterpart
  27. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  28. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  29. GRB 251003A: Kilonova-Catcher optical afterglow detection
  30. GRB 251002A: Kilonova-Catcher optical afterglow detection
  31. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  32. GRB 251001C: CALET Gamma-Ray Burst Monitor detection
  33. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  34. GRB 251003A: Swift detection of a burst
  35. Swift GRB251003A: Global MASTER-Net observations report
  36. GRB 251002A: BOOTES-6 early optical detection
  37. GRB 251002A: SAO RAS optical observations
  38. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  39. GRB 251002A: SVOM detection of a burst
  40. GRB 251001B: Swift-BAT refined analysis
  41. GRB 251001B: COLIBRÍ optical observations
  42. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  43. GRB 251001B: NOT optical observations
  44. GRB 251001C: Glowbug gamma-ray detection
  45. GRB 251001B: Further GOTO observations of optical counterpart.
  46. GRB 250930A: SVOM/GRM observation
  47. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  48. GRB 251001B: GOTO optical counterpart detection
  49. GRB 251001B: Swift detection of a burst
  50. GRB 251001A: Fermi GBM Detection
  51. GRB 250926A: CALET Gamma-Ray Burst Monitor detection
  52. LIGO/Virgo/KAGRA S250929c: Identification of a GW compact binary merger candidate
  53. GRB 250924A: SVOM/GRM observation
  54. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  55. GRB 250926A: AstroSat CZTI detection
  56. GRB 250925A: Swift-BAT refined analysis
  57. GRB 250925A: COLIBRÍ photometric redshift
  58. GRB 250925A: SVOM/GWAC-F60A upper limit
  59. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  60. GRB 250925A : MITSuME Akeno optical upper limits
  61. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  62. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  63. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  64. GRB 250924A: Swift-BAT refined analysis
  65. GRB 250925A: Swift detection of a burst
  66. GRB 250924A: 1.6m Mephisto optical upper limits
  67. GRB 250924A: SAO RAS optical observations
  68. GRB 250924A: AstroSat CZTI detection
  69. GRB 250914A: AstroSat CZTI detection
  70. GRB 250920B: AstroSat CZTI detection
  71. GRB 250924A: Swift/UVOT Detection
  72. GRB 250924A: J-band detection with WINTER
  73. GRB 250924A: KAIT optical observations
  74. GRB 250924A: Kilonova-Catcher optical afterglow detection
  75. GRB 250920C: Kilonova-Catcher optical afterglow detection
  76. GRB 250920C: TRT optical observation
  77. GRB 250924A: COLIBRÍ optical observations
  78. Swift GRB 250924A: Global MASTER-Net observations report
  79. GRB 250924A: DDOTI Detection of the Optical Counterpart
  80. GRB 250924A: Swift detection of a burst with an optical counterpart
  81. Konus-Wind detection of GRB 250920C
  82. GRB 250920C: KAIT optical observations
  83. EP250911a: e-MERLIN radio observations
  84. GRB 250920C: COLIBRÍ optical observations
  85. GRB 250922C: AstroSat CZTI detection of a short burst
  86. GRB 250920B: SAO RAS optical observations
  87. GRB 250920C: NIR observations with WINTER
  88. GRB 250920B: NIR observations with WINTER
  89. GRB 250920C: PRIME near-infrared detection
  90. Konus-Wind detection of GRB 250920B
  91. Konus-Wind detection of GRB 250920A
  92. IPN triangulation of GRB 250920A (long/bright)
  93. Konus-Wind detection of GRB 250911A
  94. GRB 250920B: Glowbug gamma-ray detection
  95. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  96. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  97. GRB 250917B: KAIT optical upper limit
  98. GRB 250920C: Swift-BAT refined analysis
  99. GRB 250920B: Swift-BAT refined analysis
  100. GRB 250920C: Swift/UVOT Detection

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