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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

32770 results found.

  1. LIGO/Virgo/KAGRA S250927cy: Updated Sky localization
  2. LIGO/Virgo/KAGRA S250927ck: Updated Sky localization
  3. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  4. GRB 250926A: triangulation location with Insight-HXMT/HE and Fermi/GBM
  5. GRB 250924A: SVOM/GRM observation
  6. LIGO/Virgo/KAGRA S250927cy: Identification of a GW compact binary merger candidate
  7. LIGO/Virgo/KAGRA S250927ck: Identification of a GW compact binary merger candidate
  8. IceCube-250926A: Upper limits from a search for additional neutrino events in IceCube
  9. GRB 250926A: Insight-HXMT detection
  10. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  11. GRB 250926A: AstroSat CZTI detection
  12. GRB 250925A: Swift/UVOT Upper Limits
  13. GRB 250925A: Swift-BAT refined analysis
  14. GRB 250925A: Mondy and AbAO optical observations
  15. GRB 250925A: COLIBRÍ photometric redshift
  16. GRB 250925A: SVOM/GWAC-F60A upper limit
  17. GRB 250925A/EP250925a: EP-WXT detection
  18. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  19. GRB 250925A : MITSuME Akeno optical upper limits
  20. GRB 250925A: JinShan optical observations
  21. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  22. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  23. Fermi GRB 250926A: Global MASTER-Net observations report
  24. GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
  25. GRB250925A: Liverpool Telescope optical observations
  26. GRB 250925A: NOT optical afterglow candidate
  27. GRB 250925A: Leavitt Observatory optical upper limit
  28. GRB 250924A: Swift-BAT refined analysis
  29. GRB 250925A: GROWTH-India Telescope Upper Limits
  30. GRB 250922A: SVOM/GRM observation
  31. GRB 250924A: 1.6m Mephisto optical upper limits
  32. GRB 250924A: SAO RAS optical observations
  33. GRB 250924A: NOT optical observations
  34. GRB 250924A: AstroSat CZTI detection
  35. GRB 250914A: AstroSat CZTI detection
  36. GRB 250920B: AstroSat CZTI detection
  37. GRB 250924A: SVOM/VT optical observation
  38. GRB 250924A: Swift/UVOT Detection
  39. GRB 250924A: J-band detection with WINTER
  40. GRB 250924A: GROWTH-India Telescope Upper Limits
  41. GRB 250924A: KAIT optical observations
  42. GRB 250924A: Mondy optical observations, afterglow fading
  43. GRB 250924A: Kilonova-Catcher optical afterglow detection
  44. GRB 250920C: Kilonova-Catcher optical afterglow detection
  45. GRB 250922B: SVOM/GRM observation
  46. GRB 250920C: TRT optical observation
  47. GRB 250924A: COLIBRÍ optical observations
  48. Swift GRB 250924A: Global MASTER-Net observations report
  49. GRB 250919A / EP250919a: further LCO optical observation
  50. GRB 250924A: DDOTI Detection of the Optical Counterpart
  51. GRB 250920B: AbAO optical upper limits
  52. Konus-Wind detection of GRB 250920C
  53. GRB 250920C: KAIT optical observations
  54. GRB 250920C: VLT redshift confirmation z = 1.399
  55. EP250911a: e-MERLIN radio observations
  56. GRB 250920B: CrAO ZTSH optical observations
  57. GRB 250920C: SALT redshift confirmation
  58. GRB 250920C: COLIBRÍ optical observations
  59. Fermi GRB 250922B: Global MASTER-Net observations report
  60. GRB 250920B: SAO RAS optical observations
  61. GRB 250920C: NIR observations with WINTER
  62. GRB 250920B: NIR observations with WINTER
  63. GRB 250920C: PRIME near-infrared detection
  64. Konus-Wind detection of GRB 250920B
  65. Konus-Wind detection of GRB 250920A
  66. IPN triangulation of GRB 250920A (long/bright)
  67. Konus-Wind detection of GRB 250911A
  68. GRB 250916A: Swift/UVOT Detection
  69. GRB 250920B: Glowbug gamma-ray detection
  70. GRB 250916A: CrAO ZTSh R-band optical observations
  71. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  72. GRB 250920B: Asiago optical observations
  73. GRB 250920B: Kitab-ISON optical upper limit
  74. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  75. GRB 250920C: SVOM/GRM observation
  76. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  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: Swift-BAT refined analysis
  81. GRB 250920B: Swift-BAT refined analysis
  82. GRB 250916A: FTW optical and NIR observations of the counterpart
  83. GRB 250920C: Swift/UVOT Detection
  84. GRB 250920B: Fermi GBM Observation
  85. GRB 250920A: Fermi GBM Detection
  86. GRB 250920C: Fermi GBM Observation
  87. Swift GRB 250920C: Global MASTER-Net observations report
  88. GRB 250920B: Swift/UVOT Detection
  89. GRB 250920B: FTW optical and NIR observations of the counterpart
  90. GRB 250920C: Optical counterpart detection by LCO
  91. GRB 250920A: SVOM/GRM observation
  92. GRB250920C: LCOGT Optical Detection
  93. GRB 250920B: SVOM/C-GFT optical observations
  94. GRB 250920C: GOTO optical counterpart candidate
  95. GRB 250919A / EP250919a: LCO optical observation
  96. Konus-Wind detection of GRB 250919A
  97. Swift GRB 250920B: Global MASTER-Net observations report
  98. GRB 250919A / EP250919a: Insight-HXMT detection
  99. GRB 250920A: AstroSat CZTI detection
  100. GRB 250919A/EP250919a: SVOM/VT optical observation

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