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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"

32537 results found.

  1. GRB 250924A: NOT optical observations
  2. GRB 250924A: AstroSat CZTI detection
  3. GRB 250914A: AstroSat CZTI detection
  4. GRB 250920B: AstroSat CZTI detection
  5. GRB 250924A: SVOM/VT optical observation
  6. GRB 250924A: Swift/UVOT Detection
  7. GRB 250924A: J-band detection with WINTER
  8. GRB 250924A: GROWTH-India Telescope Upper Limits
  9. GRB 250924A: KAIT optical observations
  10. GRB 250924A: Mondy optical observations, afterglow fading
  11. GRB 250924A: Kilonova-Catcher optical afterglow detection
  12. GRB 250920C: Kilonova-Catcher optical afterglow detection
  13. GRB 250922B: SVOM/GRM observation
  14. GRB 250920C: TRT optical observation
  15. GRB 250924A: COLIBRÍ optical observations
  16. Swift GRB 250924A: Global MASTER-Net observations report
  17. GRB 250919A / EP250919a: further LCO optical observation
  18. GRB 250924A: DDOTI Detection of the Optical Counterpart
  19. GRB 250920B: AbAO optical upper limits
  20. Konus-Wind detection of GRB 250920C
  21. GRB 250920C: KAIT optical observations
  22. GRB 250920C: VLT redshift confirmation z = 1.399
  23. EP250911a: e-MERLIN radio observations
  24. GRB 250920B: CrAO ZTSH optical observations
  25. GRB 250920C: SALT redshift confirmation
  26. GRB 250920C: COLIBRÍ optical observations
  27. Fermi GRB 250922B: Global MASTER-Net observations report
  28. GRB 250920B: SAO RAS optical observations
  29. GRB 250920C: NIR observations with WINTER
  30. GRB 250920B: NIR observations with WINTER
  31. GRB 250920C: PRIME near-infrared detection
  32. Konus-Wind detection of GRB 250920B
  33. Konus-Wind detection of GRB 250920A
  34. IPN triangulation of GRB 250920A (long/bright)
  35. Konus-Wind detection of GRB 250911A
  36. GRB 250916A: Swift/UVOT Detection
  37. GRB 250920B: Glowbug gamma-ray detection
  38. GRB 250916A: CrAO ZTSh R-band optical observations
  39. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  40. GRB 250920B: Asiago optical observations
  41. GRB 250920B: Kitab-ISON optical upper limit
  42. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  43. GRB 250920C: SVOM/GRM observation
  44. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  45. GRB 250917B: KAIT optical upper limit
  46. GRB 250920A: NuSTAR detection of bright prompt emission
  47. GRB 250920C: GROWTH-India Telescope optical observations
  48. GRB 250920C: Swift-BAT refined analysis
  49. GRB 250920B: Swift-BAT refined analysis
  50. GRB 250916A: FTW optical and NIR observations of the counterpart
  51. GRB 250920C: Swift/UVOT Detection
  52. GRB 250920B: Fermi GBM Observation
  53. GRB 250920A: Fermi GBM Detection
  54. GRB 250920C: Fermi GBM Observation
  55. Swift GRB 250920C: Global MASTER-Net observations report
  56. GRB 250920B: Swift/UVOT Detection
  57. GRB 250920B: FTW optical and NIR observations of the counterpart
  58. GRB 250920C: Optical counterpart detection by LCO
  59. GRB 250920A: SVOM/GRM observation
  60. GRB250920C: LCOGT Optical Detection
  61. GRB 250920B: SVOM/C-GFT optical observations
  62. GRB 250920C: GOTO optical counterpart candidate
  63. GRB 250919A / EP250919a: LCO optical observation
  64. Konus-Wind detection of GRB 250919A
  65. Swift GRB 250920B: Global MASTER-Net observations report
  66. GRB 250919A / EP250919a: Insight-HXMT detection
  67. GRB 250920A: AstroSat CZTI detection
  68. GRB 250919A/EP250919a: SVOM/VT optical observation
  69. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  70. GRB 250916A: Mondy R-band optical observations
  71. GRB 250919A: Glowbug gamma-ray detection
  72. GRB 250919A: Fermi GBM Observation
  73. Fermi GRB 250918A: Global MASTER-Net observations report
  74. GRB 250919A / EP250919a: NuSTAR detection of bright prompt emission
  75. GRB 250918A: SVOM/GRM observation
  76. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  77. GRB 250919A: Swift-XRT afterglow detection
  78. GRB 250919A: Fermi-LAT detection
  79. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  80. GRB 250919A: SVOM/GRM observation of a very bright GRB
  81. EP250919a: Global MASTER-Net observations report
  82. EP250919a: Einstein Probe detection of an X-ray transient
  83. Correction for GCN 41877: EP-WXT ID is 01709243841
  84. GRB 250916A: Fermi GBM Observation
  85. Fermi GRB 250919A: Global MASTER-Net observations report
  86. GRB 250916A: KAIT optical observations
  87. GRB 250917B: VLT/HAWK-I near-infrared observations
  88. GRB 250916A: NuSTAR detection of the prompt emission
  89. GRB 250916A: further SAO RAS optical observations
  90. GRB 250912A: SVOM/ECLAIRs refined analysis
  91. GRB 250917B: Swift-BAT refined analysis
  92. GRB 250917B: Swift/UVOT Upper Limits
  93. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  94. GRB 250916A: Swift-XRT observations
  95. EP250916a: EP-FXT follow-up observation
  96. GRB 250916A: MAO/AZT-22 optical observations
  97. GRB 250916A: SAO RAS optical observations
  98. GRB 250916A : GIT optical observations
  99. LIGO/Virgo/KAGRA S250917aq: Updated Sky localization
  100. GRB 250916A: Glowbug gamma-ray detection

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