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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"

21322 results found.

  1. GRB 251001B: GOTO optical counterpart detection
  2. GRB 250910A / EP250910a: VLT limits on the possible associated supernova
  3. LIGO/Virgo/KAGRA S250830bp: SOAR spectroscopy of two DESGW candidates
  4. LIGO/Virgo/KAGRA S250818k: further MeerKAT monitoring
  5. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  6. GRB 250925A: MAO/AZT-22 optical observations
  7. Fermi GRB 250929A: Global MASTER-Net observations report
  8. GRB 250925A: Mondy I-band optical observations
  9. Fermi-LAT Gamma-ray Observations of IceCube-250926A
  10. Fermi trigger No 780609036: Global MASTER-Net observations report
  11. IceCube Alert 250926.52: Global MASTER-Net observations report
  12. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  13. GRB 250925A: Swift/UVOT Upper Limits
  14. GRB 250925A: Mondy and AbAO optical observations
  15. GRB 250925A: COLIBRÍ photometric redshift
  16. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  17. GRB 250925A: JinShan optical observations
  18. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  19. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  20. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  21. Fermi GRB 250926A: Global MASTER-Net observations report
  22. GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
  23. GRB250925A: Liverpool Telescope optical observations
  24. GRB 250925A: NOT optical afterglow candidate
  25. GRB 250925A: Leavitt Observatory optical upper limit
  26. Swift GRB 250925A: Global MASTER-Net observations report
  27. GRB 250924A: 1.6m Mephisto optical upper limits
  28. GRB 250924A: SAO RAS optical observations
  29. GRB 250924A: NOT optical observations
  30. GRB 250924A: Swift/UVOT Detection
  31. GRB 250924A: J-band detection with WINTER
  32. GRB 250924A: GROWTH-India Telescope Upper Limits
  33. GRB 250924A: KAIT optical observations
  34. GRB 250924A: Mondy optical observations, afterglow fading
  35. GRB 250924A: Kilonova-Catcher optical afterglow detection
  36. GRB 250920C: Kilonova-Catcher optical afterglow detection
  37. GRB 250920C: TRT optical observation
  38. GRB 250924A: COLIBRÍ optical observations
  39. Swift GRB 250924A: Global MASTER-Net observations report
  40. GRB 250919A / EP250919a: further LCO optical observation
  41. GRB 250924A: DDOTI Detection of the Optical Counterpart
  42. GRB 250920C: KAIT optical observations
  43. GRB 250920C: VLT redshift confirmation z = 1.399
  44. EP250911a: e-MERLIN radio observations
  45. GRB 250920B: CrAO ZTSH optical observations
  46. GRB 250920C: SALT redshift confirmation
  47. GRB 250920C: COLIBRÍ optical observations
  48. Fermi GRB 250922B: Global MASTER-Net observations report
  49. GRB 250920B: SAO RAS optical observations
  50. GRB 250920C: NIR observations with WINTER
  51. GRB 250920B: NIR observations with WINTER
  52. Fermi trigger No 780156732: Global MASTER-Net observations report
  53. GRB 250920C: PRIME near-infrared detection
  54. GRB 250916A: Swift/UVOT Detection
  55. GRB 250916A: CrAO ZTSh R-band optical observations
  56. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  57. GRB 250920B: Asiago optical observations
  58. GRB 250920B: Kitab-ISON optical upper limit
  59. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  60. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  61. GRB 250920C: GROWTH-India Telescope optical observations
  62. GRB 250916A: FTW optical and NIR observations of the counterpart
  63. GRB 250920C: Swift/UVOT Detection
  64. Swift GRB 250920C: Global MASTER-Net observations report
  65. GRB 250920B: Swift/UVOT Detection
  66. GRB 250920B: FTW optical and NIR observations of the counterpart
  67. GRB 250920C: Optical counterpart detection by LCO
  68. GRB 250920B: SVOM/C-GFT optical observations
  69. GRB 250920C: GOTO optical counterpart candidate
  70. GRB 250919A / EP250919a: LCO optical observation
  71. LIGO/Virgo/KAGRA S250920bq: Coverage and upper limits from MAXI/GSC observations
  72. Swift GRB 250920B: Global MASTER-Net observations report
  73. GRB 250919A / EP250919a: MASTER bright afterglow detection 24h after GRB time
  74. GRB 250916A: Mondy R-band optical observations
  75. Fermi GRB 250918A: Global MASTER-Net observations report
  76. GRB 250919A/EP250919A: Swift/UVOT afterglow detection
  77. GRB 250919A: Swift-XRT afterglow detection
  78. EP250919a/GRB 250919A: Gemini/GMOS-S spectroscopic redshift z = 1.145
  79. EP250919a: Global MASTER-Net observations report
  80. EP250919a: Einstein Probe detection of an X-ray transient
  81. Fermi GRB 250919A: Global MASTER-Net observations report
  82. GRB 250916A: KAIT optical observations
  83. GRB 250917B: VLT/HAWK-I near-infrared observations
  84. GRB 250916A: further SAO RAS optical observations
  85. GRB 250912A: SVOM/ECLAIRs refined analysis
  86. GRB 250917B: Swift/UVOT Upper Limits
  87. GRB 250916A: OSIRIS+/GTC redshift z = 2.015
  88. GRB 250916A: Swift-XRT observations
  89. EP250916a: EP-FXT follow-up observation
  90. GRB 250916A: MAO/AZT-22 optical observations
  91. GRB 250916A: SAO RAS optical observations
  92. GRB 250916A : GIT optical observations
  93. GRB250917B: WFST optical observations
  94. GRB 250916A: Swift ToO observations
  95. GRB 250917B: Swift-XRT observations
  96. Fermi GRB 250917B: Global MASTER-Net observations report
  97. GRB 250916A: GOTO optical counterpart candidate
  98. GRB 250910A: SVOM/ECLAIRs refined analysis
  99. EP250916a: Einstein Probe detection of an X-ray transient
  100. Fermi GRB 250916A: Global MASTER-Net observations report

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