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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"

15685 results found.

  1. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  2. GRB 251003A: GOTO detection of the optical counterpart
  3. GRB 251002A: GOTO detection of optical counterpart
  4. GRB 251001C: SVOM/GRM observation
  5. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  6. GRB 251002A: AKO Early Optical Afterglow Detection
  7. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  8. GRB 251003A: Kilonova-Catcher optical afterglow detection
  9. GRB 251002A: Swift-XRT afterglow detection
  10. GRB 251001B: AbAO optical upper limit
  11. GRB 251002A: Kilonova-Catcher optical afterglow detection
  12. GRB 251002A: AbAO optical observations
  13. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  14. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  15. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  16. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  17. GRB 251002A: EP-FXT counterpart detection
  18. GRB 251003A: LCOGT Optical Detection
  19. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  20. GRB 251003A: 1.5m OSN afterglow candidate
  21. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  22. GRB 251002A: BOOTES-6 early optical detection
  23. GRB 251002A: SAO RAS optical observations
  24. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  25. GRB 251002A: FRAM-ORM afterglow detection
  26. GRB 251002A: LCO optical observation
  27. GRB 251002A: SVOM/VT optical observation
  28. GRB 251001A: SVOM/GRM observation
  29. GRB 251001B: Swift/UVOT Detection
  30. GRB 251001B: COLIBRÍ optical observations
  31. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  32. GRB 251001B: SVOM/VT optical observation
  33. GRB 251001B: NOT optical observations
  34. GRB 251001B: Further GOTO observations of optical counterpart.
  35. GRB 251001B: LCOGT Optical Observations
  36. GRB 250930A: SVOM/GRM observation
  37. GRB 251001B: TRT optical afterglow detection and potential host galaxy
  38. GRB 251001B: GOTO optical counterpart detection
  39. GRB 250910A / EP250910a: VLT/X-shooter host galaxy redshift z = 0.592
  40. GRB 250925A: MAO/AZT-22 optical observations
  41. GRB 250925A: Mondy I-band optical observations
  42. GRB 250916A: SVOM/VT optical observation
  43. GRB 250924A: SVOM/GRM observation
  44. GRB 250920C: ULL-ASTRO-MASTER early detection of the optical afterglow with LCO 40-cm telescope at Siding Spring Observatory
  45. GRB 250925A: Swift/UVOT Upper Limits
  46. GRB 250925A: Mondy and AbAO optical observations
  47. GRB 250925A: SVOM/GWAC-F60A upper limit
  48. GRB 250926A: DDOTI Optical Observations and Spatial Coincidence with the Orion Nebula
  49. GRB 250925A : MITSuME Akeno optical upper limits
  50. GRB 250925A: JinShan optical observations
  51. GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
  52. GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
  53. GRB 250925A: COLIBRÍ optical photometry of the afterglow
  54. GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
  55. GRB250925A: Liverpool Telescope optical observations
  56. GRB 250925A: NOT optical afterglow candidate
  57. GRB 250925A: Leavitt Observatory optical upper limit
  58. GRB 250922A: SVOM/GRM observation
  59. GRB 250924A: 1.6m Mephisto optical upper limits
  60. GRB 250924A: SAO RAS optical observations
  61. GRB 250924A: NOT optical observations
  62. GRB 250924A: SVOM/VT optical observation
  63. GRB 250924A: J-band detection with WINTER
  64. GRB 250924A: KAIT optical observations
  65. GRB 250924A: Mondy optical observations, afterglow fading
  66. GRB 250924A: Kilonova-Catcher optical afterglow detection
  67. GRB 250920C: Kilonova-Catcher optical afterglow detection
  68. GRB 250922B: SVOM/GRM observation
  69. GRB 250920C: TRT optical observation
  70. GRB 250924A: COLIBRÍ optical observations
  71. GRB 250919A / EP250919a: further LCO optical observation
  72. GRB 250924A: DDOTI Detection of the Optical Counterpart
  73. GRB 250924A: Swift detection of a burst with an optical counterpart
  74. GRB 250920B: AbAO optical upper limits
  75. GRB 250920C: KAIT optical observations
  76. GRB 250920C: VLT redshift confirmation z = 1.399
  77. EP250911a: e-MERLIN radio observations
  78. GRB 250920B: CrAO ZTSH optical observations
  79. GRB 250920C: SALT redshift confirmation
  80. GRB 250920C: COLIBRÍ optical observations
  81. GRB 250920B: SAO RAS optical observations
  82. GRB 250920C: NIR observations with WINTER
  83. GRB 250920B: NIR observations with WINTER
  84. GRB 250920C: PRIME near-infrared detection
  85. GRB 250916A: Swift/UVOT Detection
  86. GRB 250916A: CrAO ZTSh R-band optical observations
  87. GRB 250916A: SAO RAS Zeiss-1000 optical observations
  88. GRB 250920B: Asiago optical observations
  89. GRB 250920B: Kitab-ISON optical upper limit
  90. GRB 250917B: Mondy and Zeiss-1000 SAO RAS optical observations, optical observations, afterglow candidate
  91. GRB 250920C: SVOM/GRM observation
  92. GRB 250920C: GTC/OSIRIS+ spectroscopic redshift z = 1.40
  93. GRB 250917B: KAIT optical upper limit
  94. GRB 250920C: GROWTH-India Telescope optical observations
  95. GRB 250916A: FTW optical and NIR observations of the counterpart
  96. GRB 250920B: FTW optical and NIR observations of the counterpart
  97. GRB 250920C: Optical counterpart detection by LCO
  98. GRB 250920A: SVOM/GRM observation
  99. GRB250920C: LCOGT Optical Detection
  100. GRB 250920B: SVOM/C-GFT optical observations

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