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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"

16149 results found.

  1. GRB 251013C: ULL-ASTRO-MASTER detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  2. GRB 251013C: Asiago optical observations
  3. GRB 251013C: ABObservatory optical observations
  4. GRB 251014A: SAO RAS optical upper limit
  5. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  6. GRB 251013C: EP-FXT counterpart detection
  7. GRB 251013C: ALMA detection
  8. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) detection of the optical counterpart
  9. GRB 251013C: DDOTI detection of the optical afterglow
  10. GRB 251013C: SLKT optical afterglow photometry
  11. GRB 251013C: Swift-XRT counterpart detection
  12. GRB 251013C: GOTO optical afterglow detection
  13. GRB 251013C: SAO RAS optical observations
  14. GRB 251013C: LCO optical afterglow detection
  15. GRB 251013C: Optical Observations via Virtual Telescope Project, Italy
  16. GRB 251013C: NOT spectroscopic redshift z = 0.572
  17. GRB 251013C: LAST detection of optical counterpart
  18. GRB 251013C: BOOTES-6 early optical detection
  19. GRB 251013C: SVOM/VT optical observation
  20. GRB 251013B: SVOM/GRM observation
  21. GRB 251013A: SVOM/GRM observation
  22. GRB 251003A: Mondy optical upper limit
  23. MASTER OT J011025.98-583210.6 : SVOM/VT optical observation
  24. GRB 251011B inspection: MASTER orphan GRB detection
  25. GRB 251011B: Swift/UVOT Upper Limits
  26. GRB 251011B: SVOM/GRM observation
  27. GRB 251011B : MASTER optical observations
  28. GRB 251007B: Swift/UVOT Upper Limits
  29. GRB251007A: Swift/UVOT Detection
  30. GRB 251007A: SVOM/GRM observation
  31. GRB 251007A: 1.5m OSN and 2.2m CAHA optical follow-up
  32. GRB 251007B: COLIBRÍ optical upper limit
  33. GRB 251006B/EP251006a: EP-FXT afterglow detection
  34. GRB 250917B: iTelescope T-26 upper limit
  35. EP250911a: Koshka Zeiss-1000 Optical Upper Limit
  36. GRB 251007B: SVOM/VT optical candidate
  37. GRB 251007A: NOT optical observations
  38. GRB 251007A: AKO Optical Upper Limit
  39. GRB 251007A: SVOM/C-GFT optical observations
  40. GRB 251007B: SVOM detection of a faint burst
  41. GRB 251007B: Swift detection of a burst
  42. GRB 251007A: Swift detection of a burst with an optical counterpart
  43. EP251003a: LCO and VST fading optical counterpart
  44. GRB 251006B/EP251006a: SVOM/VT optical candidate
  45. GRB 251006B/EP251006a: EP-FXT follow-up observation
  46. GRB 251006B: SVOM/GRM observation
  47. GRB 251006B: COLIBRÍ optical upper limit
  48. GRB 251005C: SVOM/VT optical fading
  49. GRB 251005C: SVOM/GRM observation of a likely short GRB
  50. GRB 251005C: COLIBRÍ optical observations
  51. GRB 251005C: VLT/X-shooter Imaging
  52. GRB 251003A: LAST optical observations
  53. GRB 251002A: LAST optical observations
  54. GRB 251005C: SVOM/VT optical candidate
  55. GRB 251005C: Swift/UVOT Upper Limits
  56. GRB 251005C: GOTO optical upper limits
  57. GRB 251002A: Mondy/AZT-33IK optical observations
  58. GRB 251003A: J-band detection with WINTER
  59. GRB 251002A: NIR observations with WINTER
  60. Fermi GBM Sub-Threshold Detection of GRB 250910A
  61. GRB 251001B: NIR observations with WINTER
  62. GRB 251002A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  63. GRB 251003A: Swift/UVOT Upper Limits
  64. GRB 251002A: Swift/UVOT detection
  65. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay
  66. GRB 251003A: GOTO detection of the optical counterpart
  67. GRB 251002A: GOTO detection of optical counterpart
  68. GRB 251001C: SVOM/GRM observation
  69. EP250821a: iTelescope T-59 possible detection of the optical counterpart
  70. GRB 251002A: AKO Early Optical Afterglow Detection
  71. GRB 251003A: GTC/OSIRIS+ spectroscopic redshift z = 4.412
  72. GRB 251003A: Kilonova-Catcher optical afterglow detection
  73. GRB 251002A: Swift-XRT afterglow detection
  74. GRB 251001B: AbAO optical upper limit
  75. GRB 251002A: Kilonova-Catcher optical afterglow detection
  76. GRB 251002A: AbAO optical observations
  77. GRB 251002A: SVOM/COLIBRÍ (FM-GFT) optical observations
  78. GRB 251002A: J band observations by SYSU 80cm infrared telescope
  79. GRB 251002A: OHP/T193 MISTRAL optical afterglow detection
  80. GRB 251002A: VLT/X-shooter spectroscopic redshift z = 2.178
  81. GRB 251002A: EP-FXT counterpart detection
  82. GRB 251003A: LCOGT Optical Detection
  83. GRB 251003A: COLIBRÍ optical detection of the fading afterglow
  84. GRB 251003A: 1.5m OSN afterglow candidate
  85. Fermi/SVOM GRB 251002A : MASTER OT earlier detection in 2 polarization filters
  86. GRB 251002A: BOOTES-6 early optical detection
  87. GRB 251002A: SAO RAS optical observations
  88. GRB 251002A: ULL-ASTRO-MASTER early detection of the optical afterglow with the LCO 40-cm telescope at Sutherland Observatory
  89. GRB 251002A: FRAM-ORM afterglow detection
  90. GRB 251002A: LCO optical observation
  91. GRB 251002A: SVOM/VT optical observation
  92. GRB 251001A: SVOM/GRM observation
  93. GRB 251001B: Swift/UVOT Detection
  94. GRB 251001B: COLIBRÍ optical observations
  95. GRB 251001B: GTC/OSIRIS+ spectroscopic redshift z = 2.162
  96. GRB 251001B: SVOM/VT optical observation
  97. GRB 251001B: NOT optical observations
  98. GRB 251001B: Further GOTO observations of optical counterpart.
  99. GRB 251001B: LCOGT Optical Observations
  100. GRB 250930A: SVOM/GRM observation

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