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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"

16159 results found.

  1. GRB 250516A: COLIBRÍ optical upper limit
  2. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  3. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  4. GRB 250515A: 1.6m Mephisto optical detection
  5. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  6. GRB 250515A: GOTO candidate optical counterpart
  7. GRB 250424A: COLIBRÍ detection of the associated supernova
  8. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  9. EP250512a/GRB 250512B: REM optical/NIR observations
  10. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  11. EP250511a: Gemini optical counterpart observation
  12. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  13. EP250511a: FTW optical and NIR observations
  14. GRB 250512B/EP250512a: SVOM/VT optical fading
  15. GRB 250512B/EP250512a：SVOM/VT bright optical counterpart
  16. EP250511a: Mephisto optical upper limits
  17. GRB 250512B: SVOM detection of a burst
  18. EP250511a: REM optical/NIR observations
  19. EP250511a: SVOM/VT optical candidate comfirmation
  20. EP250511a: COLIBRÍ optical counterpart candidate
  21. EP250511a: BOOTES-5 optical upper limit
  22. EP250508a: Gemini NIR upper limits
  23. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  24. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  25. EP250508a: SVOM/VT optical candidate fading
  26. GRB 250506A: NOT optical upper limits
  27. EP250508a: Liverpool Telescope optical upper limits
  28. EP250508a: SVOM/VT optical candidate
  29. EP250508a: KAIT optical upper limit
  30. GRB 250507A: KAIT optical upper limit
  31. GRB 250505B: SVOM/GRM observation of a short burst
  32. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  33. EP250508a: REM optical/NIR observations
  34. GRB 250506A: SVOM/VT optical upper limit
  35. EP250508a: COLIBRÍ Optical Limit
  36. GRB 250506A: Swift/UVOT Upper Limits
  37. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  38. GRB 250507A: REM optical/NIR observations
  39. GRB 250507A: SVOM/VT optical upper limit
  40. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  41. GRB 250507A: SVOM detection of a long burst
  42. GRB 250506A: Mephisto optical upper limits
  43. GRB 250502A: Bassano Bresciano Observatory upper limit
  44. GRB 250506A: Xinglong 2.16m optical upper limit
  45. GRB 250506A: REM optical/NIR upper limits
  46. GRB 250506A: Swift XRT observations and possible counterpart detection
  47. GRB 250506A: TRT optical observations
  48. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  49. GRB 250504A: VLT/X-shooter upper limits
  50. GRB 250504A: SVOM/VT upper limit
  51. GRB 250504A: REM optical/NIR observations
  52. GRB 250502A: REM optical/NIR observations
  53. GRB 250504A: MeerLICHT optical afterglow detection
  54. GRB 250502A: Mondy and Tien-Shan Optical Observations
  55. GRB 250502A: KAIT optical observations
  56. GRB 250502A: Montarrenti Observatory optical detection
  57. GRB 250502A: Swift-XRT afterglow detection
  58. GRB 250502A: NOT optical observations
  59. GRB 250502a: Liverpool Telescope optical follow-up
  60. GRB 250502A: AKO Optical Afterglow Detection
  61. GRB 250502A: LCO optical counterpart detection
  62. GRB 250502B: DDOTI Optical Observations
  63. GRB 250502A: Early optical counterpart detection by LCO.
  64. GRB 250430A: Swift/UVOT Detection
  65. GRB 250502A: SVOM/VT optical bump
  66. GRB 250502A: TRT optical afterglow confirmation
  67. GRB 250430A: Optical Observations via Virtual Telescope Project, Italy
  68. GRB 250502A: SVOM/COLIBRÍ (FM-GFT) Detection of a Bright Optical Counterpart Candidate
  69. GRB 250502A: SVOM detection of a burst
  70. GRB 250430A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  71. GRB 250430A: SVOM/VT optical observations
  72. GRB 250430A: KAIT optical observations
  73. EP250428b: Pan-STARRS follow-up, upper limit on the optical counterpart, and possible host galaxy.
  74. GRB 250430A / EP250430a: J-band upper limits with WINTER
  75. GRB 250430A: NUTTelA-TAO Early Measurements
  76. EP250427a / GRB 250427A: OHP/T193 photometric observations: third visit
  77. GRB 250430A: DDOTI Optical Observations
  78. GRB 250430A: Leavitt Observatory optical upper limit
  79. GRB 250430A: Bassano Bresciano Observatory upper limit
  80. GRB 250430A : MITSuME Akeno optical upper limits
  81. GRB 250430A / EP250430a: VLT/X-shooter spectroscopic redshift z = 0.767
  82. GRB 250430A: AKO Optical Afterglow Detection
  83. GRB 250430A: Kanata optical upper limit
  84. EP 250427A: Optical counterpart detection by LCO.
  85. GRB 250430A: Swift detection of a burst with optical counterpart
  86. EP250428b: FTW optical and NIR observations
  87. EP250427a/GRB250427A: HCT optical follow-up
  88. EP250427a / GRB 250427A: OHP/T193 continued photometric observations
  89. SVOM/sb25043004: SVOM detection of a X-ray transient
  90. EP250428b: GROWTH-India telescope optical upper limit
  91. EP250428b: SAO RAS optical upper limit
  92. EP250428b: LAST optical upper limit
  93. GRB 250427A: Swift/UVOT Detection
  94. EP250427a / GRB 250427A: OHP/T193 photometric observations
  95. EP250427a: EP-FXT follow-up observations
  96. EP250427a/GRB 250427A: FTW optical and NIR observations of the counterpart
  97. EP250427a: Lesedi optical counterpart detection
  98. EP250427A: COLIBRÍ Continuing Optical Observations
  99. GRB250427A/EP250427a GIT optical afterglow detection:
  100. EP250427a: LT optical counterpart detection

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