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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 250101A: Terskol Zeiss-2000 optical observations
  2. EP250108a / AT 2025kg: SAO RAS optical observations
  3. EP241021a: SMA radio observation
  4. GRB 250113A: SVOM/GRM observation of a long burst
  5. EP250109b: optical upper limits with the Liverpool Telescope
  6. EP250111a: KAIT optical observations
  7. GRB 250109A / EP250109a: Mephisto optical upper limits
  8. EP250108a: Mephisto detection
  9. EP250111a: Mondy optical observation
  10. EP250108a / AT 2025kg: LCO optical observations
  11. EP250111a: Swift/XRT detection and fading
  12. EP250108a / AT 2025kg: Swift UVOT detections
  13. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  14. EP250108a: optical follow-up observations with the Liverpool Telescope
  15. EP250111a: NOT likely optical counterpart
  16. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  17. EP250108a: further NOT optical observations
  18. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  19. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  20. GRB 250101A: CMO RC-500 optical observations
  21. GRB 250109A: Fermi GBM Observation
  22. EP250108a: NOT optical observations
  23. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  24. GRB 250109a: GMG Optical Upper Limit
  25. EP250109a: Swift/UVOT non-detection
  26. EP250108a: Liverpool Telescope likely optical counterpart
  27. GRB 250108B: Gemini-North likely redshift z = 2.197
  28. GRB 250108B: 1.3m DFOT upper limit
  29. GRB 250108B: REM optical/NIR upper limits
  30. EP250109a: SVOM/VT optical candidate
  31. GRB 250101A: Terskol K-800 optical observations
  32. EP250109a: GOTO optical upper limits
  33. GRB 250108A: Swift/UVOT Upper Limits
  34. GRB 250108A: NOT optical upper limit
  35. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  36. GRB 250103A: 1.6m Mephisto optical observations
  37. GRB 250108A:SVOM/VT optical candidate
  38. GRB 250108B: Swift/UVOT Upper Limits
  39. GRB 250106A: SVOM/VT 2nd optical deep observation
  40. GRB 250101A: J band upper limit by SYSU 80cm telescope
  41. EPWXT01709129925: Xinglong optical observations
  42. GRB 250106A: NOT optical observations
  43. GRB 250103B: REM optical/NIR upper limits
  44. GRB 250101A: REM optical/NIR counterpart detection
  45. GRB 250106A: Swift-XRT observations
  46. GRB 250106A: SVOM/VT optical candidate
  47. GRB 241229A: SVOM/VT optical upperlimit
  48. GRB 250103B: LCO/1m optical afterglow candidate detection
  49. GRB 250103A: Bassano Bresciano Observatory upper limit
  50. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  51. GRB 250103A: Swift-XRT observations
  52. GRB 250101A: 1.3m DFOT optical afterglow detection
  53. GRB 241229A: 1.3m DFOT upper limit
  54. GRB 241228B: 1.3m DFOT Optical observations
  55. GRB 241228A: 1.3m DFOT upper limit
  56. GRB 250103A: NOT spectroscopic redshift
  57. GRB 250103B：SVOM/VT optical counterpart
  58. GRB 250103A: Montarrenti Observatory optical detection
  59. GRB 250101A: further LCOGT optical afterglow observations
  60. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  61. GRB 250103A: NOT optical observations
  62. GRB 250103A: TSHAO optical upper limit
  63. GRB 250103B: LCOGT Optical Upper Limit
  64. GRB 250103A: SVOM/VT optical counterpart confirmation
  65. EP250101a: Liverpool Telescope optical upper limit
  66. GRB 250101a: Liverpool Telescope optical follow-up
  67. GRB 250103A: Xinglong 2.16m Optical Candidate
  68. GRB 250101B: SVOM/GRM observation
  69. GRB 250103A: GOTO optical upper limit
  70. GRB 250103A: SVOM/C-GFT optical upper limit
  71. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  72. EP241231b: optical upper limit with the Liverpool Telescope
  73. EP250101a: Xinglong optical upper limit
  74. GRB 250101A: further SAO RAS optical observations
  75. GRB 250101A: LCO optical counterpart detection
  76. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  77. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  78. GRB 250101A: Swift/UVOT Detection
  79. GRB 250101A: 1.6m Mephisto multi-band optical followup
  80. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  81. GRB 250101A: LCOGT optical afterglow detection
  82. GRB 250101A: OASDG optical observations
  83. GRB 250101A: SAO RAS observations of optical brightening
  84. GRB 250101A: BOOTES-4/MET optical afterglow detection
  85. GRB 250101A: AKO Optical Afterglow Detection
  86. GRB 250101A: SAO RAS optical observations
  87. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  88. GRB 250101A: SVOM/C-GFT early optical observations
  89. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  90. GRB 250101A: Nanshan/HMT optical observations
  91. GRB 250101A : GIT optical detection
  92. GRB 250101A: GMG Optical Observation
  93. GRB 250101A: Swift detection of a burst with an optical counterpart
  94. GRB 241217a/EP241217b: ATCA Radio Detection
  95. GRB 241229B: Continued CrAO ZTSh observations
  96. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  97. GRB 241229B: SVOM/GRM observation
  98. EP241217A: J band upper limit by SYSU 80cm telescope
  99. GRB 241229B: SAO RAS optical upper limit
  100. GRB 241228B: SAO RAS optical observations

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