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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"

20960 results found.

  1. EP250108a / AT 2025kg: SAO RAS optical observations
  2. EP241021a: SMA radio observation
  3. EP250109b: optical upper limits with the Liverpool Telescope
  4. GRB 250106A: Swift-XRT afterglow detection
  5. Fermi trigger No 758442826: Global MASTER-Net observations report
  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: Global MASTER-Net observations report
  12. EP250108a / AT 2025kg: Swift UVOT detections
  13. EP250108a: optical follow-up observations with the Liverpool Telescope
  14. EP250111a: NOT likely optical counterpart
  15. EP250111a: a new X-ray transient detected by Einstein Probe
  16. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  17. EP250108a: further NOT optical observations
  18. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  19. GRB 250108A: Swift/XRT afterglow fading
  20. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  21. GRB 250101A: CMO RC-500 optical observations
  22. EP250108a: NOT optical observations
  23. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  24. EP250109a: Swift/UVOT non-detection
  25. EP250108a: Liverpool Telescope likely optical counterpart
  26. GRB 250108B: Gemini-North likely redshift z = 2.197
  27. GRB 250108B: 1.3m DFOT upper limit
  28. GRB 250108B: REM optical/NIR upper limits
  29. EP250109a: SVOM/VT optical candidate
  30. EP250109a: Global MASTER-Net observations report
  31. GRB 250101A: Terskol K-800 optical observations
  32. EP250109a: GOTO optical upper limits
  33. GRB 250108A: Swift/UVOT Upper Limits
  34. EP250108a: Global MASTER-Net observations report
  35. EP250109a: EP-WXT detection of an X-ray transient
  36. GRB 250108A: NOT optical upper limit
  37. EP250108a: EP-WXT detection of an X-ray transient
  38. Swift GRB 250108B: Global MASTER-Net observations report
  39. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  40. GRB 250103A: 1.6m Mephisto optical observations
  41. GRB 250108A: Swift-XRT afterglow detection
  42. GRB 250108A:SVOM/VT optical candidate
  43. GRB 250108B: Swift/UVOT Upper Limits
  44. GRB 250103A: Swift-XRT afterglow detection
  45. GRB 250108A: Swift ToO observations
  46. Fermi GRB 250107B: Global MASTER-Net observations report
  47. GRB 250107A: Swift ToO observations
  48. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  49. GRB 250106A: SVOM/VT 2nd optical deep observation
  50. GRB 250101A: J band upper limit by SYSU 80cm telescope
  51. EPWXT01709129925: Xinglong optical observations
  52. GRB 250106A: NOT optical observations
  53. GRB 250103B: REM optical/NIR upper limits
  54. GRB 250101A: REM optical/NIR counterpart detection
  55. GRB 250106A: Swift-XRT observations
  56. GRB 250106A: SVOM/VT optical candidate
  57. GRB 250106A: Swift ToO observations
  58. GRB 250106A: SVOM detection of a long burst
  59. Fermi trigger No 757753930: Global MASTER-Net observations report
  60. GRB 241229A: SVOM/VT optical upperlimit
  61. GRB 250103A: Bassano Bresciano Observatory upper limit
  62. GRB 250103A: Swift-XRT observations
  63. GRB 250101A: 1.3m DFOT optical afterglow detection
  64. GRB 241229A: 1.3m DFOT upper limit
  65. GRB 241228B: 1.3m DFOT Optical observations
  66. GRB 241228A: 1.3m DFOT upper limit
  67. GRB 250103A: NOT spectroscopic redshift
  68. GRB 250103B：SVOM/VT optical counterpart
  69. GRB 250103A: Montarrenti Observatory optical detection
  70. GRB 250101A: further LCOGT optical afterglow observations
  71. GRB 250103A: NOT optical observations
  72. Swift GRB 250103B: Global MASTER-Net observations report
  73. GRB 250103A: SVOM/VT optical counterpart confirmation
  74. GRB 250103A: Swift ToO observations
  75. GRB 250101a: Liverpool Telescope optical follow-up
  76. Fermi GRB 250102A: Global MASTER-Net observations report
  77. GRB 250103A: GOTO optical upper limit
  78. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  79. IceCube Alert 250102.58: Global MASTER-Net observations report
  80. EP241231b: optical upper limit with the Liverpool Telescope
  81. GRB 250101A: further SAO RAS optical observations
  82. GRB 250101A: LCO optical counterpart detection
  83. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  84. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  85. GRB 250101A: Swift/UVOT Detection
  86. GRB 250101A: 1.6m Mephisto multi-band optical followup
  87. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  88. GRB 250101A: LCOGT optical afterglow detection
  89. GRB 250101A: OASDG optical observations
  90. Fermi GRB 250101B: Global MASTER-Net observations report
  91. GRB 250101A: SAO RAS observations of optical brightening
  92. GRB 250101A: AKO Optical Afterglow Detection
  93. GRB 250101A: SAO RAS optical observations
  94. GRB 250101A: SVOM/C-GFT early optical observations
  95. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  96. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  97. GRB 250101A: Nanshan/HMT optical observations
  98. GRB 250101A : GIT optical detection
  99. Swift GRB250101.56: Global MASTER-Net observations report
  100. GRB 241217a/EP241217b: ATCA Radio Detection

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