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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"

20967 results found.

  1. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  2. GRB 250113A: INTEGRAL/SPI-ACS detection
  3. GRB 250114A: REM detection of the optical and NIR counterpart
  4. GRB 250114A: LCO optical observations
  5. GRB 250114A: TRT optical observations
  6. Swift GRB 250114A: Global MASTER-Net observations report
  7. GRB 250101A: Terskol Zeiss-2000 optical observations
  8. EP250108a / AT 2025kg: SAO RAS optical observations
  9. EP241021a: SMA radio observation
  10. EP250109b: optical upper limits with the Liverpool Telescope
  11. GRB 250106A: Swift-XRT afterglow detection
  12. Fermi trigger No 758442826: Global MASTER-Net observations report
  13. EP250111a: KAIT optical observations
  14. GRB 250109A / EP250109a: Mephisto optical upper limits
  15. EP250108a: Mephisto detection
  16. EP250111a: Mondy optical observation
  17. EP250108a / AT 2025kg: LCO optical observations
  18. EP250111a: Global MASTER-Net observations report
  19. EP250108a / AT 2025kg: Swift UVOT detections
  20. EP250108a: optical follow-up observations with the Liverpool Telescope
  21. EP250111a: NOT likely optical counterpart
  22. EP250111a: a new X-ray transient detected by Einstein Probe
  23. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  24. EP250108a: further NOT optical observations
  25. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  26. GRB 250108A: Swift/XRT afterglow fading
  27. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  28. GRB 250101A: CMO RC-500 optical observations
  29. EP250108a: NOT optical observations
  30. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  31. EP250109a: Swift/UVOT non-detection
  32. EP250108a: Liverpool Telescope likely optical counterpart
  33. GRB 250108B: Gemini-North likely redshift z = 2.197
  34. GRB 250108B: 1.3m DFOT upper limit
  35. GRB 250108B: REM optical/NIR upper limits
  36. EP250109a: SVOM/VT optical candidate
  37. EP250109a: Global MASTER-Net observations report
  38. GRB 250101A: Terskol K-800 optical observations
  39. EP250109a: GOTO optical upper limits
  40. GRB 250108A: Swift/UVOT Upper Limits
  41. EP250108a: Global MASTER-Net observations report
  42. EP250109a: EP-WXT detection of an X-ray transient
  43. GRB 250108A: NOT optical upper limit
  44. EP250108a: EP-WXT detection of an X-ray transient
  45. Swift GRB 250108B: Global MASTER-Net observations report
  46. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  47. GRB 250103A: 1.6m Mephisto optical observations
  48. GRB 250108A: Swift-XRT afterglow detection
  49. GRB 250108A:SVOM/VT optical candidate
  50. GRB 250108B: Swift/UVOT Upper Limits
  51. GRB 250103A: Swift-XRT afterglow detection
  52. GRB 250108A: Swift ToO observations
  53. Fermi GRB 250107B: Global MASTER-Net observations report
  54. GRB 250107A: Swift ToO observations
  55. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  56. GRB 250106A: SVOM/VT 2nd optical deep observation
  57. GRB 250101A: J band upper limit by SYSU 80cm telescope
  58. EPWXT01709129925: Xinglong optical observations
  59. GRB 250106A: NOT optical observations
  60. GRB 250103B: REM optical/NIR upper limits
  61. GRB 250101A: REM optical/NIR counterpart detection
  62. GRB 250106A: Swift-XRT observations
  63. GRB 250106A: SVOM/VT optical candidate
  64. GRB 250106A: Swift ToO observations
  65. GRB 250106A: SVOM detection of a long burst
  66. Fermi trigger No 757753930: Global MASTER-Net observations report
  67. GRB 241229A: SVOM/VT optical upperlimit
  68. GRB 250103A: Bassano Bresciano Observatory upper limit
  69. GRB 250103A: Swift-XRT observations
  70. GRB 250101A: 1.3m DFOT optical afterglow detection
  71. GRB 241229A: 1.3m DFOT upper limit
  72. GRB 241228B: 1.3m DFOT Optical observations
  73. GRB 241228A: 1.3m DFOT upper limit
  74. GRB 250103A: NOT spectroscopic redshift
  75. GRB 250103B：SVOM/VT optical counterpart
  76. GRB 250103A: Montarrenti Observatory optical detection
  77. GRB 250101A: further LCOGT optical afterglow observations
  78. GRB 250103A: NOT optical observations
  79. Swift GRB 250103B: Global MASTER-Net observations report
  80. GRB 250103A: SVOM/VT optical counterpart confirmation
  81. GRB 250103A: Swift ToO observations
  82. GRB 250101a: Liverpool Telescope optical follow-up
  83. Fermi GRB 250102A: Global MASTER-Net observations report
  84. GRB 250103A: GOTO optical upper limit
  85. GRB 250101A: NUTTelA-TAO / BSTI Optical Limits
  86. IceCube Alert 250102.58: Global MASTER-Net observations report
  87. EP241231b: optical upper limit with the Liverpool Telescope
  88. GRB 250101A: further SAO RAS optical observations
  89. GRB 250101A: LCO optical counterpart detection
  90. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  91. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  92. GRB 250101A: Swift/UVOT Detection
  93. GRB 250101A: 1.6m Mephisto multi-band optical followup
  94. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  95. GRB 250101A: LCOGT optical afterglow detection
  96. GRB 250101A: OASDG optical observations
  97. Fermi GRB 250101B: Global MASTER-Net observations report
  98. GRB 250101A: SAO RAS observations of optical brightening
  99. GRB 250101A: AKO Optical Afterglow Detection
  100. GRB 250101A: SAO RAS optical observations

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