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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"

18513 results found.

  1. GRB 250107A: Fermi GBM Observation
  2. GRB 241228B: Fermi-LAT detection
  3. GRB 250107A: Swift ToO observations
  4. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  5. GRB 250106A: NOT optical observations
  6. GRB 250103B: REM optical/NIR upper limits
  7. GRB 250101A: REM optical/NIR counterpart detection
  8. GRB 250106A: Swift-XRT observations
  9. GRB 250106A: Swift ToO observations
  10. GRB 241229A: SVOM/VT optical upperlimit
  11. GRB 250103B: Swift-XRT refined Analysis
  12. GRB 250103B: LCO/1m optical afterglow candidate detection
  13. GRB 250103A: Swift-XRT observations
  14. GRB 250101A: 1.3m DFOT optical afterglow detection
  15. GRB 241229A: 1.3m DFOT upper limit
  16. GRB 241228A: 1.3m DFOT upper limit
  17. GRB 250103B：SVOM/VT optical counterpart
  18. GRB 250101A: further LCOGT optical afterglow observations
  19. GRB 250103B: LCOGT Optical Upper Limit
  20. Swift GRB 250103B: Global MASTER-Net observations report
  21. GRB 250103A: Swift ToO observations
  22. GRB 250101a: Liverpool Telescope optical follow-up
  23. GRB 250103B: SVOM detection of a long burst
  24. GRB 250103B: Swift detection of a burst
  25. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  26. GRB 250101A: Swift-BAT refined analysis
  27. GRB 250101A: further SAO RAS optical observations
  28. GRB 250101A: LCO optical counterpart detection
  29. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  30. GRB 250101A: Swift/UVOT Detection
  31. GRB 250101A: 1.6m Mephisto multi-band optical followup
  32. GRB 250101A: Swift-XRT refined Analysis
  33. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  34. GRB 250101A: LCOGT optical afterglow detection
  35. GRB 250101A: OASDG optical observations
  36. GRB 250101A: BOOTES-4/MET optical afterglow detection
  37. GRB 250101A: SAO RAS optical observations
  38. GRB 250101A: Enhanced Swift-XRT position
  39. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  40. GRB 250101A: SVOM/C-GFT early optical observations
  41. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  42. GRB 250101A: Nanshan/HMT optical observations
  43. GRB 250101A : GIT optical detection
  44. GRB 250101A: Swift detection of a burst with an optical counterpart
  45. Swift GRB250101.56: Global MASTER-Net observations report
  46. EP241217a: VLA Radio Detection

  47. GRB 241229A: EP-FXT X-ray afterglow confirmation
  48. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto
  49. GRB 241229B: SVOM/GRM observation
  50. EP241217A: J band upper limit by SYSU 80cm telescope
  51. GRB 241228B: SAO RAS optical observations
  52. GRB 241229B: SVOM/VT optical candidate
  53. GRB 241229A: Swift-XRT observations
  54. Konus-Wind detection of GRB 241228A
  55. GRB 241229A: EP-FXT afterglow candidates
  56. GRB 240606B: 7DT Optical upper limits
  57. GRB 241229B: Swift-BAT refined analysis
  58. GRB241229B: UVOT upper limits
  59. GRB 241228B: D50 optical detection
  60. GRB 241228B: Fermi GBM Observation
  61. GRB 241228B: Swift-XRT afterglow detection
  62. GRB 241229B: Fermi GBM Observation
  63. GRB 241229A: Swift ToO observations
  64. GRB 241229B: Swift-XRT refined Analysis
  65. Swift GRB 241229B: Global MASTER-Net observations report
  66. GRB 241228A: NOT optical upper limits
  67. GRB 241228A: Swift-BAT refined analysis
  68. GRB 241228B: Swift/BAT-GUANO localization skymap of a burst
  69. GRB 241229B: Swift detection of a burst
  70. GRB 241228A: Fermi GBM Observation
  71. Swift GRB 241228A: Global MASTER-Net observations report
  72. GRB 241226A: Swift/BAT-GUANO localization skymap of a burst
  73. GRB 241228A: GROWTH-India telescope optical upper limit
  74. GRB 241228B: Swift ToO observations
  75. GRB 241228A: Swift-XRT refined Analysis
  76. GRB 241228A: Swift/UVOT Upper Limits
  77. GRB 241228A: Enhanced Swift-XRT position
  78. GRB 241228A: Swift detection of a burst
  79. GRB 241223A: Swift-XRT observations
  80. GRB241113A: 7DT Optical upper limits
  81. GRB 241223A: GOTO optical observations summary
  82. GRB 241223A: Swift ToO observations
  83. GRB 241218A: Mondy AZT-33IK optical upper limit
  84. GRB 241218A: Swift/UVOT Upper Limits
  85. EP241217a: optical upper limit with the Liverpool Telescope
  86. GRB 241209B: EP-FXT afterglow detection
  87. GRB 241218A: NOT optical upper limits
  88. GRB 241218A: Swift-BAT refined analysis
  89. EP241217a: refined EP-WXT analysis and EP-FXT follow-up observations
  90. GRB 241217A: refined SVOM/MXT data analysis. Long lasting X-ray emission.
  91. GRB 241218A: REM optical upper limit
  92. GRB 241217A/EP241217b: REM optical/NIR upper limits
  93. EP241217a: REM optical/NIR upper limits
  94. GRB 241218a: Liverpool Telescope optical follow-up
  95. GRB 241217a: Liverpool Telescope optical follow-up
  96. GRB 241218A: Swift-XRT refined Analysis
  97. GRB 241209A: ATCA radio follow-up observations
  98. GRB 241218A: LCOGT Optical Upper Limit
  99. GRB 241218A: Enhanced Swift-XRT position
  100. GRB 241218A: Swift detection of a burst

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