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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"

27777 results found.

  1. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  2. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  3. Konus-Wind detection of GRB 250107C
  4. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  5. EP250109a: Swift/UVOT non-detection
  6. Konus-Wind detection of GRB 250107D (short/hard)
  7. IPN triangulation of GRB 250107D (short/hard)
  8. IPN triangulation of GRB 250107C
  9. EP250108a: Liverpool Telescope likely optical counterpart
  10. GRB 250108B: Gemini-North likely redshift z = 2.197
  11. GRB 250108B: Swift-BAT refined analysis
  12. GRB 250108B: 1.3m DFOT upper limit
  13. GRB 250108B: REM optical/NIR upper limits
  14. GRB 250109A /EP250109a: Fermi GBM Final Localization
  15. EP250109a: GOTO optical upper limits
  16. EP250109a: Swift/XRT non-detection
  17. GRB 250108A: Swift/UVOT Upper Limits
  18. EP250109a: EP-WXT detection of an X-ray transient
  19. GRB 250108A: NOT optical upper limit
  20. EP250108a: EP-WXT detection of an X-ray transient
  21. GRB 250108B: Swift-XRT refined Analysis
  22. Swift GRB 250108B: Global MASTER-Net observations report
  23. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  24. GRB 250103A: 1.6m Mephisto optical observations
  25. GRB 250108A: Swift-XRT afterglow detection
  26. GRB 250108B: Swift/UVOT Upper Limits
  27. GRB 250103A: Swift-XRT afterglow detection
  28. GRB 250108B: Enhanced Swift-XRT position
  29. GRB 250108B: Swift detection of a burst
  30. GRB 250108A: Swift ToO observations
  31. GRB 250108A: SVOM detection of a soft long burst
  32. GRB 250107A: Fermi GBM Observation
  33. GRB 241228B: Fermi-LAT detection
  34. GRB 250107A: Swift ToO observations
  35. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  36. GRB 250107B: Fermi GBM Final Real-time Localization
  37. GRB 250107A: Fermi GBM Final Real-time Localization
  38. EPWXT01709129925: Xinglong optical observations
  39. GRB 250106A: NOT optical observations
  40. GRB 250103B: REM optical/NIR upper limits
  41. GRB 250101A: REM optical/NIR counterpart detection
  42. GRB 250106A: Swift-XRT observations
  43. GRB 250106A: Swift ToO observations
  44. GRB 250106A: SVOM detection of a long burst
  45. GRB 241229A: SVOM/VT optical upperlimit
  46. GRB 250103B: Swift-XRT refined Analysis
  47. GRB 250103B: LCO/1m optical afterglow candidate detection
  48. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  49. GRB 250103A: Swift-XRT observations
  50. GRB 250101A: 1.3m DFOT optical afterglow detection
  51. GRB 241229A: 1.3m DFOT upper limit
  52. GRB 241228B: 1.3m DFOT Optical observations
  53. GRB 241228A: 1.3m DFOT upper limit
  54. GRB 250103A: NOT spectroscopic redshift
  55. GRB 250103B:SVOM/VT optical counterpart
  56. GRB 250103A: Montarrenti Observatory optical detection
  57. GRB 250101A: further LCOGT optical afterglow observations
  58. GRB 250103A: TSHAO optical upper limit
  59. GRB 250103B: LCOGT Optical Upper Limit
  60. Swift GRB 250103B: Global MASTER-Net observations report
  61. GRB 250103A: Swift ToO observations
  62. GRB 250101a: Liverpool Telescope optical follow-up
  63. GRB 250103B: SVOM detection of a long burst
  64. GRB 250103B: Swift detection of a burst
  65. GRB 250103A: GOTO optical upper limit
  66. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  67. GRB 250103A: SVOM detection of a long burst
  68. EP250101a: Xinglong optical upper limit
  69. GRB 250102A: Fermi GBM Final Real-time Localization
  70. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  71. GRB 250101A: Swift-BAT refined analysis
  72. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  73. GRB 250101A: further SAO RAS optical observations
  74. GRB 250101A: LCO optical counterpart detection
  75. EP241231b and EP250101a: EP-WXT detection of two X-ray transients
  76. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  77. GRB 250101A: Swift/UVOT Detection
  78. GRB 250101A: 1.6m Mephisto multi-band optical followup
  79. GRB 250101A: Swift-XRT refined Analysis
  80. GRB 250101A: Montarrenti Observatory optical observations and rebrightening
  81. IceCube-250101A - IceCube observation of a high-energy neutrino candidate track-like event
  82. GRB 250101A: LCOGT optical afterglow detection
  83. GRB 250101A: OASDG optical observations
  84. GRB 250101B: Fermi GBM Final Real-time Localization
  85. GRB 250101A: BOOTES-4/MET optical afterglow detection
  86. GRB 250101A: AKO Optical Afterglow Detection
  87. GRB 250101A: SAO RAS optical observations
  88. GRB 250101A: Enhanced Swift-XRT position
  89. GRB 250101A: Xinglong-2.16m spectroscopic redshift
  90. GRB 250101A: SVOM/C-GFT early optical observations
  91. LIGO/Virgo/KAGRA S250101k: Upper limits from Fermi-GBM Observations
  92. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  93. GRB 250101A: Nanshan/HMT optical observations
  94. GRB 250101A : GIT optical detection
  95. GRB 250101A: Swift detection of a burst with an optical counterpart
  96. Swift GRB250101.56: Global MASTER-Net observations report
  97. GRB 241217a/EP241217b: ATCA Radio Detection
  98. EP241217a: VLA Radio Detection

  99. GRB 241229A: EP-FXT X-ray afterglow confirmation
  100. GRB 241228B: Multiband optical monitoring with 1.6m Mephisto

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