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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"

27803 results found.

  1. GRB 250114A: Swift-XRT refined Analysis
  2. GRB 250114A: LCOGT optical afterglow i-band detection
  3. GRB 250114B: Swift ToO observations
  4. EP250111a: SAO RAS optical upper limit
  5. GRB 250114A: Enhanced Swift-XRT position
  6. GRB 250113A: INTEGRAL/SPI-ACS detection
  7. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  8. GRB 250114A: REM detection of the optical and NIR counterpart
  9. Swift GRB250114A: Global MASTER-Net OT detection
  10. GRB 250114A: LCO optical observations
  11. GRB 250114A: TRT optical observations
  12. Swift GRB 250114A: Global MASTER-Net observations report
  13. GRB 250114A: Swift detection of a burst with an optical counterpart
  14. GRB 250107A: VZLUSAT-2 detection
  15. GRB 250109A / EP250109a: GRBAlpha detection
  16. GRB 250107D: GRBAlpha detection
  17. GRB 250106A: Swift-XRT afterglow detection
  18. GRB 250109A / EP250109a: Mephisto optical upper limits
  19. EP250108a: Mephisto detection
  20. EP250111a: Swift/XRT detection and fading
  21. EP250108a / AT 2025kg: Swift UVOT detections
  22. EP250111a: a new X-ray transient detected by Einstein Probe
  23. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  24. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  25. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  26. GRB 250108A: Swift/XRT afterglow fading
  27. GRB 250107D: CALET Gamma-Ray Burst Monitor detection
  28. GRB 250107C: CALET Gamma-Ray Burst Monitor detection
  29. Konus-Wind detection of GRB 250107C
  30. EP250109a / GRB 250109A: refined EP-WXT analysis and EP-FXT follow-up observation
  31. EP250109a: Swift/UVOT non-detection
  32. Konus-Wind detection of GRB 250107D (short/hard)
  33. IPN triangulation of GRB 250107D (short/hard)
  34. IPN triangulation of GRB 250107C
  35. EP250108a: Liverpool Telescope likely optical counterpart
  36. GRB 250108B: Gemini-North likely redshift z = 2.197
  37. GRB 250108B: Swift-BAT refined analysis
  38. GRB 250108B: 1.3m DFOT upper limit
  39. GRB 250108B: REM optical/NIR upper limits
  40. GRB 250109A /EP250109a: Fermi GBM Final Localization
  41. EP250109a: GOTO optical upper limits
  42. EP250109a: Swift/XRT non-detection
  43. GRB 250108A: Swift/UVOT Upper Limits
  44. EP250109a: EP-WXT detection of an X-ray transient
  45. GRB 250108A: NOT optical upper limit
  46. EP250108a: EP-WXT detection of an X-ray transient
  47. GRB 250108B: Swift-XRT refined Analysis
  48. Swift GRB 250108B: Global MASTER-Net observations report
  49. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  50. GRB 250103A: 1.6m Mephisto optical observations
  51. GRB 250108A: Swift-XRT afterglow detection
  52. GRB 250108B: Swift/UVOT Upper Limits
  53. GRB 250103A: Swift-XRT afterglow detection
  54. GRB 250108B: Enhanced Swift-XRT position
  55. GRB 250108B: Swift detection of a burst
  56. GRB 250108A: Swift ToO observations
  57. GRB 250108A: SVOM detection of a soft long burst
  58. GRB 250107A: Fermi GBM Observation
  59. GRB 241228B: Fermi-LAT detection
  60. GRB 250107A: Swift ToO observations
  61. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  62. GRB 250107B: Fermi GBM Final Real-time Localization
  63. GRB 250107A: Fermi GBM Final Real-time Localization
  64. EPWXT01709129925: Xinglong optical observations
  65. GRB 250106A: NOT optical observations
  66. GRB 250103B: REM optical/NIR upper limits
  67. GRB 250101A: REM optical/NIR counterpart detection
  68. GRB 250106A: Swift-XRT observations
  69. GRB 250106A: Swift ToO observations
  70. GRB 250106A: SVOM detection of a long burst
  71. GRB 241229A: SVOM/VT optical upperlimit
  72. GRB 250103B: Swift-XRT refined Analysis
  73. GRB 250103B: LCO/1m optical afterglow candidate detection
  74. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  75. GRB 250103A: Swift-XRT observations
  76. GRB 250101A: 1.3m DFOT optical afterglow detection
  77. GRB 241229A: 1.3m DFOT upper limit
  78. GRB 241228B: 1.3m DFOT Optical observations
  79. GRB 241228A: 1.3m DFOT upper limit
  80. GRB 250103A: NOT spectroscopic redshift
  81. GRB 250103B:SVOM/VT optical counterpart
  82. GRB 250103A: Montarrenti Observatory optical detection
  83. GRB 250101A: further LCOGT optical afterglow observations
  84. GRB 250103A: TSHAO optical upper limit
  85. GRB 250103B: LCOGT Optical Upper Limit
  86. Swift GRB 250103B: Global MASTER-Net observations report
  87. GRB 250103A: Swift ToO observations
  88. GRB 250101a: Liverpool Telescope optical follow-up
  89. GRB 250103B: SVOM detection of a long burst
  90. GRB 250103B: Swift detection of a burst
  91. GRB 250103A: GOTO optical upper limit
  92. GRB 250103A: SVOM detection of a long burst (duplicate submission)
  93. GRB 250103A: SVOM detection of a long burst
  94. EP250101a: Xinglong optical upper limit
  95. GRB 250102A: Fermi GBM Final Real-time Localization
  96. LIGO/Virgo/KAGRA S241230bd: Upper limits from Swift/BAT-GUANO
  97. GRB 250101A: Swift-BAT refined analysis
  98. IceCube-250102A - IceCube observation of a high-energy neutrino candidate track-like event
  99. GRB 250101A: further SAO RAS optical observations
  100. GRB 250101A: LCO optical counterpart detection

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