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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"

19190 results found.

  1. GRB 250814A: Further GRAWITA TNG NIR observations
  2. GRB 250818B: Swift-XRT afterglow detection
  3. GRB 250818A: Swift detection of a burst
  4. sb25081602: Swift-XRT observations
  5. GRB 250814A: Swift-BAT refined analysis
  6. GRB 250814A: Further COLIBRÍ optical upper limit
  7. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  8. GRB 250814A: GRAWITA TNG NIR observations
  9. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  10. GRB250814A: TRT optical upper limits
  11. GRB 250814C: SVOM/GRM observation of a short burst
  12. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  13. GRB 250813B: SVOM/GRM observation
  14. GRB 250814A: P200/WIRC observations of the afterglow candidate
  15. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  16. GRB 250814A: KAIT optical upper limit
  17. GRB 250814A: Swift-XRT refined Analysis
  18. GRB 240814A: Fermi GBM Observation
  19. GRB 250814A: Possible afterglow candidate from P200/WIRC
  20. GRB 250814A: Optical observations with MDM Hiltner 2.4m telescope
  21. Swift GRB250814.32: Global MASTER-Net observations report
  22. GRB 250814A: J-band upper limit from WINTER
  23. GRB 250813B: SVOM/VT optical observations
  24. GRB 250814A: COLIBRÍ optical upper limit
  25. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  26. GRB 250814A: DDOTI Optical Upper Limit
  27. GRB 250813B: Swift-XRT afterglow detection
  28. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  29. EP250812a: NOT, NTT, and GS observations
  30. GRB 250812A: Swift/UVOT Detection
  31. EP250812a: SVOM/VT optical counterpart
  32. GRB 250812A: Swift ToO observations
  33. GRB 250807B: Swift-BAT refined analysis
  34. EP 250812a: GOTO optical upper limit
  35. GRB 250812A: Kilonova-Catcher optical afterglow detection
  36. EP250812a: Swift-XRT counterpart detection
  37. GRB 250812A: SVOM/VT optical afterglow confirmation
  38. GRB 250812A: Swift-XRT afterglow detection
  39. GRB 250809A: Swift-BAT refined analysis
  40. GRB 250807A: Swift-BAT refined analysis
  41. GRB 250809A: Swift/UVOT Detection
  42. Corrected Swift-XRT Refined Analysis of GRB 250809A
  43. GRB 250809A: Swift-XRT refined Analysis
  44. GRB 250807B: SVOM/VT optical observation
  45. GRB 250809A: LCOGT Optical Upper Limits
  46. GRB 250702B: Chandra X-ray Detection
  47. GRB 250808A: VLT X-shooter candidate counterpart
  48. GRB 250809A: Prompt enhanced Swift-XRT position
  49. GRB 250809A: Swift detection of a gamma ray burst
  50. GRB 250808A: Swift-XRT candidate counterpart detection
  51. GRB 250807A: SVOM/VT optical continued observation
  52. Konus-Wind detection of GRB 250807A
  53. GRB 250807B: Swift/UVOT Detection
  54. GRB 250807B: Kilonova-Catcher optical afterglow detection
  55. GRB 250807A: Swift/UVOT Detection
  56. GRB 250807A: Swift-XRT refined Analysis
  57. GRB 250807B: VLT/X-Shooter spectroscopic redshift z = 1.522
  58. GRB 250806A: SVOM/MXT refined analysis
  59. GRB 250806A: SVOM/ECLAIRs refined analysis
  60. GRB 250807A: SVOM/GRM observation
  61. Swift GRB250807.45: Global MASTER-Net observations report
  62. GRB 250807A: AstroSat CZTI detection of bright long burst
  63. GRB 250807B: Swift-XRT refined Analysis
  64. GRB 250807B: NTT optical observations
  65. GRB 250807A: SVOM/VT optical observation
  66. GRB 250807B: Enhanced Swift-XRT position
  67. Swift GRB250807.65: Global MASTER-Net observations report
  68. GRB 250807A: Enhanced Swift-XRT position
  69. GRB 250807B: Swift detection of a burst with an optical counterpart.
  70. GRB 250805A: Kilonova-Catcher optical upper limits
  71. GRB 250805A: Swift/UVOT Upper Limits
  72. GRB 250806A: Swift/UVOT U-band detection
  73. GRB 250807A: Swift detection of a burst with an optical counterpart
  74. GRB 250806A: EP-FXT observation
  75. EP#01709198415/EP250806a: Swift-XRT observations
  76. GRB 250805A: Swift-BAT refined analysis
  77. GRB 250806A: KAIT optical upper limit
  78. GRB 250806A: SVOM/VT refined analysis
  79. GRB 250806A: Swift-XRT counterpart detection
  80. GRB 250805A: SVOM/VT optical counterpart
  81. GRB 250805A: ESO/VLT observations
  82. GRB 250805A: Swift-XRT refined Analysis
  83. GRB 250804B: Swift-XRT observations
  84. GRB 250805A: Enhanced Swift-XRT position
  85. GRB 250805A: TRT optical upper limits
  86. GRB 250805A: Swift-XRT observations
  87. GRB 250805A: Swift detection of a burst
  88. Swift GRB250805.26: Global MASTER-Net observations report
  89. GRB 250804B: Tiled Swift observations
  90. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  91. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  92. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  93. LIGO/Virgo/KAGRA S250727dc: Swift-UVOT follow up of AT 2025smm
  94. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  95. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  96. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  97. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  98. GRB 250725A: AstroSat CZTI detection
  99. GRB 250727A: EP-FXT follow-up observation
  100. GRB 250725A: PRIME near-infrared observations

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