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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"

17285 results found.

  1. EP260119a: Mondy and SAO RAS optical upper limits
  2. EP260119a: Xinglong optical upper limit
  3. The EP-WXT trigger 01709251871 is likely a flaring star
  4. GRB 260120B: Swift-BAT refined analysis
  5. GRB 260120B: Swift-XRT refined Analysis
  6. EP260116a: COLIBRÍ further observations
  7. EP260105a: GTC/HiPERCAM optical observations
  8. GRB 260120B: Swift/UVOT Detection
  9. GRB 260120B: COLIBRÍ optical upper limits
  10. GRB 260120B: Enhanced Swift-XRT position
  11. GRB 260120B: SVOM/C-GFT optical counterpart detection
  12. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  13. GRB 260120B: Swift detection of a burst
  14. EP260119A: Mondy I-Band Observations
  15. GRB 260114A: Swift/UVOT Upper Limits
  16. EP260119a: Liverpool Telescope optical follow-up observations
  17. GRB 251202A: further radio observations with the VLA
  18. EP260119a: KAIT optical observations
  19. EP260119a: SVOM/VT optical observation
  20. EP260119a: update of EP-FXT follow-up observation
  21. EP260119a: NOT optical observations
  22. EP260119a: SAO RAS optical observations
  23. EP260116a: COLIBRÍ detection of a fading optical source
  24. GRB 260117A: Swift-XRT afterglow detection
  25. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  26. GRB 260115A: AstroSat CZTI detection
  27. EP260119a: LCO optical observations
  28. GRB 260117A: ZTSh optical upper limit
  29. EP260119a: COLIBRÍ optical counterpart candidate
  30. EP260119a: preliminary result from the EP-FXT observation
  31. EP260119a: EP-WXT detection of a fast X-ray transient
  32. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  33. Swift trigger on the HMXB 1A 1118-61
  34. GRB 260117A: SVOM/C-GFT upper limit
  35. EP 260116a: COLIBRÍ optical upper limit
  36. Swift triggered on the HMXB 1A 1118-61
  37. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  38. EP260116a: Liverpool Telescope upper limits
  39. EP260116A: 1.3m DFOT optical upper limit
  40. GRB 260114A: VLT/MUSE spectroscopic observations
  41. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  42. EP260116a: Xinglong optical upper limit
  43. EP260116a: Einstein Probe detection of an X-ray transient
  44. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  45. Fermi GRB 260115A: Global MASTER-Net observations report
  46. GRB 251222A: radio detection with the VLA
  47. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  48. GRB 260114A: Swift-XRT refined Analysis
  49. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  50. GRB 260114A : MITSuME Akeno optical upper limits
  51. GRB 260114A: COLIBRÍ optical upper limits
  52. GRB 260114A: TNG NIR upper limit
  53. GRB 260114A: NOT optical observations
  54. GRB 260114A: SVOM/GRM observation of a short burst
  55. GRB 260114A: Mondy optical observations
  56. GRB 260114A: GMG Optical Observation
  57. GRB 260114A: Swift detection of a short burst
  58. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  59. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  60. EP260110a: TRT optical upper limits
  61. Swift Trigger 1439093: is probably not GRB 260113A
  62. GRB 260111A: COLIBRÍ optical afterglow candidate
  63. The EP-WXT trigger 01709251266 is likely a flaring star
  64. GRB 260111A: GOTO optical upper limits
  65. GRB 251230A: Mondy Optical Observations
  66. Swift trigger 1436759 is not an astrophysical event
  67. EP260110a: KAIT optical upper limit
  68. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  69. EP 260110a: COLIBRÍ optical observations
  70. EP260110a: SVOM/C-GFT upper limit
  71. EP260110a: Einstein Probe detection of an X-ray transient
  72. GRB 260109C: LCO optical upper limits
  73. GRB 260109C: Kilonova-Catcher optical upper limit
  74. Swift Trigger 1434591: possible GRB 260109C
  75. GRB 260109B: Fermi GBM Final Real-time Localization
  76. GRB 260102A: Swift-XRT afterglow detection
  77. GRB 260109A: Fermi GBM Final Real-time Localization
  78. GRB 260102A: AbAO optical observations
  79. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  80. The EP-WXT trigger 01709251112 is likely a flaring star
  81. GRB 260105A: SVOM/GRM observation
  82. GRB 260105B: SVOM/GRM observation
  83. The EP-WXT trigger 01709251028 is likely a flaring star
  84. FRB 20251229A: COLIBRÍ optical upper limits
  85. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  86. EP260105a: LCO Optical Upper limit
  87. EP260104a: Einstein Probe detection of a fast X-ray transient
  88. GRB 260101A: COLIBRÍ optical upper limits
  89. EP260105a: Einstein Probe detection of an X-ray transient
  90. GRB 260104A: COLIBRÍ optical upper limits
  91. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  92. GRB 260104A: Enhanced Swift-XRT position
  93. GRB 260101A: Swift/UVOT Detection
  94. GRB 260104A: Swift detection of a burst
  95. GRB 260101A: COLIBRÍ optical observations
  96. SVOM GRB260103.08: Global MASTER-Net observations report
  97. GRB 260102A: EP-FXT follow-up observation
  98. GRB 260102A: LCO optical upper limits
  99. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  100. EP260101a: refined analysis of the EP-WXT and EP-FXT observations

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