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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"

20358 results found.

  1. GRB 260120B: COLIBRÍ optical upper limits
  2. GRB 260120B: Enhanced Swift-XRT position
  3. GRB 260120B: SVOM/C-GFT optical counterpart detection
  4. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  5. GRB 260120B: Swift detection of a burst
  6. EP260119A: Mondy I-Band Observations
  7. GRB 260114A: Swift/UVOT Upper Limits
  8. EP260119a: Liverpool Telescope optical follow-up observations
  9. GRB 251202A: further radio observations with the VLA
  10. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  11. EP260119a: KAIT optical observations
  12. EP260119a: SVOM/VT optical observation
  13. EP260119a: NOT optical observations
  14. EP260119a: SAO RAS optical observations
  15. EP260116a: COLIBRÍ detection of a fading optical source
  16. GRB 251208D: SVOM/ECLAIRs refined analysis
  17. GRB 251208D: SVOM/ECLAIRs refined analysis
  18. GRB 260117A: Swift-XRT afterglow detection
  19. EP260119a: COLIBRÍ photometric redshift z ≈ 5.6
  20. EP260119a: LCO optical observations
  21. GRB 260117A: ZTSh optical upper limit
  22. EP260119a: COLIBRÍ optical counterpart candidate
  23. GRB 260110A: SVOM detection of a burst through offline search
  24. EP260119a: EP-WXT detection of a fast X-ray transient
  25. GRB 260117A: SVOM/COLIBRÍ (FM-GFT) optical observations
  26. Fermi-LAT Gamma-ray Observations of IceCube-260115A
  27. Swift trigger on the HMXB 1A 1118-61
  28. GRB 260117A: SVOM/C-GFT upper limit
  29. GRB 260117A: SVOM detection of a long faint burst
  30. EP 260116a: COLIBRÍ optical upper limit
  31. Swift triggered on the HMXB 1A 1118-61
  32. FRB 20251229A: COLIBRÍ further inspection of the updated localization
  33. EP260116a: Liverpool Telescope upper limits
  34. EP260116A: 1.3m DFOT optical upper limit
  35. GRB 260114A: VLT/MUSE spectroscopic observations
  36. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  37. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  38. EP260116a: Xinglong optical upper limit
  39. EP260116a: Einstein Probe detection of an X-ray transient
  40. GRB 260114A: VLT/HAWK-I further near-infrared upper limits
  41. GRB 251222A: radio detection with the VLA
  42. GRB 260114A: VLT/HAWK-I near-infrared upper limits
  43. GRB 260114A: Swift-XRT refined Analysis
  44. GRB 260114A: 6 GHz VLA observations
  45. GRB 260114A: VLT/X-shooter redshift of the putative host galaxy
  46. GRB 260114A : MITSuME Akeno optical upper limits
  47. GRB 260114A: COLIBRÍ optical upper limits
  48. GRB 260114A: TNG NIR upper limit
  49. GRB 260114A: NOT optical observations
  50. GRB 260114A: SVOM/GRM observation of a short burst
  51. GRB 260114A: Mondy optical observations
  52. GRB 260114A: GMG Optical Observation
  53. GRB 260114A: Swift detection of a short burst
  54. EP-WXT trigger 01709251266: SVOM/C-GFT confirmation of a stellar flare
  55. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  56. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  57. EP260110a: TRT optical upper limits
  58. Swift Trigger 1439093: is probably not GRB 260113A
  59. GRB 260111A: COLIBRÍ optical afterglow candidate
  60. GRB 251230A: Mondy Optical Observations
  61. Swift trigger 1436759 is not an astrophysical event
  62. EP260110a: KAIT optical upper limit
  63. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  64. EP 260110a: COLIBRÍ optical observations
  65. EP260110a: SVOM/C-GFT upper limit
  66. EP260110a: Einstein Probe detection of an X-ray transient
  67. GRB 260109C: LCO optical upper limits
  68. GRB 260109C: Kilonova-Catcher optical upper limit
  69. Swift Trigger 1434591: possible GRB 260109C
  70. GRB 260102A: Swift-XRT afterglow detection
  71. GRB 260102A: AbAO optical observations
  72. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  73. Fermi GRB 260105A: Global MASTER-Net observations report
  74. GRB 260105A: SVOM/GRM observation
  75. GRB 260105B: SVOM/GRM observation
  76. FRB 20251229A: COLIBRÍ optical upper limits
  77. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  78. EP260105a: LCO Optical Upper limit
  79. EP260104a: Einstein Probe detection of a fast X-ray transient
  80. GRB 260101A: COLIBRÍ optical upper limits
  81. EP260105a: Einstein Probe detection of an X-ray transient
  82. GRB 260104A: COLIBRÍ optical upper limits
  83. GRB 260104C: Fermi GBM Final Real-time Localization
  84. GRB 251230A/EP-WXT trigger 01709250693: Mephisto optical upper limits
  85. GRB 260104A: Enhanced Swift-XRT position
  86. GRB 260101A: Swift/UVOT Detection
  87. GRB 260104A: Swift detection of a burst
  88. Fermi-LAT Gamma-ray Observations of IceCube-251225A
  89. GRB 260101A: COLIBRÍ optical observations
  90. GRB 260102A: LCO optical upper limits
  91. GRB 260102A: SVOM/COLIBRÍ (FM-GFT) optical observations
  92. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  93. GRB 260102A: SVOM detection of a burst
  94. GRB 260101A: NOT spectroscopic observations
  95. GRB 260101A: SVOM/GRM observation
  96. GRB 260101A: Enhanced Swift-XRT position
  97. EP260101a: Einstein Probe detection of an X-ray transient
  98. GRB 260101A: LCO detection of the optical counterpart
  99. GRB 260101A: Swift detection of a burst with an optical counterpart
  100. GRB 251230A: GRANDMA/TAROT Early Detection

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