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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

16118 results found.

  1. EP250125a: REM optical counterpart detection
  2. EP250125a: Swift/XRT detection of a fading counterpart
  3. EP250125a: a new X-ray transient detected by Einstein Probe
  4. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  5. EP250108a: AbAO, CMO and Terskol optical upper limits
  6. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  7. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  8. EP 250108A: Late-time optical observation by LCO
  9. EP250108a / SN2025kg: Gemini GMOS-S confirmation of an associated broad-lined SN Ic
  10. EP250108a/AT 2025kg: NOT spectroscopy in agreement with SN Ic-BL
  11. EP250108a / AT 2025kg: the kangaroo is hopping, evidence for optical rebrightening
  12. EP250108a / AT2025kg: GMG Optical Observations
  13. EP250108a / AT2025kg: VLA radio upper limit
  14. GRB 241217A / EP241217B: radio detection with the VLA
  15. GRB 250114B: Swift-XRT afterglow detection
  16. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  17. GRB 250114B: Liverpool Telescope optical upper limit
  18. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  19. GRB 250114A: LCO optical counterpart detection.
  20. GRB 250114B: OHP/T193 optical upper limit
  21. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  22. GRB 250114A: LCOGT optical afterglow i-band detection
  23. GRB 250114B : GIT optical upper limit
  24. EP250111a: SAO RAS optical upper limit
  25. GRB 250114A: VLT/X-shooter spectroscopic redshift z = 4.732
  26. GRB 250114A: REM detection of the optical and NIR counterpart
  27. Swift GRB250114A: Global MASTER-Net OT detection
  28. GRB 250114A: LCO optical observations
  29. GRB 250114A: TRT optical observations
  30. GRB 250114A: Swift detection of a burst with an optical counterpart
  31. GRB 250101A: Terskol Zeiss-2000 optical observations
  32. EP250108a / AT 2025kg: SAO RAS optical observations
  33. EP241021a: SMA radio observation
  34. GRB 250113A: SVOM/GRM observation of a long burst
  35. EP250109b: optical upper limits with the Liverpool Telescope
  36. EP250111a: KAIT optical observations
  37. GRB 250109A / EP250109a: Mephisto optical upper limits
  38. EP250108a: Mephisto detection
  39. EP250111a: Mondy optical observation
  40. EP250108a / AT 2025kg: LCO optical observations
  41. EP250111a: Swift/XRT detection and fading
  42. EP250108a / AT 2025kg: Swift UVOT detections
  43. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  44. EP250108a: optical follow-up observations with the Liverpool Telescope
  45. EP250111a: NOT likely optical counterpart
  46. EP250109a/GRB 250109A:SVOM/VT optical counterpart
  47. EP250108a: further NOT optical observations
  48. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  49. GRB 250109A / EP250109a: Swift detection of the X-ray afterglow
  50. EP-WXT trigger EP250108a：Xinglong optical follow-up observations
  51. GRB 250101A: CMO RC-500 optical observations
  52. GRB 250109A: Fermi GBM Observation
  53. EP250108a: NOT optical observations
  54. EP-WXT trigger EP250109a：Xinglong optical follow-up observations
  55. GRB 250109a: GMG Optical Upper Limit
  56. EP250109a: Swift/UVOT non-detection
  57. EP250108a: Liverpool Telescope likely optical counterpart
  58. GRB 250108B: Gemini-North likely redshift z = 2.197
  59. GRB 250108B: 1.3m DFOT upper limit
  60. GRB 250108B: REM optical/NIR upper limits
  61. EP250109a: SVOM/VT optical candidate
  62. GRB 250101A: Terskol K-800 optical observations
  63. EP250109a: GOTO optical upper limits
  64. GRB 250108A: Swift/UVOT Upper Limits
  65. GRB 250108A: NOT optical upper limit
  66. GRB 250108B: Gemini-North Candidate Optical Afterglow Detection
  67. GRB 250103A: 1.6m Mephisto optical observations
  68. GRB 250108A:SVOM/VT optical candidate
  69. GRB 250108B: Swift/UVOT Upper Limits
  70. GRB 241228B: Fermi-LAT detection
  71. GRB 250106A: SVOM/VT 2nd optical deep observation
  72. GRB 250101A: J band upper limit by SYSU 80cm telescope
  73. EPWXT01709129925: Xinglong optical observations
  74. GRB 250106A: NOT optical observations
  75. GRB 250103B: REM optical/NIR upper limits
  76. GRB 250101A: REM optical/NIR counterpart detection
  77. GRB 250106A: Swift-XRT observations
  78. GRB 250106A: SVOM/VT optical candidate
  79. GRB 241229A: SVOM/VT optical upperlimit
  80. GRB 250103B: LCO/1m optical afterglow candidate detection
  81. GRB 250103A: Bassano Bresciano Observatory upper limit
  82. GRB 250103B: VLT/X-shooter spectroscopic redshift z = 1.416
  83. GRB 250103A: Swift-XRT observations
  84. GRB 250101A: 1.3m DFOT optical afterglow detection
  85. GRB 241229A: 1.3m DFOT upper limit
  86. GRB 241228B: 1.3m DFOT Optical observations
  87. GRB 241228A: 1.3m DFOT upper limit
  88. GRB 250103A: NOT spectroscopic redshift
  89. GRB 250103B：SVOM/VT optical counterpart
  90. GRB 250103A: Montarrenti Observatory optical detection
  91. GRB 250101A: further LCOGT optical afterglow observations
  92. GRB 250103A: Redshift 4.01 from OSIRIS+/GTC
  93. GRB 250103A: NOT optical observations
  94. GRB 250103A: TSHAO optical upper limit
  95. GRB 250103B: LCOGT Optical Upper Limit
  96. GRB 250103A: SVOM/VT optical counterpart confirmation
  97. EP250101a: Liverpool Telescope optical upper limit
  98. GRB 250101a: Liverpool Telescope optical follow-up
  99. GRB 250103A: Xinglong 2.16m Optical Candidate
  100. GRB 250101B: SVOM/GRM observation

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