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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"

15562 results found.

  1. EP251118a: VLT near-infrared observation
  2. GRB 251116D: SVOM/GRM observation of a long GRB
  3. EP251118a: GOTO optical afterglow detection
  4. EP251118a: NOT spectroscopic redshift of z = 1.216
  5. EP251118a: preliminary result of EP-FXT follow-up observation
  6. EP251118a: NOT candidate optical counterpart
  7. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  8. GRB 251117A: SVOM/GRM observation of a short burst
  9. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  10. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  11. GRB 251116B: SVOM/VT optical upper limit
  12. EP251023a: Assy AZT-20 optical observations
  13. EP251023a: UAFO and AbAO optical observations
  14. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  15. GRB 251116C: SVOM/VT optical upper limit
  16. GRB 251025B: further Mondy optical observations
  17. GRB 251111A: Mondy optical upper limit
  18. GRB 251116B: LCO optical upper limits
  19. GRB 251116C: LCO optical upper limits
  20. GRB 251116C: SVOM detection of a burst
  21. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  22. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  23. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  24. GRB 251112A: Swift/UVOT Upper Limits
  25. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  26. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  27. GRB251111A: 1.3m DFOT optical upper limit
  28. GRB 251111A: SVOM/VT optical observations with X-band data
  29. GRB 251111A: Swift-XRT observations
  30. GRB 251111A: EP-FXT counterpart detection
  31. GRB 251111A: SVOM/VT optical observations with VHF data
  32. GRB 251111A: KAIT optical upper limit
  33. GRB 251111A: LCO optical observation
  34. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  35. GRB 251106A: Swift/UVOT Upper Limits
  36. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  37. GRB 251102B: SVOM/GRM observation
  38. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  39. GRB 251106A: Swift-XRT afterglow detection
  40. GRB 251106A: Kilonova-Catcher optical upper limit
  41. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  42. GRB 251106A: MASTER optical observations
  43. GRB 251106A: SVOM detection of a burst
  44. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  45. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  46. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  47. GRB 251103B: Swift/UVOT Upper Limits
  48. GRB 251104A: SVOM detection of a burst
  49. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  50. EP251102a: FTW optical and NIR observations
  51. GRB 251103A: WFST optical observations
  52. EP251102a: OHP/T193 optical observations
  53. GRB 251103A: OHP/T193 optical observations
  54. GRB 251103A: Xinglong 2.16m optical detection
  55. GRB 251103A: KAIT optical observations
  56. GRB 251103B: Nanshan/HMT optical upper limit
  57. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  58. GRB 251103B: MITSuME Akeno optical upper limits
  59. EP251102a: NIR observations with WINTER
  60. GRB 251103A: J-band detection with WINTER
  61. GRB 251103B: GROWTH-India Telescope optical upper limits
  62. GRB 251103A: Kilonova-Catcher optical afterglow detection
  63. GRB 251103A: Swift/UVOT Detection
  64. GRB 251103A: SVOM/GRM observation
  65. GRB 251103A: Swift-XRT afterglow detection
  66. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  67. EP251102a: Einstein Probe detection of a fast X-ray transient
  68. GRB 251025B: OHP/T193 optical upper limit
  69. GRB 251103A: LCO optical observation
  70. EP251102.890: COLIBRÍ optical counterpart candidate
  71. GRB 251103A: GOTO optical afterglow detection
  72. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  73. GRB 251103A: NOT spectroscopic redshift z = 0.76
  74. GRB 251103A: BOOTES-2/TELMA optical afterglow
  75. GRB 251103A: LCO optical afterglow detection
  76. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  77. GRB 251103A: NOT optical afterglow candidate
  78. GRB 251103A: SVOM detection of a bright burst
  79. GRB 251025C: SVOM/GRM observation
  80. GRB 251028A: SVOM/GRM observation
  81. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
  82. GRB 251026B: LBT near-infrared observations
  83. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  84. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  85. GRB251026B: PRIME H-band upper limit
  86. GRB251025B: 3.6m DOT Optical Observations
  87. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  88. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  89. GRB 251023B: Swift-UVOT Upper Limits
  90. EP251027.145: COLIBRÍ optical upper limits
  91. GRB 251022A: SVOM/GRM observation
  92. GRB 251027A: LCO optical upper limit
  93. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  94. GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
  95. GRB 251023B / EP251023b: Mondy optical upper limit
  96. GRB 251017A: INASAN-Kislovodsk optical observations
  97. GRB 251026A: Mondy optical upper limit
  98. GRB 251025B: Mondy optical observations
  99. GRB 251025B: Kilonova-Catcher optical afterglow detection
  100. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003

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