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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"

20258 results found.

  1. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  2. GRB 251102B: SVOM/GRM observation
  3. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  4. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  5. GRB 251106A: Swift-XRT afterglow detection
  6. GRB 251106A: Kilonova-Catcher optical upper limit
  7. Fermi GBM Sub-Threshold Detection of GRB 251106A
  8. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  9. GRB 251106A: MASTER optical observations
  10. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  11. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  12. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  13. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  14. GRB 251103B: Swift/UVOT Upper Limits
  15. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  16. GRB 251105A: Fermi GBM Final Real-time Localization
  17. GRB 251103B: Fermi GBM observation
  18. GRB 251104A: SVOM detection of a burst
  19. GRB 251103A: WFST optical observations
  20. EP251102a: OHP/T193 optical observations
  21. GRB 251103A: OHP/T193 optical observations
  22. GRB 251103A: Xinglong 2.16m optical detection
  23. GRB 251103A: KAIT optical observations
  24. GRB 251103B: Nanshan/HMT optical upper limit
  25. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  26. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  27. GRB 251103B: MITSuME Akeno optical upper limits
  28. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  29. EP251102a: NIR observations with WINTER
  30. GRB 251103A: J-band detection with WINTER
  31. GRB 251103B: GROWTH-India Telescope optical upper limits
  32. GRB 251103A: Kilonova-Catcher optical afterglow detection
  33. GRB 251103B: Enhanced Swift-XRT position
  34. GRB 251103B: Swift detection of a burst
  35. GRB 251103A: Swift/UVOT Detection
  36. GRB 251103A: Swift-XRT afterglow detection
  37. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  38. EP251102a: Einstein Probe detection of a fast X-ray transient
  39. GRB 251025B: OHP/T193 optical upper limit
  40. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  41. GRB 251103A: LCO optical observation
  42. EP251102.890: COLIBRÍ optical counterpart candidate
  43. GRB 251102A: AstroSat CZTI detection
  44. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  45. GRB 251103A: LCO optical afterglow detection
  46. GRB 251103A: NOT optical afterglow candidate
  47. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  48. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  49. Konus-Wind detection of GRB 251028A
  50. GRB 251025C: SVOM/GRM observation
  51. GRB 251028A: GECAM-B detection
  52. GRB 251028A: SVOM/GRM observation
  53. GRB 251022A: Swift-XRT confirmation of fading
  54. GRB 250926B: VZLUSAT-2 detection
  55. GRB 250926A: VZLUSAT-2 detection
  56. GRB 250925A: VZLUSAT-2 detection
  57. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  58. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  59. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  60. GRB251026B: PRIME H-band upper limit
  61. GRB251025B: 3.6m DOT Optical Observations
  62. SVOM trigger sb25102702/GRB 251027A is not a GRB
  63. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  64. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  65. GRB 251023B: Swift-UVOT Upper Limits
  66. Konus-Wind detection of GRB 251022A
  67. GRB 251027A: Swift-XRT observations
  68. EP251027.145: COLIBRÍ optical upper limits
  69. GRB 251022A: SVOM/GRM observation
  70. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  71. GRB 251027A: LCO optical upper limit
  72. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  73. GRB 251023B / EP251023b: Mondy optical upper limit
  74. GRB 251017A: INASAN-Kislovodsk optical observations
  75. GRB 251026A: Mondy optical upper limit
  76. GRB 251025B: Mondy optical observations
  77. GRB 251025B: Kilonova-Catcher optical afterglow detection
  78. Konus-Wind detection of GRB 251016A (short/hard)
  79. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  80. GRB 251027A: SVOM detection of a faint burst
  81. GRB 251026B: Tentative GOTO optical counterpart candidate
  82. EP251023a: Mondy optical observations
  83. GRB 251025B: MAO/AZT-22 optical observations
  84. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  85. GRB 251025B: OHP/T193 optical detection
  86. GRB 251025B: J-band detection with WINTER
  87. GRB 251026A: SVOM/C-GFT upper limit
  88. IceCube-251025A: DDOTI Optical Upper Limit
  89. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  90. GRB 251026A: SVOM detection of a long burst
  91. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  92. GRB 251023A: SVOM/GRM observation
  93. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  94. Konus-Wind detection of GRB 251016B
  95. GRB 251025B: GROWTH-India Telescope optical observations
  96. GRB 251024A: Swift/UVOT Upper Limits
  97. GRB 251025B: Swift-XRT afterglow detection
  98. GRB 251025A (sb25102501): stellar flare confirmed
  99. GRB 251025B: SVOM/VT optical observations with VHF data
  100. GRB 251025B: MASTER OT detection

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