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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"

22854 results found.

  1. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  2. GRB 251105A: AstroSat CZTI detection
  3. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  4. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  5. GRB 251102B: SVOM/GRM observation
  6. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  7. IPN triangulation of GRB 251105B (possible sGRB with EE)
  8. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  9. GRB 251106A: Swift-XRT afterglow detection
  10. GRB 251106A: Kilonova-Catcher optical upper limit
  11. GRB 251106A: Swift/BAT arcminute localization of a burst
  12. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  13. GRB 251106A: MASTER optical observations
  14. GRB 251025C: TERI Gamma-ray detection
  15. GRB 251016B: TERI Gamma-ray detection
  16. GRB 251016A: TERI Gamma-ray detection of a short burst
  17. GRB 250920C: TERI Gamma-ray detection
  18. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  19. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  20. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  21. GRB 251103B: Swift/UVOT Upper Limits
  22. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  23. GRB 251103A: WFST optical observations
  24. GRB 251103A: Xinglong 2.16m optical detection
  25. GRB 251103A: KAIT optical observations
  26. GRB 251103B: Nanshan/HMT optical upper limit
  27. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  28. GRB 251103B: MITSuME Akeno optical upper limits
  29. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  30. EP251102a: NIR observations with WINTER
  31. GRB 251103A: J-band detection with WINTER
  32. GRB 251103B: GROWTH-India Telescope optical upper limits
  33. GRB 251103A: Kilonova-Catcher optical afterglow detection
  34. GRB 251103B: Enhanced Swift-XRT position
  35. GRB 251103B: Swift detection of a burst
  36. GRB 251103B: Fermi GBM Final Real-time Localization
  37. GRB 251103A: Swift/UVOT Detection
  38. GRB 251103A: Fermi GBM Observation
  39. GRB 251103A: Swift-XRT afterglow detection
  40. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  41. EP251102a: Einstein Probe detection of a fast X-ray transient
  42. GRB 251025B: OHP/T193 optical upper limit
  43. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  44. GRB 251103A: LCO optical observation
  45. EP251102.890: COLIBRÍ optical counterpart candidate
  46. GRB 251103A: GOTO optical afterglow detection
  47. GRB 251102A: AstroSat CZTI detection
  48. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  49. GRB 251103A: BOOTES-2/TELMA optical afterglow
  50. GRB 251103A: LCO optical afterglow detection
  51. GRB 251103A: NOT optical afterglow candidate
  52. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  53. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  54. GRB 251025C: SVOM/GRM observation
  55. GRB 251028A: SVOM/GRM observation
  56. GRB 251022A: Swift-XRT confirmation of fading
  57. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  58. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  59. GRB 251028B: Glowbug gamma-ray detection
  60. GRB 251028A: Glowbug gamma-ray detection
  61. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  62. GRB251026B: PRIME H-band upper limit
  63. GRB251025B: 3.6m DOT Optical Observations
  64. SVOM trigger sb25102702/GRB 251027A is not a GRB
  65. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  66. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  67. GRB 251025C: Glowbug gamma-ray detection
  68. GRB 251023B: Swift-UVOT Upper Limits
  69. GRB 251027A: Swift-XRT observations
  70. EP251027.145: COLIBRÍ optical upper limits
  71. GRB 251022A: SVOM/GRM observation
  72. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  73. GRB 251027A: LCO optical upper limit
  74. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  75. GRB 251023B / EP251023b: Mondy optical upper limit
  76. GRB 251017A: INASAN-Kislovodsk optical observations
  77. GRB 251026A: Mondy optical upper limit
  78. GRB 251025B: Mondy optical observations
  79. GRB 251025B: Kilonova-Catcher optical afterglow detection
  80. Konus-Wind detection of GRB 251016A (short/hard)
  81. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  82. GRB 251026B: Tentative GOTO optical counterpart candidate
  83. EP251023a: Mondy optical observations
  84. GRB 251025B: MAO/AZT-22 optical observations
  85. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  86. GRB 251026A: Swift-XRT observations
  87. GRB 251025B: OHP/T193 optical detection
  88. GRB 251025B: J-band detection with WINTER
  89. GRB 251026A: SVOM/C-GFT upper limit
  90. IceCube-251025A: DDOTI Optical Upper Limit
  91. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  92. GRB 251026A: SVOM detection of a long burst
  93. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  94. GRB 251023A: SVOM/GRM observation
  95. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  96. GRB 251025B: GROWTH-India Telescope optical observations
  97. GRB 251024A: Swift/UVOT Upper Limits
  98. GRB 251025B: Swift-XRT afterglow detection
  99. GRB 251024A: Swift-BAT refined analysis
  100. GRB 251025A (sb25102501): stellar flare confirmed

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