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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"

26507 results found.

  1. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  2. GRB 251106A: Swift-XRT afterglow detection
  3. GRB 251106A: Kilonova-Catcher optical upper limit
  4. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  5. GRB 251106A: MASTER optical observations
  6. GRB 251106A: SVOM detection of a burst
  7. GRB 251103B: AstroSat CZTI detection
  8. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  9. GRB 251105A: Fermi GBM Observation
  10. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  11. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  12. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  13. Fermi GBM Sub-Threshold Detection of GRB 251105B
  14. GRB 251103B: Swift/UVOT Upper Limits
  15. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  16. GRB 251103B: Fermi GBM observation
  17. GRB 251104A: SVOM detection of a burst
  18. GRB 251103A: WFST optical observations
  19. EP251102a: update of EP-FXT follow-up observation
  20. GRB 251103A: Xinglong 2.16m optical detection
  21. GRB 251103A: KAIT optical observations
  22. GRB 251103B: Nanshan/HMT optical upper limit
  23. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  24. GRB 251103B: MITSuME Akeno optical upper limits
  25. GRB 251103B: Swift-XRT refined Analysis
  26. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  27. EP251102a: NIR observations with WINTER
  28. GRB 251103A: J-band detection with WINTER
  29. GRB 251103B: GROWTH-India Telescope optical upper limits
  30. GRB 251103A: Kilonova-Catcher optical afterglow detection
  31. GRB 251103B: Enhanced Swift-XRT position
  32. GRB 251103B: Swift detection of a burst
  33. GRB 251103A: Swift/UVOT Detection
  34. GRB 251103A: Fermi GBM Observation
  35. GRB 251103A: SVOM/GRM observation
  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 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  44. GRB 251103A: BOOTES-2/TELMA optical afterglow
  45. GRB 251103A: LCO optical afterglow detection
  46. GRB 251103A: NOT optical afterglow candidate
  47. GRB 251103A: SVOM detection of a bright burst
  48. GRB 251102B: Fermi GBM Final Real-time Localization
  49. GRB 251102A: Fermi GBM Final Real-time Localization
  50. GRB 251031A: Fermi GBM Observation
  51. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  52. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  53. GRB 251025C: SVOM/GRM observation
  54. GRB 251028A: GECAM-B detection
  55. GRB 251028A: SVOM/GRM observation
  56. GRB 251028A: Fermi GBM Observation
  57. GRB 251022A: Swift-XRT confirmation of fading
  58. GRB 250926B: VZLUSAT-2 detection
  59. GRB 250926A: VZLUSAT-2 detection
  60. GRB 250925A: VZLUSAT-2 detection
  61. GRB 251026B: Fermi GBM Observation
  62. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  63. GRB 251026A/EP251026a: EP-FXT follow-up observation
  64. The EP-WXT trigger 01709247588 is likely a flaring star
  65. GRB 251028B: Fermi/GBM observation
  66. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  67. GRB 251028B: Glowbug gamma-ray detection
  68. GRB 251028A: Glowbug gamma-ray detection
  69. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  70. GRB251026B: PRIME H-band upper limit
  71. GRB251025B: 3.6m DOT Optical Observations
  72. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  73. SVOM trigger sb25102702/GRB 251027A is not a GRB
  74. IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube
  75. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  76. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  77. GRB 251025C: Glowbug gamma-ray detection
  78. Fermi-LAT Gamma-ray Observations of IceCube-251025A
  79. Konus-Wind detection of GRB 251022A
  80. GRB 251027A: Swift-XRT observations
  81. EP251027.145: COLIBRÍ optical upper limits
  82. GRB 251022A: SVOM/GRM observation
  83. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  84. GRB 251027A: LCO optical upper limit
  85. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  86. GRB 251023B / EP251023b: Mondy optical upper limit
  87. GRB 251017A: INASAN-Kislovodsk optical observations
  88. GRB 251026A: Mondy optical upper limit
  89. GRB 251025B: Mondy optical observations
  90. GRB 251025B: Kilonova-Catcher optical afterglow detection
  91. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  92. GRB 251027A: SVOM detection of a faint burst
  93. GRB 251025C: AstroSat CZTI detection
  94. EP251023a: Mondy optical observations
  95. GRB 251025B: MAO/AZT-22 optical observations
  96. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  97. GRB 251026A: Swift-XRT observations
  98. GRB 251025B: J-band detection with WINTER
  99. GRB 251026A: SVOM/C-GFT upper limit
  100. IceCube-251025A: DDOTI Optical Upper Limit

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