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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"

25979 results found.

  1. GRB 251103A: WFST optical observations
  2. GRB 251103A: OHP/T193 optical observations
  3. GRB 251103A: Xinglong 2.16m optical detection
  4. GRB 251103A: KAIT optical observations
  5. GRB 251103B: Nanshan/HMT optical upper limit
  6. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  7. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  8. GRB 251103B: MITSuME Akeno optical upper limits
  9. GRB 251103B: Swift-XRT refined Analysis
  10. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  11. EP251102a: NIR observations with WINTER
  12. GRB 251103A: J-band detection with WINTER
  13. GRB 251103B: GROWTH-India Telescope optical upper limits
  14. GRB 251103A: Kilonova-Catcher optical afterglow detection
  15. GRB 251103B: Enhanced Swift-XRT position
  16. GRB 251103B: Swift detection of a burst
  17. GRB 251103A: Swift/UVOT Detection
  18. GRB 251103A: Fermi GBM Observation
  19. GRB 251103A: Swift-XRT afterglow detection
  20. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  21. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  22. EP251102a: Einstein Probe detection of a fast X-ray transient
  23. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  24. GRB 251103A: LCO optical observation
  25. EP251102.890: COLIBRÍ optical counterpart candidate
  26. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  27. GRB 251103A: LCO optical afterglow detection
  28. GRB 251103A: NOT optical afterglow candidate
  29. GRB 251031A: Fermi GBM Observation
  30. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  31. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  32. GRB 251031A: BALROG localization (Fermi Trigger 783588065 / GRB 251031306)
  33. GRB 251025C: SVOM/GRM observation
  34. GRB 251028A: SVOM/GRM observation
  35. GRB 251028A: Fermi GBM Observation
  36. GRB 251022A: Swift-XRT confirmation of fading
  37. GRB 250926A: VZLUSAT-2 detection
  38. GRB 251026B: Fermi GBM Observation
  39. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  40. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  41. GRB 251028B: Glowbug gamma-ray detection
  42. GRB 251028A: Glowbug gamma-ray detection
  43. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  44. GRB251026B: PRIME H-band upper limit
  45. GRB251025B: 3.6m DOT Optical Observations
  46. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  47. GRB 251028A: MAXI/GSC detection
  48. SVOM trigger sb25102702/GRB 251027A is not a GRB
  49. IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube
  50. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  51. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  52. GRB 251025C: Glowbug gamma-ray detection
  53. Fermi-LAT Gamma-ray Observations of IceCube-251025A
  54. GRB 251027A: Swift-XRT observations
  55. EP251027.145: COLIBRÍ optical upper limits
  56. GRB 251022A: SVOM/GRM observation
  57. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  58. GRB 251027A: LCO optical upper limit
  59. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  60. GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
  61. GRB 251023B / EP251023b: Mondy optical upper limit
  62. GRB 251017A: INASAN-Kislovodsk optical observations
  63. GRB 251026A: Mondy optical upper limit
  64. GRB 251025B: Mondy optical observations
  65. GRB 251025B: Kilonova-Catcher optical afterglow detection
  66. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  67. GRB 251027A: SVOM detection of a faint burst
  68. EP251023a: Mondy optical observations
  69. GRB 251025B: MAO/AZT-22 optical observations
  70. LIGO/Virgo/KAGRA S251026bn: Updated Sky localization
  71. Fermi GRB 251025C: Global MASTER-Net observations report
  72. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  73. GRB 251026A: Swift-XRT observations
  74. GRB 251025B: OHP/T193 optical detection
  75. GRB 251025B: J-band detection with WINTER
  76. GRB 251026A: SVOM/C-GFT upper limit
  77. IceCube-251025A: DDOTI Optical Upper Limit
  78. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  79. GRB 251026A: SVOM detection of a long burst
  80. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  81. GRB 251023A: SVOM/GRM observation
  82. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  83. GRB 251025B: GROWTH-India Telescope optical observations
  84. GRB 251024A: Swift/UVOT Upper Limits
  85. GRB 251025B: Swift-XRT afterglow detection
  86. GRB 251024A: Swift-BAT refined analysis
  87. GRB 251024A: Swift-XRT refined Analysis
  88. GRB 251025A (sb25102501): stellar flare confirmed
  89. GRB 251025B: SVOM/VT optical observations with VHF data
  90. GRB 251025B: MASTER OT detection
  91. GRB 251025B: SVOM/C-GFT optical counterpart detection
  92. GRB 251025B: SVOM detection of a burst
  93. GRB 251025A (sb25102501): Likely a stellar flare by SVOM/VT
  94. GRB 251025A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  95. GRB 251025A: SVOM/VT VHF optical upper limit
  96. GRB 251025A: SVOM detection of a faint burst
  97. GRB 251003A: VLA Detection
  98. GRB 251024A: Enhanced Swift-XRT position
  99. GRB 251023C: Glowbug gamma-ray detection
  100. GRB 251024A: LCOGT Optical Afterglow Detection

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