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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"

27399 results found.

  1. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  2. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  3. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  4. GRB 251106A: Swift-XRT afterglow detection
  5. GRB 251106A: Kilonova-Catcher optical upper limit
  6. Fermi GBM Sub-Threshold Detection of GRB 251106A
  7. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  8. GRB 251106A: MASTER optical observations
  9. GRB 251025C: TERI Gamma-ray detection
  10. GRB 251016B: TERI Gamma-ray detection
  11. GRB 251016A: TERI Gamma-ray detection of a short burst
  12. GRB 250920C: TERI Gamma-ray detection
  13. Fermi trigger No 784034269: Global MASTER-Net observations report
  14. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  15. GRB 251105A: Fermi GBM Observation
  16. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  17. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  18. Fermi GBM Sub-Threshold Detection of GRB 251105B
  19. GRB 251103B: Swift/UVOT Upper Limits
  20. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  21. GRB 251103B: Fermi GBM observation
  22. GRB 251103A: WFST optical observations
  23. GRB 251103A: OHP/T193 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 251103A: Swift/BAT-GUANO arcminute localization of a burst
  29. GRB 251103B: MITSuME Akeno optical upper limits
  30. GRB 251103B: Swift-XRT refined Analysis
  31. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  32. EP251102a: NIR observations with WINTER
  33. GRB 251103A: J-band detection with WINTER
  34. GRB 251103B: GROWTH-India Telescope optical upper limits
  35. GRB 251103A: Kilonova-Catcher optical afterglow detection
  36. GRB 251103B: Enhanced Swift-XRT position
  37. GRB 251103B: Swift detection of a burst
  38. GRB 251103A: Swift/UVOT Detection
  39. GRB 251103A: Fermi GBM Observation
  40. GRB 251103A: Swift-XRT afterglow detection
  41. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  42. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  43. EP251102a: Einstein Probe detection of a fast X-ray transient
  44. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  45. GRB 251103A: LCO optical observation
  46. EP251102.890: COLIBRÍ optical counterpart candidate
  47. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  48. GRB 251103A: LCO optical afterglow detection
  49. GRB 251103A: NOT optical afterglow candidate
  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 251031A: BALROG localization (Fermi Trigger 783588065 / GRB 251031306)
  54. GRB 251025C: SVOM/GRM observation
  55. GRB 251028A: SVOM/GRM observation
  56. GRB 251028A: Fermi GBM Observation
  57. GRB 251022A: Swift-XRT confirmation of fading
  58. GRB 250926A: VZLUSAT-2 detection
  59. GRB 251026B: Fermi GBM Observation
  60. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  61. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  62. GRB 251028B: Glowbug gamma-ray detection
  63. GRB 251028A: Glowbug gamma-ray detection
  64. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  65. GRB251026B: PRIME H-band upper limit
  66. GRB251025B: 3.6m DOT Optical Observations
  67. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  68. GRB 251028A: MAXI/GSC detection
  69. SVOM trigger sb25102702/GRB 251027A is not a GRB
  70. IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube
  71. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  72. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  73. GRB 251025C: Glowbug gamma-ray detection
  74. Fermi-LAT Gamma-ray Observations of IceCube-251025A
  75. GRB 251027A: Swift-XRT observations
  76. EP251027.145: COLIBRÍ optical upper limits
  77. GRB 251022A: SVOM/GRM observation
  78. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  79. GRB 251027A: LCO optical upper limit
  80. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  81. GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
  82. GRB 251023B / EP251023b: Mondy optical upper limit
  83. GRB 251017A: INASAN-Kislovodsk optical observations
  84. GRB 251026A: Mondy optical upper limit
  85. GRB 251025B: Mondy optical observations
  86. GRB 251025B: Kilonova-Catcher optical afterglow detection
  87. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  88. GRB 251027A: SVOM detection of a faint burst
  89. EP251023a: Mondy optical observations
  90. GRB 251025B: MAO/AZT-22 optical observations
  91. LIGO/Virgo/KAGRA S251026bn: Updated Sky localization
  92. Fermi GRB 251025C: Global MASTER-Net observations report
  93. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  94. GRB 251026A: Swift-XRT observations
  95. GRB 251025B: OHP/T193 optical detection
  96. GRB 251025B: J-band detection with WINTER
  97. GRB 251026A: SVOM/C-GFT upper limit
  98. IceCube-251025A: DDOTI Optical Upper Limit
  99. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  100. GRB 251026A: SVOM detection of a long burst

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