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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"

27397 results found.

  1. GRB 251106A: Kilonova-Catcher optical upper limit
  2. Fermi GBM Sub-Threshold Detection of GRB 251106A
  3. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  4. GRB 251106A: MASTER optical observations
  5. GRB 251025C: TERI Gamma-ray detection
  6. GRB 251016B: TERI Gamma-ray detection
  7. GRB 251016A: TERI Gamma-ray detection of a short burst
  8. GRB 250920C: TERI Gamma-ray detection
  9. Fermi trigger No 784034269: Global MASTER-Net observations report
  10. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  11. GRB 251105A: Fermi GBM Observation
  12. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  13. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  14. Fermi GBM Sub-Threshold Detection of GRB 251105B
  15. GRB 251103B: Swift/UVOT Upper Limits
  16. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  17. GRB 251103B: Fermi GBM observation
  18. GRB 251103A: WFST optical observations
  19. GRB 251103A: OHP/T193 optical observations
  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 251103A: Swift/BAT-GUANO arcminute localization of a burst
  25. GRB 251103B: MITSuME Akeno optical upper limits
  26. GRB 251103B: Swift-XRT refined Analysis
  27. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  28. EP251102a: NIR observations with WINTER
  29. GRB 251103A: J-band detection with WINTER
  30. GRB 251103B: GROWTH-India Telescope optical upper limits
  31. GRB 251103A: Kilonova-Catcher optical afterglow detection
  32. GRB 251103B: Enhanced Swift-XRT position
  33. GRB 251103B: Swift detection of a burst
  34. GRB 251103A: Swift/UVOT Detection
  35. GRB 251103A: Fermi GBM Observation
  36. GRB 251103A: Swift-XRT afterglow detection
  37. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  38. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  39. EP251102a: Einstein Probe detection of a fast X-ray transient
  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: LCO optical afterglow detection
  45. GRB 251103A: NOT optical afterglow candidate
  46. GRB 251031A: Fermi GBM Observation
  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. GRB 251031A: BALROG localization (Fermi Trigger 783588065 / GRB 251031306)
  50. GRB 251025C: SVOM/GRM observation
  51. GRB 251028A: SVOM/GRM observation
  52. GRB 251028A: Fermi GBM Observation
  53. GRB 251022A: Swift-XRT confirmation of fading
  54. GRB 250926A: VZLUSAT-2 detection
  55. GRB 251026B: Fermi GBM Observation
  56. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  57. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  58. GRB 251028B: Glowbug gamma-ray detection
  59. GRB 251028A: Glowbug gamma-ray detection
  60. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  61. GRB251026B: PRIME H-band upper limit
  62. GRB251025B: 3.6m DOT Optical Observations
  63. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  64. GRB 251028A: MAXI/GSC detection
  65. SVOM trigger sb25102702/GRB 251027A is not a GRB
  66. IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube
  67. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  68. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  69. GRB 251025C: Glowbug gamma-ray detection
  70. Fermi-LAT Gamma-ray Observations of IceCube-251025A
  71. GRB 251027A: Swift-XRT observations
  72. EP251027.145: COLIBRÍ optical upper limits
  73. GRB 251022A: SVOM/GRM observation
  74. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  75. GRB 251027A: LCO optical upper limit
  76. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  77. GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
  78. GRB 251023B / EP251023b: Mondy optical upper limit
  79. GRB 251017A: INASAN-Kislovodsk optical observations
  80. GRB 251026A: Mondy optical upper limit
  81. GRB 251025B: Mondy optical observations
  82. GRB 251025B: Kilonova-Catcher optical afterglow detection
  83. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  84. GRB 251027A: SVOM detection of a faint burst
  85. EP251023a: Mondy optical observations
  86. GRB 251025B: MAO/AZT-22 optical observations
  87. LIGO/Virgo/KAGRA S251026bn: Updated Sky localization
  88. Fermi GRB 251025C: Global MASTER-Net observations report
  89. LIGO/Virgo/KAGRA S251026bn: Identification of a GW compact binary merger candidate
  90. GRB 251026A: Swift-XRT observations
  91. GRB 251025B: OHP/T193 optical detection
  92. GRB 251025B: J-band detection with WINTER
  93. GRB 251026A: SVOM/C-GFT upper limit
  94. IceCube-251025A: DDOTI Optical Upper Limit
  95. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  96. GRB 251026A: SVOM detection of a long burst
  97. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  98. GRB 251023A: SVOM/GRM observation
  99. GRB 251025B: ULL-ASTRO-MASTER optical counterpart detection with IAC80 telescope at Teide Observatory
  100. GRB 251025B: GROWTH-India Telescope optical observations

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