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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"

26009 results found.

  1. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  2. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  3. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  4. Fermi trigger No 784329591: Global MASTER-Net observations report
  5. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  6. Fermi trigger No 784279167: Global MASTER-Net observations report
  7. SVOM GRB251108.54: Global MASTER-Net observations report
  8. GRB 251102B: SVOM/GRM observation
  9. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  10. SVOM GRB251106.83: Global MASTER-Net observations report
  11. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  12. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  13. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  14. GRB 251106A: Swift-XRT afterglow detection
  15. GRB 251106A: Kilonova-Catcher optical upper limit
  16. Fermi GBM Sub-Threshold Detection of GRB 251106A
  17. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  18. GRB 251106A: MASTER optical observations
  19. GRB 251025C: TERI Gamma-ray detection
  20. GRB 251016B: TERI Gamma-ray detection
  21. GRB 251016A: TERI Gamma-ray detection of a short burst
  22. GRB 250920C: TERI Gamma-ray detection
  23. Fermi trigger No 784034269: Global MASTER-Net observations report
  24. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  25. GRB 251105A: Fermi GBM Observation
  26. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  27. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  28. Fermi GBM Sub-Threshold Detection of GRB 251105B
  29. GRB 251103B: Swift/UVOT Upper Limits
  30. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  31. GRB 251103B: Fermi GBM observation
  32. GRB 251103A: WFST optical observations
  33. GRB 251103A: OHP/T193 optical observations
  34. GRB 251103A: Xinglong 2.16m optical detection
  35. GRB 251103A: KAIT optical observations
  36. GRB 251103B: Nanshan/HMT optical upper limit
  37. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  38. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  39. GRB 251103B: MITSuME Akeno optical upper limits
  40. GRB 251103B: Swift-XRT refined Analysis
  41. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  42. EP251102a: NIR observations with WINTER
  43. GRB 251103A: J-band detection with WINTER
  44. GRB 251103B: GROWTH-India Telescope optical upper limits
  45. GRB 251103A: Kilonova-Catcher optical afterglow detection
  46. GRB 251103B: Enhanced Swift-XRT position
  47. GRB 251103B: Swift detection of a burst
  48. GRB 251103A: Swift/UVOT Detection
  49. GRB 251103A: Fermi GBM Observation
  50. GRB 251103A: Swift-XRT afterglow detection
  51. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  52. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  53. EP251102a: Einstein Probe detection of a fast X-ray transient
  54. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  55. GRB 251103A: LCO optical observation
  56. EP251102.890: COLIBRÍ optical counterpart candidate
  57. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  58. GRB 251103A: LCO optical afterglow detection
  59. GRB 251103A: NOT optical afterglow candidate
  60. GRB 251031A: Fermi GBM Observation
  61. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  62. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  63. GRB 251031A: BALROG localization (Fermi Trigger 783588065 / GRB 251031306)
  64. GRB 251025C: SVOM/GRM observation
  65. GRB 251028A: SVOM/GRM observation
  66. GRB 251028A: Fermi GBM Observation
  67. GRB 251022A: Swift-XRT confirmation of fading
  68. GRB 250926A: VZLUSAT-2 detection
  69. GRB 251026B: Fermi GBM Observation
  70. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  71. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  72. GRB 251028B: Glowbug gamma-ray detection
  73. GRB 251028A: Glowbug gamma-ray detection
  74. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  75. GRB251026B: PRIME H-band upper limit
  76. GRB251025B: 3.6m DOT Optical Observations
  77. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  78. GRB 251028A: MAXI/GSC detection
  79. SVOM trigger sb25102702/GRB 251027A is not a GRB
  80. IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube
  81. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  82. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  83. GRB 251025C: Glowbug gamma-ray detection
  84. Fermi-LAT Gamma-ray Observations of IceCube-251025A
  85. GRB 251027A: Swift-XRT observations
  86. EP251027.145: COLIBRÍ optical upper limits
  87. GRB 251022A: SVOM/GRM observation
  88. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  89. GRB 251027A: LCO optical upper limit
  90. GRB 251027A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  91. GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
  92. GRB 251023B / EP251023b: Mondy optical upper limit
  93. GRB 251017A: INASAN-Kislovodsk optical observations
  94. GRB 251026A: Mondy optical upper limit
  95. GRB 251025B: Mondy optical observations
  96. GRB 251025B: Kilonova-Catcher optical afterglow detection
  97. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  98. GRB 251027A: SVOM detection of a faint burst
  99. EP251023a: Mondy optical observations
  100. GRB 251025B: MAO/AZT-22 optical observations

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