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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"

26329 results found.

  1. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  2. GRB251111A: 1.3m DFOT optical upper limit
  3. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  4. GRB 251106B: Glowbug gamma-ray detection of a likely short burst
  5. GRB 251111A: Swift-XRT afterglow detection
  6. GRB 251111A: SVOM/VT optical observations with X-band data
  7. SVOM GRB251111.42: Global MASTER-Net observations report
  8. GRB 251111A: Swift-XRT observations
  9. SVOM GRB251111.22: Global MASTER-Net observations report
  10. GRB 251111A: EP-FXT counterpart detection
  11. GRB 251013C: Chandra X-ray observations and jet break detection
  12. GRB 251111A: SVOM/VT optical observations with VHF data
  13. GRB 251111A: LCO optical observation
  14. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  15. GRB 251103B: Swift-BAT refined analysis
  16. GRB 251106A: Swift/UVOT Upper Limits
  17. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  18. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  19. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  20. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  21. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  22. Fermi trigger No 784329591: Global MASTER-Net observations report
  23. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  24. Fermi trigger No 784279167: Global MASTER-Net observations report
  25. SVOM GRB251108.54: Global MASTER-Net observations report
  26. GRB 251102B: SVOM/GRM observation
  27. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  28. SVOM GRB251106.83: Global MASTER-Net observations report
  29. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  30. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  31. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  32. GRB 251106A: Swift-XRT afterglow detection
  33. GRB 251106A: Kilonova-Catcher optical upper limit
  34. Fermi GBM Sub-Threshold Detection of GRB 251106A
  35. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  36. GRB 251106A: MASTER optical observations
  37. GRB 251025C: TERI Gamma-ray detection
  38. GRB 251016B: TERI Gamma-ray detection
  39. GRB 251016A: TERI Gamma-ray detection of a short burst
  40. GRB 250920C: TERI Gamma-ray detection
  41. Fermi trigger No 784034269: Global MASTER-Net observations report
  42. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  43. GRB 251105A: Fermi GBM Observation
  44. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  45. GRB 251104A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  46. Fermi GBM Sub-Threshold Detection of GRB 251105B
  47. GRB 251103B: Swift/UVOT Upper Limits
  48. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  49. GRB 251103B: Fermi GBM observation
  50. GRB 251103A: WFST optical observations
  51. GRB 251103A: OHP/T193 optical observations
  52. GRB 251103A: Xinglong 2.16m optical detection
  53. GRB 251103A: KAIT optical observations
  54. GRB 251103B: Nanshan/HMT optical upper limit
  55. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  56. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  57. GRB 251103B: MITSuME Akeno optical upper limits
  58. GRB 251103B: Swift-XRT refined Analysis
  59. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  60. EP251102a: NIR observations with WINTER
  61. GRB 251103A: J-band detection with WINTER
  62. GRB 251103B: GROWTH-India Telescope optical upper limits
  63. GRB 251103A: Kilonova-Catcher optical afterglow detection
  64. GRB 251103B: Enhanced Swift-XRT position
  65. GRB 251103B: Swift detection of a burst
  66. GRB 251103A: Swift/UVOT Detection
  67. GRB 251103A: Fermi GBM Observation
  68. GRB 251103A: Swift-XRT afterglow detection
  69. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  70. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  71. EP251102a: Einstein Probe detection of a fast X-ray transient
  72. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  73. GRB 251103A: LCO optical observation
  74. EP251102.890: COLIBRÍ optical counterpart candidate
  75. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) confirmation of the optical counterpart
  76. GRB 251103A: LCO optical afterglow detection
  77. GRB 251103A: NOT optical afterglow candidate
  78. GRB 251031A: Fermi GBM Observation
  79. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  80. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  81. GRB 251031A: BALROG localization (Fermi Trigger 783588065 / GRB 251031306)
  82. GRB 251025C: SVOM/GRM observation
  83. GRB 251028A: SVOM/GRM observation
  84. GRB 251028A: Fermi GBM Observation
  85. GRB 251022A: Swift-XRT confirmation of fading
  86. GRB 250926A: VZLUSAT-2 detection
  87. GRB 251026B: Fermi GBM Observation
  88. GRB 251026A/EP251026a: SVOM/VT optical counterpart
  89. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  90. GRB 251028B: Glowbug gamma-ray detection
  91. GRB 251028A: Glowbug gamma-ray detection
  92. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  93. GRB251026B: PRIME H-band upper limit
  94. GRB251025B: 3.6m DOT Optical Observations
  95. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  96. GRB 251028A: MAXI/GSC detection
  97. SVOM trigger sb25102702/GRB 251027A is not a GRB
  98. IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube
  99. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  100. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf

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