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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"

21320 results found.

  1. GRB 251111A: SVOM/ECLAIRs refined analysis
  2. GRB 251025B: SVOM/ECLAIRs refined analysis
  3. GRB 251112A: Swift/UVOT Upper Limits
  4. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  5. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  6. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  7. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  8. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  9. Fermi trigger No 784621743: Global MASTER-Net observations report
  10. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  11. GRB251111A: 1.3m DFOT optical upper limit
  12. GRB 251111A: Swift-XRT afterglow detection
  13. GRB 251111A: SVOM/VT optical observations with X-band data
  14. SVOM GRB251111.42: Global MASTER-Net observations report
  15. GRB 251111A: Swift-XRT observations
  16. SVOM GRB251111.22: Global MASTER-Net observations report
  17. GRB 251013C: Chandra X-ray observations and jet break detection
  18. GRB 251111A: SVOM/VT optical observations with VHF data
  19. GRB 251111A: KAIT optical upper limit
  20. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  21. GRB 251106A: Swift/UVOT Upper Limits
  22. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  23. Fermi trigger No 784329591: Global MASTER-Net observations report
  24. Fermi trigger No 784279167: Global MASTER-Net observations report
  25. SVOM GRB251108.54: Global MASTER-Net observations report
  26. SVOM GRB251106.83: Global MASTER-Net observations report
  27. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) fading of the optical counterpart
  28. GRB 251106A: Swift-XRT afterglow detection
  29. GRB 251106A: Kilonova-Catcher optical upper limit
  30. Fermi GBM Sub-Threshold Detection of GRB 251106A
  31. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  32. GRB 251106A: MASTER optical observations
  33. Fermi trigger No 784034269: Global MASTER-Net observations report
  34. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  35. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  36. GRB 251105A: Swift/BAT-GUANO localization skymap of a burst
  37. GRB 251023A: SVOM/ECLAIRs detection of a burst through targeted search
  38. Fermi GBM Sub-Threshold Detection of GRB 251105B
  39. GRB 251103B: Swift/UVOT Upper Limits
  40. Fermi GRB 251105A: Global MASTER-Net observations report
  41. EP251102a: FTW optical and NIR observations
  42. GRB 251103A: WFST optical observations
  43. EP251102a: OHP/T193 optical observations
  44. GRB 251103A: OHP/T193 optical observations
  45. GRB 251103A: KAIT optical observations
  46. GRB 251103B: Nanshan/HMT optical upper limit
  47. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  48. GRB 251103A: Swift/BAT-GUANO arcminute localization of a burst
  49. Fermi GRB 251103A: Global MASTER-Net observations report
  50. EP251102a: NIR observations with WINTER
  51. GRB 251103A: J-band detection with WINTER
  52. Swift GRB 251103B: Global MASTER-Net observations report
  53. GRB 251103A: Kilonova-Catcher optical afterglow detection
  54. GRB 251103A: Swift/UVOT Detection
  55. GRB 251103A: Swift-XRT afterglow detection
  56. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  57. GRB 251025B: OHP/T193 optical upper limit
  58. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  59. GRB 251103A: LCO optical observation
  60. EP251102.890: COLIBRÍ optical counterpart candidate
  61. GRB 251103A: GOTO optical afterglow detection
  62. GRB 251103A: NOT optical afterglow candidate
  63. Fermi GRB 251102A: Global MASTER-Net observations report
  64. GRB 251031A: Swift/BAT-GUANO localization skymap of a burst
  65. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  66. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
  67. GRB 251022A: Swift-XRT confirmation of fading
  68. GRB 251026B: LBT near-infrared observations
  69. GRB 251026A/EP251026a: EP-FXT follow-up observation
  70. GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
  71. Fermi GRB 251028B: Global MASTER-Net observations report
  72. GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
  73. GRB251026B: PRIME H-band upper limit
  74. GRB251025B: 3.6m DOT Optical Observations
  75. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  76. GRB 251026B: Swift-XRT observations of GOTO25jgl/AT2025absf
  77. Fermi-LAT Gamma-ray Observations of IceCube-251025A
  78. GRB 251023B: Swift-UVOT Upper Limits
  79. GRB 251027A: Swift-XRT observations
  80. GRB 251026B: Swift ToO observations
  81. GRB 251026A/EP251026a: Einstein Probe detection of a fast X-ray transient
  82. GRB 251017A: Mondy AZT-33IK and Koshka Zeiss-1000 optical observations
  83. GRB 251017A: INASAN-Kislovodsk optical observations
  84. GRB 251025B: Mondy optical observations
  85. GRB 251025B: Kilonova-Catcher optical afterglow detection
  86. GRB 251027A: SVOM detection of a faint burst
  87. GRB 251026B: Tentative GOTO optical counterpart candidate
  88. EP251023a: Mondy optical observations
  89. GRB 251025B: MAO/AZT-22 optical observations
  90. Fermi GRB 251026B: Global MASTER-Net observations report
  91. Fermi GRB 251025C: Global MASTER-Net observations report
  92. GRB 251026A: Swift-XRT observations
  93. GRB 251025B: OHP/T193 optical detection
  94. GRB 251025B: J-band detection with WINTER
  95. GRB 251026A: SVOM/C-GFT upper limit
  96. IceCube-251025A: DDOTI Optical Upper Limit
  97. GRB 251026A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  98. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  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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