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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"

20480 results found.

  1. EP251118a: Global MASTER-Net observations report
  2. LAT GRB251118.86: Global MASTER-Net observations report
  3. EP251118a: NOT candidate optical counterpart
  4. GRB 251118A: Swift ToO observations
  5. EP251118a: Einstein Probe detected of a fast X-ray transient
  6. Fermi GRB 251118B: Global MASTER-Net observations report
  7. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  8. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  9. GRB 251116C: SVOM/ECLAIRs refined analysis
  10. GRB 251116B: SVOM/ECLAIRs refined analysis
  11. GRB 251013C: Koshka, SAO RAS, Mondy, and CrAO optical observations, possible SN detection
  12. GRB 251115A: Swift-XRT observations
  13. GRB 251117A: Tiled Swift observations
  14. LAT GRB251117.51: Global MASTER-Net observations report
  15. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  16. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  17. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  18. GRB 251116C: Swift-XRT observations
  19. EP251023a: Assy AZT-20 optical observations
  20. EP251023a: UAFO and AbAO optical observations
  21. LIGO/Virgo/KAGRA S251112cm: EP-FXT follow-up observations
  22. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  23. GRB 251025B: further Mondy optical observations
  24. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  25. SVOM GRB251116C: Global MASTER-Net observations report
  26. GRB 251116B: SVOM detection of a burst
  27. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  28. LIGO/Virgo/KAGRA S251112cm: AT2025adht follow-up at Maidanak observatory by GRANDMA
  29. GRB 251115A: Tiled Swift observations
  30. Fermi GRB 251115A: Global MASTER-Net observations report
  31. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  32. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  33. Fermi trigger No 784717756: Global MASTER-Net observations report
  34. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  35. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  36. Fermi GRB 251114A: Global MASTER-Net observations report
  37. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  38. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  39. Fermi GRB 251113A: Global MASTER-Net observations report
  40. GRB 251111A: SVOM/ECLAIRs refined analysis
  41. GRB 251025B: SVOM/ECLAIRs refined analysis
  42. GRB 251112A: Swift/UVOT Upper Limits
  43. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  44. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  45. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  46. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  47. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  48. Fermi trigger No 784621743: Global MASTER-Net observations report
  49. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  50. GRB251111A: 1.3m DFOT optical upper limit
  51. GRB 251111A: Swift-XRT afterglow detection
  52. GRB 251111A: SVOM/VT optical observations with X-band data
  53. SVOM GRB251111.42: Global MASTER-Net observations report
  54. GRB 251111A: Swift-XRT observations
  55. SVOM GRB251111.22: Global MASTER-Net observations report
  56. GRB 251013C: Chandra X-ray observations and jet break detection
  57. GRB 251111A: SVOM/VT optical observations with VHF data
  58. GRB 251111A: KAIT optical upper limit
  59. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  60. GRB 251106A: Swift/UVOT Upper Limits
  61. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  62. Fermi trigger No 784329591: Global MASTER-Net observations report
  63. Fermi trigger No 784279167: Global MASTER-Net observations report
  64. SVOM GRB251108.54: Global MASTER-Net observations report
  65. SVOM GRB251106.83: Global MASTER-Net observations report
  66. GRB 251106A: Swift-XRT afterglow detection
  67. GRB 251106A: Kilonova-Catcher optical upper limit
  68. GRB 251106A: SVOM/COLIBRÍ (FM-GFT) detection of a likely optical counterpart
  69. GRB 251106A: MASTER optical observations
  70. Fermi trigger No 784034269: Global MASTER-Net observations report
  71. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  72. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  73. GRB 251103B: Swift/UVOT Upper Limits
  74. Fermi GRB 251105A: Global MASTER-Net observations report
  75. EP251102a: FTW optical and NIR observations
  76. GRB 251103A: WFST optical observations
  77. EP251102a: OHP/T193 optical observations
  78. GRB 251103A: OHP/T193 optical observations
  79. GRB 251103A: KAIT optical observations
  80. GRB 251103B: Nanshan/HMT optical upper limit
  81. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  82. Fermi GRB 251103A: Global MASTER-Net observations report
  83. EP251102a: NIR observations with WINTER
  84. GRB 251103A: J-band detection with WINTER
  85. Swift GRB 251103B: Global MASTER-Net observations report
  86. GRB 251103A: Kilonova-Catcher optical afterglow detection
  87. GRB 251103A: Swift/UVOT Detection
  88. GRB 251103A: Swift-XRT afterglow detection
  89. GRB 251103A: SVOM/COLIBRÍ (FM-GFT) optical observations
  90. GRB 251025B: OHP/T193 optical upper limit
  91. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  92. GRB 251103A: LCO optical observation
  93. EP251102.890: COLIBRÍ optical counterpart candidate
  94. GRB 251103A: GOTO optical afterglow detection
  95. GRB 251103A: NOT optical afterglow candidate
  96. Fermi GRB 251102A: Global MASTER-Net observations report
  97. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  98. GRB 251026B: SOAR Classification of GOTO25jgl/SN2025absf as a Type Ia supernova
  99. GRB 251022A: Swift-XRT confirmation of fading
  100. GRB 251026B: LBT near-infrared observations

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