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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"

5513 results found.

  1. GRB 251115A: Fermi-LAT detection
  2. Fermi GRB 251115A: Global MASTER-Net observations report
  3. GRB 251115A: Fermi GBM Final Real-time Localization
  4. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  5. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  6. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  7. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  8. GRB 251108B: Glowbug gamma-ray detection
  9. GRB 251111A: Swift-XRT afterglow detection
  10. GRB 251013C: Chandra X-ray observations and jet break detection
  11. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  12. Fermi trigger No 784279167: Global MASTER-Net observations report
  13. SVOM GRB251108.54: Global MASTER-Net observations report
  14. SVOM GRB251106.83: Global MASTER-Net observations report
  15. GRB 251106A: MASTER optical observations
  16. GRB 251103B: AstroSat CZTI detection
  17. GRB 251103B: Fermi GBM observation
  18. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  19. EP251102a: OHP/T193 optical observations
  20. GRB 251103A: OHP/T193 optical observations
  21. GRB 251103A: Xinglong 2.16m optical detection
  22. GRB 251103B: Nanshan/HMT optical upper limit
  23. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  24. GRB 251103B: MITSuME Akeno optical upper limits
  25. Fermi GRB 251103A: Global MASTER-Net observations report
  26. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  27. Swift GRB 251103B: Global MASTER-Net observations report
  28. GRB 251103B: GROWTH-India Telescope optical upper limits
  29. GRB 251103B: Prompt enhanced Swift-XRT position
  30. GRB 251103A: Fermi GBM Observation
  31. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  32. GRB 251103A: LCO optical observation
  33. EP251102.890: COLIBRÍ optical counterpart candidate
  34. GRB 251102A: AstroSat CZTI detection
  35. GRB 251103A: Fermi GBM Final Localization
  36. GRB 251103A: NOT optical afterglow candidate
  37. GRB 251102A: Fermi GBM Final Real-time Localization
  38. Konus-Wind detection of GRB 251028A
  39. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  40. GRB 251028A: Fermi GBM Observation
  41. GRB 251028A: Glowbug gamma-ray detection
  42. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  43. GRB 251028A: MAXI/GSC detection
  44. GRB 251028A: Fermi GBM Final Real-time Localization
  45. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  46. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  47. GRB 251026B: Tentative GOTO optical counterpart candidate
  48. Fermi GRB 251025C: Global MASTER-Net observations report
  49. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  50. EP251023a: OHP/T193 optical observations
  51. GRB 251022A: Swift-XRT detection of GOTO25iym
  52. GRB 251023B: CALET Gamma-Ray Burst Monitor detection
  53. GRB 251022A: MASTER OT detection
  54. GRB 251023B / MAXI J0451+122: MAXI/GSC detection
  55. Fermi GRB 251023A: Global MASTER-Net observations report
  56. GRB 251022A: GOTO optical counterpart detection
  57. LAT GRB251022A: Global MASTER-Net observations report
  58. EP251021b: BOOTES-7 optical upper limit
  59. GRB 250911A: MAXI/GSC detection
  60. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  61. IceCube-251018A: DDOTI Optical Upper Limit
  62. GRB 251018A: Fermi GBM Observation
  63. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  64. IceCube-251018A: Global MASTER-Net observations report
  65. GRB 251017A: COLIBRÍ photometric redshift
  66. GRB 251018A: MASTER OT detection
  67. GRB 251018A: TRT optical afterglow detection
  68. Swift GRB 251018A: Global MASTER-Net observations report
  69. GRB 251018A: Swift detection of a burst with an optical counterpart
  70. GRB 251018A: Fermi GBM Final Real-time Localization
  71. GRB 251011A: Fermi GBM Observation
  72. GRB 251013C: Leavitt Observatory optical photometry
  73. Fermi GRB 251016B: Global MASTER-Net observations report
  74. GRB 251017A: Swift detection of a burst with an optical counterpart
  75. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  76. GRB 251013C: VLA detection
  77. GRB 251013D: Swift/UVOT Observations
  78. GRB 251013C: Swift/UVOT Detection
  79. GRB 251014D: BOOTES-6/DPRT optical upper limit
  80. GRB 251013C: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an bright optical counterpart
  81. GRB 251013C: Bassano Bresciano Observatory optical observations
  82. GRB 251013C: ABObservatory optical observations
  83. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  84. GRB 251013C: ALMA detection
  85. GRB 251013C: DDOTI detection of the optical afterglow
  86. GRB 251013C: SLKT optical afterglow photometry
  87. GRB 251013C: Swift-XRT counterpart detection
  88. GRB 251013C: Optical Observations via Virtual Telescope Project, Italy
  89. GRB 251011B inspection: MASTER orphan GRB detection
  90. GRB 251011A: AstroSat CZTI detection
  91. GRB 251011A: Fermi GBM Final Real-time Localization
  92. GRB 251003A: Fermi GBM Observation
  93. GRB 251007A: AKO Optical Upper Limit
  94. EP251003a: LCO and VST fading optical counterpart
  95. Fermi GRB 251006B: Global MASTER-Net observations report
  96. GRB 251003A: LAST optical observations
  97. GRB 251002A: Mondy/AZT-33IK optical observations
  98. GRB 251002A: NIR observations with WINTER
  99. Fermi GBM Sub-Threshold Detection of GRB 250910A
  100. GRB 251001B: COLIBRÍ further observations and evidence of a multi-wavelength shallow decay

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