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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"

5515 results found.

  1. EP251118a: NOT candidate optical counterpart
  2. SVOM GRB251116C: Global MASTER-Net observations report
  3. GRB 251115A: Fermi-LAT detection
  4. Fermi GRB 251115A: Global MASTER-Net observations report
  5. GRB 251115A: Fermi GBM Final Real-time Localization
  6. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  7. LIGO/Virgo/KAGRA S251112cm: Swift XRT observations, 20 X-ray sources
  8. LIGO/Virgo/KAGRA S251112cm: Detection of two young transients by BlackGEM/MeerLICHT: AT2025adgp and AT2025adgq
  9. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  10. GRB 251108B: Glowbug gamma-ray detection
  11. GRB 251111A: Swift-XRT afterglow detection
  12. GRB 251013C: Chandra X-ray observations and jet break detection
  13. GRB 251111A: SVOM/COLIBRÍ (FM-GFT) optical counterpart detection
  14. Fermi trigger No 784279167: Global MASTER-Net observations report
  15. SVOM GRB251108.54: Global MASTER-Net observations report
  16. SVOM GRB251106.83: Global MASTER-Net observations report
  17. GRB 251106A: MASTER optical observations
  18. GRB 251103B: AstroSat CZTI detection
  19. GRB 251103B: Fermi GBM observation
  20. GRB 251103A: Optical afterglow detection by ZTF’s public survey
  21. EP251102a: OHP/T193 optical observations
  22. GRB 251103A: OHP/T193 optical observations
  23. GRB 251103A: Xinglong 2.16m optical detection
  24. GRB 251103B: Nanshan/HMT optical upper limit
  25. GRB 251013C: 7DT detection and Medium-band SED of Afterglow
  26. GRB 251103B: MITSuME Akeno optical upper limits
  27. Fermi GRB 251103A: Global MASTER-Net observations report
  28. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  29. Swift GRB 251103B: Global MASTER-Net observations report
  30. GRB 251103B: GROWTH-India Telescope optical upper limits
  31. GRB 251103B: Prompt enhanced Swift-XRT position
  32. GRB 251103A: Fermi GBM Observation
  33. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  34. GRB 251103A: LCO optical observation
  35. EP251102.890: COLIBRÍ optical counterpart candidate
  36. GRB 251102A: AstroSat CZTI detection
  37. GRB 251103A: Fermi GBM Final Localization
  38. GRB 251103A: NOT optical afterglow candidate
  39. GRB 251102A: Fermi GBM Final Real-time Localization
  40. Konus-Wind detection of GRB 251028A
  41. IceCube-251025A: Two Transient Candidates from the Zwicky Transient Facility
  42. GRB 251028A: Fermi GBM Observation
  43. GRB 251028A: Glowbug gamma-ray detection
  44. GRB 251028A: BALROG localization (Fermi Trigger 783314796 / GRB 251028143)
  45. GRB 251028A: MAXI/GSC detection
  46. GRB 251028A: Fermi GBM Final Real-time Localization
  47. GRB 251013C : 3.4-m telescope of Iranian National Observatory (INO340) optical observations
  48. GRB 251025B: VLT/MUSE spectroscopic redshift z = 2.003
  49. GRB 251026B: Tentative GOTO optical counterpart candidate
  50. Fermi GRB 251025C: Global MASTER-Net observations report
  51. GRB 251025B: SVOM/COLIBRÍ (FM-GFT) strong rebrightening of the optical counterpart
  52. EP251023a: OHP/T193 optical observations
  53. GRB 251022A: Swift-XRT detection of GOTO25iym
  54. GRB 251023B: CALET Gamma-Ray Burst Monitor detection
  55. GRB 251022A: MASTER OT detection
  56. GRB 251023B / MAXI J0451+122: MAXI/GSC detection
  57. Fermi GRB 251023A: Global MASTER-Net observations report
  58. GRB 251022A: GOTO optical counterpart detection
  59. LAT GRB251022A: Global MASTER-Net observations report
  60. EP251021b: BOOTES-7 optical upper limit
  61. GRB 250911A: MAXI/GSC detection
  62. LIGO/Virgo/KAGRA S251021u: Identification of a GW compact binary merger candidate
  63. IceCube-251018A: DDOTI Optical Upper Limit
  64. GRB 251018A: Fermi GBM Observation
  65. GRB 251018A: BOOTES-5 and BOOTES-7 early optical detections
  66. IceCube-251018A: Global MASTER-Net observations report
  67. GRB 251017A: COLIBRÍ photometric redshift
  68. GRB 251018A: MASTER OT detection
  69. GRB 251018A: TRT optical afterglow detection
  70. Swift GRB 251018A: Global MASTER-Net observations report
  71. GRB 251018A: Swift detection of a burst with an optical counterpart
  72. GRB 251018A: Fermi GBM Final Real-time Localization
  73. GRB 251011A: Fermi GBM Observation
  74. GRB 251013C: Leavitt Observatory optical photometry
  75. Fermi GRB 251016B: Global MASTER-Net observations report
  76. GRB 251017A: Swift detection of a burst with an optical counterpart
  77. GRB 251013C: SVOM/COLIBRÍ (FM-GFT) observations of a strong and late rebrightening of the optical counterpart
  78. GRB 251013C: VLA detection
  79. GRB 251013D: Swift/UVOT Observations
  80. GRB 251013C: Swift/UVOT Detection
  81. GRB 251014D: BOOTES-6/DPRT optical upper limit
  82. GRB 251013C: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an bright optical counterpart
  83. GRB 251013C: Bassano Bresciano Observatory optical observations
  84. GRB 251013C: ABObservatory optical observations
  85. GRB 251013C: J band observations by SYSU 80cm infrared telescope
  86. GRB 251013C: ALMA detection
  87. GRB 251013C: DDOTI detection of the optical afterglow
  88. GRB 251013C: SLKT optical afterglow photometry
  89. GRB 251013C: Swift-XRT counterpart detection
  90. GRB 251013C: Optical Observations via Virtual Telescope Project, Italy
  91. GRB 251011B inspection: MASTER orphan GRB detection
  92. GRB 251011A: AstroSat CZTI detection
  93. GRB 251011A: Fermi GBM Final Real-time Localization
  94. GRB 251003A: Fermi GBM Observation
  95. GRB 251007A: AKO Optical Upper Limit
  96. EP251003a: LCO and VST fading optical counterpart
  97. Fermi GRB 251006B: Global MASTER-Net observations report
  98. GRB 251003A: LAST optical observations
  99. GRB 251002A: Mondy/AZT-33IK optical observations
  100. GRB 251002A: NIR observations with WINTER

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