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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"

4179 results found.

  1. EP250404a: Nanshan 0.43m Telescope optical observatios
  2. Fermi trigger No 766148493: Global MASTER-Net observations report
  3. Fermi trigger No 766173972: Global MASTER-Net observations report
  4. Fermi GRB 250407A: Global MASTER-Net observations report
  5. Fermi GRB 250406A: Global MASTER-Net observations report
  6. GRB 250402A: Mondy optical observations
  7. EP250402a: Einstein Probe detection of a fast X-ray transient
  8. Fermi GRB 250331E: Global MASTER-Net observations report
  9. GRB 250329A: AbAO, Mondy and SAO RAS optical upper limits
  10. IceCube-250330A: Upper limits from a search for additional neutrino events in IceCube
  11. SVOM/sb25033102: SVOM detection of an X-ray transient
  12. GRB 250328A: 1.6m Mephisto optical observations
  13. GRB 250327B: ALMA detection
  14. GRB 250327B: VLA detection
  15. GRB 250327B: SVOM/COLIBRÍ (F-GFT) Further Observations
  16. GRB 250329B: 1.6m Mephisto Optical Upper Limits
  17. GRB250329A: REM optical afterglow detection
  18. GRB 250329A: Swift-XRT afterglow detection
  19. GRB 250329A: Fading optical counterpart detection by LCO.
  20. GRB 250328A: SVOM/COLIBRÍ (F-GFT) optical afterglow candidate
  21. GRB 250328A: VLT/HAWK-I near-infrared afterglow candidate
  22. GRB 250329A: SVOM/VT optical counterpart confirmation
  23. GRB 250329A: SVOM/COLIBRÍ (F-GFT) Detection of a Bright Optical Counterpart Candidate
  24. GRB 250327B: further optical observations by LCOGT
  25. GRB 250327B: SVOM/VT optically bright counterpart
  26. GRB 250327B: SAO RAS optical candidate
  27. IPN triangulation of GRB 250322B
  28. EP-WXT trigger 01709133021: Optical upper limit through Kinder observations
  29. FRB 250316A: DDOTI Continued Optical Observations
  30. GRB 250322A: MASTER optical observation
  31. FRB 20250316A: detection of a candidate associated X-ray source EP J120944.2+585060 by Einstein Probe
  32. EP250321a: SVOM/VT optical observation
  33. GRB 250320B: AstroSat CZTI detection
  34. Fermi GRB 250320B: Global MASTER-Net observations report
  35. GRB 250321A: GOTO optical upper limits
  36. GRB 250319B: Fermi GBM Final Localization
  37. Fermi trigger No 763933627: Global MASTER-Net observations report
  38. GRB 250316A: Swift/UVOT Upper Limits
  39. GRB 250317A: Fermi GBM Final Real-time Localization
  40. Fermi GRB 250313A: Global MASTER-Net observations report
  41. EP250311a/GRB 250311A: EP-FXT follow-up observation
  42. Fermi GRB 250312B: Global MASTER-Net observations report
  43. IceCube-250309A: MITSuME Akeno and Seimei/TriCCS optical observations
  44. GRB 250309B / AT2025dws: SAO RAS optical observations
  45. IceCube Alert 250309.32: Global MASTER-Net observations report
  46. EP250304A: Upper limits from Fermi-GBM Observations
  47. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  48. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  49. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  50. EP250302a: Mondy Continued Optical Observations
  51. Fermi GRB 250302A: Global MASTER-Net observations report
  52. Fermi GRB 250225A: Global MASTER-Net observations report
  53. GRB 250225B: Swift detection of a burst
  54. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: AstroSat CZTI non-detection and upper limits
  55. EP250223a: REM NIR upper limit
  56. GRB 250223B: Fermi GBM Final Localization
  57. Fermi trigger No 762020305: Global MASTER-Net observations report
  58. GRB 250221A: continued Assy optical observations, brightening afterglow confirmation
  59. GRB 250221A: continued Mondy optical observations, brightening afterglow
  60. GRB 250213A: Swift-XRT observations
  61. Fermi GRB 250217A: Global MASTER-Net observations report
  62. EP250215a: Global MASTER-Net observations report
  63. Fermi trigger No 761206993: Global MASTER-Net observations report
  64. EP250212a: Xinglong optical upper limit
  65. EP250207b: VLA radio upper limits
  66. Fermi GRB 250212A: Global MASTER-Net observations report
  67. Fermi trigger No 760945500: Global MASTER-Net observations report
  68. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  69. LIGO/VIRGO/KAGRA S250206dm: AT 2025bbo spectroscopic observations with NIRES on Keck II
  70. GRB 241128A: VIRT Optical Upper Limit
  71. GRB 250210A: AstroSat CZTI detection
  72. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  73. Fermi GRB 250210A: Global MASTER-Net observations report
  74. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  75. IceCube Alert 250207.09: Global MASTER-Net observations report
  76. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  77. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  78. LIGO/Virgo/KAGRA S250206dm: Candidates from the Zwicky Transient Facility
  79. EP250207a: EP-WXT detection and XRT follow-up observation
  80. LIGO/Virgo/KAGRA S250206dm: DDOTI Upper Limits
  81. LIGO/Virgo/KAGRA S250207bg: Identification of a GW compact binary merger candidate
  82. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  83. GRB 250207B: MAXI/GSC detection
  84. GRB 250202B: Fermi GBM Detection
  85. The EP-WXT trigger 01709131196 is likely a flaring star
  86. Swift GRB250129A: MASTER 4 days observations report
  87. GRB 250129A: optical photometry from Konkoly
  88. GRB 250128B: VLA possible radio detection
  89. GRB 250129A: AKO Optical Afterglow Detection
  90. GRB 250127A: EP-FXT second observation epoch and confirmation of the x-ray afterglow fading
  91. GRB 250128B: SAO RAS Zeiss-1000 and CrAO ZTSh optical upper limits
  92. GRB 250128B: VLA radio upper limit
  93. GRB 250129A: Skynet optical observations
  94. GRB 250128B: Gemini-North optical extended source detection
  95. GRB 250128B: TNG optical upper limit
  96. GRB 250129A: REM optical/NIR afterglow detection
  97. GRB 250129A: Early afterglow detection by LCO.
  98. GRB 250129A: LCO optical observations
  99. GRB 250129A: GOTO optical observations show brightening afterglow
  100. Swift GRB 250129A: Global MASTER-Net observations report

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