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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. EP250302a:Xinglong optical observations
  2. GRB 250306A: AstroSat CZTI detection
  3. Fermi trigger No 762963055: Global MASTER-Net observations report
  4. Swift GRB 250306A: Global MASTER-Net observations report
  5. GRB 250305A: SVOM/GRM observation of a burst
  6. The EP-WXT trigger 01709132323 is likely a flaring star
  7. EP250304A: Upper limits from Fermi-GBM Observations
  8. Fermi GRB 250305A: Global MASTER-Net observations report
  9. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  10. EP250302a: Optical Observations at CrAO and SAO RAS
  11. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  12. EP 250304A: Optical counterpart detection by LCO
  13. EP250302A: 1.3m DFOT optical afterglow detection
  14. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  15. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  16. EP250302a: Mondy Continued Optical Observations
  17. EP250304a: TRT optical counterpart detection
  18. LIGO/Virgo/KAGRA S250304cb: Identification of a GW compact binary merger candidate
  19. EP250304a: Global MASTER-Net observations report
  20. EP250304a: Einstein Probe detection of an X-ray transient
  21. EP250302a : GIT optical follow-up
  22. LIGO/Virgo/KAGRA S250302av: 2 counterpart neutrino candidate events from an IceCube neutrino search
  23. EP250302a: NUTTelA-TAO Early Measurments
  24. EP250302a: REM NIR upper limits
  25. EP250302a: Mondy Observations and Optical Light Curve
  26. INTEGRAL: end of scientific operations
  27. EP250302a: OHP/T193 optical and spectroscopic observations
  28. EP250302a: Global MASTER-Net observations report
  29. EP250302a: Xinglong F60B optical observation
  30. EP250302a: Einstein Probe detection of an X-ray transient
  31. EP250302a: SVOM/C-GFT optical observations
  32. EP250302a: Montarrenti Observatory optical detection
  33. Fermi GRB 250302A: Global MASTER-Net observations report
  34. EP250302a: FTW optical and NIR detection
  35. EP250302a: Nanshan/HMT optical counterpart detection
  36. IceCube-250302A - IceCube observation of a high-energy neutrino candidate track-like event
  37. The EP-WXT trigger 01709132140 is likely a flaring star
  38. Fermi trigger No 762205158: Global MASTER-Net observations report
  39. Fermi GRB 250225A: Global MASTER-Net observations report
  40. GRB 250225B: Swift detection of a burst
  41. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  42. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  43. GRB 250202B: VZLUSAT-2 detection
  44. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  45. Konus-Wind detection of GRB 250221A
  46. GRB 250221A: REM optical/NIR afterglow detection
  47. GRB 250221A: COLIBRÍ/DDRAGO Confirmation of a Bright Optical Counterpart
  48. GRB 250221A: Swift detection of a burst with an optical counterpart
  49. Swift GRB250221.15: Global MASTER-Net OT detection
  50. Swift GRB250221.15: Global MASTER-Net observations report
  51. GRB 250217C: DDOTI Upper Limits on the Optical Afterglow
  52. Fermi GRB 250217A: Global MASTER-Net observations report
  53. EP250215a: Global MASTER-Net observations report
  54. EP250215A/GRB 250215A: INTEGRAL SPI-ACS detection
  55. EP250215a: EP-WXT detection and FXT follow-up observation of an X-ray transient
  56. EP250207b: NOT optical counterpart candidate
  57. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  58. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  59. GRB 250207A: Skynet optical afterglow observations
  60. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  61. LIGO/Virgo/KAGRA S250206dm: COLIBRÍ/DDRAGO Observations of AT2025bbo and Galaxies in the Localization Volume
  62. IceCube Alert 250207.09: Global MASTER-Net observations report
  63. LIGO/Virgo/KAGRA S250206dm & FRB 20250206A: MASTER observations and possible mother galaxy
  64. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  65. GRB 250208A: Fermi GBM Final Real-time Localization
  66. LIGO/Virgo/KAGRA S250208ad: Identification of a GW compact binary merger candidate
  67. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  68. GRB 250207B: MAXI/GSC detection
  69. GRB 250207A: Fermi GBM Final Real-time Localization
  70. Fermi-LAT Gamma-ray Observations of IceCube-250203A
  71. GRB 250205A: COLIBRÍ/DDRAGO Optical Afterglow Detection
  72. Konus-Wind detection of GRB 250202B
  73. IPN triangulation of GRB 250204B (short/hard)
  74. IPN triangulation of GRB 250202B
  75. GRB 250129A: LCO late afterglow detection
  76. GRB 250129A: COLIBRÍ/DDRAGO Afterglow Detection
  77. GRB 250202B: NuSTAR detection of the prompt emission
  78. GRB 250202B: Fermi GBM Detection
  79. IceCube-250203A - IceCube observation of a high-energy neutrino candidate track-like event
  80. GRB 250202B: AstroSat CZTI detection of a bright long GRB
  81. GRB 250202B: Fermi GBM Final Real-time Localization
  82. Swift GRB250129A: MASTER 4 days observations report
  83. GRB 250202A: Fermi GBM Final Real-time Localization
  84. LIGO/Virgo/KAGRA S250201i: Coverage and upper limits from MAXI/GSC observations
  85. Fermi GRB 250128B: Global MASTER-Net observations report
  86. GRB 250127A: Swift-XRT observations
  87. Fermi GRB 250127B: Global MASTER-Net observations report
  88. GRB 250127A: LCO optical upper limit
  89. GRB 250126A: MAXI/GSC detection
  90. EP250125a: Swift/XRT detection of a fading counterpart
  91. EP250108a: AbAO, CMO and Terskol optical upper limits
  92. Konus-Wind detection of GRB 250118B
  93. IPN triangulation of GRB 250118B
  94. GRB 250114B: Swift-XRT afterglow detection
  95. GRB 250114B: Swift-XRT observations
  96. GRB 250101A: Terskol Zeiss-2000 optical observations
  97. EP241021a: SMA radio observation
  98. GRB 250109A / EP250109a: Mephisto optical upper limits
  99. EP250111a: Global MASTER-Net observations report
  100. EP250108a: Liverpool Telescope likely optical counterpart

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