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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"

5157 results found.

  1. EP250223a: REM NIR upper limit
  2. EP250223a: TRT optical afterglow observation
  3. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  4. Fermi trigger No 761805304: Global MASTER-Net observations report
  5. GRB 250221A: Swift-XRT refined Analysis
  6. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  7. GRB 250220B: Fermi GBM Final Real-time Localization
  8. IPN triangulation of GRB 250217C (short)
  9. GRB 250215A: Swift-XRT refined Analysis
  10. GRB 250213A: SVOM detection of a burst
  11. Fermi trigger No 760945500: Global MASTER-Net observations report
  12. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  13. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  14. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  15. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  16. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  17. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  18. IceCube Alert 250207.09: Global MASTER-Net observations report
  19. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  20. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  21. GRB 250207A: Swift-XRT refined Analysis
  22. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  23. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  24. The EP-WXT trigger 01709131347 is likely a flaring star
  25. EP250205a/GRB 250205A: Einstein Probe observation
  26. GRB250205A: SVOM/VT optical afterglow detection
  27. GRB 250205A: SVOM detection of a burst
  28. Swift GRB250129A: MASTER 4 days observations report
  29. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  30. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  31. GRB 250129A: NOT optical observations of continuining activity
  32. Ep250125A: 1.3m DFOT optical upper limit
  33. GRB 250129A: Swift-XRT refined Analysis
  34. GRB 250128B: VLT/HAWKI near-infrared observations
  35. Fermi GRB 250128B: Global MASTER-Net observations report
  36. GRB 250128B: Swift-XRT refined Analysis
  37. GRB 250128B: Swift detection of a short burst
  38. GRB 250127B: DDOTI Upper Limit on the Afterglow
  39. Fermi GRB 250127B: Global MASTER-Net observations report
  40. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  41. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  42. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  43. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  44. GRB 241217A / EP241217B: radio detection with the VLA
  45. EP250108a: MeerKAT radio upper limit
  46. Konus-Wind detection of GRB 250113A
  47. IPN triangulation of GRB 250113A
  48. GRB 250114A: Swift-XRT refined Analysis
  49. GRB 250113A: INTEGRAL/SPI-ACS detection
  50. Swift GRB250114A: Global MASTER-Net OT detection
  51. GRB 250113A: SVOM/GRM observation of a long burst
  52. EP250111a: a new X-ray transient detected by Einstein Probe
  53. GRB 250108B: Swift-XRT refined Analysis
  54. GRB 250108B: Swift detection of a burst
  55. Fermi trigger No 757753930: Global MASTER-Net observations report
  56. GRB 250103B: Swift-XRT refined Analysis
  57. GRB 241229A: 1.3m DFOT upper limit
  58. GRB 241228B: 1.3m DFOT Optical observations
  59. GRB 250101A: further LCOGT optical afterglow observations
  60. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  61. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  62. GRB 250101A: Swift-XRT refined Analysis
  63. GRB 250101A: SVOM/C-GFT early optical observations
  64. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  65. GRB 250101A: Nanshan/HMT optical observations
  66. GRB 250101A: GMG Optical Observation
  67. GRB 250101A: Swift detection of a burst with an optical counterpart
  68. Swift GRB250101.56: Global MASTER-Net observations report
  69. GRB 241217a/EP241217b: ATCA Radio Detection
  70. GRB 241229A: EP-FXT X-ray afterglow confirmation
  71. GRB 241229B: SAO RAS optical upper limit
  72. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  73. Fermi GRB 241228B: Global MASTER-Net observations report
  74. GRB 241228A: Swift-XRT refined Analysis
  75. GRB 241228B: GOTO possible optical counterpart candidate
  76. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  77. Fermi GRB 241226A: Global MASTER-Net observations report
  78. EP241223a: Mondy AZT-33IK optical observations
  79. Fermi trigger No 756678579: Global MASTER-Net observations report
  80. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  81. IceCube Alert 241224.30: Global MASTER-Net observations report
  82. EP241223a: Global MASTER-Net observations report
  83. GRB 241217A / EP241217b: Non-detection in ATCA Radio Follow-up Observations
  84. EP241217a: 1.6m Mephisto multi-band optical observations
  85. GRB 241218A: Swift-XRT refined Analysis
  86. GRB 241214A: GRBAlpha detection
  87. GRB 241214A: Swift/BAT-GUANO localization skymap of a burst
  88. Konus-Wind detection of GRB 241213A (EP 241213a)
  89. GRB 241214A: SVOM/GRM observation
  90. GRB 241213A: Swift-XRT refined Analysis
  91. GRB 241212A: SVOM detection of a bright long burst
  92. GRB 241207A: EIRSAT-1 GMOD Detection
  93. GRB 241209A: Swift-XRT refined Analysis
  94. EP241208a: Optical upper limit with Kinder observations
  95. Fermi trigger No 755485387: Global MASTER-Net observations report
  96. GRB 241209D: Swift-XRT refined Analysis
  97. GRB 241209A: VLT/HAWK-I near-IR counterpart candidate
  98. LIGO/Virgo/KAGRA S241102br: continued GRAWITA observations and detection of an optical transient (AT2024adip)
  99. Fermi GRB 241209A: Global MASTER-Net observations report
  100. Fermi trigger No 755277791: Global MASTER-Net observations report

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