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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"

5050 results found.

  1. IPN triangulation of GRB 250217C (short)
  2. GRB 250215A: Swift-XRT refined Analysis
  3. GRB 250213A: SVOM detection of a burst
  4. Fermi trigger No 760945500: Global MASTER-Net observations report
  5. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  6. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  7. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  8. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  9. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  10. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  11. IceCube Alert 250207.09: Global MASTER-Net observations report
  12. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  13. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  14. GRB 250207A: Swift-XRT refined Analysis
  15. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  16. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  17. The EP-WXT trigger 01709131347 is likely a flaring star
  18. EP250205a/GRB 250205A: Einstein Probe observation
  19. GRB250205A: SVOM/VT optical afterglow detection
  20. GRB 250205A: SVOM detection of a burst
  21. Swift GRB250129A: MASTER 4 days observations report
  22. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  23. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  24. GRB 250129A: NOT optical observations of continuining activity
  25. Ep250125A: 1.3m DFOT optical upper limit
  26. GRB 250129A: Swift-XRT refined Analysis
  27. GRB 250128B: VLT/HAWKI near-infrared observations
  28. Fermi GRB 250128B: Global MASTER-Net observations report
  29. GRB 250128B: Swift-XRT refined Analysis
  30. GRB 250128B: Swift detection of a short burst
  31. GRB 250127B: DDOTI Upper Limit on the Afterglow
  32. Fermi GRB 250127B: Global MASTER-Net observations report
  33. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  34. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  35. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  36. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  37. GRB 241217A / EP241217B: radio detection with the VLA
  38. EP250108a: MeerKAT radio upper limit
  39. Konus-Wind detection of GRB 250113A
  40. IPN triangulation of GRB 250113A
  41. GRB 250114A: Swift-XRT refined Analysis
  42. GRB 250113A: INTEGRAL/SPI-ACS detection
  43. Swift GRB250114A: Global MASTER-Net OT detection
  44. GRB 250113A: SVOM/GRM observation of a long burst
  45. EP250111a: a new X-ray transient detected by Einstein Probe
  46. GRB 250108B: Swift-XRT refined Analysis
  47. GRB 250108B: Swift detection of a burst
  48. Fermi trigger No 757753930: Global MASTER-Net observations report
  49. GRB 250103B: Swift-XRT refined Analysis
  50. GRB 241229A: 1.3m DFOT upper limit
  51. GRB 241228B: 1.3m DFOT Optical observations
  52. GRB 250101A: further LCOGT optical afterglow observations
  53. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  54. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  55. GRB 250101A: Swift-XRT refined Analysis
  56. GRB 250101A: SVOM/C-GFT early optical observations
  57. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  58. GRB 250101A: Nanshan/HMT optical observations
  59. GRB 250101A: GMG Optical Observation
  60. GRB 250101A: Swift detection of a burst with an optical counterpart
  61. Swift GRB250101.56: Global MASTER-Net observations report
  62. GRB 241217a/EP241217b: ATCA Radio Detection
  63. GRB 241229A: EP-FXT X-ray afterglow confirmation
  64. GRB 241229B: SAO RAS optical upper limit
  65. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  66. Fermi GRB 241228B: Global MASTER-Net observations report
  67. GRB 241228A: Swift-XRT refined Analysis
  68. GRB 241228B: GOTO possible optical counterpart candidate
  69. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  70. Fermi GRB 241226A: Global MASTER-Net observations report
  71. EP241223a: Mondy AZT-33IK optical observations
  72. Fermi trigger No 756678579: Global MASTER-Net observations report
  73. IceCube-241224A - IceCube observation of a high-energy neutrino candidate track-like event
  74. IceCube Alert 241224.30: Global MASTER-Net observations report
  75. EP241223a: Global MASTER-Net observations report
  76. GRB 241217A / EP241217b: Non-detection in ATCA Radio Follow-up Observations
  77. EP241217a: 1.6m Mephisto multi-band optical observations
  78. GRB 241218A: Swift-XRT refined Analysis
  79. GRB 241214A: GRBAlpha detection
  80. GRB 241214A: Swift/BAT-GUANO localization skymap of a burst
  81. Konus-Wind detection of GRB 241213A (EP 241213a)
  82. GRB 241214A: SVOM/GRM observation
  83. GRB 241213A: Swift-XRT refined Analysis
  84. GRB 241212A: SVOM detection of a bright long burst
  85. GRB 241207A: EIRSAT-1 GMOD Detection
  86. GRB 241209A: Swift-XRT refined Analysis
  87. EP241208a: Optical upper limit with Kinder observations
  88. Fermi trigger No 755485387: Global MASTER-Net observations report
  89. GRB 241209D: Swift-XRT refined Analysis
  90. GRB 241209A: VLT/HAWK-I near-IR counterpart candidate
  91. LIGO/Virgo/KAGRA S241102br: continued GRAWITA observations and detection of an optical transient (AT2024adip)
  92. Fermi GRB 241209A: Global MASTER-Net observations report
  93. Fermi trigger No 755277791: Global MASTER-Net observations report
  94. Fermi GRB 241207A: Global MASTER-Net observations report
  95. EP241113a: Keck/LRIS spectroscopic observation and tentative redshift
  96. GRB 241130A: EIRSAT-1 GMOD Detection
  97. The EP-WXT trigger 01709126243 is not a real source
  98. Fermi trigger No 754701230: Global MASTER-Net observations report
  99. GRB 241128A: Swift-XRT refined Analysis
  100. Swift GRB241127.91: Global MASTER-Net OT detection

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