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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"

4879 results found.

  1. Konus-Wind detection of GRB 250222A
  2. IPN triangulation of GRB 250222A
  3. EP250302a: Global MASTER-Net observations report
  4. Fermi GRB 250302A: Global MASTER-Net observations report
  5. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  6. EP250228a: Optical observations with Kinder and Swift/UVOT
  7. GRB 250225B: VLT/HAWKI near-infrared observations
  8. EP250223a: J band upper limit by SYSU 80cm telescope
  9. GRB 250205A / EP250205A: further radio observations with the VLA
  10. Fermi GRB 250226B: Global MASTER-Net observations report
  11. GRB 250221A: ATCA Detections and Upper Limits
  12. GRB 250225B: VLT/FORS2 candidate optical afterglow
  13. Fermi GRB 250226A: Global MASTER-Net observations report
  14. Fermi trigger No 762205158: Global MASTER-Net observations report
  15. Fermi GRB 250225A: Global MASTER-Net observations report
  16. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  17. EP250223a: Kinder optical follow-up observations
  18. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  19. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  20. EP250223a: GOTO optical afterglow detections
  21. GRB 250222A: SVOM/GRM observation of a burst
  22. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  23. EP250223a: REM NIR upper limit
  24. EP250223a: TRT optical afterglow observation
  25. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  26. Fermi trigger No 761805304: Global MASTER-Net observations report
  27. GRB 250221A: Swift-XRT refined Analysis
  28. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  29. GRB 250220B: Fermi GBM Final Real-time Localization
  30. IPN triangulation of GRB 250217C (short)
  31. GRB 250215A: Swift-XRT refined Analysis
  32. GRB 250213A: SVOM detection of a burst
  33. Fermi trigger No 760945500: Global MASTER-Net observations report
  34. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  35. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  36. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  37. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  38. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  39. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  40. IceCube Alert 250207.09: Global MASTER-Net observations report
  41. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  42. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  43. GRB 250207A: Swift-XRT refined Analysis
  44. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  45. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  46. The EP-WXT trigger 01709131347 is likely a flaring star
  47. EP250205a/GRB 250205A: Einstein Probe observation
  48. GRB250205A: SVOM/VT optical afterglow detection
  49. GRB 250205A: SVOM detection of a burst
  50. Swift GRB250129A: MASTER 4 days observations report
  51. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  52. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  53. GRB 250129A: NOT optical observations of continuining activity
  54. Ep250125A: 1.3m DFOT optical upper limit
  55. GRB 250129A: Swift-XRT refined Analysis
  56. GRB 250128B: VLT/HAWKI near-infrared observations
  57. Fermi GRB 250128B: Global MASTER-Net observations report
  58. GRB 250128B: Swift-XRT refined Analysis
  59. GRB 250128B: Swift detection of a short burst
  60. GRB 250127B: DDOTI Upper Limit on the Afterglow
  61. Fermi GRB 250127B: Global MASTER-Net observations report
  62. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  63. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  64. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  65. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  66. GRB 241217A / EP241217B: radio detection with the VLA
  67. EP250108a: MeerKAT radio upper limit
  68. Konus-Wind detection of GRB 250113A
  69. IPN triangulation of GRB 250113A
  70. GRB 250114A: Swift-XRT refined Analysis
  71. GRB 250113A: INTEGRAL/SPI-ACS detection
  72. Swift GRB250114A: Global MASTER-Net OT detection
  73. GRB 250113A: SVOM/GRM observation of a long burst
  74. EP250111a: a new X-ray transient detected by Einstein Probe
  75. GRB 250108B: Swift-XRT refined Analysis
  76. GRB 250108B: Swift detection of a burst
  77. Fermi trigger No 757753930: Global MASTER-Net observations report
  78. GRB 250103B: Swift-XRT refined Analysis
  79. GRB 241229A: 1.3m DFOT upper limit
  80. GRB 241228B: 1.3m DFOT Optical observations
  81. GRB 250101A: further LCOGT optical afterglow observations
  82. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  83. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  84. GRB 250101A: Swift-XRT refined Analysis
  85. GRB 250101A: SVOM/C-GFT early optical observations
  86. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  87. GRB 250101A: Nanshan/HMT optical observations
  88. GRB 250101A: GMG Optical Observation
  89. GRB 250101A: Swift detection of a burst with an optical counterpart
  90. Swift GRB250101.56: Global MASTER-Net observations report
  91. GRB 241217a/EP241217b: ATCA Radio Detection
  92. GRB 241229A: EP-FXT X-ray afterglow confirmation
  93. GRB 241229B: SAO RAS optical upper limit
  94. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  95. Fermi GRB 241228B: Global MASTER-Net observations report
  96. GRB 241228A: Swift-XRT refined Analysis
  97. GRB 241228B: GOTO possible optical counterpart candidate
  98. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  99. Fermi GRB 241226A: Global MASTER-Net observations report
  100. EP241223a: Mondy AZT-33IK optical observations

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