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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"

4878 results found.

  1. IPN triangulation of GRB 250222A
  2. EP250302a: Global MASTER-Net observations report
  3. Fermi GRB 250302A: Global MASTER-Net observations report
  4. LIGO/Virgo/KAGRA S250206dm: early X-ray upper limits from Einstein Probe WXT and preliminary results of FXT observations
  5. EP250228a: Optical observations with Kinder and Swift/UVOT
  6. GRB 250225B: VLT/HAWKI near-infrared observations
  7. EP250223a: J band upper limit by SYSU 80cm telescope
  8. GRB 250205A / EP250205A: further radio observations with the VLA
  9. Fermi GRB 250226B: Global MASTER-Net observations report
  10. GRB 250221A: ATCA Detections and Upper Limits
  11. GRB 250225B: VLT/FORS2 candidate optical afterglow
  12. Fermi GRB 250226A: Global MASTER-Net observations report
  13. Fermi trigger No 762205158: Global MASTER-Net observations report
  14. Fermi GRB 250225A: Global MASTER-Net observations report
  15. LIGO/Virgo/KAGRA S250223dk and Swift/BAT-GUANO ID 762004910: DECam GW-MMADS candidates
  16. EP250223a: Kinder optical follow-up observations
  17. LIGO/Virgo/KAGRA S250223dk: DECam DESGW Candidates
  18. GOTO observations of LVK S250223dk/Swift-BAT RAVEN alert
  19. EP250223a: GOTO optical afterglow detections
  20. GRB 250222A: SVOM/GRM observation of a burst
  21. EP250223a: COLIBRÍ/DDRAGO Detection of the Optical Counterpart and Slow Fading
  22. EP250223a: REM NIR upper limit
  23. EP250223a: TRT optical afterglow observation
  24. LIGO/Virgo/KAGRA S250223dk: DDOTI Upper Limits on the Optical Counterpart
  25. Fermi trigger No 761805304: Global MASTER-Net observations report
  26. GRB 250221A: Swift-XRT refined Analysis
  27. IceCube-250207A: MASTER flaring blazar QSOJ0854+2006 with Zhirkov effect
  28. GRB 250220B: Fermi GBM Final Real-time Localization
  29. IPN triangulation of GRB 250217C (short)
  30. GRB 250215A: Swift-XRT refined Analysis
  31. GRB 250213A: SVOM detection of a burst
  32. Fermi trigger No 760945500: Global MASTER-Net observations report
  33. GRB 250211A: SVOM trigger sb25021103 is not a GRB
  34. LIGO/Virgo/KAGRA S250206dm: GECKO Continued Observaiton with 7DT
  35. LIGO/Virgo/KAGRA S250206dm: continued in SOAR galaxy targeted observations and identification of one possible transient
  36. LIGO/Virgo/KAGRA S250206dm: Gemini-North spectroscopic observation of AT2025bbo and its host galaxy
  37. GRB 250209A: MAXI/GSC detection (possible detection of an X-ray flare from 1RXS J145110.3+310648)
  38. LIGO/Virgo/KAGRA S250206dm: Global MASTER-Net observations report
  39. IceCube Alert 250207.09: Global MASTER-Net observations report
  40. LIGO/Virgo/KAGRA S250206dm: GECKO Observation with 7DT and KMTNet
  41. LIGO/Virgo/KAGRA S250206dm: ePESSTO+ classification of AT2025bar
  42. GRB 250207A: Swift-XRT refined Analysis
  43. LIGO/Virgo/KAGRA S250206dm: ATLAS observations of the skymap
  44. LIGO/Virgo/KAGRA S250206dm: SOAR galaxy targeted observations
  45. The EP-WXT trigger 01709131347 is likely a flaring star
  46. EP250205a/GRB 250205A: Einstein Probe observation
  47. GRB250205A: SVOM/VT optical afterglow detection
  48. GRB 250205A: SVOM detection of a burst
  49. Swift GRB250129A: MASTER 4 days observations report
  50. GRB 250129A: Liverpool Telescope observations suggest continued engine activity
  51. GRB 250129A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations
  52. GRB 250129A: NOT optical observations of continuining activity
  53. Ep250125A: 1.3m DFOT optical upper limit
  54. GRB 250129A: Swift-XRT refined Analysis
  55. GRB 250128B: VLT/HAWKI near-infrared observations
  56. Fermi GRB 250128B: Global MASTER-Net observations report
  57. GRB 250128B: Swift-XRT refined Analysis
  58. GRB 250128B: Swift detection of a short burst
  59. GRB 250127B: DDOTI Upper Limit on the Afterglow
  60. Fermi GRB 250127B: Global MASTER-Net observations report
  61. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  62. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  63. EP250108a / SN2025kg: Non-detection from ATCA radio follow-up observations
  64. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  65. GRB 241217A / EP241217B: radio detection with the VLA
  66. EP250108a: MeerKAT radio upper limit
  67. Konus-Wind detection of GRB 250113A
  68. IPN triangulation of GRB 250113A
  69. GRB 250114A: Swift-XRT refined Analysis
  70. GRB 250113A: INTEGRAL/SPI-ACS detection
  71. Swift GRB250114A: Global MASTER-Net OT detection
  72. GRB 250113A: SVOM/GRM observation of a long burst
  73. EP250111a: a new X-ray transient detected by Einstein Probe
  74. GRB 250108B: Swift-XRT refined Analysis
  75. GRB 250108B: Swift detection of a burst
  76. Fermi trigger No 757753930: Global MASTER-Net observations report
  77. GRB 250103B: Swift-XRT refined Analysis
  78. GRB 241229A: 1.3m DFOT upper limit
  79. GRB 241228B: 1.3m DFOT Optical observations
  80. GRB 250101A: further LCOGT optical afterglow observations
  81. GRB 250101A NUTTelA-TAO / BSTI Early Measurements
  82. GRB 250101A: GMG spectroscopic redshift at z ~ 2.481
  83. GRB 250101A: Swift-XRT refined Analysis
  84. GRB 250101A: SVOM/C-GFT early optical observations
  85. GRB 250101A: MASTER earlier OT observations with SOSS emission features
  86. GRB 250101A: Nanshan/HMT optical observations
  87. GRB 250101A: GMG Optical Observation
  88. GRB 250101A: Swift detection of a burst with an optical counterpart
  89. Swift GRB250101.56: Global MASTER-Net observations report
  90. GRB 241217a/EP241217b: ATCA Radio Detection
  91. GRB 241229A: EP-FXT X-ray afterglow confirmation
  92. GRB 241229B: SAO RAS optical upper limit
  93. IceCube-241224A: No transient candidates from the Zwicky Transient Facility
  94. Fermi GRB 241228B: Global MASTER-Net observations report
  95. GRB 241228A: Swift-XRT refined Analysis
  96. GRB 241228B: GOTO possible optical counterpart candidate
  97. IceCube-241224A: Upper limits from a search for additional neutrino events in IceCube
  98. Fermi GRB 241226A: Global MASTER-Net observations report
  99. EP241223a: Mondy AZT-33IK optical observations
  100. Fermi trigger No 756678579: Global MASTER-Net observations report

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