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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"

24376 results found.

  1. GRB 251208A: Fermi GBM Final Real-time Localization
  2. GRB 251205A: FTW optical and NIR observations
  3. SVOM GRB251206.86: Global MASTER-Net observations report
  4. EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5
  5. The EP-WXT trigger 01709249380 is likely a flaring star
  6. GRB 251205A: ZTF and ATLAS optical afterglow detections
  7. GRB 251205A: GROWTH-India Telescope optical observations
  8. GRB 251205A: Swift-BAT refined analysis
  9. GRB 251205A: Swift-XRT refined Analysis
  10. Konus-Wind detection of GRB 251118A
  11. GRB 251205A: NOT optical observations
  12. Swift GRB 251205A : MASTER OT detection with host galaxy
  13. Swift GRB251205A: Global MASTER-Net observations report
  14. GRB 251126B: Fermi GBM Final Localization
  15. GRB 251203C: SVOM/ECLAIRs refined analysis
  16. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  17. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  18. GRB 251202A: SVOM/GRM observation
  19. GRB 251203A: SVOM/GRM observation
  20. EP251130a: JinShan near-infrared observations
  21. GRB 251203C: SVOM/VT optical counterpart
  22. GRB 251203C: EP-FXT follow-up observation
  23. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  24. GRB 251203C: LCO optical upper limits
  25. GRB 251203B: LCO optical upper limits
  26. GRB 251203C: SVOM detection of a burst
  27. SVOM GRB251203.77: Global MASTER-Net observations report
  28. SVOM GRB251203B: Global MASTER-Net observations report
  29. GRB 251203B: SVOM detection of a burst
  30. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  31. GRB 251203A: Fermi GBM Final Real-time Localization
  32. GRB 251202A / EP251202a: SVOM/VT optical observation
  33. GRB 251201B: Fermi GBM Observation
  34. EP251202a/GRB 251202A: KAIT optical observations
  35. Fermi GRB 251202B: Global MASTER-Net observations report
  36. GRB 251202B: Fermi GBM Final Real-time Localization
  37. IPN triangulation of GRB 251129B (short/hard)
  38. GRB 251202A: Fermi GBM Observation
  39. GRB 251130B: Glowbug gamma-ray detection
  40. EP251130a: continued NOT optical observations indicate steep fading phase
  41. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  42. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  43. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  44. GRB 251126A: SVOM/VT optical observation
  45. EP251130a: SVOM/VT optical observation
  46. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  47. Fermi GRB 251202A: Global MASTER-Net observations report
  48. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  49. GRB 251201B: Swift-XRT refined Analysis
  50. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  51. GRB 251202A: Fermi GBM Final Real-time Localization
  52. GRB 251201A: SVOM/GRM observation of a burst
  53. GRB 251201B: SVOM/VT optical fading
  54. Swift GRB 251201B : MASTER optical counterpart detection
  55. Swift GRB 251201B: Global MASTER-Net observations report
  56. GRB 251201B: Fermi GBM Final Real-time Localization
  57. SVOM GRB251201.19: Global MASTER-Net observations report
  58. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  59. EP251130a: KAIT optical observations
  60. EP251130A: Optical observation from 1.3m DFOT
  61. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  62. EP251130a: JinShan optical observations
  63. Fermi GRB 251130B: Global MASTER-Net observations report
  64. GRB 251127A: SVOM/GRM observation
  65. IceCube Alert 251130.75: Global MASTER-Net observations report
  66. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  67. GRB 251130B: Fermi GBM Final Localization Correction
  68. EP251130a: Global MASTER-Net observations report
  69. GRB 251130B: Fermi GBM Final Real-time Localization
  70. EP251129a/GRB 251129A: EP-FXT follow-up observations
  71. GRB 251130A: Fermi GBM Final Real-time Localization
  72. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  73. GRB 251128A: SVOM/GRM observation of a long burst
  74. SVOM GRB 251129A : MASTER optical counterpart detection
  75. GRB 251129A / EP251129a: SVOM/VT optical fading
  76. EP251129a: Global MASTER-Net observations report
  77. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  78. GRB 251128A: Fermi GBM Observation
  79. GRB 251129A: SVOM detection of a burst
  80. SVOM GRB251129A: Global MASTER-Net observations report
  81. GRB 251129A: SVOM detection of a burst
  82. GRB 251126A: Swift-BAT refined analysis
  83. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  84. Fermi GRB 251128A: Global MASTER-Net observations report
  85. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  86. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  87. GRB 251126A NUTTelA-TAO Early Measurements
  88. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  89. GRB 251128A: Fermi GBM Final Real-time Localization
  90. GRB251126A: Continued optical observation from 1.3m DFOT
  91. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  92. GRB 251126A: 1.3m DFOT optical afterglow detection
  93. GRB 251125B: GECAM-B detection
  94. Fermi GRB 251127A: Global MASTER-Net observations report
  95. GRB 251127A: Fermi GBM Final Real-time Localization
  96. GRB 251126A: Asiago i-band detection
  97. Swift GRB 251126A: Global MASTER-Net observations report
  98. GRB 251121A: Fermi GBM Observation
  99. GRB 251126A: Swift detection of a burst
  100. EP251124b follow-up observation by EP-FXT

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