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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"

8474 results found.

  1. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  2. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  3. EP251214a: Optical upper limit with Kinder observations
  4. GRB 251202A: radio detection with the VLA
  5. GRB 251215A: Swift ToO observations
  6. GRB 251214B: Swift detection of a burst with an optical counterpart
  7. IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
  8. IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube
  9. IceCube-251210A - IceCube observation of a high-energy neutrino candidate track-like event
  10. Fermi GBM Sub-Threshold Detection of GRB 251205A
  11. GRB 251208B: COLIBRÍ optical upper limits
  12. GRB 251208D: Swift-XRT observations
  13. GRB 251208B: Swift ToO observations
  14. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  15. EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5
  16. GRB 251205A: Swift detection of a burst with an optical afterglow
  17. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  18. GRB 251203C: LCO optical afterglow confirmation
  19. GRB 251203B: Swift-XRT observations
  20. GRB 251203B: SVOM/VT optical observation
  21. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  22. GRB 251201B: Swift detection of a burst with an optical counterpart
  23. EP251130a: JinShan optical observations
  24. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  25. EP251130a: Swift-XRT counterpart detection
  26. EP251130a: COLIBRÍ optical counterpart candidate
  27. GRB 251129A: Swift ToO observations
  28. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  29. EP251124a: Pan-STARRS ri-band imaging and photometry
  30. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  31. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  32. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  33. EP251124a: Swift-XRT observations
  34. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  35. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  36. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  37. GRB 251122A / EP251122a: LCO optical upper limits
  38. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  39. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  40. EP251118a: Continued Optical Detection with Kinder observations
  41. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  42. EP251118a: Optical detection with Kinder observations
  43. GRB 251116C: NOT optical observations
  44. EP251118a: NOT candidate optical counterpart
  45. GRB 251118A: Swift ToO observations
  46. EP251118a: Einstein Probe detected of a fast X-ray transient
  47. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  48. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  49. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  50. GRB 251117A: Tiled Swift observations
  51. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  52. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  53. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  54. GRB 251116C: Swift-XRT observations
  55. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  56. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  57. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  58. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  59. GRB 251115A: Tiled Swift observations
  60. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  61. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  62. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  63. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  64. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  65. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  66. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  67. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  68. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  69. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  70. Swift Trigger 1413695: a possible GRB 251112A
  71. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  72. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  73. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  74. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  75. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  76. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  77. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  78. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  79. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  80. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  81. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  82. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  83. GRB 251106A: Swift-XRT afterglow detection
  84. Fermi GBM Sub-Threshold Detection of GRB 251106A
  85. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  86. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  87. Fermi GBM Sub-Threshold Detection of GRB 251105B
  88. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  89. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  90. GRB 251103B: Swift detection of a burst
  91. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  92. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  93. EP251102.890: COLIBRÍ optical counterpart candidate
  94. GRB 251103A: LCO optical afterglow detection
  95. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  96. GRB 251103A: NOT optical afterglow candidate
  97. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  98. GRB 251026B: LBT near-infrared observations
  99. GRB251026B: PRIME H-band upper limit
  100. IceCube-251025A: Upper limits from a search for additional neutrino events in IceCube

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