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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"

8475 results found.

  1. GRB 251221A: Swift detection of a burst
  2. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube
  3. IceCube-251218A - IceCube observation of a high-energy neutrino candidate track-like event
  4. EP251214a: Optical upper limit with Kinder observations
  5. GRB 251202A: radio detection with the VLA
  6. GRB 251215A: Swift ToO observations
  7. GRB 251214B: Swift detection of a burst with an optical counterpart
  8. IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
  9. IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube
  10. IceCube-251210A - IceCube observation of a high-energy neutrino candidate track-like event
  11. Fermi GBM Sub-Threshold Detection of GRB 251205A
  12. GRB 251208B: COLIBRÍ optical upper limits
  13. GRB 251208D: Swift-XRT observations
  14. GRB 251208B: Swift ToO observations
  15. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  16. EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5
  17. GRB 251205A: Swift detection of a burst with an optical afterglow
  18. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  19. GRB 251203C: LCO optical afterglow confirmation
  20. GRB 251203B: Swift-XRT observations
  21. GRB 251203B: SVOM/VT optical observation
  22. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  23. GRB 251201B: Swift detection of a burst with an optical counterpart
  24. EP251130a: JinShan optical observations
  25. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  26. EP251130a: Swift-XRT counterpart detection
  27. EP251130a: COLIBRÍ optical counterpart candidate
  28. GRB 251129A: Swift ToO observations
  29. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  30. EP251124a: Pan-STARRS ri-band imaging and photometry
  31. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  32. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  33. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  34. EP251124a: Swift-XRT observations
  35. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  36. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  37. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  38. GRB 251122A / EP251122a: LCO optical upper limits
  39. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  40. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  41. EP251118a: Continued Optical Detection with Kinder observations
  42. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  43. EP251118a: Optical detection with Kinder observations
  44. GRB 251116C: NOT optical observations
  45. EP251118a: NOT candidate optical counterpart
  46. GRB 251118A: Swift ToO observations
  47. EP251118a: Einstein Probe detected of a fast X-ray transient
  48. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  49. GRB 251117A: FTW Observations of Swift candidate X-ray sources
  50. LIGO/Virgo/KAGRA S251117dq: Updated Sky localization
  51. GRB 251117A: Tiled Swift observations
  52. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  53. LIGO/Virgo/KAGRA S251112cm: Classification of reported candidates with SOAR/Goodman
  54. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  55. GRB 251116C: Swift-XRT observations
  56. LIGO/Virgo/KAGRA S251116en: Updated Sky localization
  57. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  58. IceCube-Cascade 251112A: Upper limits from a search for additional neutrino events in IceCube
  59. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  60. GRB 251115A: Tiled Swift observations
  61. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 4-Update Localization Volume
  62. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  63. LIGO/Virgo/KAGRA S251112cm: Updated Sky localization and false alarm rate estimate
  64. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  65. LIGO/Virgo/KAGRA S251112cm: Candidates from the Zwicky Transient Facility
  66. LIGO/Virgo/KAGRA S251112cm: TROVE Vetting of TNS Candidates
  67. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  68. LIGO/Virgo/KAGRA S251112cm: ATLAS pre-detections of AT2025adgp and AT2025adgq
  69. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  70. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  71. Swift Trigger 1413695: a possible GRB 251112A
  72. LIGO/Virgo/KAGRA S251112cm: Upper limits from Fermi-GBM Observations
  73. LIGO/Virgo/KAGRA S251112cm: NED Galaxies in the 3-Initial Localization Volume
  74. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  75. LIGO/Virgo/KAGRA S251108fi: DDOTI Optical Candidate
  76. LIGO/Virgo/KAGRA S251108fi: One counterpart neutrino candidate from IceCube neutrino searches
  77. IceCube-Cascade 251107A: Upper limits from a search for additional neutrino events in IceCube
  78. LIGO/Virgo/KAGRA S251108fi: Updated Sky localization
  79. LIGO/Virgo/KAGRA S251108dn: Updated Sky localization
  80. LIGO/Virgo/KAGRA S251108fi: Identification of a GW compact binary merger candidate
  81. LIGO/Virgo/KAGRA S251108dn: Identification of a GW compact binary merger candidate
  82. LIGO/Virgo/KAGRA S251105aj: Updated Sky localization
  83. LIGO/Virgo/KAGRA S251103f: Updated Sky localization
  84. GRB 251106A: Swift-XRT afterglow detection
  85. Fermi GBM Sub-Threshold Detection of GRB 251106A
  86. EP251102a: Xinglong 2.16-m clear-band observations of the optical counterpart
  87. LIGO/Virgo/KAGRA S251031dw: Candidates from the Zwicky Transient Facility
  88. Fermi GBM Sub-Threshold Detection of GRB 251105B
  89. LIGO/Virgo/KAGRA S251105aj: Identification of a GW compact binary merger candidate
  90. LIGO/Virgo/KAGRA S251103f: Identification of a GW compact binary merger candidate
  91. GRB 251103B: Swift detection of a burst
  92. LIGO/Virgo/KAGRA S251031cq: Updated Sky localization
  93. EP251102a (WXT 11900459650): LCO observations confirm COLIBRÍ candidate
  94. EP251102.890: COLIBRÍ optical counterpart candidate
  95. GRB 251103A: LCO optical afterglow detection
  96. GRB 251103A: NOT optical afterglow candidate (duplicate submission)
  97. GRB 251103A: NOT optical afterglow candidate
  98. LIGO/Virgo/KAGRA S251031cq: Identification of a GW compact binary merger candidate
  99. GRB 251026B: LBT near-infrared observations
  100. GRB251026B: PRIME H-band upper limit

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