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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

20388 results found.

  1. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  2. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  3. GRB 251126A: SAO RAS optical marginal detection
  4. GRB 251202A: Swift-XRT afterglow detection
  5. EP251129a/GRB 251129A: NOWT Detection
  6. GRB 251126A: SVOM/VT optical observation
  7. EP251130a: SVOM/VT optical observation
  8. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  9. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  10. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  11. GRB 251201A: SVOM/GRM observation of a burst
  12. GRB 251201B: SVOM/VT optical fading
  13. Swift GRB 251201B : MASTER optical counterpart detection
  14. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  15. GRB 251201B: Enhanced Swift-XRT position
  16. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  17. GRB 251130B: AstroSat CZTI detection
  18. GRB 251201B: Swift detection of a burst with an optical counterpart
  19. EP251130a: Mondy optical observations
  20. EP251130a: Optical detections with Kinder observations
  21. EP251130a: SAO RAS optical observations
  22. EP251130A: Optical observation from 1.3m DFOT
  23. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  24. EP251130a: JinShan optical observations
  25. GRB 251127A: SVOM/GRM observation
  26. EP251130a: COLIBRÍ optical counterpart candidate
  27. EP251130a: Einstein Probe detection of an X-ray transient
  28. GRB 251129A / EP251129a: SAO RAS optical observations
  29. GRB 251126A: SAO RAS optical observations
  30. GRB 251128A: GECAM-B detection
  31. GRB 251128A: SVOM/GRM observation of a long burst
  32. SVOM GRB 251129A : MASTER optical counterpart detection
  33. GRB 251129A: Swift-XRT afterglow detection
  34. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  35. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  36. GRB 251129A: SVOM detection of a burst
  37. GRB 251129A: SVOM detection of a burst
  38. GRB 251126A: Swift-BAT refined analysis
  39. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  40. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  41. GRB 251126A: further SAO RAS optical observations
  42. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  43. GRB251126A: MAO/AZT-22 optical observations
  44. GRB251126A: Continued optical observation from 1.3m DFOT
  45. GRB 251126A: Swift/UVOT Detection
  46. EP251124a: Pan-STARRS ri-band imaging and photometry
  47. GRB 251126A: Mondy and SAO RAS optical observations
  48. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  49. GRB 251126A: 1.3m DFOT optical afterglow detection
  50. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  51. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  52. GRB 251126A: Enhanced Swift-XRT position
  53. GRB 251126A: Kilonova-Catcher optical afterglow detection
  54. GRB 251126A: Nanshan/HMT optical afterglow detection
  55. GRB 251126A: GIT discovery of the likely optical afterglow
  56. GRB 251126A: Swift detection of a burst
  57. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  58. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  59. EP251124b: NOT r- and z-band optical upper limits
  60. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  61. EP251124b: EP-WXT detection of a fast X-ray transient
  62. EP251124a: Xinglong GWAC-F60A optical observation
  63. EP251124a: NOT r- and z-band optical upper limits
  64. EP251124a: Swift-XRT observations
  65. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  66. EP251124a: Optical upper limit with Kinder observations
  67. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  68. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  69. EP251124a: GROWTH-India Telescope optical upper limits
  70. EP251124a: Einstein Probe detection of an X-ray transient
  71. GRB 251116C: Swift-XRT confirmation of fading
  72. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  73. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  74. EP251118A: 3.6m DOT optical afterglow detection
  75. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  76. GRB 251122A / EP251122a: WFST optical observations
  77. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  78. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  79. GRB 251122A / EP251122a: LCO optical upper limits
  80. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  81. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  82. GRB 251122A / EP251122a: SVOM detection of a long burst
  83. EP251122a: Einstein Probe detection of an X-ray transient
  84. EP251118a: Continued Optical Detection with Kinder observations
  85. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  86. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  87. EP251118a: Xinglong-2.16m optical observation
  88. EP251118A: 1.3m DFOT optical afterglow detection
  89. GRB 251118A: Swift/UVOT Detection
  90. EP251118a / GRB 251118C: SAO RAS optical observations
  91. GRB 251118A: Swift-XRT afterglow detection
  92. GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
  93. EP251118a: Optical detection with Kinder observations
  94. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  95. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  96. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  97. EP251118A / GRB 251118C : MASTER optical counterpart observations
  98. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  99. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  100. EP251118a: VLT near-infrared observation

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