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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').
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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"

21798 results found.

  1. GRB 251201B: SVOM/VT optical fading
  2. Swift GRB 251201B : MASTER optical counterpart detection
  3. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  4. GRB 251201B: Enhanced Swift-XRT position
  5. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  6. GRB 251130B: AstroSat CZTI detection
  7. GRB 251201B: Swift detection of a burst with an optical counterpart
  8. EP251130a: Mondy optical observations
  9. EP251130a: Optical detections with Kinder observations
  10. EP251130a: SAO RAS optical observations
  11. EP251130A: Optical observation from 1.3m DFOT
  12. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  13. EP251130a: JinShan optical observations
  14. GRB 251127A: SVOM/GRM observation
  15. EP251130a: COLIBRÍ optical counterpart candidate
  16. EP251130a: Einstein Probe detection of an X-ray transient
  17. GRB 251128A: AstroSat CZTI detection
  18. GRB 251129A / EP251129a: SAO RAS optical observations
  19. GRB 251126A: SAO RAS optical observations
  20. GRB 251128A: SVOM/GRM observation of a long burst
  21. SVOM GRB 251129A : MASTER optical counterpart detection
  22. GRB 251129A: Swift-XRT afterglow detection
  23. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  24. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  25. GRB 251129A: SVOM detection of a burst
  26. GRB 251129A: SVOM detection of a burst
  27. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  28. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  29. GRB 251126A: further SAO RAS optical observations
  30. GRB 251126A NUTTelA-TAO Early Measurements
  31. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  32. GRB251126A: MAO/AZT-22 optical observations
  33. GRB251126A: Continued optical observation from 1.3m DFOT
  34. GRB 251126A: Swift/UVOT Detection
  35. GRB 251126A: Mondy and SAO RAS optical observations
  36. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  37. GRB 251126A: 1.3m DFOT optical afterglow detection
  38. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  39. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  40. GRB 251126A: Enhanced Swift-XRT position
  41. GRB 251126A: Kilonova-Catcher optical afterglow detection
  42. GRB 251126A: Nanshan/HMT optical afterglow detection
  43. GRB 251121A: Fermi GBM Observation
  44. GRB 251126A: GIT discovery of the likely optical afterglow
  45. GRB 251126A: Swift detection of a burst
  46. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  47. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  48. EP251124b: NOT r- and z-band optical upper limits
  49. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  50. EP251124b: EP-WXT detection of a fast X-ray transient
  51. EP251124a: Xinglong GWAC-F60A optical observation
  52. EP251124a: NOT r- and z-band optical upper limits
  53. EP251124a: Swift-XRT observations
  54. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  55. EP251124a: Optical upper limit with Kinder observations
  56. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  57. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  58. EP251124a: GROWTH-India Telescope optical upper limits
  59. EP251124a: Einstein Probe detection of an X-ray transient
  60. GRB 251116C: Swift-XRT confirmation of fading
  61. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  62. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  63. EP251118A: 3.6m DOT optical afterglow detection
  64. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  65. GRB 251122A / EP251122a: WFST optical observations
  66. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  67. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  68. GRB 251122A / EP251122a: LCO optical upper limits
  69. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  70. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  71. GRB 251122A / EP251122a: SVOM detection of a long burst
  72. EP251122a: Einstein Probe detection of an X-ray transient
  73. EP251118a: Continued Optical Detection with Kinder observations
  74. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  75. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  76. EP251118a: Xinglong-2.16m optical observation
  77. EP251118A: 1.3m DFOT optical afterglow detection
  78. GRB 251118A: Swift/UVOT Detection
  79. EP251118a / GRB 251118C: SAO RAS optical observations
  80. GRB 251118A: Swift-XRT afterglow detection
  81. EP251118a: Optical detection with Kinder observations
  82. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  83. GRB 251118A: NuSTAR detection of bright prompt emission
  84. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  85. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  86. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  87. EP251118a: FTW optical and NIR observations
  88. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  89. EP251118a: VLT near-infrared observation
  90. GRB 251116D: SVOM/GRM observation of a long GRB
  91. GRB 251119A: SVOM detection of a possible burst
  92. EP251118a: NOT candidate optical counterpart
  93. EP251118a: Einstein Probe detected of a fast X-ray transient
  94. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  95. GRB 251116C: SVOM/ECLAIRs refined analysis
  96. GRB 251116B: SVOM/ECLAIRs refined analysis
  97. GRB 251116D: Insight-HXMT/HE detection
  98. GRB 251115A: Swift-XRT observations
  99. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  100. GRB 251117A: SVOM/GRM observation of a short burst

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