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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"

23415 results found.

  1. EP251130a: continued NOT optical observations indicate steep fading phase
  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. GRB 251201B: Swift-XRT refined Analysis
  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: Swift-XRT counterpart detection
  27. EP251130a: COLIBRÍ optical counterpart candidate
  28. EP251130a: Einstein Probe detection of an X-ray transient
  29. GRB 251129A / EP251129a: SAO RAS optical observations
  30. GRB 251126A: SAO RAS optical observations
  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: TShAO, Mondy, and AbAO optical observations
  39. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  40. GRB 251127A: Glowbug gamma-ray detection
  41. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  42. GRB 251126A: further SAO RAS optical observations
  43. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  44. GRB251126A: MAO/AZT-22 optical observations
  45. GRB251126A: Continued optical observation from 1.3m DFOT
  46. GRB 251126A: Swift/UVOT Detection
  47. EP251124a: Pan-STARRS ri-band imaging and photometry
  48. GRB 251126A: Mondy and SAO RAS optical observations
  49. GRB 251126A: Swift-XRT refined Analysis
  50. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  51. GRB 251126A: 1.3m DFOT optical afterglow detection
  52. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  53. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  54. GRB 251126A: Enhanced Swift-XRT position
  55. GRB 251126A: Kilonova-Catcher optical afterglow detection
  56. GRB 251126A: Nanshan/HMT optical afterglow detection
  57. GRB 251126A: GIT discovery of the likely optical afterglow
  58. GRB 251126A: Swift detection of a burst
  59. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  60. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  61. EP251124b: NOT r- and z-band optical upper limits
  62. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  63. EP251124b: EP-WXT detection of a fast X-ray transient
  64. EP251124a: Xinglong GWAC-F60A optical observation
  65. EP251124a: NOT r- and z-band optical upper limits
  66. EP251124a: Swift-XRT observations
  67. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  68. EP251124a: Optical upper limit with Kinder observations
  69. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  70. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  71. EP251124a: GROWTH-India Telescope optical upper limits
  72. EP251124a: Einstein Probe detection of an X-ray transient
  73. GRB 251116C: Swift-XRT confirmation of fading
  74. GRB 251122A/EP251122a: FTW optical and NIR observations
  75. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  76. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  77. EP251118A: 3.6m DOT optical afterglow detection
  78. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  79. GRB 251122A / EP251122a: WFST optical observations
  80. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  81. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  82. GRB 251122A / EP251122a: LCO optical upper limits
  83. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  84. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  85. GRB 251122A / EP251122a: SVOM detection of a long burst
  86. EP251122a: Einstein Probe detection of an X-ray transient
  87. EP251118a: Continued Optical Detection with Kinder observations
  88. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  89. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  90. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  91. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  92. EP251118a: Xinglong-2.16m optical observation
  93. EP251118A: 1.3m DFOT optical afterglow detection
  94. GRB 251118A: Swift/UVOT Detection
  95. EP251118a / GRB 251118C: SAO RAS optical observations
  96. GRB 251118A: Glowbug gamma-ray detection
  97. GRB 251118A: Swift-XRT afterglow detection
  98. EP251118a: Optical detection with Kinder observations
  99. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  100. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO

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