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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"

15558 results found.

  1. EP251130a: continued NOT optical observations indicate steep fading phase
  2. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  3. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  4. GRB 251202A: GOTO optical afterglow detection
  5. GRB 251126A: SAO RAS optical marginal detection
  6. GRB 251202A: Swift-XRT afterglow detection
  7. EP251129a/GRB 251129A: NOWT Detection
  8. GRB 251126A: SVOM/VT optical observation
  9. EP251130a: SVOM/VT optical observation
  10. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  11. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  12. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  13. GRB 251201A: SVOM/GRM observation of a burst
  14. GRB 251201B: SVOM/VT optical fading
  15. Swift GRB 251201B : MASTER optical counterpart detection
  16. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  17. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  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: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  23. EP251130a: KAIT optical observations
  24. EP251130A: Optical observation from 1.3m DFOT
  25. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  26. EP251130a: JinShan optical observations
  27. GRB 251127A: SVOM/GRM observation
  28. EP251130a: Swift-XRT counterpart detection
  29. EP251130a: COLIBRÍ optical counterpart candidate
  30. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  31. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  32. GRB 251129A / EP251129a: SAO RAS optical observations
  33. GRB 251126A: SAO RAS optical observations
  34. GRB 251128A: SVOM/GRM observation of a long burst
  35. SVOM GRB 251129A : MASTER optical counterpart detection
  36. GRB 251129A: Swift-XRT afterglow detection
  37. GRB 251129A / EP251129a: SVOM/VT optical fading
  38. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  39. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  40. GRB 251129A: Correction to the position of the optical counterpar
  41. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  42. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  43. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  44. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  45. GRB 251126A: further SAO RAS optical observations
  46. GRB 251126A NUTTelA-TAO Early Measurements
  47. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  48. GRB251126A: MAO/AZT-22 optical observations
  49. GRB251126A: Continued optical observation from 1.3m DFOT
  50. GRB 251126A: Swift/UVOT Detection
  51. EP251124a: Pan-STARRS ri-band imaging and photometry
  52. GRB 251126A: Mondy and SAO RAS optical observations
  53. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  54. GRB 251126A: NOT optical observations
  55. GRB 251126A: 1.3m DFOT optical afterglow detection
  56. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  57. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  58. GRB 251126A: Kilonova-Catcher optical afterglow detection
  59. GRB 251126A: Asiago i-band detection
  60. GRB 251126A: Nanshan/HMT optical afterglow detection
  61. GRB 251126A: GIT discovery of the likely optical afterglow
  62. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  63. EP251124b: NOT r- and z-band optical upper limits
  64. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  65. EP251124a: Xinglong GWAC-F60A optical observation
  66. EP251124a: NOT r- and z-band optical upper limits
  67. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  68. EP251124a: Optical upper limit with Kinder observations
  69. EP251118A: 6 GHz VLA Detection
  70. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  71. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  72. EP251124a: GROWTH-India Telescope optical upper limits
  73. GRB 251122A/EP251122a: FTW optical and NIR observations
  74. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  75. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  76. EP251118A: 3.6m DOT optical afterglow detection
  77. GRB 251122A / EP251122a: EP-FXT counterpart 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. EP251118a: Continued Optical Detection with Kinder observations
  85. EP251118a: Xinglong-2.16m optical observation
  86. EP251118A: 1.3m DFOT optical afterglow detection
  87. EP251118a / GRB 251118C: SAO RAS optical observations
  88. EP251118a: Optical detection with Kinder observations
  89. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  90. EP251118a / GRB 251118C: SVOM/VT optical observation
  91. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  92. GRB 251116C: NOT optical observations
  93. GRB 251018A: FRAM-Auger optical detection
  94. EP251118A / GRB 251118C : MASTER optical counterpart observations
  95. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  96. EP251118a: FTW optical and NIR observations
  97. EP251118a: VLT near-infrared observation
  98. GRB 251116D: SVOM/GRM observation of a long GRB
  99. EP251118a: GOTO optical afterglow detection
  100. EP251118a: NOT spectroscopic redshift of z = 1.216

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