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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"

31638 results found.

  1. EP251130a: Optical detections with Kinder observations
  2. EP251130a: SAO RAS optical observations
  3. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  4. EP251130a: KAIT optical observations
  5. EP251130A: Optical observation from 1.3m DFOT
  6. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  7. EP251130a: JinShan optical observations
  8. Fermi GRB 251130B: Global MASTER-Net observations report
  9. GRB 251127A: SVOM/GRM observation
  10. EP251130a: Swift-XRT counterpart detection
  11. EP251130a: Global MASTER-Net observations report
  12. EP251130a: COLIBRÍ optical counterpart candidate
  13. EP251129a/GRB 251129A: EP-FXT follow-up observations
  14. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  15. GRB 251128A: AstroSat CZTI detection
  16. GRB 251129A / EP251129a: SAO RAS optical observations
  17. GRB 251126A: SAO RAS optical observations
  18. GRB 251128A: GECAM-B detection
  19. GRB 251128A: SVOM/GRM observation of a long burst
  20. GRB 251128A: Insight-HXMT/HE detection
  21. SVOM GRB 251129A : MASTER optical counterpart detection
  22. GRB 251129A: Swift-XRT afterglow detection
  23. GRB 251129A: Swift ToO observations
  24. GRB 251129A / EP251129a: SVOM/VT optical fading
  25. EP251129a: Global MASTER-Net observations report
  26. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  27. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  28. GRB 251129A: Correction to the position of the optical counterpar
  29. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  30. GRB 251128A: Fermi GBM Observation
  31. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  32. GRB 251126A: Swift-BAT refined analysis
  33. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  34. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  35. Fermi GRB 251128A: Global MASTER-Net observations report
  36. GRB 251127A: Glowbug gamma-ray detection
  37. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  38. GRB 251126A: further SAO RAS optical observations
  39. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  40. GRB 251126A NUTTelA-TAO Early Measurements
  41. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  42. GRB251126A: MAO/AZT-22 optical observations
  43. GRB251126A: Continued optical observation from 1.3m DFOT
  44. GRB 251126A: Swift/UVOT Detection
  45. EP251124a: Pan-STARRS ri-band imaging and photometry
  46. GRB 251126A: Mondy and SAO RAS optical observations
  47. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  48. GRB 251126A: NOT optical observations
  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 251125B: GECAM-B detection
  53. Fermi GRB 251127A: Global MASTER-Net observations report
  54. GRB 251126A: Kilonova-Catcher optical afterglow detection
  55. GRB 251126A: Asiago i-band detection
  56. GRB 251126A: Nanshan/HMT optical afterglow detection
  57. Swift GRB 251126A: Global MASTER-Net observations report
  58. GRB 251121A: Fermi GBM Observation
  59. GRB 251126A: GIT discovery of the likely optical afterglow
  60. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  61. EP251124b follow-up observation by EP-FXT
  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. Fermi GRB 251125B: Global MASTER-Net observations report
  66. EP251124b: Global MASTER-Net observations report
  67. EP251124a: Xinglong GWAC-F60A optical observation
  68. EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
  69. Fermi GRB 251125A: Global MASTER-Net observations report
  70. EP251124a: NOT r- and z-band optical upper limits
  71. EP251124a: Global MASTER-Net observations report
  72. GRB 251124A: Fermi GBM Localization by automated pipeline
  73. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  74. EP251124a: Optical upper limit with Kinder observations
  75. EP251118A: 6 GHz VLA Detection
  76. Fermi GRB 251124a: Global MASTER-Net observations report
  77. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  78. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  79. EP251124a: GROWTH-India Telescope optical upper limits
  80. GRB 251116C: Swift-XRT confirmation of fading
  81. GRB 251122A/EP251122a: FTW optical and NIR observations
  82. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  83. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  84. EP251118A: 3.6m DOT optical afterglow detection
  85. GRB 251122A / EP251122a: EP-FXT counterpart detection
  86. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  87. GRB 251122A / EP251122a: WFST optical observations
  88. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  89. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  90. GRB 251122A / EP251122a: LCO optical upper limits
  91. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  92. EP251122a: Global MASTER-Net observations report
  93. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  94. GRB 251122A / EP251122a: SVOM detection of a long burst
  95. EP251118a: Continued Optical Detection with Kinder observations
  96. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  97. LIGO/Virgo/KAGRA S251112cm: SOAR spectroscopy of three TROVE TNS candidates
  98. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  99. GRB 251121A: Glowbug gamma-ray detection of a likely short burst
  100. EP251118a: Xinglong-2.16m optical observation

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