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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"

21263 results found.

  1. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  2. GRB 251126A: 1.3m DFOT optical afterglow detection
  3. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  4. GRB 251126A: COLIBRÍ photometric redshift z = 3.5
  5. GRB 251126A: Enhanced Swift-XRT position
  6. GRB 251126A: Kilonova-Catcher optical afterglow detection
  7. GRB 251126A: Nanshan/HMT optical afterglow detection
  8. GRB 251121A: Fermi GBM Observation
  9. GRB 251126A: GIT discovery of the likely optical afterglow
  10. GRB 251126A: Swift detection of a burst
  11. GRB 251125B: COLIBRÍ further observations and photometric redshift upper limit of z < 3
  12. GRB 251125B: COLIBRÍ observations of fading of the MASTER OT candidate
  13. EP251124b: NOT r- and z-band optical upper limits
  14. Fermi GRB 251125B : MASTER OT J155558.56+581224.1 optical counterpart discovery
  15. EP251124b: EP-WXT detection of a fast X-ray transient
  16. EP251124a: Xinglong GWAC-F60A optical observation
  17. EP251124a: NOT r- and z-band optical upper limits
  18. EP251124a: Swift-XRT observations
  19. LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
  20. EP251124a: Optical upper limit with Kinder observations
  21. LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
  22. LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
  23. EP251124a: GROWTH-India Telescope optical upper limits
  24. EP251124a: Einstein Probe detection of an X-ray transient
  25. GRB 251116C: Swift-XRT confirmation of fading
  26. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  27. GRB 251122A / EP251122a: Xinglong 2.16m optical observation
  28. EP251118A: 3.6m DOT optical afterglow detection
  29. EP251122a: refined analysis of the EP-WXT and EP-FXT observations
  30. GRB 251122A / EP251122a: WFST optical observations
  31. GRB 251122A/EP251122a: SVOM/VT optical observations with VHF data
  32. GRB 251122A/EP251122a: Additional, deeper LCO optical r band upper limit
  33. GRB 251122A / EP251122a: LCO optical upper limits
  34. EP251122a / GRB 251122A: optical counterpart candidate with Kinder observations
  35. GRB 251122A/EP251122a: SVOM/C-GFT upper limit
  36. GRB 251122A / EP251122a: SVOM detection of a long burst
  37. EP251122a: Einstein Probe detection of an X-ray transient
  38. EP251118a: Continued Optical Detection with Kinder observations
  39. LIGO/Virgo/KAGRA S251105aj: SVOM/ECLAIRs detection of a high-energy transient SVOM J2320.0-2901 through targeted search
  40. GRB 251121A: Swift/BAT-GUANO localization skymap of a short burst
  41. EP251118a: Xinglong-2.16m optical observation
  42. EP251118A: 1.3m DFOT optical afterglow detection
  43. GRB 251118A: Swift/UVOT Detection
  44. EP251118a / GRB 251118C: SAO RAS optical observations
  45. GRB 251118A: Swift-XRT afterglow detection
  46. EP251118a: Optical detection with Kinder observations
  47. LIGO/Virgo/KAGRA S251112cm: SVOM/VT optical observations and preliminary results
  48. GRB 251118A: NuSTAR detection of bright prompt emission
  49. EP251118a / GRB 251118C: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at CTIO
  50. GRB 251118C: Swift/BAT rates detection of a burst with a possible association with EP 251118A
  51. GRB 251118C: SVOM/GRM observation of a possible gamma-ray counterpart of EP251118a
  52. EP251118a: FTW optical and NIR observations
  53. GRB 251119A: SVOM trigger sb25111901 is not a GRB
  54. EP251118a: VLT near-infrared observation
  55. GRB 251116D: SVOM/GRM observation of a long GRB
  56. GRB 251119A: SVOM detection of a possible burst
  57. EP251118a: NOT candidate optical counterpart
  58. EP251118a: Einstein Probe detected of a fast X-ray transient
  59. LIGO/Virgo/KAGRA S251112cm: Upper limits from Glowbug gamma-ray observations
  60. GRB 251116C: SVOM/ECLAIRs refined analysis
  61. GRB 251116B: SVOM/ECLAIRs refined analysis
  62. GRB 251116D: Insight-HXMT/HE detection
  63. GRB 251115A: Swift-XRT observations
  64. GRB 251117A: Swift/BAT-GUANO localization skymap of a short burst
  65. GRB 251117A: SVOM/GRM observation of a short burst
  66. GRB 251117A: Fermi-LAT detection
  67. LIGO/Virgo/KAGRA S251117dq: Identification of a GW compact binary merger candidate
  68. LIGO/Virgo/KAGRA S251112cm: J-GEM follow-up observations
  69. LIGO/Virgo/KAGRA S251112cm: WFST follow-up observations and preliminary results
  70. EP251023a: Assy AZT-20 optical observations
  71. EP251023a: UAFO and AbAO optical observations
  72. The EP-WXT trigger 01709247588: more evidence of flaring star from Mondy optical observations
  73. GRB 251025B: further Mondy optical observations
  74. GRB 251111A: Mondy optical upper limit
  75. LIGO/Virgo/KAGRA S251116en: Identification of a GW compact binary merger candidate
  76. LIGO/Virgo/KAGRA S251112cm: Observations with the NSF-DOE Vera C. Rubin Observatory
  77. GRB 251116B: LCO optical upper limits
  78. GRB 251116C: LCO optical upper limits
  79. GRB 251116C: SVOM detection of a burst
  80. LIGO/Virgo/KAGRA S251112cm: GRANDMA observations of the skymap
  81. GRB 251115A: Fermi-LAT detection
  82. GRB 251013C: joint SVOM/ECLAIRs-GRM refined analysis
  83. LIGO/Virgo/KAGRA S251112cm: DECam GW-MMADS candidates
  84. GRB 251113A: AstroSat CZTI detection
  85. Konus-Wind detection of GRB 251108C
  86. LIGO/Virgo/KAGRA S251112cm: ATLAS targeted observations of the skymap
  87. IPN triangulation of GRB 251108C
  88. LIGO/Virgo/KAGRA S251112cm: FTW observations of galaxies within localization region
  89. GRB 251111A: SVOM/ECLAIRs refined analysis
  90. GRB 251025B: SVOM/ECLAIRs refined analysis
  91. GRB 251112A: Swift/UVOT Upper Limits
  92. LIGO/Virgo/KAGRA S251112cm: Coverage and upper limits from MAXI/GSC observations
  93. LIGO/Virgo/KAGRA S251112cm: Initial GOTO-South observations
  94. Swift Trigger 1413695: a possible GRB 251112A
  95. GRB251111A: 1.3m DFOT optical upper limit
  96. LIGO/Virgo/KAGRA S251112cm: Identification of a GW compact binary merger candidate
  97. GRB 251111A: Swift-XRT afterglow detection
  98. GRB 251111A: SVOM/VT optical observations with X-band data
  99. GRB 251111A: SVOM/VT optical observations with VHF data
  100. GRB 251111A: LCO optical observation

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