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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"

24603 results found.

  1. GRB 250316A: Fermi GBM Observation
  2. GRB 250316A: Swift-XRT observations
  3. GRB 250314A: SVOM/GRM analysis
  4. GRB 250316A: Swift/BAT-GUANO arcminute localization of a burst
  5. GRB 250314A: GTC z-band upper limit and updated photo-z ~ 7.27
  6. GRB 250315A/EP250315A: Fermi-GBM Sub-Threshold Detection
  7. GRB 250314A: EP-FXT afterglow detection
  8. EP250315a: refined analysis of the EP-WXT and EP-FXT observations
  9. GRB 250314A: Swift/UVOT Upper Limits
  10. GRB 250313.89 / Fermi trigger 763594063: bright OT AT 2025ehi detection
  11. GRB 250314A: Swift XRT Detection
  12. EP250315a: optical counterpart candidate detected by Gemini North
  13. GRB 250314A: VLT/X-shooter dropout, redshift z ~ 7.3
  14. EP250315a: Einstein Probe detection of an X-ray transient
  15. GRB 250226A: Mondy AZT-33IK and Koshka Zeiss-1000 Optical Upper Limits
  16. SVOM/MXT upper limit on GRB 250314A
  17. GRB 250314A: SVOM/VT upper limit
  18. GRB 250314A: NOT near-infrared candidate counterpart
  19. GRB 250313A: Fermi GBM Detection
  20. GRB 250312B: Fermi GBM Observation
  21. GRB 250313A: Swift-XRT observations
  22. GRB250314A: SVOM/VT lack of bright optical candidate from VHF data
  23. GRB 250314A: SVOM detection of a burst
  24. GRB 250313A: AstroSat CZTI detection of a bright long burst
  25. IceCube-250309A: MASTER detection of J140105.33-091631.6 blazar flare with Zhirkov effect
  26. GRB 250313A: Fermi-LAT detection
  27. EP250304a: Pan-STARRS r and i-band imaging and photometry
  28. GRB 250312B: Swift/BAT-GUANO localization skymap of a burst
  29. GRB 250309B: PRIME near-infrared upper limits in 2nd epoch
  30. GRB 250313A???: BALROG localization (Fermi Trigger / GRB 250313607)
  31. ATCA detection of the radio counterpart of GRB 250309B-AT2025dws
  32. GRB 250312A: Swift-XRT refined Analysis
  33. GRB 250312A: Enhanced Swift-XRT position
  34. LIGO/Virgo/KAGRA S250304cb: Upper limits from Swift/BAT-GUANO
  35. GRB 250226B: Fermi GBM Observation
  36. GRB 250302A: Fermi GBM Observation
  37. GRB 250309B/AT2025dws: Daochen/RC-10 optical counterpart observation
  38. GRB 250312A: Swift detection of a burst
  39. GRB 241213A: VIRT Optical Upper Limit
  40. GRB 241228A: VIRT Optical Upper Limit
  41. GRB 250311A/EP250311a: Optical upper limits with Kinder observations
  42. GRB 250311A: Swift-XRT observations
  43. GRB 230509B: 1.3m DFOT Optical observations
  44. IceCube-250309A: Upper limits from a search for additional neutrino events in IceCube
  45. GRB 250308A: Swift/BAT-GUANO localization skymap of a short burst
  46. GRB 250302A: Swift/BAT-GUANO localization skymap of a burst
  47. GRB 250228A: Swift/BAT-GUANO localization skymap of a likely short burst
  48. GRB 250226B: Swift/BAT-GUANO localization skymap of a likely long GRB
  49. GRB 250226A: Swift/BAT-GUANO localization skymap of a long GRB
  50. GRB 250223B: Swift/BAT-GUANO localization skymap of a short burst
  51. GRB 250309B: PRIME near-infrared detection
  52. GRB 250225B: Swift-BAT refined analysis
  53. GRB 250311A/EP250311a: TRT optical upper limit
  54. EP250311a/GRB 250311A: EP-WXT detection
  55. GRB 250311B: SVOM detection of a burst
  56. GRB 250311A/MAXI J1457-026: MAXI/GSC detection
  57. GRB 250309B / AT2025dws: further SAO RAS optical observations
  58. EP250308a: 1.6m Mephisto optical upper limits
  59. Konus-Wind detection of GRB 250309B
  60. IPN triangulation of GRB 250308A (short)
  61. IceCube-241224A: MASTER detection of PKS 1217+02 blazar flare with Zhirkov effect
  62. GRB 250309B/AT2025dws : COLIBRÍ Detection of the Optical Counterpart
  63. GRB 250309B: Swift-XRT refined Analysis
  64. GRB 250309B / IceCube-250309A: GECAM-B observations
  65. GRB 250309B / AT2025dws: SAO RAS optical observations
  66. AT 2025dws, likely optical counterpart of GRB 250309B: LCO confirmation of fast fading
  67. GRB 250309B: Fermi GBM Observation
  68. GRB250309B: One candidate counterpart from the Zwicky Transient Facility
  69. IceCube-250309A: No candidates from the Zwicky Transient Facility
  70. Fermi-LAT gamma-ray observations of IceCube-250309A
  71. IceCube-250309A - IceCube observation of a high-energy neutrino candidate track-like event
  72. GRB 250309B: BALROG localization (Fermi Trigger 763198715 / GRB 250309318)
  73. EP250308a: GSP optical upper limit
  74. EP250308a: Einstein Probe detection of an X-ray transient
  75. EP250308a: NOT optical upper limit
  76. GRB 250306A: EIRSAT-1 GMOD detection
  77. GRB 250306A: Swift-BAT refined analysis
  78. GRB 250306A: NuSTAR detection of the prompt emission
  79. EP250304a: MeerKAT detection of a possible radio counterpart
  80. IceCube-241016A: MASTER flaring blazar 5BZU J073038.29-320820.2 with Zhirkov effect
  81. GRB 250305A: AstroSat CZTI detection
  82. EP250302a:Xinglong optical observations
  83. LIGO/Virgo/KAGRA S250207bg: Update-5 NED Galaxies in the Localization Volume
  84. LIGO/Virgo/KAGRA S250207bg: Updated Sky localization
  85. GRB250101A: Radio upper limits from VLA observations
  86. GRB 250305A: SVOM/GRM observation of a burst
  87. The EP-WXT trigger 01709132323 is likely a flaring star
  88. EP250304A: Upper limits from Fermi-GBM Observations
  89. Fermi-LAT Gamma-ray Observations of IceCube-250302A
  90. EP250302a: Optical Observations at CrAO and SAO RAS
  91. GRB 250219A: SVOM/C-GFT optical upper limit at early phase
  92. EP 250304A: Optical counterpart detection by LCO
  93. EP250302A: 1.3m DFOT optical afterglow detection
  94. IceCube-250302A: Upper limits from a search for additional neutrino events in IceCube
  95. EP250304a: refined analysis of the EP-WXT and EP-FXT observations
  96. EP250304a: REM NIR upper limits
  97. EP250304a: Swift/UVOT detection of an optical counterpart with a rising light curve
  98. EP250302a: Mondy Continued Optical Observations
  99. EP250304a: Swift-XRT detection of a fading X-ray source
  100. EP250304a: TRT optical counterpart detection

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