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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"

11756 results found.

  1. EP250827a: Einstein Probe detection of an X-ray transient
  2. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  3. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  4. Fermi GRB 250824B: Global MASTER-Net observations report
  5. GRB 250821B: AstroSat CZTI detection
  6. GRB 250819A: AstroSat CZTI detection
  7. LIGO/Virgo/KAGRA S250818k: FTW Observations Show Continued Reddening of AT 2025ulz
  8. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  9. The EP-WXT trigger 01709200707 is likely a flaring star
  10. The EP-WXT trigger 01709200706 is likely a flaring star
  11. GRB 250823A: Fermi GBM Observation
  12. GRB 250823A: BOOTES6/DPRT early optical detection
  13. GRB 250823A: Swift detection of a burst
  14. GRB 250823A: Fermi GBM Final Real-time Localization
  15. Swift GRB250823.84: Global MASTER-Net observations report
  16. Konus-Wind detection of GRB 250821B
  17. LIGO/Virgo/KAGRA S250818k: HST nIR detection of AT 2025ulz
  18. LIGO/Virgo/KAGRA S250818k: J-GEM follow-up observation for AT2025ulz
  19. LIGO/Virgo/KAGRA S250818k: PRIME nIR observations of AT2025ulz
  20. GRB 250806A: Gemini observations of host galaxy candidate
  21. GRB 250821A: Kilonova-Catcher optical upper limits
  22. EP250821a: Swift/XRT counterpart fading
  23. LIGO/Virgo/KAGRA S250818k: Pan-STARRS coverage of the skymap and candidate counterparts
  24. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  25. GRB 250821A: Swift-XRT refined Analysis
  26. LIGO/Virgo/KAGRA S250818k : Tautenburg observations, upper limits
  27. EP250821a: Swift XRT and UVOT counterpart detection
  28. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  29. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  30. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  31. GRB 250821A: Swift detection of a burst
  32. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  33. EP250821a: Einstein Probe detection of an X-ray transient
  34. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  35. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  36. GRB 250818B: Liverpool Telescope optical detections
  37. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  38. Fermi Gamma-ray Burst Monitor trigger 777342746/250820022 is not a GRB
  39. GRB 250820A: Fermi GBM Final Real-time Localization
  40. Swift GRB 250818A: Global MASTER-Net observations report
  41. LIGO/Virgo/KAGRA S250818k: Coverage and upper limits from MAXI/GSC observations
  42. GRB 250818B: Swift-XRT afterglow detection
  43. GRB 250818B: SVOM detection of a short burst
  44. sb25081602: Swift-XRT observations
  45. SVOM/sb25081602: detection of a likely X-ray transient
  46. GRB 250814A: Further COLIBRÍ optical upper limit
  47. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  48. GRB 250814A: GRAWITA TNG NIR observations
  49. GRB 250812A: SVOM/VT optical continued observation
  50. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  51. GRB 250814A: P200/WIRC observations of the afterglow candidate
  52. GRB 250814A: possible optical afterglow candidate at Spanish observatories
  53. GRB 250814A: Possible afterglow candidate from P200/WIRC
  54. Subject GRB 250813B: SVOM/MXT refined analysis
  55. GRB 250813A: AstroSat CZTI detection
  56. Fermi-LAT Gamma-ray Observations of IceCube-250813A
  57. GRB 250813B: Swift-XRT afterglow detection
  58. GRB 250814A: Swift detection of a burst coincident with a subthreshold GW trigger
  59. GRB 250813B: Ondrejov D50 fast decay
  60. LIGO/Virgo/KAGRA S250813k: NED Galaxies in the 4-Update Localization Volume
  61. GRB 250812A: NTT spectroscopic redshift z = 2.57
  62. EP250812a: refined analysis of the EP-WXT and EP-FXT observations
  63. IceCube Alert 250813.14: Global MASTER-Net observations report
  64. GRB 250812A: Kilonova-Catcher optical afterglow detection
  65. EP250812a: Swift-XRT counterpart detection
  66. EP250812a: Einstein Probe detection of an X-ray transient
  67. GRB 250812A: Swift-XRT afterglow detection
  68. Fermi-LAT Gamma-ray Observations of IceCube-250804A
  69. LIGO/Virgo/KAGRA S250810ck: Identification of a GW compact binary merger candidate
  70. Corrected Swift-XRT Refined Analysis of GRB 250809A
  71. GRB 250808A: Swift-XRT candidate counterpart detection
  72. GRB 250808A: SVOM detection of a long burst
  73. Konus-Wind detection of GRB 250807A
  74. IceCube-250804A: Upper limits from a search for additional neutrino events in IceCube
  75. GRB 250807A: Swift-XRT refined Analysis
  76. GRB 250806A: SVOM/ECLAIRs refined analysis
  77. GRB 250807A: AstroSat CZTI detection of bright long burst
  78. GRB 250807B: Swift-XRT refined Analysis
  79. GRB 250806A: EP-FXT observation
  80. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  81. EP250806a: SVOM /VT optical candidate
  82. GRB 250806A: Swift-XRT counterpart detection
  83. EP250806a: Einstein Probe detection of an X-ray transient
  84. GRB 250806A: SVOM detection of a soft burst
  85. GRB 250805A: Swift-XRT refined Analysis
  86. GRB 250804C: AstroSat CZTI detection of a long burst
  87. IceCube-250804A - IceCube observation of a high-energy neutrino candidate track-like event
  88. GRB 250805A: Swift-XRT observations
  89. Swift GRB250805.26: Global MASTER-Net observations report
  90. Fermi Gamma-ray Burst Monitor trigger 775945985/250803856 is not a GRB
  91. The EP-WXT trigger 01709198251 is likely a flaring star
  92. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  93. The EP-WXT trigger 01709198202 is likely a flaring star
  94. EP250711a: CrAO and Assy optical observations
  95. EP250730a: Einstein Probe detection of an X-ray transient
  96. LIGO/Virgo/KAGRA S250726ak: Upper limits from Swift/BAT-GUANO
  97. LIGO/Virgo/KAGRA S250725l: Upper limits from Swift/BAT-GUANO
  98. LIGO/Virgo/KAGRA S250727dc: Upper limits from Swift/BAT-GUANO
  99. GRB 250725A: AstroSat CZTI detection
  100. Fermi trigger No 775387550: Global MASTER-Net observations report

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