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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"

24611 results found.

  1. GRB 250114B: OHP/T193 optical upper limit
  2. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  3. GRB 250114A: Swift-XRT refined Analysis
  4. GRB 250114A: LCOGT optical afterglow i-band detection
  5. GRB 250114B : GIT optical upper limit
  6. EP250111a: SAO RAS optical upper limit
  7. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  8. GRB 250114B: a short GRB detected with INTEGRAL
  9. GRB 250114A: Enhanced Swift-XRT position
  10. GRB 250114A: REM detection of the optical and NIR counterpart
  11. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  12. Swift GRB250114A: Global MASTER-Net OT detection
  13. GRB 250114A: LCO optical observations
  14. GRB 250114A: TRT optical observations
  15. GRB 250114A: Swift detection of a burst with an optical counterpart
  16. GRB 250101A: Terskol Zeiss-2000 optical observations
  17. EP250108a / AT 2025kg: SAO RAS optical observations
  18. EP241021a: SMA radio observation
  19. GRB 250113A: SVOM/GRM observation of a long burst
  20. GRB 250107A: VZLUSAT-2 detection
  21. EP250109b: optical upper limits with the Liverpool Telescope
  22. GRB 250106A: Swift-XRT afterglow detection
  23. EP250111a: KAIT optical observations
  24. GRB 250109A / EP250109a: Mephisto optical upper limits
  25. EP250108a: Mephisto detection
  26. EP250111a: Mondy optical observation
  27. EP250108a / AT 2025kg: LCO optical observations
  28. EP250108a / AT 2025kg: Swift UVOT detections
  29. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  30. EP250111a: NOT likely optical counterpart
  31. GRB 250101B: Fermi GBM Observation
  32. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  33. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  34. GRB 250108A: Swift/XRT afterglow fading
  35. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  36. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  37. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  38. EP-WXT trigger EP250108a:Xinglong optical follow-up observations
  39. GRB 250101A: CMO RC-500 optical observations
  40. GRB 250109A: Fermi GBM Observation
  41. EP250108a: NOT optical observations
  42. EP-WXT trigger EP250109a:Xinglong optical follow-up observations
  43. GRB 250109a: GMG Optical Upper Limit
  44. EP250109a: Swift/UVOT non-detection
  45. IPN triangulation of GRB 250107D (short/hard)
  46. EP250108a: Liverpool Telescope likely optical counterpart
  47. GRB 250108B: Swift-BAT refined analysis
  48. GRB 250108B: 1.3m DFOT upper limit
  49. GRB 250108B: REM optical/NIR upper limits
  50. GRB 250101A: Terskol K-800 optical observations
  51. EP250109a: Swift/XRT non-detection
  52. GRB 250108A: Swift/UVOT Upper Limits
  53. LIGO/Virgo/KAGRA S250109bi: Identification of a GW compact binary merger candidate
  54. GRB 250108A: NOT optical upper limit
  55. EP250108a: EP-WXT detection of an X-ray transient
  56. LIGO/Virgo/KAGRA S250109f: Identification of a GW compact binary merger candidate
  57. GRB 250108B: Swift-XRT refined Analysis
  58. GRB 250103A: 1.6m Mephisto optical observations
  59. GRB 250108A: Swift-XRT afterglow detection
  60. GRB 250108A:SVOM/VT optical candidate
  61. LIGO/Virgo/KAGRA S250108eo: Identification of a GW compact binary merger candidate
  62. GRB 250108B: Swift/UVOT Upper Limits
  63. GRB 250103A: Swift-XRT afterglow detection
  64. GRB 250108B: Enhanced Swift-XRT position
  65. GRB 250108B: Swift detection of a burst
  66. GRB 250107A: Fermi GBM Observation
  67. GRB 250107A: Swift/BAT-GUANO arcminute localization of a burst
  68. GRB 250106A: SVOM/VT 2nd optical deep observation
  69. GRB 250101A: J band upper limit by SYSU 80cm telescope
  70. EPWXT01709129925: Xinglong optical observations
  71. GRB 250106A: NOT optical observations
  72. LIGO/Virgo/KAGRA S250104v: Updated Sky localization
  73. GRB 250103B: REM optical/NIR upper limits
  74. GRB 250101A: REM optical/NIR counterpart detection
  75. GRB 250106A: Swift-XRT observations
  76. GRB 250106A: SVOM/VT optical candidate
  77. The EP-WXT trigger 01709129925 is likely a flaring star
  78. GRB 250103B: Swift-XRT refined Analysis
  79. GRB 250103B: LCO/1m optical afterglow candidate detection
  80. GRB 250103A: Bassano Bresciano Observatory upper limit
  81. GRB 250103A: Swift-XRT observations
  82. GRB 250101A: 1.3m DFOT optical afterglow detection
  83. GRB 241229A: 1.3m DFOT upper limit
  84. GRB 241228B: 1.3m DFOT Optical observations
  85. GRB 241228A: 1.3m DFOT upper limit
  86. LIGO/Virgo/KAGRA S250104v: Identification of a GW compact binary merger candidate
  87. GRB 250103A: Montarrenti Observatory optical detection
  88. GRB 250101A: further LCOGT optical afterglow observations
  89. GRB 250103A: TSHAO optical upper limit
  90. GRB 250103A: Fermi GBM Observation
  91. GRB 250103B: LCOGT Optical Upper Limit
  92. IceCube-250102A: Upper limits from a search for additional neutrino events in IceCube
  93. EP250101a: Liverpool Telescope optical upper limit
  94. IceCube-250101A: Upper limits from a search for additional neutrino events in IceCube
  95. GRB 250101a: Liverpool Telescope optical follow-up
  96. GRB 250103B: Swift detection of a burst
  97. GRB 250103A: Xinglong 2.16m Optical Candidate
  98. GRB 250101B: SVOM/GRM observation
  99. GRB 250103A: GOTO optical upper limit
  100. GRB 250103A: SVOM/C-GFT optical upper limit

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