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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"

24665 results found.

  1. EP250125a: Optical upper limit with Kinder observations
  2. EP250125a: REM optical counterpart detection
  3. GRB 250119C: Fermi GBM Observation
  4. EP250125a: Swift/XRT detection of a fading counterpart
  5. EP250125a: a new X-ray transient detected by Einstein Probe
  6. EP250125a: Gemini-South optical afterglow discovery and redshift z = 2.89
  7. GRB 250121A: Swift/BAT-GUANO localization skymap of a burst
  8. EP250108a: AbAO, CMO and Terskol optical upper limits
  9. GRB 250121A: Fermi GBM Observation
  10. IPN triangulation of GRB 250118B
  11. IPN triangulation of GRB 250119B
  12. GRB 250114A: Swift-BAT refined analysis
  13. LIGO/Virgo S250119cv: Swift XRT observations, 5 X-ray sources
  14. GRB 250119C: Swift/BAT-GUANO localization skymap of a short burst
  15. GRB 250119B: Swift/BAT-GUANO localization skymap of a long burst
  16. Fermi-LAT Gamma-ray Observations of IceCube-241224A
  17. GRB 250118A: Swift/BAT-GUANO localization skymap of a short burst
  18. GRB 250119B: Fermi GBM Observation
  19. EP250108a/AT2025kg: 1.3m DFOT Optical observations
  20. IPN triangulation of GRB 250117A (short)
  21. LIGO/Virgo/KAGRA S250119cv: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  22. EP 250108A: Late-time optical observation by LCO
  23. LIGO/Virgo/KAGRA S250105bn: 1 counterpart neutrino candidate event from an IceCube neutrino search
  24. LIGO/Virgo/KAGRA S250119cv: Updated NED Galaxies in the Localization Volume
  25. LIGO/Virgo/KAGRA S250119cv: Updated Sky localization and EM Bright Classification
  26. LIGO/Virgo/KAGRA S250119cv: NED Galaxies in the Localization Volume
  27. GRB 250117A: Swift/BAT-GUANO localization skymap of a short burst
  28. LIGO/Virgo/KAGRA S250119cv: Identification of a GW compact binary merger candidate
  29. LIGO/Virgo/KAGRA S250119ag: Updated Sky localization
  30. GRB 250117A: GECAM observation of a short burst
  31. LIGO/Virgo/KAGRA S250118dp: Updated Sky localization
  32. GRB 250119B: BALROG localization (Fermi Trigger 758968026 / GRB 250119352)
  33. LIGO/Virgo/KAGRA S250119ag: Identification of a GW compact binary merger candidate
  34. LIGO/Virgo/KAGRA S250118dp: Identification of a GW compact binary merger candidate
  35. LIGO/Virgo/KAGRA S250118t: Updated Sky localization
  36. LIGO/Virgo/KAGRA S250118az: Identification of a GW compact binary merger candidate
  37. EP250108a / AT2025kg: GMG Optical Observations
  38. LIGO/Virgo/KAGRA S250118t: Identification of a GW compact binary merger candidate
  39. GRB 241217A / EP241217B: radio detection with the VLA
  40. GRB 250116A: Fermi GBM Observation of an Extremely Interesting Burst
  41. GRB 250114B: Swift-XRT afterglow detection
  42. EP250108a: MeerKAT radio upper limit
  43. LIGO/Virgo/KAGRA S250114ax: Updated NED Galaxies in the Localization Volume
  44. GRB 250101A: Calapai Observatory, Massa S. Giorgio (Messina), optical observations and rebrightening.
  45. LIGO/Virgo/KAGRA S250114ax: Updated Sky localization
  46. IPN triangulation of GRB 250113A
  47. GRB 250114B: Liverpool Telescope optical upper limit
  48. LIGO/Virgo/KAGRA S250114ax: GLADEnet Completeness: Potential Host Galaxies in the 90% Credible Volume
  49. GRB 250114B : MITSuME Akeno optical afterglow candidate detection
  50. GRB 250114B: Swift-XRT observations
  51. GRB 250114A: LCO optical counterpart detection.
  52. GRB 250114B: OHP/T193 optical upper limit
  53. GRB 250114A: GRANDMA/TAROT optical afterglow detection
  54. GRB 250114A: Swift-XRT refined Analysis
  55. GRB 250114A: LCOGT optical afterglow i-band detection
  56. GRB 250114B : GIT optical upper limit
  57. EP250111a: SAO RAS optical upper limit
  58. LIGO/Virgo/KAGRA S250114ax: NED Galaxies in the Localization Volume
  59. GRB 250114B: a short GRB detected with INTEGRAL
  60. GRB 250114A: Enhanced Swift-XRT position
  61. GRB 250114A: REM detection of the optical and NIR counterpart
  62. LIGO/Virgo/KAGRA S250114ax: Identification of a GW compact binary merger candidate
  63. Swift GRB250114A: Global MASTER-Net OT detection
  64. GRB 250114A: LCO optical observations
  65. GRB 250114A: TRT optical observations
  66. GRB 250114A: Swift detection of a burst with an optical counterpart
  67. GRB 250101A: Terskol Zeiss-2000 optical observations
  68. EP250108a / AT 2025kg: SAO RAS optical observations
  69. EP241021a: SMA radio observation
  70. GRB 250113A: SVOM/GRM observation of a long burst
  71. GRB 250107A: VZLUSAT-2 detection
  72. EP250109b: optical upper limits with the Liverpool Telescope
  73. GRB 250106A: Swift-XRT afterglow detection
  74. EP250111a: KAIT optical observations
  75. GRB 250109A / EP250109a: Mephisto optical upper limits
  76. EP250108a: Mephisto detection
  77. EP250111a: Mondy optical observation
  78. EP250108a / AT 2025kg: LCO optical observations
  79. EP250108a / AT 2025kg: Swift UVOT detections
  80. EP250108a / AT 2025kg (the "kangaroo”): VLT/X-shooter spectroscopic redshift z = 0.176 and LFBOT classification
  81. EP250111a: NOT likely optical counterpart
  82. GRB 250101B: Fermi GBM Observation
  83. GRB 250109A / EP250109a: Terskol (INASAN) and SAO RAS observations
  84. GRB 250109A / EP250109A: Swift/BAT-GUANO localization skymap of a burst
  85. GRB 250108A: Swift/XRT afterglow fading
  86. LIGO/Virgo/KAGRA S250109bi: Updated Sky localization
  87. LIGO/Virgo/KAGRA S250109f: Updated Sky localization
  88. LIGO/Virgo/KAGRA S250108eo: Updated Sky localization
  89. EP-WXT trigger EP250108a:Xinglong optical follow-up observations
  90. GRB 250101A: CMO RC-500 optical observations
  91. GRB 250109A: Fermi GBM Observation
  92. EP250108a: NOT optical observations
  93. EP-WXT trigger EP250109a:Xinglong optical follow-up observations
  94. GRB 250109a: GMG Optical Upper Limit
  95. EP250109a: Swift/UVOT non-detection
  96. IPN triangulation of GRB 250107D (short/hard)
  97. EP250108a: Liverpool Telescope likely optical counterpart
  98. GRB 250108B: Swift-BAT refined analysis
  99. GRB 250108B: 1.3m DFOT upper limit
  100. GRB 250108B: REM optical/NIR upper limits

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