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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.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

24818 results found.

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

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