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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"

20359 results found.

  1. EP250806a: Einstein Probe detection of an X-ray transient
  2. GRB 250806A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  3. GRB 250806A: SVOM/VT optical upper limit
  4. GRB 250806A: SVOM detection of a soft burst
  5. GRB 250805A: SVOM/VT optical counterpart
  6. GRB 250805A: Enhanced Swift-XRT position
  7. GRB 250805A: TRT optical upper limits
  8. GRB 250805A: Swift-XRT observations
  9. GRB 250804B: SVOM/GRM observation of a short burst
  10. EP250802a: additional Liverpool Telescope upper limits
  11. EP250730a: SVOM/VT optical upper limit
  12. EP250802a: Liverpool Telescope optical upper limits
  13. EP250802a: GROWTH-India Telescope optical upper limit
  14. EP250802a: Einstein Probe detection of an X-ray transient
  15. LIGO/Virgo/KAGRA S250802dn: Identification of a GW compact binary merger candidate
  16. LIGO/Virgo/KAGRA S250727dc: GRANDMA/OPD observations of AT2025smm
  17. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS candidates
  18. LIGO/Virgo/KAGRA S250725j: GOTO pre-trigger detection of AT2025sib
  19. EP250711a: CrAO and Assy optical observations
  20. LIGO/Virgo/KAGRA S250727dc: DECam DESGW Epoch 1 Candidates
  21. EP250730a: COLIBRÍ optical upper limit
  22. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  23. EP250730a: Einstein Probe detection of an X-ray transient
  24. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  25. GRB 250725A: PRIME near-infrared observations
  26. LIGO/Virgo/KAGRA S250727dc: DECam GW-MMADS upper limits of AT 2025smm
  27. LIGO/Virgo/KAGRA S250727dc: PRIME J-band upper limits of AT 2025smm
  28. GRB 250727A: SVOM/ECLAIRs refined analysis
  29. GRB 250728A: COLIBRÍ optical upper limit
  30. LIGO/Virgo/KAGRA S250727dc: Identification of a GW compact binary merger candidate
  31. LIGO/Virgo/KAGRA S250727cl: Identification of a GW compact binary merger candidate
  32. LIGO/Virgo/KAGRA S250725j: DECam GW-MMADS candidates
  33. LIGO/Virgo/KAGRA S250726ak: Identification of a GW compact binary merger candidate
  34. GRB 250725A: SVOM/GRM observation
  35. GRB 250725A: Global MASTER-Net: First Optical Synchronous Observatios of Short GRB.
  36. GRB 250725A: Swift/UVOT Upper Limits
  37. GRB 250725A: SVOM/VT optical candidate
  38. LIGO/Virgo/KAGRA S250725l: Identification of a GW compact binary merger candidate
  39. LIGO/Virgo/KAGRA S250725j: Identification of a GW compact binary merger candidate
  40. GRB 250725A: Enhanced Swift-XRT position
  41. GRB 250725A: Swift detection of a burst
  42. EP250702a/GRB250702 B,E,D: MeerKAT radio observations at 3.06 GHz
  43. SVOM J195836+32283 is not a real source
  44. EP250702a/GRB250702 B,D,E: uGMRT Radio detection in 1.26 GHz
  45. SVOM J195836+32283/sb25072103: Liverpool Telescope detection of an extended source
  46. SVOM J195836+32283/sb25072103: NIR observations with WINTER
  47. GRB 250721A: Swift-XRT observations
  48. GRB 250713A : SVOM/ECLAIRs refined analysis
  49. GRB 250717B: SVOM/GRM observation
  50. The SVOM alert sb25072103 is not due to a GRB, but to a new galactic transient SVOM J195836+32283.
  51. GRB 250717B: COLIBRÍ optical upper limit
  52. Swift Trigger 1334535 / GRB 250718A: COLIBRÍ optical upper limits
  53. GRB 270713A: Kitab and AbAO Optical Observations
  54. Konus-Wind detection of GRB 250716A
  55. GRB 250716A: Swift-XRT afterglow detection
  56. GRB 250714A: SVOM/GRM observation
  57. EP250702a / GRB 250702B,D,E: Hubble Space Telescope Observations
  58. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  59. GRB 250713A: Mephisto optical upper limits
  60. GRB 250713A: SVOM/VT optical upper limit
  61. GRB 250713A: NOT optical upper limits
  62. GRB 250713A: OHP/T193 upper limit
  63. GRB 250713A: SVOM/C-GFT upper limit
  64. GRB 250706B/C: 7DT Follow-up Observations
  65. GRB 250713A: EP-FXT counterpart detection
  66. EP250711a: COLIBRÍ continuous optical observations
  67. GRB 250713A: JinShan optical upper limits
  68. GRB 250713A: SVOM detection of a long burst
  69. GRB 250711A: DDOTI Optical Upper Limit
  70. LIGO/Virgo/KAGRA S250712cd: Identification of a GW compact binary merger candidate
  71. EP250711a: COLIBRÍ refined photometry and optical confirmation of the candidate
  72. GRB 250711A: SVOM/GRM observation
  73. EP250711a: NOT optical counterpart candidate
  74. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  75. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  76. EP250702a: gamma-ray upper limits from joint observations by the LST-1 and MAGIC telescopes
  77. GRB 250704A: GRANDMA observations
  78. GRB 250704A: SVOM/ECLAIRs refined analysis
  79. LIGO/Virgo/KAGRA S250711q: Identification of a GW compact binary merger candidate
  80. GRB 250702B,D,E/EP250702A: JCMT sub-mm observations at 350 GHz
  81. IceCube-250708A: No Candidates from WINTER
  82. IceCube-250708A: No Candidate Transients from the Zwicky Transient Facility
  83. IceCube-250708A: Upper limits from a search for additional neutrino events in IceCube
  84. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  85. EP250704a/GRB 250704B: 10 GHz VLA detection
  86. LIGO/Virgo/KAGRA S250704ab: NED Galaxies in the 4-Update Localization Volume
  87. IceCube-250706A: No Candidates from WINTER
  88. IceCube-250706A: No Candidates from the Zwicky Transient Facility
  89. IceCube-250706A: Upper limits from a search for additional neutrino events in IceCube
  90. EP250704a/GRB250704B : HCT optical and NIR upper limits
  91. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  92. GRB 250706B: SVOM observations interpreted as the afterglow of GRB 250706C
  93. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  94. GRB 250704B / EP250704a: Mondy and AbAO optical observations
  95. GRB 250702F: radio detection with the VLA
  96. Fermi-LAT Gamma-ray Observations of IceCube-250706A
  97. GRB 250706B/C: Fermi-LAT detection
  98. GRB 250704A: SVOM/COLIBRÍ (FM-GFT) optical observations
  99. EP250702a/GRB250702 B,D,E: GRANDMA Upper Limit
  100. GRB 250706B: Swift/UVOT Detection

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