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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"
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submitter:"Judith Racusin"

32568 results found.

  1. LIGO/Virgo/KAGRA S250818k: NOT optical observations of AT2025ulz
  2. EP250821a: Swift/UVOT further observations.
  3. EP250821a: VLT X-shooter spectroscopic redshift z = 0.577
  4. LIGO/Virgo/KAGRA S250818k: GRAWITA TNG NIR observations of AT2025ulz
  5. GRB 250821A: VLT/FORS2 Optical Observation
  6. GRB 250821A: GECAM-B detection
  7. GRB 250821B: SVOM/GRM observation
  8. EP250821a: SVOM/VT optical observation
  9. Fermi GRB 250821B: Global MASTER-Net observations report
  10. GRB 250821A: NOT z-band upper limit
  11. GRB 250821A: KAIT optical upper limit
  12. LIGO/Virgo/KAGRA S250818k: Continued fading and reddening of AT2025ulz from Keck/LRIS imaging observations
  13. Swift GRB 250821A: Global MASTER-Net observations report
  14. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  15. LIGO/Virgo/KAGRA S250818k : Tautenburg observations, upper limits
  16. GRB 250821A: Swift/UVOT Upper Limits
  17. EP250821a: Rapidly fading optical source detected in Las Cumbres followup
  18. EP250821a: Swift XRT and UVOT counterpart detection
  19. LIGO/Virgo/KAGRA S250818k: GOTO counterpart search and upper limits
  20. EP250821a: Preliminary analysis of the EP-WXT and EP-FXT observations
  21. GRB 250821A: LCOGT Optical Upper Limits
  22. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  23. LIGO/Virgo/KAGRA S250818k: 10 GHz VLA observations of AT2025ulz
  24. LIGO/Virgo/KAGRA S250818k: WFST pre-discovery limits and follow-up observations of AT 2025ulz
  25. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  26. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  27. LIGO/Virgo/KAGRA S250818k: WINTER J-band observations of AT 2025ulz
  28. GRB 250818B: 10 GHz VLA detection
  29. LIGO/Virgo/KAGRA S250818k: Pan-STARRS grizy-band imaging and photometry of AT2025ulz
  30. LIGO/Virgo/KAGRA S250818k: Swift observations of AT 2025ulz
  31. LIGO/Virgo/KAGRA S250818k: Multi-band Gemini GMOS Detections
  32. LIGO/Virgo/KAGRA S250818k: ATLAS pre-discovery limits for AT2025ulz
  33. GRB 250814A: Swift/UVOT Upper Limits
  34. GRB 250813B: Swift/UVOT Upper Limit
  35. IPN triangulation of GRB 250816A (short)
  36. IPN triangulation of GRB 250814C (short)
  37. IPN triangulation of GRB 250804B (short)
  38. GRB 250818B: FTW optical and NIR observations show reddening of the counterpart
  39. GRB 250818B: Kilonova-Catcher optical afterglow detection
  40. LIGO/Virgo/KAGRA S250818k: AstroSat CZTI non-detection and upper limits
  41. GRB 250818B: Liverpool Telescope optical detections
  42. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  43. LIGO/Virgo/KAGRA S250818k: Updated Sky localization and EM Bright Classification
  44. LIGO/Virgo/KAGRA S250818k: Pan-STARRS pre-detection limits for AT2025ulz
  45. GRB 250818A: AstroSat CZTI detection
  46. LIGO/Virgo/KAGRA S250818k: Properties of the low-significance GW compact binary merger candidate potentially associated with AT 2025ulz
  47. LIGO/Virgo/KAGRA S250818k: Keck I LRIS spectroscopy of ZTF25abjmnps (AT2025ulz)
  48. GRB 250818B: Swift/UVOT Detection
  49. LIGO/Virgo/KAGRA S250818k: FTW Fast reddening of AT 2025ulz
  50. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  51. GRB 250818B: TRT Optical Observation
  52. Fermi GRB 250816A: Global MASTER-Net observations report
  53. GRB 250818B: SAO RAS optical observations
  54. Swift GRB 250818A: Global MASTER-Net observations report
  55. GRB 250818B: NOT optical observations
  56. GRB 250818B: EP-FXT counterpart detection
  57. GRB 250818A: Swift-BAT refined analysis
  58. LIGO/Virgo/KAGRA S250818k: FTW optical and NIR observations of AT 2025ulz
  59. GRB 250818B: Keck redshift of the optical afterglow
  60. GRB 250818B: KAIT optical observations
  61. GRB 250818A: Swift/UVOT Upper Limits
  62. LIGO/Virgo/KAGRA S250818t: Updated Sky localization
  63. GRB 250813B: SVOM/ECLAIRs refined analysis
  64. GRB 250818A: Fermi GBM Observation
  65. GRB 250818B: SVOM/VT optical observation
  66. GRB 250814A: Further GRAWITA TNG NIR observations
  67. GRB 250818B: Swift-XRT afterglow detection
  68. GRB 250818B: GOTO optical counterpart candidate
  69. GRB 250818B: SVOM detection of a short burst
  70. LIGO/Virgo/KAGRA S250818t: Identification of a GW compact binary merger candidate
  71. sb25081602: Swift-XRT observations
  72. GRB 250816A: SVOM/GRM observation of a short burst
  73. Fermi GRB 250814B: Global MASTER-Net observations report
  74. GRB 250814A: Swift-BAT refined analysis
  75. GRB 250813B: Liverpool Telescope optical upper limits
  76. GRB 250814A: Further COLIBRÍ optical upper limit
  77. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope
  78. GRB 250814A: GRAWITA TNG NIR observations
  79. GRB 250812A: SVOM/VT optical continued observation
  80. GRB 250814A: Mondy optical observations of the candidate counterpart to LVK S250814bg
  81. GRB 250813B: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  82. GRB250814A: TRT optical upper limits
  83. GRB 250814B: SVOM/GRM observation
  84. GRB 250813B: SVOM/GRM observation
  85. GRB 250814A: P200/WIRC observations of the afterglow candidate
  86. GRB 250814A: KAIT optical upper limit
  87. GRB 240814A: Fermi GBM Observation
  88. GRB 250814A: Possible afterglow candidate from P200/WIRC
  89. GRB 250813B: Fermi GBM Observation
  90. GRB 250814A: J-band upper limit from WINTER
  91. IceCube-250813A: Upper limits from a search for additional neutrino events in IceCube
  92. GRB 250813B: NOT observations of the optical afterglow
  93. GRB 250813B: SVOM/VT optical observations
  94. Subject GRB 250813B: SVOM/MXT refined analysis
  95. GRB 250814A: COLIBRÍ optical upper limit
  96. GRB 250813A: AstroSat CZTI detection
  97. LIGO/Virgo/KAGRA S250814bg: Identification of a GW compact binary merger candidate possibly associated with GRB 250814A detected by Fermi GBM and Swift BAT
  98. GRB 250813B: VLT X-shooter spectroscopic redshift z = 1.752
  99. GRB 250814A: DDOTI Optical Upper Limit
  100. GRB 250813B: EP-FXT counterpart detection

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