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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"

4055 results found.

  1. LIGO/Virgo/KAGRA S240422ed: Las Cumbres Observatory Follow-up Observations of the Localization Region
  2. LIGO/Virgo/KAGRA S240513ei: Updated Sky localization
  3. LIGO/Virgo/KAGRA S240514x: Identification of a GW compact binary merger candidate
  4. LIGO/Virgo/KAGRA S240514c: Identification of a GW compact binary merger candidate
  5. LIGO/Virgo/KAGRA S240507p: Upper limits from Swift/BAT-GUANO
  6. LIGO/Virgo/KAGRA S240505av: Upper limits from Swift/BAT-GUANO
  7. LIGO/Virgo/KAGRA S240505av: Upper limits from Swift/BAT-GUANO
  8. LIGO/Virgo/KAGRA S240513ei: Identification of a GW compact binary merger candidate
  9. LIGO/Virgo/KAGRA S240513cx: Coverage and upper limits from MAXI/GSC observations
  10. LIGO/Virgo/KAGRA S240512r: Updated Sky localization and EM Bright Classification
  11. LIGO/Virgo/KAGRA S240512r: Identification of a GW compact binary merger candidate
  12. LIGO/Virgo/KAGRA S240511i: Updated Sky localization
  13. LIGO/Virgo/KAGRA S240511i: Identification of a GW compact binary merger candidate
  14. LIGO/Virgo/KAGRA S240422ed: GMOS-S photometry of J-GEM24a
  15. LIGO/Virgo/KAGRA S240422ed: P200 observations of AT2024hit
  16. LIGO/Virgo/KAGRA S240422ed: Candidates from the latest GW-MMADS DECam Observations
  17. LIGO/Virgo/KAGRA S240507p: Updated Sky localization and EM Bright Classification
  18. LIGO/Virgo/KAGRA S240422ed: Upper limits from a two-week IceCube neutrino search
  19. LIGO/Virgo/KAGRA S240507p: Identification of a GW compact binary merger candidate
  20. LIGO/Virgo/KAGRA S240422ed: Additional WINTER near-infrared J-band observations
  21. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfr and AT2024hfs
  22. LIGO/Virgo/KAGRA S240505av: Updated Sky localization and EM Bright Classification
  23. LIGO/Virgo/KAGRA S240505av: Identification of a GW compact binary merger candidate
  24. LIGO/Virgo/KAGRA S240501an: Updated Sky localization and EM Bright Classification
  25. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  26. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet Transient Candidates
  27. LIGO/Virgo/KAGRA S240422ed: Host redshifts of AT2024hfq, AT2024hfu, and AT2024hmo from DBSP
  28. LIGO/Virgo/KAGRA S240501an: Identification of a GW compact binary merger candidate
  29. LIGO/Virgo/KAGRA S240430ca: Updated Sky localization and EM Bright Classification
  30. LIGO/Virgo/KAGRA S240430ca: Identification of a GW compact binary merger candidate
  31. LIGO/Virgo/KAGRA S240422ed: GECKO/7DT ToO observations
  32. Additional DECam GW-MMADS Candidates from three nights of observations
  33. LIGO/Virgo/KAGRA S240426s: Updated Sky localization
  34. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limit for EP240426a
  35. LIGO/Virgo/KAGRA S240426dl: Updated Sky localization
  36. LIGO/Virgo/KAGRA S240428dr: Updated Sky localization
  37. LIGO/Virgo/KAGRA S240422ed: GECKO/KMTNet ToO observations
  38. LIGO/Virgo/KAGRA S240429an: Retraction of GW compact binary merger candidate
  39. LIGO/Virgo/KAGRA S240422ed: ENGRAVE VLT/XShooter spectroscopy of the host galaxy of J-GEM24a
  40. LIGO/Virgo/KAGRA S240428dr: Identification of a GW compact binary merger candidate
  41. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of J-GEM24a
  42. LIGO/Virgo/KAGRA S240422ed: DDOTI Optical Upper Limit for J-GEM24a
  43. LIGO/Virgo/KAGRA S240422ed: Observations with 1.6m Mephisto
  44. LIGO/Virgo/KAGRA S240422ed: A transient discovered from Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  45. LIGO/Virgo S240422ed: Swift XRT observation of EP240426a
  46. LIGO/Virgo/KAGRA S240422ed: NOT optical observations of EP240426a
  47. LIGO/Virgo/KAGRA S240422ed: Archival radio detection of EP240426a
  48. LIGO/Virgo/KAGRA S240422ed: Swope Follow-up of AT2024hfq, AT2024hfr, AT2024hfs, and AT2024hfx
  49. LIGO/Virgo/KAGRA S240422ed: BOOTES-6/DPRT optical upper limits for EP240426a
  50. LIGO/Virgo/KAGRA S240422ed: GRANDMA Optical Upper Limits for EP240426a
  51. LIGO/VIRGO/KAGRA S240422ed: Historical variability for EP240426a
  52. EP240426a: YAHPT optical upper limit
  53. XMM-Newton observation of EP240426a
  54. LIGO/Virgo/KAGRA S240426dl: Identification of a GW compact binary merger candidate
  55. LIGO/Virgo/KAGRA S240422ed: BOOTES-4/MET Optical Upper Limits for EP240426a
  56. LIGO/Virgo/KAGRA S240422ed: EP-FXT Detection of the Potential Opitcal Electromagnetic Counterpart AT 2024hfq Reported by DECam
  57. LIGO/Virgo/KAGRA S240422ed: EP240426a possible optical detection
  58. LIGO/Virgo/KAGRA S240422ed: Continued Magellan Observations
  59. LIGO/Virgo/KAGRA S240422ed: EP-FXT detection of a candidate counterpart EP240426a
  60. LIGO/Virgo/KAGRA S240426s: Identification of a GW compact binary merger candidate
  61. LIGO/Virgo/KAGRA S240422ed: Magellan Follow-up Observations of Swift/XRT candidates
  62. LIGO/Virgo/KAGRA S240422ed: Zwicky Transient Facility contuinued observations of S240422ed and candidate analysis
  63. IceCube-240424A: Upper limits from a search for additional neutrino events in IceCube
  64. LIGO/Virgo/KAGRA S240422ed: GOTO counterpart search update and AT2024hfx, AT2024hgl observations
  65. LIGO/Virgo/KAGRA S240422ed: PRIME near-infrared observations
  66. LIGO/Virgo/KAGRA S240422ed: 2.5m PRL Telescope follow-up of the Swift/XRT source S240422ed_X190
  67. LIGO/Virgo/KAGRA S240422ed: Second night Pan-STARRS observations of the skymap
  68. LIGO/Virgo/KAGRA S240422ed: Further near-infrared observations with Subaru/MOIRCS by J-GEM Collaboration
  69. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-FXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  70. LIGO/Virgo/KAGRA S240422ed: Upper limits from GECAM Observations
  71. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA and Kilonova-Catcher galaxy targeting observations
  72. LIGO/Virgo/KAGRA S240422ed: Additional DECam GW-MMADS Candidates from the first two nights of observations
  73. LIGO/Virgo/KAGRA S240422ed: ANU 2.3m followup of candidate counterparts
  74. LIGO/Virgo/KAGRA S240422ed: Magellan Spectrum of GW-MMADS Candidate AT2024hdo Indicates a Type II SN
  75. LIGO/Virgo/KAGRA S240422ed: SRG/eROSITA archival upper limits for Swift/XRT candidates
  76. LIGO/Virgo/KAGRA S240422ed: Archival BlackGEM/MeerLICHT detections of AT 2024hdr & AT 2024hdq
  77. LIGO/Virgo/KAGRA S240413p: DESGW DECam Follow-Up
  78. LIGO/Virgo/KAGRA S240422ed: Himalayan Chandra Telescope follow-up of the Swift/XRT source S240422ed_X101
  79. LIGO/Virgo/KAGRA S240422ed: No significant counterpart candidates in HAWC observations
  80. LIGO/Virgo/KAGRA S240422ed: Vetting of DECam Candidates Using Real-Time Resources and SAGUARO Infrastructure
  81. LIGO/Virgo/KAGRA S240422ed: No significant candidates in GRANDMA/FRAM Observations
  82. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Potential Electromagnetic Counterparts Reported by Swift and DECam
  83. LIGO/Virgo/KAGRA S240422ed: MOSFIRE spectroscopy of the DECam GW-MMADS candidate AT 2024hdn
  84. LIGO/Virgo/KAGRA S240422ed: ATCA follow-up of candidate counterparts
  85. LIGO/Virgo/KAGRA S240422ed: MOSFIRE imaging of the DECam GW-MMADS candidate AT 2024hdm
  86. LIGO/Virgo S240422ed: Swift-XRT detection of 3 possible counterparts
  87. LIGO/Virgo/KAGRA S240422ed: Early X-ray Upper Limits from EP-WXT for the LVK Sky Localization Region
  88. LIGO/Virgo/KAGRA S240422ed: J-band non-detection of Mag24a
  89. LIGO/Virgo/KAGRA S240422ed: Continued Imaging of Mag24a
  90. LIGO/Virgo/KAGRA S240422ed: Archival DECaPSs2 observations of the field of Mag24a
  91. LIGO/Virgo/KAGRA S240422ed: DECam GW-MMADS Candidates
  92. LIGO/Virgo/KAGRA S240422ed: Potential Magellan candidates from GCN 36263 are unrelated.
  93. LIGO/Virgo/KAGRA S240422ed: NOT J-band upper limit on the Swift/XRT source S240422ed_X61
  94. LIGO/Virgo/KAGRA S240422ed: X-ray Upper Limits from EP-WXT for the Three Potential Electromagnetic Counterparts Reported So Far
  95. LIGO/Virgo/KAGRA S240422ed: Magellan Detection of a Potential Electromagnetic Counterpart
  96. LIGO/Virgo/KAGRA S240422ed: SAGUARO upper limits from CSS
  97. LIGO/Virgo/KAGRA S240422ed: Subaru/MOIRCS near-infrared observations by J-GEM Collaboration
  98. LIGO/Virgo/KAGRA S240422ed: LAST optical observations
  99. LIGO/Virgo/KAGRA S240422ed: Potential Candidates from Magellan galaxy-based search
  100. LIGO/Virgo/KAGRA S240422ed: WINTER J-band upper limits on the Swift/XRT source S240422ed_X61

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