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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"
  1. GRB 200219B: Fermi GBM Final Real-time Localization
  2. GRB 200219A: MASTER catalog automatic possible Host Galaxy candidate
  3. GRB 200219A: Swift detection of a short burst
  4. Swift GRB200219.32: Global MASTER-Net observations report
  5. GRB 200219A: Fermi GBM Final Real-time Localization
  6. GRB 200216B: Mondy and AbAO optical upper limits
  7. LIGO/Virgo (S200213t/IceCube neutrino candidate: No counterpart candidates in the Swift-XRT Observations
  8. GRB 200216B: Swift-XRT refined Analysis
  9. LIGO/Virgo S200213t: No EM counterparts found from continued GECKO observation of host galaxy candidates
  10. LIGO/Virgo S200213t: APO Upper Limits for ZTF20aanakes/AT2020cly
  11. GRB 200216B: Swift-BAT refined analysis
  12. LIGO/Virgo S200213t : No significant candidates in FRAM - OAJ - TAROT - GRANDMA observations
  13. Further Swift-XRT observations of Swift J0840.7-3516
  14. GRB 200216B - possible IR counterpart from VLT
  15. GRB 200215A: CALET Gamma-Ray Burst Monitor detection
  16. GRB 200216A: Fermi GBM detection
  17. LIGO/Virgo S200213t: AstroSat CZTI upper limits
  18. GRB 200216B: z-band limit from NOT
  19. GRB 200216B: Fermi GBM observation
  20. GRB 200216B: Swift/UVOT Upper Limits
  21. GRB 200216A: Swift/BAT detection and arcminute localization from GUANO
  22. GRB 200216B: Enhanced Swift-XRT position
  23. GRB 200215A: RATIR Optical Observations
  24. GRB 200216B: Nanshan/NEXT early optical upper limit and possible host galaxy
  25. GRB 200216B: GMG upper limit
  26. GRB 200216B: Swift detection of a burst
  27. GRB 200216B: Fermi GBM Final Real-time Localization
  28. Swift GRB200216.56: Global MASTER-Net observations report
  29. GRB 200215A: UKIRT H-band observations
  30. GRB 200215A: Swift-BAT refined analysis
  31. GRB 200216A: Fermi GBM Final Real-time Localization
  32. LIGO/Virgo S200213t: Updated Sky Localization
  33. LIGO/Virgo S200213t: Updated coverage and candidate list for the Zwicky Transient Facility
  34. LIGO/Virgo S200213t: CLU/NED Galaxies in the 4-Update Localization Volume
  35. LIGO/Virgo S200213t: Possible host galaxies in the bilby skymap
  36. LIGO/Virgo S200213t: Updated Sky Localization
  37. GRB 200215A: Swift-XRT refined Analysis
  38. GRB 200215A: Swift/UVOT Upper Limits
  39. GRB 200215A: Enhanced Swift-XRT position
  40. GRB 200215A: Optical observations form Calar Alto 2.2m
  41. GRB 200215A: Fermi GBM detection
  42. GRB 200215A: Liverpool Telescope upper limits
  43. LIGO/Virgo S200213t: Pre-discovery detections of MASTER OT J044008.76-651302.3
  44. LIGO/Virgo S200213t: No transient candidates in CALET observations
  45. GRB 200215A Possible host galaxy in PanSTARRS
  46. LIGO/Virgo S200213t: Lulin Follow-Up Observations
  47. GRB 200215A: Nanshan/NEXT optical upper limit
  48. Swift GRB200215.61: Global MASTER-Net observations report
  49. GRB 200215A: Swift detection of a burst
  50. GRB 200215A: Fermi GBM Final Real-time Localization
  51. LIGO/Virgo S200213t: MASTER possible Kilonova candidate in PGC315337
  52. LIGO/Virgo S200213t: No neutrino candidates at Pierre Auger Observatory
  53. LIGO/Virgo S200213t: P200 Spectroscopy of ZTF20aanakcd/AT2020cmr
  54. LIGO/Virgo S200213t: DBSP spectroscopy of AT2020cjb/ZTF20aamvnth, AT2020cja/ZTF20aamvmzj, AT2020cjc/ZTF20aamvoeh
  55. LIGO/Virgo S200114f: Gemini Spectra of AT 2020vu, AT 2020vw, AT 2020vy, and AT 2020vz
  56. LIGO/Virgo S200213t: MASTER OT detection in PGC673735
  57. LIGO/Virgo S200213t: Upper limits from Insight-HXMT/HE observations
  58. LIGO/Virgo S200213t: No counterpart candidates from Nanshan-0.6m observations
  59. LIGO/Virgo S200213t: No notable candidates in GOTO imaging
  60. LIGO/Virgo S200213t: One additional candidate from the Zwicky Transient Facility
  61. LIGO/Virgo S200213t: No Counterparts from GECKO observation of host galaxy candidates in GW-neutrino detection overlap area
  62. LIGO/Virgo S200213t: No candidates found in J-GEM follow-up observations
  63. LIGO/Virgo S200213t: More Candidates from the Zwicky Transient Facility
  64. LIGO/Virgo S200213t: No counterpart candidates in KAIT observations
  65. LIGO/Virgo S200213t: AT2020ciz/ZTF20aamvnat, AT2020cjb/ZTF20aamvnth and 2020cjf/ZTF20aamvodd 10.4m GTC spectroscopy
  66. LIGO/Virgo S200213t: No counterpart candidates in Fermi-LAT observations
  67. LIGO/Virgo S200213t: No Counterparts in DDOTI/OAN Optical Observations
  68. LIGO/Virgo S200213t: AT2020ciy/ZTF20aamvqxl, AT2020cjg/ZTF20aamvoxx and AT2020cje/ZTF20aamvtip 10.4m GTC spectroscopy
  69. LIGO/Virgo S200213t: MANGROVE catalog galaxy ranking
  70. LIGO/Virgo S200213t: Swift/BAT in the South Atlantic Anomaly
  71. LIGO/Virgo S191213g: AT2019wxt Wendelstein optical observations
  72. LIGO/Virgo S200213t: not observable by Fermi-GBM
  73. LIGO/Virgo S200213t: upper limits from AGILE/GRID observations
  74. LIGO/Virgo S200208q : No significant candidates in TAROT - FRAM - GRANDMA observations
  75. LIGO/Virgo S200208q: no counterpart candidate in SVOM/C-GFT observations
  76. LIGO/VIRGO S200213t: upper limits from AGILE/MCAL observations
  77. LIGO/Virgo S200213t: Candidates from the Zwicky Transient Facility
  78. LIGO/Virgo S200213t: No counterpart candidates in INTEGRAL SPI-ACS prompt observation
  79. LIGO/Virgo S200213t : no neutrino counterpart candidate in ANTARES search
  80. LIGO/Virgo S200213t: Coverage and upper limits from MAXI/GSC observations
  81. LIGO/Virgo S200213t: Neutrino and galaxies cross-match
  82. GRB 2002011A: AstroSat CZTI detection
  83. LIGO/Virgo trigger S200213t: Possible host galaxies
  84. LIGO/Virgo S200213t: NED Galaxies in the 90% Localization Volume
  85. LIGO/Virgo S200213t: 1 counterpart neutrino candidate from IceCube neutrino searches
  86. LIGO/Virgo S200213t: Identification of a GW compact binary merger candidate
  87. LIGO/Virgo S200213t: Global MASTER-Net observations report
  88. GRB 200212A: Fermi GBM Final Localization Correction
  89. ZTF20aajnksq: Upper limits from Konus-Wind observations
  90. Fermi trigger No 603197394: Global MASTER-Net observations report
  91. GRB 200212A: Fermi GBM Final Real-time Localization
  92. LIGO/Virgo S200208q: Updated Sky Localization
  93. GRB 200131A: Tautenburg observations
  94. Konus-Wind observation of GRB 200205B
  95. LIGO/Virgo S200208q: No counterpart candidates in KAIT observations
  96. GRB 200211A: BALROG localization (Fermi Trigger 603098793 / GRB 200211310)
  97. GRB 200211A: Fermi GBM Final Real-time Localization
  98. LIGO/Virgo S200208q: Not observable by CALET
  99. GRB 200207A: AstroSat CZTI detection
  100. LIGO/Virgo S200208q: No counterpart candidates in Fermi-LAT observations

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