| Full text | |
| Author(s): |
Moritani, Yuki
[1]
;
Kawano, Takafumi
[2]
;
Chimasu, Sho
[3]
;
Kawachi, Akiko
[3]
;
Takahashi, Hiromitsu
[2]
;
Takata, Jumpei
[4]
;
Carciofi, Alex C.
[5]
Total Authors: 7
|
| Affiliation: | [1] Univ Tokyo, Inst Adv Study, Kavli Inst Phys & Math Universe WPI, 5-1-5 Kashiwanoha, Kashiwa, Chiba 2778583 - Japan
[2] Hiroshima Univ, Dept Phys Sci, 1-3-1 Kagamiyama, Higashihiroshima, Hiroshima 7398526 - Japan
[3] Tokai Univ, Sch Sci, Dept Phys, 4-1-1 Kitakaname, Hiratsuka, Kanagawa 2591292 - Japan
[4] Huazhong Univ Sci & Technol, Sch Phys, Wuhan 430074, Hubei - Peoples R China
[5] Univ Sao Paulo, Inst Astron Geofis & Ciencias Atmosfer, Rua Matao 1226, Cidade Univ, BR-05508090 Sao Paulo, SP - Brazil
Total Affiliations: 5
|
| Document type: | Journal article |
| Source: | PUBLICATIONS OF THE ASTRONOMICAL SOCIETY OF JAPAN; v. 70, n. 4 AUG 2018. |
| Web of Science Citations: | 1 |
| Abstract | |
High-dispersion spectroscopic monitoring of HESS J0632+057 has been carried out over four orbital cycles in order to search for orbital modulation, covering the entire orbital phase. We have measured the radial velocity of the H alpha emission line with the method introduced by Shafter, Szkody, and Thorstensen (1986, ApJ, 308, 765), which has been successfully applied to some Be stars. The velocity is seen to increase much earlier than expected for the orbital period of 315 d, and much more steeply than expected at around ``apastron.{''} The period of the H alpha modulation is found to be 308(-23)(+26) d. We have also analyzed Swift/XRT data from 2009 to 2015 to study the orbital modulation, selecting the data with good statistics (>= 30 counts). With additional two-year data to the previous works, the orbital period has been updated to 313(-8)(+11) d, which is consistent with the previous X-ray periods and the spectroscopic one. Previous XMM-Newton and Chandra observations prefer a period of 313 d. With the new period, assuming that H alpha velocities accurately trace the motion of the Be star, we have derived a new set of orbital parameters. In the new orbit, which is less eccentric (e similar or equal to 0.6), two outbursts occur: after apastron and just after periastron. Also, the column density in bright phase (4.7(-08)(+0.9) x 10(21) cm(-2)) is higher than in faint phase (2.2 +/- 0.5 x 10(21) cm(-2)). These facts suggest that outbursts occur when the compact object passes nearby/through the Be disk. The mass function implies that the mass of the compact object is less than 2.5 M-circle dot, assuming that the mass of the Be star is 13.2-18.2 M-circle dot (Aragona et al. 2010, ApJ, 724, 306), unless the inclination is extremely small. The photon index indicates that the spectra become softer when the system is bright. These suggest that the compact object is a pulsar. (AU) | |
| FAPESP's process: | 15/17967-7 - Viscous decretion disks: theory and observations |
| Grantee: | Alex Cavaliéri Carciofi |
| Support Opportunities: | Regular Research Grants |