[
    {
        "id": "thesis:3313",
        "collection": "thesis",
        "collection_id": "3313",
        "cite_using_url": "https://resolver.caltech.edu/CaltechETD:etd-09022008-132322",
        "type": "thesis",
        "title": "Hard X-Ray Detection and Timing of Accretion-Powered Pulsars with BATSE",
        "author": [
            {
                "family_name": "Chakrabarty",
                "given_name": "Deepto",
                "orcid": "0000-0001-8804-8946",
                "clpid": "Chakrabarty-Deepto"
            }
        ],
        "thesis_advisor": [
            {
                "family_name": "Prince",
                "given_name": "Thomas A.",
                "clpid": "Prince-T-A"
            }
        ],
        "thesis_committee": [
            {
                "family_name": "Prince",
                "given_name": "Thomas A.",
                "clpid": "Prince-T-A"
            },
            {
                "family_name": "Blandford",
                "given_name": "Roger D.",
                "clpid": "Blandford-R-D"
            },
            {
                "family_name": "Schmidt",
                "given_name": "Maarten",
                "clpid": "Schmidt-M"
            },
            {
                "family_name": "Soifer",
                "given_name": "B. Thomas",
                "clpid": "Soifer-B-T"
            }
        ],
        "local_group": [
            {
                "literal": "Space Radiation Laboratory"
            },
            {
                "literal": "Astronomy Department"
            },
            {
                "literal": "div_pma"
            }
        ],
        "abstract": "<p>The BATSE all-sky monitor on the <i>Compton Gamma Ray Observatory</i> is a superb tool for the study of accretion-powered pulsars. In the first part of this thesis, I describe its capabilities for hard X-ray observations above 20 keV, present techniques for timing analysis of the BATSE data, and discuss general statistical issues for the detection of pulsed periodic signals in both the time and frequency domains. BATSE's 1-day pulsed sensitivity in the 20-60 keV range is \u2248 15 mCrab for pulse periods 2 s \u2272 P<sub>pulse</sub> \u2272 400 s, covering most of the known accreting pulsars. Its sensitivity degrades substantially outside of this range.</p>\r\n\r\n<p>In the second part of this thesis, I present the results of several science investigations applying these techniques. Half the 42 known accreting pulsars have been detected with BATSE and are monitored whenever they are active. Except for a few which lie outside of BATSE's sensitivity range, the rest are all transient sources which may eventually be detected in outburst. The detected systems include four new transients discovered by BATSE, one of which is discussed in detail. A new technique used to localize this source, GRO J1948+32, is described.</p>\r\n\r\n<p>Observations of the 38-s pulsar OAO 1657-415 discovered that it is in a 10.4-d eccentric orbit and undergoes regular X-ray eclipses by its massive companion, making it only the seventh known eclipsing X-ray pulsar. Constraints placed by the pulsar mass function and the eclipse duration indicate that the undetected binary companion must be an OB supergiant. If the companion can be identified and its orbital velocity measured, the neutron star mass can be determined.</p>\r\n\r\n<p>The 7.7-s pulsar 4U 1626-67 was found to be in an extended spin-down state, ending over a decade of rapid, steady spin-up. It is only the second steady-state disk accreter known to have undergone a torque reversal. The other, the 2-min pulsar GX 1+4, underwent two torque reversals during our observations and is detected up to 160 keV. During spin-down, we find that pulsed flux and torque in GX 1+4 are <i>anticorrelated</i>, the opposite of what is predicted by the usual theories of magnetic accretion torques.</p>\r\n",
        "doi": "10.7907/6K2P-2A91",
        "publication_date": "1996",
        "thesis_type": "phd",
        "thesis_year": "1996"
    }
]